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Publisher: Elsevier   (Total: 3161 journals)

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Showing 1 - 200 of 3161 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 9)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 33, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 23, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 95, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 35, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 5)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 410, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 27, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 2)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 10, SJR: 0.18, CiteScore: 1)
Acta Haematologica Polonica     Free   (Followers: 1, SJR: 0.128, CiteScore: 0)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 250, SJR: 3.263, CiteScore: 6)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.504, CiteScore: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.542, CiteScore: 1)
Acta Oecologica     Hybrid Journal   (Followers: 12, SJR: 0.834, CiteScore: 2)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription  
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 2, SJR: 0.307, CiteScore: 0)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1, SJR: 1.793, CiteScore: 6)
Acta Poética     Open Access   (Followers: 4, SJR: 0.101, CiteScore: 0)
Acta Psychologica     Hybrid Journal   (Followers: 27, SJR: 1.331, CiteScore: 2)
Acta Sociológica     Open Access   (Followers: 1)
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.052, CiteScore: 2)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 3, SJR: 0.374, CiteScore: 1)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 2)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 3, SJR: 0.344, CiteScore: 1)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 1)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 6, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 6)
Acute Pain     Full-text available via subscription   (Followers: 14, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 16, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 8, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 9, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 22)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 148, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 16, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 8, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 12, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 28, SJR: 0.126, CiteScore: 0)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 2)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 10, SJR: 0.992, CiteScore: 1)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 1.551, CiteScore: 4)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 14, SJR: 0.572, CiteScore: 2)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.61, CiteScore: 7)
Advances in Botanical Research     Full-text available via subscription   (Followers: 2, SJR: 0.686, CiteScore: 2)
Advances in Cancer Research     Full-text available via subscription   (Followers: 32, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 8, SJR: 1.453, CiteScore: 2)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 1.992, CiteScore: 5)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 3)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27, SJR: 0.156, CiteScore: 1)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.713, CiteScore: 1)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 10, SJR: 1.316, CiteScore: 2)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 19, SJR: 1.977, CiteScore: 8)
Advances in Computers     Full-text available via subscription   (Followers: 14, SJR: 0.205, CiteScore: 1)
Advances in Dermatology     Full-text available via subscription   (Followers: 15)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 9)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 24)
Advances in Ecological Research     Full-text available via subscription   (Followers: 44, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 28, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 44, SJR: 5.39, CiteScore: 8)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 1)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 9)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 57, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 16, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 8, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 21, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 12, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 22)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.193, CiteScore: 0)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.433, CiteScore: 6)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 1.163, CiteScore: 2)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 2, SJR: 1.938, CiteScore: 3)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6, SJR: 0.176, CiteScore: 0)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 3)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.682, CiteScore: 2)
Advances in Lipobiology     Full-text available via subscription   (Followers: 1)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 11, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 21)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 8)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 7, SJR: 0.182, CiteScore: 0)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 3)
Advances in Oncobiology     Full-text available via subscription   (Followers: 1)
Advances in Organ Biology     Full-text available via subscription   (Followers: 1)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 17, SJR: 1.875, CiteScore: 4)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.174, CiteScore: 0)
Advances in Parasitology     Full-text available via subscription   (Followers: 5, SJR: 1.579, CiteScore: 4)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 10)
Advances in Pharmacology     Full-text available via subscription   (Followers: 16, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.574, CiteScore: 1)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.109, CiteScore: 1)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 9)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 18)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 0.791, CiteScore: 2)
Advances in Psychology     Full-text available via subscription   (Followers: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (SJR: 0.263, CiteScore: 1)
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 3, SJR: 0.101, CiteScore: 0)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 398, SJR: 0.569, CiteScore: 2)
Advances in Structural Biology     Full-text available via subscription   (Followers: 5)
Advances in Surgery     Full-text available via subscription   (Followers: 10, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 31, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 17)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 47, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 343, SJR: 0.796, CiteScore: 3)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.42, CiteScore: 2)
African J. of Emergency Medicine     Open Access   (Followers: 6, SJR: 0.296, CiteScore: 0)
Ageing Research Reviews     Hybrid Journal   (Followers: 11, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 445, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 17, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 43, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 2)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 57, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 6, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 9)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.604, CiteScore: 3)
Alexandria J. of Medicine     Open Access   (Followers: 1, SJR: 0.191, CiteScore: 1)
Algal Research     Partially Free   (Followers: 11, SJR: 1.142, CiteScore: 4)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 2)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.504, CiteScore: 1)
Allergology Intl.     Open Access   (Followers: 5, SJR: 1.148, CiteScore: 2)
Alpha Omegan     Full-text available via subscription   (SJR: 3.521, CiteScore: 6)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 50, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 6)
American Heart J.     Hybrid Journal   (Followers: 50, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 54, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 45, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 10)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 34, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 28, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 34, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 46)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3, SJR: 1.967, CiteScore: 2)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 205, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 62, SJR: 3.184, CiteScore: 4)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5, SJR: 0.265, CiteScore: 0)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.289, CiteScore: 1)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, CiteScore: 1)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.139, CiteScore: 4)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 28, SJR: 2.164, CiteScore: 4)
American J. of Surgery     Hybrid Journal   (Followers: 38, SJR: 1.141, CiteScore: 2)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.767, CiteScore: 1)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 62, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 17, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 3, SJR: 0.277, CiteScore: 0)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription  
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 5, SJR: 4.849, CiteScore: 10)
Analytica Chimica Acta     Hybrid Journal   (Followers: 43, SJR: 1.512, CiteScore: 5)
Analytical Biochemistry     Hybrid Journal   (Followers: 176, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 11, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 11)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 23, SJR: 0.683, CiteScore: 2)
Angiología     Full-text available via subscription   (SJR: 0.121, CiteScore: 0)
Angiologia e Cirurgia Vascular     Open Access   (Followers: 1, SJR: 0.111, CiteScore: 0)
Animal Behaviour     Hybrid Journal   (Followers: 190, SJR: 1.58, CiteScore: 3)

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Journal Cover
Advances in Space Research
Journal Prestige (SJR): 0.569
Citation Impact (citeScore): 2
Number of Followers: 398  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 0273-1177
Published by Elsevier Homepage  [3161 journals]
  • List of Referees
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s):
       
  • Exospheric escape: A parametrical study
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Rosemary M. Killen, Matthew H. Burger, William M. Farrell The study of exospheres can help us understand the long-term loss of volatiles from planetary bodies due to interactions of planets, satellites, and small bodies with the interplanetary medium, solar radiation, and internal forces including diffusion and outgassing. Recent evidence for water and OH on the Moon has spurred interest in processes involving chemistry and sequestration of volatile species at the poles and in voids. In recent years, NASA has sent spacecraft to asteroids including Vesta and Ceres, and ESA sent Rosetta to comet 67P/Churyumov–Gerasimenko and the asteroids Lutetia and Steins. Japan's Hayabusa spacecraft returned a sample from asteroid Itakowa, and OSIRIS-REX will return a sample from a primitive asteroid, Bennu, to Earth. In a surface-bounded exosphere, the gases are derived from the surface and thus reflect the composition of the body's regolith, although not in a one-to-one ratio. Observation of an escaping exosphere, termed a corona, is challenging. We have therefore embarked on a parametrical study of exospheres as a function of mass of the exospheric species, mass of the primary body and source velocity distribution, specifically thermal (Maxwell-Boltzmann) and sputtering. The goal is to provide a quick look to determine under what conditions and for what mass of the primary body the species of interest are expected to be bound or escaping and to quickly estimate the observability of exospheric species. This work does not provide a comprehensive model but rather serves as a starting point for further study. These parameters will be useful for mission planning as well as for students beginning a study of planetary exospheres.
       
  • Genetic analysis of parameters of near earth asteroids for determining
           parent bodies of meteoroid streams
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): M. Sokolova, M. Sergienko, Y. Nefedyev, A. Andreev, L. Nefediev The present paper is focusing on determining genetic connections between small bodies of the Solar system and their parent bodies (PB) on the basis of analysis of Near Earth Asteroids (NEAs) parameters. In order to search for parent bodies of meteoroid streams, the asteroid groups, including Atira, Apollo, Amor and Aten, have been investigated. Currently, it is considered that surface of asteroids with elongated orbit is exposed to temperature fall: in perihelion it is heated and in aphelion it is cooled. At small orbital periods around the Sun (about 2–4 years) this may lead to formation of meteoroid clusters. On the basis of comparative analysis of orbit, size and chemical and mineralogical composition of NEAs, it is found that asteroids from Apollo group are most likely to be parent bodies of the studied meteoroid streams.
       
  • Continuum definition for ∼3.1, ∼3.4 and ∼4.0 µm absorption bands in
           Ceres spectra and evaluation of effects of smoothing procedure in the
           retrieved spectral parameters
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): A. Galiano, E. Palomba, A. Longobardo, A. Zinzi, M.C. De Sanctis, A. Raponi, F.G. Carrozzo, M. Ciarniello, F. Dirri NASA’s Dawn spacecraft acquired images and hyperspectral data of Ceres by means of FC and VIR instruments, and identified some widespread bright areas or bright spots (BS). The most peculiar BS is inside Occator crater and it is characterized by spectral properties very dissimilar from the rest of Ceres’ surface. To perform a mineralogical analysis, absorption bands in reflectance spectra must be properly isolated by removal of continuum, and related descriptors (such as band centers and band depths) can be computed. The method for continuum removal must be applicable to all Ceres spectra, relative to different areas, so that a comparison among spectral parameters can be made and mineralogical interpretation can be achieved. This work focuses on the definition of the most appropriate continuum to isolate absorption bands located at ∼3.1, ∼3.4 and ∼4.0 µm. The ∼3.1 µm feature is related to ammoniated phyllosilicates, while the ∼3.4 and ∼4.0 µm absorption bands are indicative of carbonates. Thermal emission affects the continuum for these bands in the VIR spectral range, which extends up to 5.1 µm, moreover all thermal-removed reliable data stop at 4.2 µm. This implies that the shoulder of bands at longer wavelength cannot be identified. We therefore defined alternative continua, i.e., a linear and two polynomial ones, able to describe spectra of any area (i.e. bright or dark) and regardless of spatial resolution. We found that the linear definition satisfies these requirements best. For the first time, we performed an error evaluation on band depths and band centers introduced by the applied method, which is relevant for comparison of spectral parameters of Ceres regions and to better interpret mineralogy and photometric effects.
       
  • Small Bodies Near and Far (SBNAF): A benchmark study on physical and
           thermal properties of small bodies in the Solar System
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): T.G. Müller, A. Marciniak, Cs. Kiss, R. Duffard, V. Alí-Lagoa, P. Bartczak, M. Butkiewicz-Bąk, G. Dudziński, E. Fernández-Valenzuela, G. Marton, N. Morales, J.-L. Ortiz, D. Oszkiewicz, T. Santana-Ros, R. Szakáts, P. Santos-Sanz, A. Takácsné Farkas, E. Varga-Verebélyi The combination of visible and thermal data from the ground and astrophysics space missions is key to improving the scientific understanding of near-Earth, main-belt, trojans, centaurs, and trans-Neptunian objects. To get full information on a small sample of selected bodies we combine different methods and techniques: lightcurve inversion, stellar occultations, thermophysical modelling, radiometric methods, radar ranging and adaptive optics imaging. The SBNAF project will derive size, spin and shape, thermal inertia, surface roughness, and in some cases bulk densities and even internal structure and composition, for objects out to the most distant regions in the Solar System. The applications to objects with ground-truth information allows us to advance the techniques beyond the current state-of-the-art and to assess the limitations of each method. We present results from our project’s first phase: the analysis of combined Herschel-KeplerK2 data and Herschel-occultation data for TNOs; synergy studies on large MBAs from combined high-quality visual and thermal data; establishment of well-known asteroids as celestial calibrators for far-infrared, sub-millimetre, and millimetre projects; first results on near-Earth asteroids properties from combined lightcurve, radar and thermal measurements, as well as the Hayabusa-2 mission target characterisation. We also introduce public web-services and tools for studies of small bodies in general.
       
  • Production and 3D visualization of high-level data of minor bodies: The
           MATISSE tool in the framework of VESPA-Europlanet 2020 activity
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): A. Longobardo, A. Zinzi, M.T. Capria, S. Erard, M. Giardino, S. Ivanovski, S. Fonte, E. Palomba, G. Di Persio, L.A. Antonelli The main goal of the VESPA (Virtual European Solar and Planetary Access) activity, developed in the framework of the EU-funded project Europlanet 2020 Research Infrastructure, is the application of Virtual Observatory standards to planetary data, in order to increase their sharing, visualization, interoperability and combination. The VESPA main search interface already uses some tools for analysis of planetary data, whereas other developed tools are going to be integrated on VESPA, e.g. MATISSE (Multi-purpose Advanced Tool for Instruments for the Solar System Exploration). This tool works on PDS data allowing analysis and 3D visualization of hyperspectral images. It is particularly suitable for minor bodies, where data projection on the shape model is fundamental to relate data to topographic and geological context.This paper shows the new functions implemented on the MATISSE tool for the study of minor bodies, aimed at the development of derived and high-level products, such as reflectance, photometrically corrected reflectance, absorption band descriptors and spectral ratios, and at their visualization on shape models. The developed products are commonly used to analyze hyperspectral data and hence a web based tool allowing their retrieval and visualization is important to hasten and support research activity on minor bodies.
       
  • The SSDC contribution to the improvement of knowledge by means of 3D data
           projections of minor bodies
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Angelo Zinzi, Mauro Ciarniello, Vincenzo Della Corte, Stavro Ivanovski, Andrea Longobardo, Alessandra Migliorini, Maria Teresa Capria, Ernesto Palomba, Alessandra Rotundi The latest developments of planetary exploration missions devoted to minor bodies required new solutions to correctly visualize and analyze data acquired over irregularly shaped bodies.ASI Space Science Data Center (SSDC – ASI, formerly ASDC – ASI Science Data Center) worked on this task since early 2013, when started developing the web tool MATISSE (Multi-purpose Advanced Tool for the Instruments of the Solar System Exploration) mainly focused on the Rosetta/ESA space mission data.In order to visualize very high-resolution shape models, MATISSE uses a Python module (vtpMaker), which can also be launched as a stand-alone command-line software.MATISSE and vtpMaker are part of the SSDC contribution to the new challenges imposed by the “orbital exploration” of minor bodies: (1) MATISSE allows to search for specific observations inside datasets and then analyze them in parallel, providing high-level outputs; (2) the 3D capabilities of both tools are critical in inferring information otherwise difficult to retrieve for non-spherical targets and, as in the case for the GIADA instrument onboard Rosetta, to visualize data related to the coma.New tasks and features adding valuable capabilities to the minor bodies SSDC tools are planned for the near future thanks to new collaborations.
       
  • Preliminary orbital analysis for a CubeSat mission to the Didymos binary
           asteroid system
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Riccardo Lasagni Manghi, Dario Modenini, Marco Zannoni, Paolo Tortora Nanosatellite missions represent a promising option for the exploration of the near-Earth asteroid population since they provide low-cost versatile platforms for scientific observations. This paper describes the preliminary orbital and navigation analyses for the DustCube mission, which was pre-selected to reach the binary asteroid system Didymos on-board ESA’s AIM spacecraft. Possible candidate orbits that exploit the binary nature of the system are identified and traded off to produce a preliminary concept of operations. The overall feasibility of the proposed scenario is then addressed by integrating the spacecraft trajectories in a realistic dynamical environment, evaluating their sensitivity to state errors, and estimating the accuracy of the orbit determination system.Preliminary results suggest that autonomous navigation of a Cubesat platform within a binary asteroid system is technically feasible. The proposed solution, which combines an initial parking orbit at the L4 equilibrium point with a Distant Retrograde Orbit for proximity operations, is shown to be consistent with the estimated orbit determination accuracy and allows to fulfil the mission requirements.
       
  • Radio science investigations with the Asteroid impact mission
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Marco Zannoni, Giacomo Tommei, Dario Modenini, Paolo Tortora, Ruaraidh Mackenzie, Mehdi Scoubeau, Ulrich Herfort, Ian Carnelli The Asteroid Impact & Deflection Assessment (AIDA) mission is a joint ESA/NASA collaboration to study the binary Near-Earth Asteroid (65,803) Didymos and assess the feasibility of the kinetic impactor technique to deflect an asteroid. The European contribution to AIDA is the Asteroid Impact Mission (AIM), which will characterize in detail the Didymos system, investigating the surface, subsurface, and internal properties of the asteroid.This paper presents a possible Radio Science Experiment (RSE) to be performed with AIM focused at its precise orbit determination within the Didymos system, providing an assessment of the accuracies achievable in the estimation of the scientific parameters of interest, like the masses and the extended gravity fields of Didymos primary and secondary, their relative orbit, and their rotational states. The experiment expected performances were assessed through numerical simulations, based upon a complete and realistic dynamical model of the Didymos system and the AIM spacecraft.Given the small mass of the Didymos system, optical navigation images proved to be crucial to obtain good accuracies for the scientific parameters of interest, even keeping AIM at relatively large distances from Didymos. At 10 km, after 8 flybys dedicated to gravity science, the masses of the primary and secondary can be estimated to about 0.2% and 1.6% (1-sigma), respectively, with the mass of the secondary being mainly given by observing the wobble of the primary around the common center of mass due to the mutual orbital motion; the orbital motion of the secondary around the primary can be estimated to about 1 m, and the pole orientation of the primary and the secondary can be estimated to about 0.1 deg and 0.4 deg, respectively (1-sigma).
       
  • European component of the AIDA mission to a binary asteroid:
           Characterization and interpretation of the impact of the DART mission
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Patrick Michel, Michael Kueppers, Holger Sierks, Ian Carnelli, Andy F. Cheng, Karim Mellab, Mikael Granvik, Antti Kestilä, Tomas Kohout, Karri Muinonen, Antti Näsilä, Antti Penttila, Tuomas Tikka, Paolo Tortora, Valérie Ciarletti, Alain Hérique, Naomi Murdoch, Erik Asphaug, Andy Rivkin, Olivier Barnouin The European component of the joint ESA-NASA Asteroid Impact & Deflection Assessment (AIDA) mission has been redesigned from the original version called Asteroid Impact Mission (AIM), and is now called Hera. The main objectives of AIDA are twofold: (1) to perform an asteroid deflection test by means of a kinetic impactor under detailed study at NASA (called DART, for Double Asteroid Redirection Test); and (2) to investigate with Hera the changes in geophysical and dynamical properties of the target binary asteroid after the DART impact. This joint mission will allow extrapolating the results of the kinetic impact to other asteroids and therefore fully validate such asteroid deflection techniques. Hera leverages technology and payload pre-developments of the previous AIM, and focuses on key measurements to validate impact models such as the detailed characterisation of the impact crater. As such, AIDA will be the first documented deflection experiment and binary asteroid investigation. In particular, it will be the first mission to investigate a binary asteroid, and return new scientific knowledge with important implications for our understanding of asteroid formation and solar system history. Hera will investigate the smallest asteroid visited so far therefore providing a unique opportunity to shed light on the role cohesion and Van der Waals forces may play in the formation and resulting internal structure of such small bodies.
       
  • Ballistic landing design on binary asteroids: The AIM case study
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Fabio Ferrari, Michèle Lavagna The close-proximity exploration of small celestial bodies of our Solar System is the current frontier of space exploration. Trajectory design and exploitation of the natural dynamics around such bodies represents a very challenging astrodynamics problem, due to their weak and highly chaotic gravitational environment. The paper discusses design solutions for the ballistic landing of a small and passive probe, released to land on the smaller of a binary asteroid couple. The work is focused on the Asteroid Impact Mission (AIM) case study, although the methods and analyses presented are general and applicable to any binary asteroid scenario. The binary system is modeled using a shape-based three-body problem and three-body solutions are investigated within the Didymos binary system. Manifold dynamics near libration points associated to the asteroid three-body system are exploited to find low-energy and high-success landing trajectories. The validity of implemented approach and solutions found are discussed and results in terms of success rate and landing dispersion are shown.
       
  • Feasibility of asteroid exploration using CubeSats—ASPECT case study
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Tomas Kohout, Antti Näsilä, Tuomas Tikka, Mikael Granvik, Antti Kestilä, Antti Penttilä, Janne Kuhno, Karri Muinonen, Kai Viherkanto, Esa Kallio Operation of a small CubeSat in the deep-space microgravity environment brings additional challenging factors including the increased radiation environment, the significant contribution of non-gravitational forces to the satellite orbit, or the limited communication opportunities. These factors need to be taken into account in the form of modifications to the classic CubeSat architecture. Increased radiation resistance, the semi-autonomous satellite operation, navigation, and the active orbit correction are required. Such a modified CubeSat platform can potentially deliver a high performance to mass and cost ratios. The Asteroid Spectral Imaging Mission (ASPECT) is a three unit (3U) CubeSat mission built on these principles. It is part of the AIDA (Asteroid Impact & Deflection Assessment) project to the binary asteroid Didymos. ASPECT is equipped with a visible to near-infrared hyperspectral imager and will deliver both technological knowledge as well as scientific data about the origin and evolution of Solar System small bodies.
       
  • DePhine – The Deimos and Phobos Interior Explorer
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Jürgen Oberst, Kai Wickhusen, Konrad Willner, Klaus Gwinner, Sofya Spiridonova, Ralph Kahle, Andrew Coates, Alain Herique, Dirk Plettemeier, Marina Díaz-Michelena, Alexander Zakharov, Yoshifumi Futaana, Martin Pätzold, Pascal Rosenblatt, David J. Lawrence, Valery Lainey, Alison Gibbings, Ingo Gerth DePhine – Deimos and Phobos Interior Explorer – is a mission proposed in the context of ESA’s Cosmic Vision program, for launch in 2030. The mission will explore the origin and the evolution of the two Martian satellites, by focusing on their interior structures and diversity, by addressing the following open questions: Are Phobos and Deimos true siblings, originating from the same source and sharing the same formation scenario' Are the satellites rubble piles or solid bodies' Do they possess hidden deposits of water ice in their interiors' The DePhine spacecraft will be inserted into Mars transfer and will initially enter a Deimos quasi-satellite orbit to carry out a comprehensive global mapping. The goal is to obtain physical parameters and remote sensing data for Deimos comparable to data expected to be available for Phobos at the time of the DePhine mission for comparative studies. As a highlight of the mission, close flybys will be performed at low velocities, which will increase data integration times, enhance the signal strength and data resolution. 10–20 flyby sequences, including polar passes, will result in a dense global grid of observation tracks. The spacecraft orbit will then be changed into a Phobos resonance orbit to carry out multiple close flybys and to perform similar remote sensing as for Deimos. The spacecraft will carry a suite of remote sensing instruments, including a camera system, a radio science experiment, a high-frequency radar, a magnetometer, and a Gamma Ray/Neutron Detector. A steerable antenna will allow simultaneous radio tracking and remote sensing observations (which is technically not possible for Mars Express). Additional instrumentation, e.g. a dust detector and a solar wind sensor, will address further science goals of the mission. If Ariane 6–2 and higher lift performance are available for launch (the baseline mission assumes a launch on a Soyuz Fregat), we expect to have greater spacecraft mobility and possibly added payloads.
       
  • Shaking as means to detach adhered regolith for manned Phobos exploration
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Christine M. Hartzell, William Farrell, John Marshall Recent work has shown that cohesion drives the behavior of surficial regolith grains up to centimeters in size on the surface of small planetary bodies such as asteroids. Mars’ moon Phobos is similar in morphology and size to asteroids. Additionally, Phobos has been discussed as a possible target for human exploration, due to its relatively small gravity well. Dust adhering to spacesuits (and subsequently detaching in a pressurized spacecraft) was a source of concern during the Apollo era. We apply improved understanding of the forces active on regolith grains to compare their relative strength, showing that Phobian regolith up to millimeters in size is likely to be dominated by Van der Waals cohesion. Additionally, we show that astronauts will be unable to detach dust grains smaller than 1–100 μm that are adhered to their gloves through shaking alone, with the size range for detachment depending on the material properties of the regolith and spacesuit.
       
  • The possible contribution of dielectric breakdown to space weathering on
           Phobos
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): A.P. Jordan, T.J. Stubbs, J.K. Wilson, N.A. Schwadron, H.E. Spence The origins of Phobos and Deimos are uncertain; both are so space weathered that their surface compositions are difficult to determine using spectral reflectance measurements. We show how the winter temperatures and associated conditions in the polar regions of Phobos could make the regolith susceptible to space weathering from dielectric breakdown caused by solar energetic particles (SEPs). During SEP events, charged particles accumulate throughout the top ∼1 mm of the regolith, which has low conductivity, and create subsurface electric fields that act to dissipate any net buildup of charge. The faster the net charge accumulates, the larger the electric field needed to dissipate it. If the magnitude of the subsurface electric field exceeds ∼106 V m−1, then dielectric breakdown is likely. This process rapidly dissipates the buildup of charge by vaporizing electrically conducting channels through the regolith. Dielectric breakdown is expected to be more prevalent in colder regions, where the electrical conductivity of the regolith is lower and the dissipation of charge is consequently slower. If the regolith on Phobos is made of silicates, or possibly phyllosilicates, we predict that dielectric breakdown weathering has melted or vaporized 5–10% of the impact gardened regolith in the polar regions, although this percentage depends on how long the regolith has been exposed to SEPs. This, in addition to the long exposure time of the regolith to other forms of space weathering, may help explain why both Phobos and Deimos are highly space weathered compared to other airless bodies in the Solar System, such as Earth’s Moon.
       
  • Science exploration architecture for Phobos and Deimos: The role of Phobos
           and Deimos in the future exploration of Mars
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Ariel N. Deutsch, James W. Head, Kenneth R. Ramsley, Carle M. Pieters, Ross W.K. Potter, Ashley M. Palumbo, Michael S. Bramble, James P. Cassanelli, Erica R. Jawin, Lauren M. Jozwiak, Hannah H. Kaplan, Connor F. Lynch, Alyssa C. Pascuzzo, Le Qiao, David K. Weiss Phobos and Deimos are the only natural satellites of the terrestrial planets, other than our Moon. Despite decades of revolutionary Mars exploration and plans to send humans to the surface of Mars in the 2030’s, there are many strategic knowledge gaps regarding the moons of Mars, specifically regarding the origin and evolution of these bodies. Addressing those knowledge gaps is itself important, while it can also be seen that Phobos and Deimos are positioned to support martian surface operations as a staging point for future human exploration. Here, we present a science exploration architecture that seeks to address the role of Phobos and Deimos in the future exploration of Mars. Phobos and Deimos are potentially valuable destinations, providing a wealth of science return, as well as telecommunications capabilities, resource utilization, radiation protection, transportation and operations infrastructure, and may have an influence on the path of the martian exploration program. A human mission to the moons of Mars would maintain programmatic focus and public support, while serving as a catalyst for a successful human mission to the surface of Mars.
       
  • The exploration of PHOBOS: Design of a Sample Return mission
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Antonella Ferri, Stewart Pelle, Maurizio Belluco, Thomas Voirin, Rolando Gelmi The long-term goal of enabling human exploration of the Moon and Mars drives International space exploration plans. Robotic space missions must therefore develop and demonstrate the feasibility and robustness of the enabling technologies and capabilities.The Phobos Sample Return mission is a candidate mission of the Mars Robotic Exploration Preparation programme. Its objective is to acquire and return a sample from the Mars moon Phobos. The main science goal of this mission will be to understand the formation of the Martian moons Phobos and Deimos and acquire further data on the evolution of the solar system. From a technology standpoint, it would be a big step forward in the development of many technologies, ranging from low-gravity body landing capabilities to Earth re-entry of samples from deep space, from semi-autonomous robotic acquisition of surface samples to sample preservation and further analysis in dedicated ground laboratories.Thales Alenia Space represents one of two industrial contractors studying the mission to Phase A level. This phase involves investigation of all aspects of the mission and spacecraft design to ensure its feasibility and robustness. The planned launch date for the mission is between 2025 and 2027. The Ariane 5 ECA launch vehicle will be launched from Kourou. A chemical propulsion module will transfer the spacecraft composite to the Martian system, and will then be separated at Phobos. A full characterization campaign of Phobos at different altitudes from orbit will follow. This will include quasi-satellite orbits and flybys, using a payload suite of cameras and spectrometers. When the preferred landing site is identified, a controlled descent and touchdown onto the surface of Phobos will be performed, with a touchdown accuracy of 50 m. A robotic arm and sampling mechanism will obtain and verify a sample of surface regolith, and insert it into the Earth re-entry capsule. Part of the Spacecraft will return to the Earth from Phobos and deliver the re-entry capsule to the Earth’s atmosphere. The capsule will perform a fully passive Earth entry, descent and landing in Woomera, Australia. It will then be recovered and transferred to a sample curation facility for sample extraction and analysis. This paper summarises the results of the Thales Alenia Space Phobos Sample Return mission and spacecraft design, with a focus on the key elements and mass drivers.
       
  • Direct observations of asteroid interior and regolith structure: Science
           measurement requirements
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): A. Herique, B. Agnus, E. Asphaug, A. Barucci, P. Beck, J. Bellerose, J. Biele, L. Bonal, P. Bousquet, L. Bruzzone, C. Buck, I. Carnelli, A. Cheng, V. Ciarletti, M. Delbo, J. Du, X. Du, C. Eyraud, W. Fa, J. Gil Fernandez Our knowledge of the internal structure of asteroids is, so far, indirect – relying entirely on inferences from remote sensing observations of the surface, and theoretical modeling of formation and evolution. What are the bulk properties of the regolith and deep interior' And what are the physical processes that shape asteroid internal structures' Is the composition and size distribution observed on the surface representative of the bulk' These questions are crucial to understand small bodies’ history from accretion in the early Solar System to the present, and direct measurements are needed to answer these questions for the benefit of science as well as for planetary defense or exploration.Radar is one of the main instruments capable of sounding asteroids to characterize internal structure from sub-meter to global scale. In this paper, we review the science case for direct observation of the deep internal structure and regolith of a rocky asteroid of kilometer size or smaller. We establish the requirements and model dielectric properties of asteroids to outline a possible instrument suite, and highlight the capabilities of radar instrumentation to achieve these observations. We then review the expected science return including secondary objectives contributing to the determination of the gravitational field, the shape model, and the dynamical state. This work is largely inherited from MarcoPolo-R and AIDA/AIM studies.
       
  • Spacecraft design of a multiple asteroid orbiter with re-docking lander
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Alena Probst, Roger Förstner Almost two years after the landing of Rosetta’s Philae on the comet 67P/Churyumov-Gerasimenko, the triggered enthusiasm for small planetary bodies has not stagnated. Moreover, the interest has spread from mostly scientific enlargement of knowledge to a beginning curiosity about the exploitation of resources and their usage in space.Within this context, this paper is focusing on the design of the multiple asteroid orbiter Titius-Bode. Titius-Bode consist of an orbiter Titius and a lander Bode which aims for the characterization, resource determination and internal composition of a sequence of asteroids in the main belt. The mission objectives and spacecraft systems are described in detail, taking into account the constraints of the overall mission goal and concept. The mass and power budget for both lander and orbiter are listed as final result.The overall spacecraft design can be used for asteroid mining prospection as well as for purely scientific missions.
       
  • Numerical simulations of the contact between the lander MASCOT and a
           regolith-covered surface
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Clara Maurel, Patrick Michel, Jens Biele, Ronald-Louis Ballouz, Florian Thuillet In 2018, the mother spacecraft of the Hayabusa2 mission will release the lander MASCOT above the surface of the asteroid (162173) Ryugu. The lander will impact the regolith layer of the asteroid at low speed. While the descent trajectory of MASCOT is well determined before its release, its behavior once it touches the surface of Ryugu remains a great unknown. Predictions of the contact properties as a function of the assumed regolith properties and landing geometry (e.g., energy after bounce if not zero, collision duration…) are extremely valuable in terms of landing site selection and interpretation of the data acquired during and after landing. In this study, we use the N-body code pkdgrav to perform more than 480 numerical simulations of the first contact between the lander MASCOT and a granular medium representing the regolith layer. We explore the influence of several input parameters on the outcomes of the contact. These parameters are related to the lander, the grains of the regolith and the layer thickness. We identify a certain number of trends for the lander’s behavior, depending on the configuration of the contact, and perform a statistical analysis of the most critical output parameters. We also investigate the ejected material and show that, in addition to the data acquired from the lander itself, a post-impact visualization of the contact site(s) may help to infer non-observable properties of the regolith layer. Our results provide some insights on several input parameters that are implemented in the study of MASCOT’s whole trajectory. This work is a starting point of a much broader study, aiming to explore as widely as possible the parameter space associated with a low-speed impact of a lander onto a regolith layer.
       
  • Multiple near-earth asteroid rendezvous mission: Solar-sailing options
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Alessandro Peloni, Bernd Dachwald, Matteo Ceriotti The scientific interest in near-Earth asteroids (NEAs) and the classification of some of those as potentially hazardous for the Earth stimulated the interest in their exploration. Close-up observations of these objects will drastically increase our knowledge about the overall NEA population. For this reason, a multiple NEA rendezvous mission through solar sailing is investigated, taking advantage of the propellantless nature of this propulsion technology. Considering a spacecraft based on the DLR/ESA Gossamer technology, this work focuses on a method for searching possible sequences of NEA encounters. The effectiveness of the approach is demonstrated through a number of fully-optimised trajectories. The results show that it is possible to visit five NEAs within 10 years with near-term solar-sail technology. Moreover, a study on a reduced NEA database demonstrates the reliability of the approach used, showing that 58% of the sequences found with an approximated trajectory model can be converted into real feasible solar-sail trajectories. Overall, the study shows the effectiveness of the proposed automatic optimisation algorithm, which is able to find solutions for a large number of mission scenarios without any input required from the user.
       
  • Exploring small bodies: Nano- and microlander options derived from the
           Mobile Asteroid Surface Scout
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Caroline Lange, Tra-Mi Ho, Christian D. Grimm, Jan T. Grundmann, Christian Ziach, Roy Lichtenheldt The MASCOT lander currently flying on-board of the Japanese Hayabusa2 spacecraft, both set to explore the C-type Near-Earth Asteroid (162173) Ryugu, is not the first, but certainly one of the more complex nanolander systems having been designed for being carried along a bigger interplanetary spacecraft. Other concepts and current missions have shown the attractiveness of the class of nanosystems now increasing its application range from Earth orbiting cubesats to interplanetary scientific exploration endeavors, from orbiting to landing missions. This paper is intended to investigate nanolander options derived based on the MASCOT lander concept. For this purpose we gather interesting target bodies and analyze their respective environmental properties as well as their influence on the nanolander design, for example the landing system, the surface mobility, the power subsystem and the communication architecture. Further, an expansion of the scientific objectives of the current MASCOT lander from geological surface scout to other scientific objectives opens a range of new possibilities. For deeper analysis on this, we provide an overview over possible alternative payloads to the ones already flying on MASCOT and analyze their influence on the system design as it is. Obviously, the experience that has been gained with MASCOT provides us with a head start for future missions, if it is properly exploited. With this paper we intend to recommend MASCOT type of nanolanders for a range of possible future applications.
       
  • Robust finite time control of heliostationary flight over asteroids
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Fengdi Zhang, Jisheng Zhang, Yonglong Zhang, Zhanggang Lv Maintaining a heliostationary flight over an asteroid is challenging because of the complex dynamical environment. During exploration, external disturbances and uncertainties make it difficult for a spacecraft to stably hover at the libration point to complete its mission. In this paper, a globally robust finite time control law is proposed to solve this problem. First, we design a time variant sliding mode control law for the convergence of the tracking error to zero. Based on this, a nonsingular terminal sliding mode control law is designed to maintain the underlying track error at zero. The performance of the proposed control law is demonstrated through numerical simulations.
       
  • Low-thrust tour of the main belt asteroids
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Marilena Di Carlo, Massimiliano Vasile, Jamie Dunlop This work presents some initial results on a possible low-thrust tour of the main asteroid belt. The asteroids are visited through a series of fly-by’s to be completed within a given time-frame and limit on the mass of the spacecraft at launch. The asteroids to be visited are automatically selected out of a large database of possible candidates. The initial shortlist of targets is based on the Minimum Orbit Intersection Distance (MOID) between the orbit of the asteroids in the database and the initial orbit of the spacecraft traversing the main belt. The final sequence is then obtained with an efficient deterministic branch and prune algorithm. The transfers between asteroids are designed using a low-thrust analytical model that provides a good estimation of the propellant consumption and transfer time. The mission analysis is completed with a study of the cost of the launch. In this paper two databases will be analysed: one containing only targets with a particular scientific relevance and one containing all available asteroids.
       
  • CASTAway: An asteroid main belt tour and survey
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): N.E. Bowles, C. Snodgrass, A. Gibbings, J.P. Sanchez, J.A. Arnold, P. Eccleston, T. Andert, A. Probst, G. Naletto, A.C. Vandaele, J. de Leon, A. Nathues, I.R. Thomas, N. Thomas, L. Jorda, V. Da Deppo, H. Haack, S.F. Green, B. Carry, K.L. Donaldson Hanna CASTAway is a mission concept to explore our Solar System’s main asteroid belt. Asteroids and comets provide a window into the formation and evolution of our Solar System and the composition of these objects can be inferred from space-based remote sensing using spectroscopic techniques. Variations in composition across the asteroid populations provide a tracer for the dynamical evolution of the Solar System. The mission combines a long-range (point source) telescopic survey of over 10,000 objects, targeted close encounters with 10–20 asteroids and serendipitous searches to constrain the distribution of smaller (e.g. 10 m) size objects into a single concept. With a carefully targeted trajectory that loops through the asteroid belt, CASTAway would provide a comprehensive survey of the main belt at multiple scales. The scientific payload comprises a 50 cm diameter telescope that includes an integrated low-resolution (R = 30–100) spectrometer and visible context imager, a thermal (e.g. 6–16 µm) imager for use during the flybys, and modified star tracker cameras to detect small (∼10 m) asteroids. The CASTAway spacecraft and payload have high levels of technology readiness and are designed to fit within the programmatic and cost caps for a European Space Agency medium class mission, while delivering a significant increase in knowledge of our Solar System.
       
  • Imaging the interior of a comet from bistatic microwave measurements: Case
           of a scale comet model
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): C. Eyraud, A. Hérique, J.-M. Geffrin, W. Kofman Imaging the internal structure of comets and asteroids is an important way to provide information about their formation process. In this paper, we investigate the possibility to image the interior of such structures with electromagnetic waves in the microwave domain (radar system) using an inverse algorithm adapted to take advantage of a bistatic configuration, considering the polarization effects, and which presents low memory requirement. To this end, a scale model of a comet/asteroid was built and was used for an experimental simulation. The scattered fields of this scale model were measured in a perfectly controlled environment, in an anechoic chamber, to avoid measurement disturbances and to focus this study only on which structural information can be obtained with such measurements. To profit from the spatial diversity of information, a vectorial-induced current reconstruction algorithm was used. Two configurations were tested and analyzed including one with very few measurements. From the qualitative reconstructed maps, we have shown that it is possible to detect the presence of a core in both cases.
       
  • The Castalia mission to Main Belt Comet 133P/Elst-Pizarro
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): C. Snodgrass, G.H. Jones, H. Boehnhardt, A. Gibbings, M. Homeister, N. Andre, P. Beck, M.S. Bentley, I. Bertini, N. Bowles, M.T. Capria, C. Carr, M. Ceriotti, A.J. Coates, V. Della Corte, K.L. Donaldson Hanna, A. Fitzsimmons, P.J. Gutiérrez, O.R. Hainaut, A. Herique We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC’s activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA’s highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these.
       
  • The proposed Caroline ESA M3 mission to a Main Belt Comet
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Geraint H. Jones, Jessica Agarwal, Neil Bowles, Mark Burchell, Andrew J. Coates, Alan Fitzsimmons, Amara Graps, Henry H. Hsieh, Carey M. Lisse, Stephen C. Lowry, Adam Masters, Colin Snodgrass, Cecilia Tubiana We describe Caroline, a mission proposal submitted to the European Space Agency in 2010 in response to the Cosmic Visions M3 call for medium-sized missions. Caroline would have travelled to a Main Belt Comet (MBC), characterizing the object during a flyby, and capturing dust from its tenuous coma for return to Earth. MBCs are suspected to be transition objects straddling the traditional boundary between volatile–poor rocky asteroids and volatile–rich comets. The weak cometary activity exhibited by these objects indicates the presence of water ice, and may represent the primary type of object that delivered water to the early Earth. The Caroline mission would have employed aerogel as a medium for the capture of dust grains, as successfully used by the NASA Stardust mission to Comet 81P/Wild 2. We describe the proposed mission design, primary elements of the spacecraft, and provide an overview of the science instruments and their measurement goals. Caroline was ultimately not selected by the European Space Agency during the M3 call; we briefly reflect on the pros and cons of the mission as proposed, and how current and future mission MBC mission proposals such as Castalia could best be approached.
       
  • Formamide-based prebiotic chemistry in the Phlegrean Fields
    • Abstract: Publication date: 15 October 2018Source: Advances in Space Research, Volume 62, Issue 8Author(s): Lorenzo Botta, Raffaele Saladino, Bruno M. Bizzarri, Beatrice Cobucci-Ponzano, Roberta Iacono, Rosario Avino, Stefano Caliro, Antonio Carandente, Fabio Lorenzini, Alessandra Tortora, Ernesto Di Mauro, Marco Moracci Understanding the formation of biogenic molecules in abiotic conditions is a prerequisite in the origin-of-life studies. Determining the conditions allowing an efficient one-pot synthesis of the largest possible panel of biogenic compounds may shed light on the plausible scenario in which the processes that kick-started life might have occurred. We report a set of experiments describing the syntheses taking place from formamide (NH2CHO) and thermal water in the presence of meteorites, in the hydrothermal physical-chemical environment of the Phlegrean Fields. The results show that meteorites catalyse the synthesis of a large panel of organic compounds of biological relevance, including carboxylic acids, nucleobases, amino acids and sugars. The simplicity of the system (a one-carbon molecule as starting compound, a volcanic hydrothermal environment, meteorites as catalysts) hints to a possible extension of the results to similar environments present in other planetary bodies and space objects.
       
  • How do interplanetary shock impact angles control the size of the
           geoeffective magnetosphere'
    • Abstract: Publication date: Available online 22 September 2018Source: Advances in Space ResearchAuthor(s): J.T. Rudd, D.M. Oliveira, A. Bhaskar, A.J. Halford In this paper, we investigate temporal and spatial magnetosphere response to the impact of interplanetary (IP) shocks with different inclinations and speeds on the Earth’s magnetosphere. A data set with more than 500 IP shocks is used to identify positive sudden impulse (SI+) events as expressed by the SuperMAG partial ring current index. The SI+ rise time (RT), defined as the time interval between compression onset and maximum SI+ signature, is obtained for each event. We use RT and a model suggested by Takeuchi et al. (2002) to calculate the geoeffective magnetospheric distance (GMD) in the shock propagation direction as a function of shock impact angle and speed for each event. GMD is a generalization of the geoeffective magnetosphere length (GML) suggested by Takeuchi et al. (2002), defined from the subsolar point along the X line toward the tail. We estimate statistical GMD and GML values which are then reported for the first time. We also show that, similarly to well-known results for RT, the highest correlation coefficient for the GMD and impact angle is found for shocks with high speeds and small impact angles, and the faster and more frontal the shock, the smaller the GMD. This result indicates that the magnetospheric response depends heavily on shock impact angle. With these results, we argue that the prediction and forecasting of space weather events, such as those caused by coronal mass ejections, will not be accurately accomplished if the disturbances’ angles of impact are not considered as an important parameter within model and observation scheme capabilities.
       
  • A method for automatic detection of equatorial spread-F in ionograms
    • Abstract: Publication date: Available online 21 September 2018Source: Advances in Space ResearchAuthor(s): Carlo Scotto, Alessandro Ippolito, Dario Sabbagh A method is presented for automatic detection of spread-F. The method is based on an image recognition technique and is applied to ionograms recorded at the ionospheric station of Tucumán (-26.9°, 294.6°). The performance achieved is statistically evaluated and demonstrated with significant examples. The proposed method improves Autoscala's ability to reject ionograms with insufficient information, including those featuring Spread-F. Automatic identification of cases of spread-F is of additional interest in Space Weather applications, when it helps detect degraded radio propagation conditions.The present data analysis is a retrospective study but forms the basis for real-time application as an extension of Autoscala’s capabilities.
       
  • Object-based rice mapping using time-series and phenological data
    • Abstract: Publication date: Available online 21 September 2018Source: Advances in Space ResearchAuthor(s): Meng Zhang, Hui Lin Remote sensing techniques are often used in mapping rice, but high quality time-series remote sensing data are difficult to obtain due to the cloudy weather of rice growing areas and long satellite revisit interval. As such, rice mapping is usually based on mono-temporal Landsat TM/ETM+ data, which have large uncertainties due to the spectral similarity of different vegetation types. Moreover, conventional pixel-based classification method is unable to meet the required accuracy for rice mapping. Therefore, this study proposes a new strategy for mapping rice in cloud-prone areas using fused data of Landsat-8 OLI time-series and phenological parameters, based on the object-based method. We determine the critical growth stages of paddy rice from observed phenological data and MODIS-NDVI time-series data. The spatial and temporal adaptive reflectance fusion model (STARFM) is used to blend the MODIS and Landsat data to obtain a multi-temporal Landsat-like dataset for classification. Finally, an object-oriented algorithm is used to extract rice paddies from the Landsat-like, time-series dataset. The validation experiments show that the proposed method can provide high accuracy rice mapping, with an overall accuracy of 92.38% and a kappa coefficient of 0.85.
       
  • Comparison of Ionospheric Total Electron Content (TEC) over Sonmiani
           (Pakistan) with NeQuick-2 and IRI-2012 during July 2014 - June 2015
    • Abstract: Publication date: Available online 20 September 2018Source: Advances in Space ResearchAuthor(s): Muhammmad Ayyaz Ameen, Mehak Abdul Jabbar, Xiao YU, Weimin Zhen, Ghulam Murtaza, Farrukh Chishtie, Haqqa Khursheed, Muhammad Atiq In this study, Total Electron Content (TEC) observations acquired by a GNSS receiver installed at Sonmiani (Geog. Coord. 25.19°N, 66.74°E, Geomag. Coord. 17.62°N, 141.5°E) are being reported for the first time. The data utilized is hourly instantaneous TEC values during 10 International Quiet Days (IQDs) per month from Jul-14 to Jun-15, totaling 120 observation days for monitoring nominal TEC. The findings confirm the semi-annual trend of TEC over Sonmiani, which lies at the northern crest of Equatorial Ionization Anomaly (EIA) region. The TEC measurements are then compared with NeQuick-2 and International Reference Ionosphere (IRI-2012) models. It was found that the TEC values derived from NeQuick-2 are in better agreement with GNSS measurements than those from IRI-2012. The TEC measurements also show seasonal variation which is largest during Equinox months. The TEC value in Dec solstice is higher than the Jun solstice, which confirms that the seasonal anomaly is playing a major role in this region during the course of study.
       
  • Autonomous space target tracking through state estimation techniques via
           ground-based passive optical telescope
    • Abstract: Publication date: Available online 19 September 2018Source: Advances in Space ResearchAuthor(s): Peerapong Torteeka, Peng-qi Gao, Ming Shen, Xiao-zhong Guo, Da-tao Yang, Huan-huan Yu, Wei-ping Zhou, Liu Tong, You Zhao The presence of operational satellites or small-body space debris is a challenge for autonomous ground-based space object observation. Although most space objects exceeding 10 cm in diameter have been cataloged, the position of each space object (based on six orbital parameters) remains important and should be updated periodically, as the Earth’s orbital perturbations cause disturbances. Modern ground-based passive optical telescopes equipped with complementary metal-oxide semiconductors have become widely used in astrometry engineering, being combined with image processing techniques for target signal enhancement. However, the detection and tracking performance of this equipment when employed with image processing techniques primarily depends on the size and brightness of the space target, which appears on the monitor screen under variable background interference conditions. A small and dim target has a highly sensitive tracking error compared to a bright target. Moreover, most image processing techniques for target signal enhancement require large computational power and memory; therefore, automatic tracking of a space target is difficult. The present work investigates autonomous space target detection and tracking to achieve high-sensitivity detection and improved tracking ability for non-Gaussian and dynamic backgrounds with a simple system mechanism and computational efficiency. We develop an improved particle filter (PF) using the ensemble Kalman filter (KF) for track-before-detect (TBD) frameworks, by modifying and optimizing the computational formula for our non-linear measurement function. We call this extended version the “ensemble Kalman PF-TBD (EnKPF-TBD).” Three sequential astronomical image datasets taken by the Asia-Pacific Ground-Based Optical Space Objects Observation System (APOSOS) telescope under different conditions are used to evaluate three proposed TBD baseline frameworks. Given an optimal random sample size, the EnKPF-TBD exhibits superior performance to PF-TBD and threshold-based unscented KF with two-dimensional peak search (2dPS). The EnKPF-TBD scheme achieves satisfactory performance for all variable background interference conditions, especially for a small and dim space target, in terms of tracking accuracy and computational efficiency.
       
  • Application of an Evolution Strategy in Planetary Ephemeris Modeling
    • Abstract: Publication date: Available online 19 September 2018Source: Advances in Space ResearchAuthor(s): Enrico Mai, Jürgen Müller, Jürgen Oberst Classical planetary ephemeris construction comprises three major steps which are to be performed iteratively: numerical integration of coupled equations of motion of a multi-body system (propagator step), reduction of observations (reduction step), and optimization of model parameters (adjustment step). In future, this approach may become challenged by further refinements in force modeling (e.g. inclusion of much more significant minor bodies than in the past), an ever-growing number of planetary observations (e.g. the vast amount of spacecraft tracking data), and big data issues in general. In order to circumvent the need for both the inversion of normal equation matrices and the determination of partial derivatives, and to prepare the ephemeris for applications apart from stand-alone solar-system planetary orbit calculations, here we propose an alternative ephemeris construction method. The main idea is to solve it as an optimization problem by straightforward direct evaluation of the whole set of mathematical formulas, rather than to solve it as an inverse problem with all its tacit mathematical assumptions and potential numerical difficulties. The usual gradient search is replaced by a stochastic search, namely an evolution strategy, the latter of which is perfect for the exploitation of parallel computing capabilities. Furthermore, this new approach allows for multi-criteria optimization and time-varying optima. These issues will become important in future once ephemeris construction is just one part of even larger optimization problems, e.g. the combined and consistent determination of a generalized physical state (orbit, size, shape, rotation, gravity,…) of celestial bodies (planets, satellites, asteroids, or comets), and/or if one seeks near real-time solutions. Here, we outline the general idea and exemplarily optimize high-correlated asteroidal ring model parameters (total mass and heliocentric radius), and individual asteroid masses, based on simulated observations.
       
  • Error Constrainted Control of a Pseudo-Satellite with Disturbance
    • Abstract: Publication date: Available online 19 September 2018Source: Advances in Space ResearchAuthor(s): Kang Lin, Zewei Zheng, Zhe Wu, Qiang Wang This paper presents the control scheme of a pseudo-satellite in situations where error constraints, uncertainties, and external disturbances occur. The control scheme of a pseudo-satellite includes planar path following control scheme and altitude control scheme. In order to control the altitude of a pseudo-satellite, the backstepping technique is used to control the quality of air in the air balloon. To deal with the error constrained requirements of a pseudo-satellite’s position, a tan-type barrier Lyapunov function (TBLF) is proposed and incorporated with the guidance control schemes. Adaptive fuzzy disturbance observers are presented to estimate uncertainties and external disturbances. Rigorous stability analysis proves that the altitude error of the pseudo-satellite can be uniformly bounded, and the position error of which can be maintained within the range of constrained requirements, while all closed-loop signals are uniformly bounded regardless of uncertainties and disturbances.
       
  • Robust Three-Dimensional Path-Following Control for an Under-Actuated
           Stratospheric Airship
    • Abstract: Publication date: Available online 15 September 2018Source: Advances in Space ResearchAuthor(s): Lin Cheng, Zongyu Zuo, Jiawei Song, Xiao Liang This paper proposes a robust three-dimensional (3-D) path-following controller for an under-actuated stratospheric airship in the presence of uncertainties. The resultant control system exhibits an inner-outer loop control structure. In the outer control loop, the path-following error dynamics is constructed in a moving Serret-Frenet frame and a new guidance law with the sideslip and attack angle compensation is designed, which decreases the path-following steady-state error. In the inner control loop, a disturbance observer based backstepping control law is proposed to achieve the desired dynamic behavior on the path. Furthermore, a new velocity tracking control strategy is developed which aligns the resultant velocity tangent to the path. Finally, numerical simulation results are shown to verify the effectiveness of the proposed controller.
       
  • Contactless Electrostatic Detumbling of Axi-Symmetric GEO Objects with
           Nominal Pushing or Pulling
    • Abstract: Publication date: Available online 15 September 2018Source: Advances in Space ResearchAuthor(s): Trevor Bennett, Hanspeter Schaub Large asset values of satellites and demand for orbital slots in the Geostationary orbit belt motivates on-orbit servicing and active debris removal strategies. The challenge of on-orbit capture of tumbling serviceable satellites or debris targets is primarily overcome by including a target detumble prior to any mechanical interface. Of the many methods proposed, touchless electrostatic detumbling shows significant advantages in collision avoidance and preservation of the target object. Previous studies demonstrated that the electrostatic interaction is sufficient to touchlessly despin the fixed-axis rotation of a rocket body-sized object within several days. This work focuses on large, generally tumbling axi-symmetric targets in the Geostationary Orbit which form a large component of the GEO debris population. The deep-space controller is augmented for tugging, pushing, and nominal detumbling configurations, providing a complete analysis of the stability and convergence properties. The effectiveness of this detumble control is numerically illustrated by simultaneously detumbling and tugging the target in GEO. The controller reduces the tumbling to the order of the mean motion allowing for mechanical docking methods.
       
  • Optical/radio/pulsars integrated navigation for Mars orbiter
    • Abstract: Publication date: Available online 13 September 2018Source: Advances in Space ResearchAuthor(s): Long Gu, Xiuqiang Jiang, Shuang Li, Wendan Li In this paper, we address the issue of the integrated navigation algorithm with different combination of measurements for Mars orbiter. First, system dynamic model and navigation measurement models using optical measurement information, radio measurement information and X-ray pulsars measurement information are respectively established. Second, optical/radio/pulsars integrated navigation algorithm is proposed, and observability analysis of the integrated navigation system is also conducted. Third, adaptive extended Kalman filter is adopted to fuse measurement information and suppress measurement and process noise to optimally estimate the state of Mars orbiter. Monte Carlo simulation results show that optical/radio/pulsars integrated navigation can effectively improve the navigation accuracy and satisfy the navigation requirements of Mars orbiter.
       
  • Precision analysis of troposphere sensing using GPS single-frequency
           signals
    • Abstract: Publication date: Available online 13 September 2018Source: Advances in Space ResearchAuthor(s): K. Wang, A. Khodabandeh, P.J.G. Teunissen Various studies have been performed to investigate the accuracy of troposphere zenith wet delays (ZWDs) determined from GPS. Most of these studies use dual-frequency GPS data of large-scale networks with long baselines to determine the absolute ZWDs. For small-scale networks the estimability of the absolute ZWDs deteriorates due to high correlation between the solutions of the ZWDs and satellite-specific parameters as satellite clocks. However, as relative ZWDs (rZWDs) can always be estimated, irrespective of the size of the network, it is of interest to understand how the large-scale network rZWD-performance of dual-frequency GPS using an ionosphere-float model compares to the small-scale network rZWD-performance of single-frequency GPS using an ionosphere-weighted model. In this contribution such an analysis is performed using undifferenced and uncombined network parametrization modelling. In this context we demonstrate the ionosphere weighted constraints, which allows the determination of the rZWDs independent from signals on the second frequency. Based on an analysis of both simulated and real data, it is found that under quiet ionosphere conditions, the accuracy of the single-frequency determined rZWDs in the ionosphere-weighted network is comparable to that of the large-scale dual-frequency network without ionospheric constraints. Making use of the real data from two baselines of 15 days, it was found that the absolute differences of the rZWDs applying the two strategies are within 1 cm in over 90% and 95% of the time for ambiguity-float and -fixed cases, respectively.
       
  • Investigation of PMSE dependence on high energy particle precipitation
           during their simultaneous occurrence
    • Abstract: Publication date: Available online 13 September 2018Source: Advances in Space ResearchAuthor(s): Abdur Rauf, Hailong Li, Safi Ullah, Lin Meng, Bin Wang, Maoyan Wang This paper is based on the observations of Polar Mesosphere Summer Echoes (PMSE) with the EISCAT VHF 224 MHz radar during the summer month 08–12 July 2013. The effect of high energy particle precipitation on PMSE intensity, particularly during their simultaneous occurrence for longer time interval (longer than or equal to 3-hours) has been investigated. The correlation between the two phenomena has been computed using the Spearman rank and Pearson linear correlation coefficient. The variations in high energy particle precipitation reaching down to altitude of 91 km and PMSE intensity in the altitude range of 80–90 km are positively correlated. The electron density irregularity due to ionization caused by precipitating particles might be one of the possible reasons for this positive correlation. Moreover, some other background parameters i.e. K-indices (proxy of high energy particle precipitation) and electron fluxes during the simultaneous occurrence of the two phenomena also support one of the possible reasons given for explanation of the observed positive correlation. The X-rays and proton fluxes have no noticeable effect on PMSE echoes in this study.
       
  • Dynamical cartography of Earth satellite orbits
    • Abstract: Publication date: Available online 12 September 2018Source: Advances in Space ResearchAuthor(s): Aaron J. Rosengren, Despoina K. Skoulidou, Kleomenis Tsiganis, George Voyatzis We have carried out a numerical investigation of the coupled gravitational and non-gravitational perturbations acting on Earth satellite orbits in an extensive grid, covering the whole circumterrestrial space, using a suitably modified version of the SWIFT symplectic integrator, which is suitable for long-term (∼120 y) integrations of the non-averaged equations of motion. Hence, we characterize the long-term dynamics and the phase-space structure of the Earth-orbiter environment, starting from low altitudes (∼400 km) and going up to the GEO region and beyond. This investigation was done in the framework of the EC-funded “ReDSHIFT” project, with the purpose of enabling the definition of passive debris removal strategies, based on the use of physical mechanisms inherent in the complex dynamics of the problem (i.e., resonances). Accordingly, the complicated interactions among resonances, generated by different perturbing forces (i.e., lunisolar gravity, solar radiation pressure, tesseral harmonics in the geopotential) are accurately depicted in our results, where we can identify the regions of phase space where the motion is regular and long-term stable and regions for which eccentricity growth and even instability due to chaotic behavior can emerge. The results are presented in an “atlas” of dynamical stability maps for different orbital zones, with a particular focus on the (drag-free) range of semimajor axes, where the perturbing effects of the Earth’s oblateness and lunisolar gravity are of comparable order. In some regions, the overlapping of the predominant lunisolar secular and semi-secular resonances furnish a number of interesting disposal hatches at moderate to low eccentricity orbits. All computations were repeated for an increased area-to-mass ratio, simulating the case of a satellite equipped with an on-board, area-augmenting device. We find that this would generally promote the deorbiting process, particularly at the transition region between LEO and MEO. Although direct reentry from very low eccentricities is very unlikely in most cases of interest, we find that a modest “delta-v” (ΔV) budget would be enough for satellites to be steered into a relatively short-lived resonance and achieve reentry into the Earth’s atmosphere within reasonable timescales (∼50 y).
       
  • A Robust Homotopic Approach for Continuous Variable Low-Thrust Trajectory
           Optimization
    • Abstract: Publication date: Available online 8 September 2018Source: Advances in Space ResearchAuthor(s): Mohammadreza Saghamanesh, Hexi Baoyin This paper presents an improved understanding of the interaction of hybrid optimization method with variable low-thrust trajectory optimization requirements. To analyze fuel-optimal bang-bang control problem, a new version of homotopic algorithm, termed robust homotopic method, is investigated with the prospect of improving the efficiency and automation of the homotopic approach to achieve a high-level of robustness, and consequently enlarge its range of application. Such desired characteristics are promoted via a combination of several techniques. As an effective approach, a modified methodology of the switching detection process is presented for the bang-bang optimal-control problem. Moreover, the value of unknown costates and switching functions are mapped to new normalized intervals throughout the computational process. As a result, the optimal solution is rapidly designed to obtain the global robust-convergence to satisfy all constraints without any ambiguity. The fitting process of all iterations robustly find the unknown variables with the percent of converged solutions to maximum, and the penalty terms are quickly satisfied with predetermined high-accuracy, from the energy-optimal to the fuel-optimal solution, especially close to zero point as a critical point. Accordingly, two advanced interplanetary trajectories are optimized using two dynamic modeling approaches for the instantaneous and constant maximal thrust magnitude as a way to analyze and substantiate the robustness of the proposed algorithm. Results and performances are compared with existing solutions of the same mission problem.
       
  • Numerical integration of stochastic differential equations: a parallel
           cosmic ray modulation implementation on Africa’s fastest computer
    • Abstract: Publication date: Available online 8 September 2018Source: Advances in Space ResearchAuthor(s): K.D. Moloto, N.E. Engelbrecht, R.D. Strauss, D.M. Moeketsi, J.P. den Berg Three-dimensional studies of the transport and modulation of cosmic ray particles in turbulent astrospheres require large-scale simulations using specialized scientific codes. Essentially, a multi-dimensional Fokker-Planck type equation (a parabolic diffusion equation) must be integrated numerically. One such approach is to convert the relevant transport equation into a set of stochastic differential equations (SDEs), with the latter much easier to handle numerically. Due to the growing demand for high performance computing resources, research into the application of effective and suitable numerical algorithms to solve such equations is needed. We present a case study of the performance of a custom-written FORTRAN SDE numerical solver on the CHPC (Centre for High Performance Computing) Lengau cluster in South Africa for a realistic test problem with different set-ups. It is shown that SDE codes can scale very well on large parallel computing platforms. Finally, we consider an extremely computationally expensive application of the SDE approach to cosmic ray modulation, studying the behaviour of galactic cosmic ray proton latitude gradients and relative amplitudes in a physics-first manner. This is done using a modulation code that employs diffusion coefficients derived from first principles, which in turn are functions of turbulence quantities in reasonable agreement with spacecraft observations and modelled using a two-component turbulence transport model (TTM). We show that this approach leads to reduced latitude gradients qualitatively in line with spacecraft observations of the same, without making ad hoc assumptions as to anisotropic perpendicular diffusion coefficients as are often made in many cosmic ray modulation studies.
       
  • Trajectory Optimization of Multiple Asteroids Exploration with Asteroid
           2010TK7 as Main Target
    • Abstract: Publication date: Available online 7 September 2018Source: Advances in Space ResearchAuthor(s): Youtao Gao, Xi Lu, Yuming Peng, Bo Xu, Tanran Zhao In this study, the Earth’s Trojan asteroid 2010 TK7 is selected as the rendezvous target. The multiple flyby sequence of asteroid exploration was proposed by optimizing the probe’s orbit. Impulsive maneuvers and low-thrust propulsion were used respectively to design the trajectories of the multiple asteroids exploration mission. Under impulsive maneuvers, gravity assist technique was adopted to reduce fuel consumption. First a reference orbit with only 2010 TK7 as the rendezvous target was designed. Then five asteroids near the reference orbit were selected as candidates. Finally, we obtained a multiple asteroids exploration sequence of three asteroids based on gravity assist technique and genetic algorithm, and an additional velocity impulse of 0.4 km/s was required. In the subsequent section, a sixth-degree inverse polynomial shape-based method is applied to the low-thrust trajectory design of 2010 TK7, and the exploration sequence under the action of low-thrust propulsion was provided.
       
  • Reconnection and fast particle production in tokamak and solar plasmas
    • Abstract: Publication date: Available online 7 September 2018Source: Advances in Space ResearchAuthor(s): K.G. McClements Detailed in situ studies of magnetic reconnection and particle acceleration, which play a crucial role in the release and redistribution of energy in solar flares, can be performed in tokamak plasmas under conditions resembling those of the flaring solar corona. Recent measurements and modelling of fast particle production during reconnection events in the Mega-Amp Spherical Tokamak (MAST) are described. Specifically, observations in this device of electron acceleration during edge localised modes, and of both ion and electron acceleration during merging-compression plasma start-up, are presented, and possible implications of these studies for particle acceleration in flares are discussed. The results from MAST lend weight to the conjecture that large numbers of ions are accelerated to sub-MeV energies in flares.
       
  • Identification of Window Frequency at different Places of India
    • Abstract: Publication date: Available online 7 September 2018Source: Advances in Space ResearchAuthor(s): S. Mondal, M. Maiti, S. Sil, P.K. Karmakar Millimeterwave window frequencies between the two successive absorption maxima of 60 GHz and 120 GHz respectively, play a significant role in the context of radar and communication applications. Atmospheric parameters like temperature, water vapour and oxygen play major roles for determination of window frequencies which are latitude dependent. Radiosonde data were analyzed to identify a frequency at which minimum signal attenuation occurs in the millimeterwave band, between 60 GHz and 120 GHz, at various places in India. The data are taken from British Atmospheric Data Centre (BADC, U.K). Analysis shows that water vapour plays a dominant role for determining window frequency during the monsoon season. On the other hand, temperature dominates water vapour in shifting window frequency during the winter and summer seasons. The results obtained also show that minimum attenuation occurs at 73 GHz and maximum at 83 GHz over the chosen places in India during January to December depending on the latitudinal position. Another salient result obtained from our analyses is that water vapour is mainly responsible for lowering the window frequency from its conventionally accepted value, over certain places in India. Hence, these climatological parameters play a major role in determining window frequency over certain places of choice in India throughout the year.
       
  • Radiometric microwave field measurements of the complex dielectric
           constant of the water surface
    • Abstract: Publication date: Available online 6 September 2018Source: Advances in Space ResearchAuthor(s): V.V. Sterlyadkin The paper describes the new remote method of radiometric in situ measurements of the real and imaginary parts of the dielectric constant (permittivity) of the underlying sea surface, which is an important parameter for remote sensing of the Earth. The method does not require absolute calibration of a radiometer, but uses the black body with the underlying surface temperature, which simplifies the measurement and allows one to measure the effective reflection coefficientat specified polarizations. It is shown that, for a fixed value of the reflection coefficient in sensing to the nadir, R(θ = 0°) = const, the reflection coefficient at the horizontal polarization is almost independent of the of dielectric loss angle. The reflection coefficient at the vertical polarization is most sensitive to the loss angle in the vicinity of the Brewster angle Rv(θ = θBr). The paper presents the results of measurements of the sea surface reflection coefficient using the radiometer operating at frequency of 37.5 GHz. The reflection coefficients at vertical and horizontal polarizations are calculated taking into account the antenna pattern and the distribution of slopes of a weakly roughened sea surface. The paper presents the example of determining the real and imaginary parts of the permittivity based on experimentally measured values of reflection coefficients at incidence angles close to the nadir and the reflection coefficient Rv(θ = θBr) at the Brewster angle. The obtained experimental values correspond to the theory within the limits of diversity of existing models.
       
  • A fast algorithm for the detection of faint orbital debris tracks in
           optical images
    • Abstract: Publication date: Available online 3 September 2018Source: Advances in Space ResearchAuthor(s): P. Hickson Moving objects leave extended tracks in optical images acquired with a telescope that is tracking stars or other targets. By searching images for these tracks, one can obtain statistics on populations of space debris in Earth orbit. The algorithm described here combines matched filtering with a Fourier implementation of the discrete Radon transform and can detect long linear tracks with high sensitivity and speed. Monte-Carlo simulations show that such tracks, in a background of Poisson random noise, can be reliably detected even if they are invisible to the eye. On a 2.2 GHz computer the algorithm can process a 4096×4096-pixel image in less than a minute.
       
  • Multi-objective Optimization of Agile Satellite Orbit Design
    • Abstract: Publication date: Available online 3 September 2018Source: Advances in Space ResearchAuthor(s): Zhiming Song, Xiaoyu Chen, Xin Luo, Maocai Wang, Guangming Dai Satellite orbit design is a fundamental and important task during the mission analysis and the agile satellite design. In this paper we first investigate the design of a more realistic repeating ground track orbit in an accurate geopotential model of Earth. Furthermore, by considering the view field of the resource equipped on an agile satellite, we calculate the variation of the orbital altitude, the tilt angle, and the off-nadir resolution with the desired revisit time. Additionally, we analyze the distribution of all feasible solutions. In considering the spatial resolution and temporal resolution simultaneously, we propose a multi-objective optimization technique for optimal feasible orbits generation. Finally, through various case studies, the application of multi-objective optimization in orbit design of agile satellite is successfully demonstrated. Results also illustrate the validity and effectiveness of the proposed technique.
       
  • Using Only Two Magnetorquers to De-Tumble a 2U CubeSAT
    • Abstract: Publication date: Available online 3 September 2018Source: Advances in Space ResearchAuthor(s): Matthew Monkell, Carlos Montalvo, Edmund Spencer A CubeSAT is a small satellite on the order of 10 centimeters along each axis. A 1U satellite is a small cube with 10 cm sides. A 2U CubeSAT has the volume of two single 1U satellites. The size of the satellite is 10x10x20 cm. These satellites are used for a variety of missions and created by a variety of different organizations. When deployed from a rocket, a CubeSAT may obtain a large angular velocity which must be reduced before most science missions or communications can take place. Maximizing solar energy charging also involves better pointing accuracy. To control the attitude of these small satellites, thrusters, reaction wheels or magnetorquers are used. On a standard CubeSAT, 3 reaction wheels are used as well as 3 magnetorquers. In the initial phase of the CubeSAT mission, the magnetorquers are used to reduce the angular velocity of the satellite down to a manageable level. Once the norm of the angular velocity is low enough, the reaction wheels can spin up reducing the angular velocity to zero. This paper derives a simple control scheme that allows the performance of the de-tumbling maneuever to decline while reducing the number magnetorquers by 1. Thus, the de-tumbling maneuver is completed using 2 magnetorquers rather than 3. This reduces complexity of the satellite, saves weight and reduces energy consumed by the satellite which can be used for other power hungry devices.
       
  • A Combination Method using Evolutionary Algorithms in Initial Orbit
           Determination for Too Short Arc
    • Abstract: Publication date: Available online 1 September 2018Source: Advances in Space ResearchAuthor(s): Xin-Ran Li, Xin Wang, Yong-qing Xiong With the combination of two evolutionary algorithms EDA and DE, a new method of initial orbit determination for satellites based on ground-based too-short-arc is established. Compared with other algorithms, the proposed method focuses on the most densely populated region in the solution space rather than the individual with best fitness value. Both the global information and local information are well fused in the search of optimum. In the method (a,e,M) are treated as variables of the optimization, and the optimization procedure is carried out as a two-stage hierarchical optimization problem which has three variables for each stage. Kernel density estimation is applied to build the probability distribution model without any assumptions of the specified distribution, accompanied by handling semi-major axis and eccentricity as a pair of dependent variables in the construction of the probability for the correlation between them in the practice. Numerical experiments with real ground-based observations show that the proposed method is applicable to too-short-arc with even 3 seconds, and the result of bias in several kilometers can be achieved with 5″ error added to angular measurements.
       
  • Improving Galileo orbit determination using zero-difference ambiguity
           fixing in a Multi-GNSS processing
    • Abstract: Publication date: Available online 1 September 2018Source: Advances in Space ResearchAuthor(s): Georgia Katsigianni, Sylvain Loyer, Felix Perosanz, Flavien Mercier, Radosław Zajdel, Krzysztof Sośnica Ambiguity fixing to integer numbers of the phase measurements has been proven to ameliorate the accuracy of GNSS data processing. Until now there are two strategies to achieve ambiguity resolution; by forming double differences and by using undifferenced phase measurements. In this article, the potentiality of using the latter method for fixing the phase ambiguities for the Galileo system combined with GPS measurements in a Multi-GNSS solution is proved. The integer property of the Galileo phase clocks is demonstrated. GPS and Galileo phase fixed orbit and “integer” clock products are compared to the float solutions. Both orbit overlaps and orbit validation using satellite laser ranging (SLR) validation methods showed that there is an improvement mainly in the normal and the along track direction.
       
  • Achievable orbit determination and prediction accuracy using short-arc
           space-based observations of space debris
    • Abstract: Publication date: Available online 1 September 2018Source: Advances in Space ResearchAuthor(s): Bin Li, Jizhang Sang, Junyu Chen The space-based space surveillance (SBSS) technique is promising in the current and future space surveillance with advantages of global coverage, high covering rate, and strong exploring capacity. This paper focuses on the key problems of this new technique, the accurate orbit determination (OD) and prediction (OP) using short-arc tracking data. 200 debris objects are simulated to be tracked by the satellite in a sun-synchronous orbit. The real-time OD using short-arc space-based optical data of debris from only one pass is performed, and an OP accuracy of 10″ for angles and 100m for distances over 150s OP arc is achieved, which is accurate for the pointing guidance of blind space-based lasers operation. The OD/OP performances using multiple passes of short-arc space-based optical data are also assessed. Using at least 2 passes of 120s short-arc space-based optical data, separated by about 24 hours, the determined position accuracy is better than 50m, and the subsequent 7-day position prediction errors are less than 300m, which is believed sufficient enough for space applications requiring high accuracy, like the orbit catalogue maintenance, space conjunction analysis for hundreds of thousands of debris.
       
  • A method for the repair of cycle slip using double-differenced velocity
           estimation for GNSS RTK positioning
    • Abstract: Publication date: Available online 30 August 2018Source: Advances in Space ResearchAuthor(s): Dezhong Chen, Shirong Ye, Caijun xu, Weiping Jiang, Shuwen Li, Pengfei Xia, Peng Jiang Due to the disturbances along the signal path, it’s inevitable that the loss of lock or data interruption interval of a few satellites reach to decades of seconds or even minutes. It will be difficult to recover data and evaluate cycle slips after a long gap in real time kinematic (RTK) positioning. A double-differenced (DD) velocity estimation method is proposed for the repair of cycle slip in RTK positioning, assuming available of fixed coordinate solutions for the previous epoch. We achieve the precise coordinate solution of the current epoch by using triple-differenced (TD) combinations. The dual-frequency observed minus computed (OMC) combinations are then calculated by using the observations and coordinate solutions. The differenced OMC values between two epochs are used to repair cycle slips. Two kinematic experiments carried out to evaluate the performance of the proposed method are for velocities less than 2 m s-1 for a boat and about 10 m s-1 for a vehicle. The averaged distance of boat and vehicle relative to the reference are about 11 km and 24.5 km, respectively. The experimental results of the boat case indicate that all cycle slips are corrected within 0.25 cycles even though sampling interval reaches to 120 s. The cycle slips fixing uncertainty is close to 0.3 cycles for a sampling interval of 30 s and 60 s vehicle experiments. As the sampling interval increases to 90 s and 120 s, the uncertainty rises to 0.35 cycles for the vehicle-dynamic vehicle experiment.
       
  • Characteristics of GOCE orbits based on Satellite Laser Ranging
    • Abstract: Publication date: Available online 30 August 2018Source: Advances in Space ResearchAuthor(s): Dariusz Strugarek, Krzysztof Sośnica, Adrian Jäggi The Gravity field and steady-state Ocean Circulation Explorer (GOCE) was the first European Space Agency’s (ESA) Earth Explorer core mission. Through its extremely low, about 260 km above the Earth, circular, sun-synchronous orbit, the satellite gained high spatial resolution and accuracy gravity gradient, and ocean circulation data. Global Positioning System (GPS) receivers, mounted on the spacecraft, allowed the determination of reduced-dynamic and kinematic GOCE orbits, whereas Laser Retroreflector Array (LRA) dedicated to Satellite Laser Ranging (SLR) allowed an independent validation of GPS-derived orbits. In this paper, residuals between different GPS-based orbit types and SLR observations are used to investigate the sensitivity and the influence of solar, geomagnetic, and ionospheric activities on the quality of kinematic and reduced-dynamic GOCE orbits. We also analyze the quality of data provided by individual SLR sites, by detecting time biases using ascending and descending sun-synchronous GOCE orbit passes, and the residual analysis of the measurement characteristics, i.e., the dependency of SLR residuals as a function of nadir and horizontal angles. Results show a substantial vulnerability of kinematic orbit solutions to the solar F10.7 index and the ionospheric activity measured by the variations of the Total Electron Content (TEC) values. The sensitivity of kinematic orbits to the three-hour-range KP index is rather minor. The reduced-dynamic orbits are almost insensitive to indices describing ionospheric, solar, and geomagnetic activities. The investigation of individual SLR sites shows that some of them are affected by time bias errors, whereas other demonstrate systematics, such as a dependency between observation residuals and the satellite nadir angle or the horizontal azimuth angle from the SLR station to the direction of the satellite.
       
  • Some Remarks on Geometric Dilution of Precision (GDOP) at user level in
           Multi-GNSS Positioning
    • Abstract: Publication date: Available online 27 August 2018Source: Advances in Space ResearchAuthor(s): Changhai Li, Yunlong Teng, Ronglei Kang The geometric dilution of precision (GDOP) is an important index with positioning, navigation and timing (PNT) applications. In multi-GNSS positioning, the system time offsets between different systems can be determined at user level, namely, calculated by the receiver at the cost of at least one additional satellite from each additional time reference frame. In this paper, we focus on some characteristics of the GDOP at user level (short for GDOPU) in multi-GNSS positioning, including the impact of the number of satellites on the GDOPU, and the calculation of the GDOPU minimum. The theoretical derivations show that the GDOPU decreases with respect to the number of satellites. Moreover, the detailed expression of GDOPU minimum together with the optimal condition leading to the minimum is also given. The experimental results using real data validate these discussions.
       
  • List of Referees
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s):
       
  • Atmospheric test environments for planetary in-situ missions: Never quite
           “Test as you fly”
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Ralph D. Lorenz The planetary atmospheric and surface environments that planetary probes, landers and rovers may encounter cannot be perfectly replicated in tests on Earth. The temperature, pressure and composition of atmospheric test environments for previous missions are reviewed, and the differences between the conditions used in tests and the actual conditions at the target body are discussed. Generally, it has been the practice to replicate only those few key parameters that determine the phenomena of interest, and the effects of gravity and of minor atmospheric constituents are rarely simulated explicitly. Typically tests have been performed in nitrogen atmospheres (rather than carbon dioxide for Mars and Venus) or Helium (instead of hydrogen for Jupiter): exceptions are a handful of specific tests where the composition was considered critical. In-flight thermal anomalies are generally attributable to differences between the static conditions in a test chamber and the dynamic environment of flight, rather than to the composition of test atmospheres.
       
  • Rain fade duration prediction models for A high elevation angle based on
           measured data in tropical climate
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Hassan Dao, Megat Farez Azril Zuhairi, MD Rafiqul Islam Rain fade duration is one of the essential components for engineers to design and plan satellite communication systems at high frequency bands. In this paper, rain fade duration was obtained for twelve consecutive months at Ku-band with 77.4° elevation angle from MEASAT3 in Kuala Lumpur, Malaysia. Empirically, the fade duration was found discrepant to the results predicted by models. Therefore, a modification of fade duration model is proposed based on measured data for this tropical climate and high elevation angle.
       
  • Grid fins shape design of a launch vehicle based on sequential
           approximation optimization
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Ke Peng, Fan Hu, Donghui Wang, Patrick N. Okolo, Min Xiang, Gareth J. Bennett, Weihua Zhang This paper performed the optimization of grid fins shape of a launch vehicle based on Sequential Approximation Optimization (SAO) and Computational Fluid Dynamics (CFD) simulation coupling. An efficient and reliable method is proposed for determining the width of Gaussian functions based on a logical relationship between the width and local density. The performance of the proposed method is evaluated using five classical test functions. The proposed method for width determination generates almost no excessive calculation costs, and improves the accuracy, reliability, and stability of the Radial Basis Function (RBF) surrogate model notably. Based on the improved RBF surrogate model, a framework and detailed procedure for the SAO algorithm is presented, and the performance of the proposed SAO algorithm is tested, with obtained results showing that the proposed SAO algorithm reduces the calling times of the original model and improves the optimization efficiency remarkably. The objective function is strictly deduced and reflects the momentum loss caused by aerodynamic drag directly. Three constraints are imposed to ensure the static stability and controllability of the launch vehicle. Finally, grid fins shape optimization problem of the launch vehicle is solved, with the objective function and constraints calculation tasks accomplished automatically by batch mode CFD simulations. The global optimal solution is obtained after 54 calling times of the original model, and 92 h (3.84 days) of computation on a 96-core cluster. Once the baseline shape is replaced with the optimized shape, it is detected that (1) taking the minimum fuel as an objective function, the take-off mass is 2.07% lighter than the take-off mass of the baseline shape, (2) taking the maximum payload mass as an objective function, the payload mass is 14.3% heavier than the payload mass of the baseline shape.
       
  • Space tether deployment with explicit maximum libration angle constraint
           and tension disturbance
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Ming Liu, Zheng H. Zhu, Xingqun Zhan This paper investigates the deployment control problem of tethered space systems subject to an explicit constraint of maximum libration angle and disturbance of tether tension. A two-stage control procedure is developed to design a simple and effective tension control law that is capable of limiting the magnitude of libration angle and suppressing the tension disturbance in the tether deployment process. First, the deployment reference trajectory is designed by a modified barrier Lyapunov function with an explicit constraint on the maximum libration angle. Then, a disturbance observer-based tension control law is developed to track the reference trajectory with the consideration of tension disturbance. Stability analysis of the controller shows that the estimate and tracking errors are bounded to desired ranges. Simulation results demonstrate the proposed simple tension control law is effective and robust in restricting the maximum amplitude of libration angle and suppressing tension disturbance, while guaranteeing a stable deployment without tether slack.
       
  • A transfer network linking Earth, Moon, and the triangular libration point
           regions in the Earth-Moon system
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Lucia R. Capdevila, Kathleen C. Howell In the near future, several space applications in the Earth-Moon system may require a spacecraft to hold a stable motion, but the transfer trajectory infrastructure to access such stable motions has not been fully investigated yet. The triangular libration points, L4 and L5, in the Earth-Moon system have long been thought of as potential locations for a communications satellite. Recently, Distant Retrograde Orbits (DROs) and Near-Rectilinear Halo Orbits (NRHOs) in the vicinity of the Moon have been identified as orbits of interest for manned and unmanned missions with a focus on operations in cislunar space. The triangular libration points, as well as lunar DROs and NRHOs describe special types of possible motion for a spacecraft/satellite that is influenced solely by the gravitational fields of the Earth and the Moon. What is common to the three types of solutions is that they are practically stable, that is, a spacecraft/satellite can naturally follow the solution for extended periods of time without requiring significant course adjustment maneuvers. This investigation proposes the lunar region as the central link to a transfer network that enables travel throughout the Earth-Moon system, connecting the lunar region to the vicinity of the Earth and the neighborhood of the triangular libration points. The work presented here also contributes to the infrastructure supporting such a network by expanding the transfer options available between these regions. Several new transfer options between regions of stability are presented and discussed, including transfer options between Low Earth Orbit (LEO) and lunar DRO, lunar DRO and periodic orbits near L4 and L5, as well as lunar DRO and L2 NRHOs. Underlying dynamical mechanisms enabling transfers between selected orbits are analyzed, and sample itineraries are provided.
       
  • Fractional order PDD control of spacecraft rendezvous
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Niloofar Sarafnia, Maryam Malekzadeh, Javad Askari In this study, a rendezvous mission between two spacecraft is programmed. The system is modelled as a 6-DOF formation flying. It is expected that this system be robust against various uncertainties and disturbances while minimizing the energy consumption, considering thrusters and control torques limitations. For this purpose, three robust fractional-order PDD (FOPDD) controllers are designed. The first one is designed based on robust constraint on transfer function. In the second method, the controller gains are tuned by using Particle Swarm Optimization (PSO) algorithm. The third designed controller is implemented according to Model Reference Adaptive Controller with Fractional Order Adjustment Rules (FOAR-MRAC) which is a combination of FOPDD controller tuned by PSO algorithm and an adaptive time variable gain. The performance of these controllers are compared in—various uncertain conditions (disturbances, mass and inertia uncertainty and sensor noises) considering actuators limitations.
       
  • Physics and human-based information fusion for improved resident space
           object tracking
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Emmanuel Delande, Jérémie Houssineau, Moriba Jah Maintaining a catalog of Resident Space Objects (RSOs) can be cast in a typical Bayesian multi-object estimation problem, where the various sources of uncertainty in the problem – the orbital mechanics, the kinematic states of the identified objects, the data sources, etc. – are modeled as random variables with associated probability distributions. In the context of Space Situational Awareness, however, the information available to a space analyst on many uncertain components is scarce, preventing their appropriate modeling with a random variable and thus their exploitation in a RSO tracking algorithm. A typical example are human-based data sources such as Two-Line Elements (TLEs), which are publicly available but lack any statistical description of their accuracy. In this paper, we propose the first exploitation of uncertain variables in a RSO tracking problem, allowing for a representation of the uncertain components reflecting the information available to the space analyst, however scarce, and nothing more. In particular, we show that a human-based data source and a physics-based data source can be embedded in a unified and rigorous Bayesian estimator in order to track a RSO. We illustrate this concept on a scenario where real TLEs queried from the U.S. Strategic Command are fused with realistically simulated radar observations in order to track a Low-Earth Orbit satellite.
       
  • Vertical coupling between the mesopause region and sporadic-E layer during
           equatorial counter electrojet events – A case study
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): A. Ajesh, T.K. Pant, C. Vineeth, N. Mridula, K.K. Kumar This paper presents a case study exploring the variability of daytime ionospheric sporadic E (Es) during Counter Equatorial Electrojet (CEJ) events over Trivandrum (8.5°N, 77°E, 0.5°N dip lat.), a dip equatorial station in India. It makes use of collocated measurements of (a) daytime mesopause temperature estimated using a Multiwavelength Dayglow Photometer, (b) base height of sporadic E-layer i.e. Esq obtained from a Digital Ionosonde, (c) Equatorial Electrojet (EEJ) induced magnetic field at the surface measured using a Proton Precession Magnetometer and (d) neutral meridional and zonal winds measured using meteor wind radar. The study addresses why, only on certain CEJ days, the Es layer turns into a blanketing Es layer, also referred to as Esb layer, appearing for a brief period and almost simultaneously as the CEJ induced magnetic field on the surface is either zero or very small, and not on all the CEJ days despite the reversal of the zonal winds in the dynamo region (∼98 km). Further, a simulation using the simultaneously measured zonal wind and temperature shows that during CEJ, especially when the zonal wind reverses and the mesopause temperature lowers, the conditions are in fact less favourable for the ionization to converge resulting in Esb. On the other hand, on such occasions, the meridional wind exhibits a tendency to turn equatorward with time with the changeover gradually happening as the altitude decreases. These observations have been discussed to allude to the possible role of the overall wind system and its spatio-temporal changes in the ionospheric altitudes which could influence the gradual transition of Esq to Esb over the dip equator.
       
  • Horizontal spatial correlation of the ionospheric TEC derived from GPS
           global ionospheric maps
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Shuo Liu, Jinsong Yang, Tao Yu, Zhiqiang Zhang The spatial correlations of ionospheric day-to-day variability are investigated by statistical analysis on TEC production that provided by the Jet Propulsion Laboratory (JPL). First, we use the monthly-averaged TEC over the world to calculate the deviation of the TEC and then the spatial correlation coefficient matrix of the deviation is also derived. According to the definition of correlation distance in statistics, the spatial characteristic scale is retrieved in the Zonal and meridian directions, and their variation of solar activity levels, geomagnetic field configuration conditions and seasonal conditions are investigated in details. Our study indicates strong correlations between geomagnetic conjugate points, which are large at low-latitudes than at mid-latitudes. Furthermore, in the equatorial anomaly region, due to the process of forming double crest structure, the electron distribution at low-latitudes will be affected by the upwelling of the plasma, thus the anomaly of correlation scale is notable. The correlation scale, which usually increases in LT 6:00, peaks at LT 12:00 and LT 14:00 and then decreases. It is overall larger in the daytime and smaller in the nighttime. These spatial correlations are important for understanding the physical mechanisms that cause ionospheric weather variability. For the potential application in development of ionospheric data assimilation model, the spatial correlations are fitted by elliptic Gaussian formula scale. In general, the correlation scale is regressed better in the Zonal direction than in the Meridional direction, better in low-latitude than in middle-latitude, and better in spring and autumn than in winter and summer. These results can help us to accurately construct the background field error covariance matrix in ionospheric data assimilation.
       
  • The relationship between equatorial ionization anomaly and nighttime
           equatorial spread F in East Africa
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Ephrem Beshir Seba, Melessew Nigussie, Mark B. Moldwin We study the relationship of equatorial ionization anomaly (EIA) to the occurrence of nighttime equatorial spread F (ESF) using data from ground-based GPS stations and a horizontal meridional neutral wind model for the East African sector. Anomaly strength, symmetry of anomaly crests, horizontal meridional wind magnitude and direction, and magnitude of rate of TEC index (ROTI) are computed and analyzed. We find mean crest to trough ratio (CTR) greater than or equal to 1.4 and mean north crest to south crest ratio (CCR) within 0.9 and 1.1 in the time between 16:00 UT (19:00 LT) and 18:00 UT (21:00 LT) as good conditions for the occurrence of ESF. EIA strength and symmetry of anomaly crests are better related with ESF occurrence between conjugate stations (≈ ± 11.5o magnetic latitudes) than between other north-south stations. ROTI is found to be relatively large when CCR of EIA are symmetrical (CCR between 0.9 and 1.1) and CTR is greater than or equal to 1.4, but decreases as the CCR of EIA shows asymmetry and/or CTR of EIA is less than 1.4. EIA strength and symmetry of anomaly crests between 18:00 UT to 20:45 UT are not well related with spread F occurrences. Post-sunset spread F occurrence close to anomaly crest locations are found to be greater than spread F occurrence at magnetic equatorial station. Shifting of EIA crest locations on either side of the magnetic equator is found to depend on season and meridional wind magnitude and direction. The relative difference in spread F occurrence among the four seasons is also discussed.
       
  • On the growth rate instability of nonextensively opposite polarity dusty
           plasmas
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): S.K. Zaghbeer, E.K. El-Shewy, A.M. El-Hanbaly, H.H. Salah, N.H. Sheta, A. Elgarayh Nonlinear obliquely and wave instability features in a magnetized collisionless dusty plasma containing negative- positive dusty grains are theoretically explored. The equation of Zakharov Kuznetsov is derived by reductive perturbation calculations and three dimensional wave instability is examined using small k expansion procedure. The system parameters namely, cyclotron frequency, the polarity grain charges ratio, nonextensive effects on DA wave properties and instability growth rate are discussed. Present dissection can be important in phenomena of nonlinear perception in astrophysical plasma of space.
       
  • Construction of a BDSPHERE solar radiation pressure model for BeiDou GEOs
           at vernal and autumn equinox periods
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Xiaojie Li, Rui Guo, Xiaogong Hu, Chengpan Tang, Shan Wu, Zhiqiao Chang, Shuai Liu Geostationary Earth Orbit (GEO) satellites are important components of the BeiDou System (BDS). Long-term orbit ephemeris accuracy monitoring in the Operational Control System (OCS) of BDS indicates that the orbit accuracy for the BDS GEOs is unstable and degraded by several meters during the vernal and autumn equinox periods of each year. The SPHERE solar radiation pressure (SRP) model does not do a good job of reflecting the characteristics of the SRP during equinox periods. In view of this problem, this study proposes to replace SPHERE with BDSPHERE for the BDS GEOs during both equinox and non-equinox periods. We smooth the orbits of the BDS GEOs provided in SP3 precise orbit file format of Wuhan University (WHU, Wuhan, China) in the Multi-GNSS Pilot Project (MGEX), re-estimate the SRP parameter over a 2-year period and construct a 2-year continuous time series of the SRP model parameter. By analyzing the time series, a BDSPHERE model is constructed. The polynomial coefficients during the equinox periods are determined based on historical data and new data. Experiments with Beidou data show that during the equinox periods the orbit-only contribution to the signal-in-space range error (SISRE(ORB)) using the BDSPHERE model for GEOs in orbit determination arc and the 8-h and 24-h orbit predictions arc are 0.77, 0.80 and 1.62 m, respectively, which are smaller than those of the conventional SPHERE model by 53%, 60% and 61%, respectively. An evaluation based on global satellite laser ranging (SLR) data shows that during the equinox periods the BDSPHERE model can provide a radial orbit accuracy of 0.61 m, which is 70% better than that of the SPHERE model, and reach the SPHERE model's orbit accuracy in non-eclipsing periods. The BDSPHERE model during equinox periods considerably improves the orbit accuracy and stability of the BDS GEOs. This paper can provide technical support for constructing SRP models for the BDS.
       
  • Lithological discrimination using ASTER and Sentinel-2A in the Shibanjing
           ophiolite complex of Beishan orogenic in Inner Mongolia, China
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Wenyan Ge, Qiuming Cheng, Linhai Jing, Costas Armenakis, Haifeng Ding The Shibanjing ophiolite complex, located in the Mingshui-Shibanjing-Xiaohuangshan ophiolite belt of Beishan collage, is one of the most important components in the Beishan orogenic belt, Inner Mongolia, China. It comprises tectonic slices of ophiolite rocks including mylonitic gabbros, meta-ultramafic rocks, metabasalts, and clastic rock in a matrix of turbidites, and the mélange contains blocks of schists, gneiss, and marble. In this study, multispectral data Sentinel-2A and ASTER were employed to discriminate lithological units in the unvegetated arid region. Several image enhancement algorithms, including Band Ratio (BR), Principal Components Analysis (PCA), Minimum Noise Fraction (MNF), and Support Vector Machine (SVM), were applied to the data for lithological mapping. A specialized band ratio, (Sentinel-2A band 3+ASTER band 9)/(Sentinel-2A band 12+ASTER band 8), combining ASTER and Sentinel-2A data was designed to distinguish serpentine minerals in the ophiolite complex. Color composites of principal components (PCs) of ASTER and Sentinel-2A data were utilized to differentiate rock units within the ophiolite complex. It was found that the color composites of PCs of Sentinel-2A have higher color contrast and saturation than ASTER, enabling to better visually interpret the ophiolite rock units and provide a more detailed geological map of the study area. The SVM classification results of the original and MNF versions of the ASTER data indicate that the image processing methods such as MNF could highlight specific rock units and improve classification accuracy. In addition, with the comparison between MNF images for lithological classification of Sentinel-2A and ASTER data, it was demonstrated that Sentinel-2A data outperformed ASTER in lithological mapping in the Shibanjing ophiolite complex.
       
  • Atmospheric chaoticity and complexity from radio refractivity derived from
           Akure station
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): B.O. Ogunsua, J.S. Ojo, A.T. Adediji Understanding the hidden dynamics of the atmosphere and its effect on radio wave propagation is paramount. Therefore proper characterization of atmospheric dynamics especially for its annual and seasonal variation is necessary. In this paper, atmospheric weather parameters (pressure, relative humidity and temperature), were used to obtain the radio refractivity at the surface Ns level, at 100 m height, N100 and the differential radio refractivity dN/dH. The extracted radio refractivity parameters were characterized based on chaoticity and dynamical complexity, for Akure meteorological station (7°15′9.22″N, 5°11′35.23″E). The data analysis has been based on the Combined application of Largest Lyapunov Exponent and Tsallis Entropy (CLLETE). The data sets for the year 2011 and 2012 have been used for the computation. It was observed that the CLLETE parameters follow similar trend in most cases, and the Lyapunov exponent is generally positive indicating the presence of chaos for all radio refractivity data sets. It was further revealed that the pattern of the dynamical complexity variations in 2012 follow a similar trend from July to December for N100 and dN/dH with the values of the dynamical complexity parameters computed for NS having a huge departure from the other two heights with lower complexity values. However, the dynamical complexity parameters computed for NS and N100 a have similar a trend from the beginning of the year to June. The values of the Chaos and complexity parameters also show a similar variation in 2011 with NS following the same trend between July and December. This indicates the dynamical response of radio refractivity to varying weather conditions.
       
  • Passive microwave response associated with two main earthquakes in Tibetan
           Plateau, China
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): Feng Jing, Ramesh P. Singh, Ke Sun, Xuhui Shen The thermal anomalies associated with earthquakes using satellite infrared data are being studied in different parts of the world for more than three decades. The thermal anomalies have emerged as one of the potential earthquake precursor. However, often cloud cover obstructs detection of the thermal anomalies. Compared to infrared, passive microwave sensors provide information about the thermal radiations under any weather conditions. In the present study, we have carried out detailed analysis of brightness temperature data derived from the Defense Meteorological Space Program (DMSP) Special Sensor Microwave/Imager (SSM/I) to determine thermal anomalies associated with the 1997 Manyi and 2001 Kokoxili earthquakes. Brightness temperature data for 13 years period from 1996 to 2008 observed from F13 satellite were considered to avoid difference in the sensor sensitivity. Based on 9 years background data that ignoring data for the years in which strong earthquake occurred, we computed Index of Microwave Radiation Anomaly (IMRA) over the Manyi-Yushu Fault (MYF) and Kun Lun Fault (KLF) zones, Tibetan Plateau. Our results indicate that the microwave brightness temperature at 19.35 GHz has higher sensitivity to the seismic anomalies in comparison to the other higher frequency channels. The IMRA with multi-region, multi-frequency, and multi-parameter variation were analyzed to validate our results. In addition, variation of different parameters (microwave brightness temperature, near surface air temperature and carbon monoxide-CO) observed for Kokoxili earthquake shows the transfer process of thermal anomalies from the focal region to the atmosphere during the preparation and occurrence of earthquake. Passive microwave satellite data combined with other surface and atmospheric parameters provide better understanding of physical mechanism of thermal anomalies associated with earthquakes.
       
  • PL612 LOFAR station sensitivity measurements in the context of its
           application for pulsar observations
    • Abstract: Publication date: 1 October 2018Source: Advances in Space Research, Volume 62, Issue 7Author(s): L.P. Błaszkiewicz, W. Lewandowski, A. Krankowski, J. Kijak, A. Froń, T. Sidorowicz, B. Dąbrowski, K. Kotulak, M. Hajduk The Low Frequency Array (LOFAR) is relatively new interferometric radio telescope. LOFAR operates in poorly explored part of the spectrum (10–240 MHz). In this frequency range pulsars are bright, and LOFAR observations of pulsars are import for probing fundamental physics and the interstellar medium. In this work we present the description of the international LOFAR station frontend and backend parameters related to pulsar observations with a single LOFAR station, based on observations with the Polish station, located in Bałdy near Olsztyn. We present new results from observations aimed at better characterizing the telescope sensitivity. These measurements are important for efficient planning of pulsar observating campaigns. Observations show good sensitivity for pulsar measurements above 25° elevation and show the noise level rises significantly for elevations below 25°.
       
  • The influence of several Atmospheric variables on Cosmic Ray Muons
           observed by KACST Detector
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): A. Maghrabi, M. Almutairi In this study, the effects of atmospheric pressure and temperature on cosmic ray muons have been investigated using data recorded by the KACST detector (Riyadh, Saudi Arabia; Rc= 14.4 GV) for the beginning of the quiet periods of the 24th solar cycle. The muon data were, initially, correlated with the atmospheric pressure, and the desired coefficient was obtained and used to eliminate the pressure effect from the muon measurements. The pressure-corrected data are then analysed to study the effect of the atmospheric temperature on cosmic ray muons, using five methods. Four methods investigate the effect of the ground temperature, the atmospheric temperatures and atmospheric heights at several atmospheric levels, on the measured muon rate. In the fifth method, the muon data were correlated with the atmospheric weighted temperatures integrated up to different atmospheric heights. For all cases, the desired correction coefficients were obtained, and their variations at several atmospheric levels were studied. The obtained coefficients were then used to correct the cosmic ray data. We found that the atmospheric pressure effect shows the greatest differences between the corrected and uncorrected rate (up to 1%). Instead, corrections made to the muon data using the remainder of the considered parameters modify the muon rate by a small amount (less than 0.5%) compared to the uncorrected rate.
       
  • An improved augmented X-ray pulsar navigation algorithm based on the norm
           of pulsar direction error
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): Qiang Xu, Hong-li Wang, Lei Feng, Wei Jiang, Si-hai You, Yi-yang He Pulsar position error in the Celestial Coordinate System can cause pulsar direction error in the Barycentric Celestial Reference System, which may seriously affect the accuracy of X-ray pulsar navigation. In order to improve the robustness of X-ray pulsar navigation algorithm against the pulsar direction error, an improved augmented X-ray pulsar navigation algorithm is proposed. Different from the previously proposed augmented algorithm, the algorithm introduces the norm of pulsar direction error as the augmented state rather than the systematic bias. At the same time, after the linearization of observation equation, the algorithm uses extended Kalman filter (EKF) as the basic filter, which has faster computation speed and better engineering applicability. The observability of the algorithm is proved by theoretical analysis. Finally, numerical simulations demonstrate that under different error conditions, the improved algorithm not only can effectively reduce the dependence on the state initial value, but also has better real-time performance compared with the previous algorithm.
       
  • Joint analysis of seasonal oscillations derived from GPS observations and
           hydrological loading for mainland China
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): Yunfei Xiang, Jianping Yue, Zhen Li Hydrological loading effects are one of the principal sources of the seasonal oscillations in GPS position time series, and they should be taken into account for improving GPS system accuracy. In this study, the daily vertical position time series of 23 GPS stations derived from the Crustal Movement Observation Network of China (CMONOC) are used to investigate the hydrological loading contributors of seasonal oscillations in GPS observations. The hydrological loading deformations at each GPS station are estimated by the Global Land Surface Discharge Model (LSDM). The result of period analysis suggests that the hydrological loading primarily results in the annual oscillation in GPS observations. Therefore, Multichannel Singular Spectrum Analysis (MSSA) is utilized to derive the annual signal from GPS observations and LSDM-derived deformations simultaneously for each GPS station. Compared with Singular Spectrum Analysis (SSA), the percentage of the variance of the annual signal estimated by MSSA and SSA differs by 6% on average, indicating that MSSA can effectively separate annual signal from other signals and clear noise. Meanwhile, Cross Wavelet Transform (XWT) is performed to measure the correlation and phase relationship between GPS observations and LSDM-derived deformations in the time-frequency space. The result demonstrates that the hydrological loading can only explain the annual oscillation in GPS observations at 5 stations (namely LHAS, LUZH, KMIN, QION, and XIAG) well. For the most GPS stations, other factors (e.g., other geophysical factors, hydrological modeling errors, and systematic errors) and hydrological loading jointly contribute to the annual oscillation in GPS observations. After hydrological loading correction, the Root Mean Square (RMS) values of GPS observations are reduced at 15 stations, especially for the GPS stations located in regions with significant water storage variations (up to 2.46 mm at KMIN). Moreover, the percentage of the variance of the annual signal estimated by MSSA correlates well with the RMS reduction, implying that the RMS reduction may be related to the annual signal derived from hydrological loading deformations.
       
  • Past, Present and Future of Small Body Science and Exploration
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): Ernesto Palomba, M.A. Shea
       
  • Performance assessment of uncombined precise point positioning using
           Multi-GNSS real-time streams: Computational efficiency and RTS
           interruption
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): Xinyun Cao, Jiancheng Li, Shoujian Zhang, Lin Pan, Kaifa Kuang The International GNSS Service (IGS) has established the Real-time Services (RTS) that support the real-time precise point positioning (RT-PPP) and related applications. Due to the increasing number of unknown parameters and network instability issues, both the computational efficiency and the RTS stream outage are the key points to realize real-time uncombined GNSS PPP. To improve the computational efficiency of uncombined PPP, the recursive Kalman based on single observation is implemented rather than the standard Kalman filter. The differences between the RTS orbits and the corresponding ultra-rapid predicted orbits reveal that the ultra-rapid predicted orbits can be used as alternatives of the GNSS real-time orbits. During the RTS clock outage period, the linear and sinusoidal terms are determined by the ultra-rapid observed part in advance, while the constant term of clock offsets is determined by the latest available RTS clock corrections. The PPP results have revealed that the proposed prediction method is much more effective than that of directly using the ultra-rapid predicted products. Even when the prediction duration reaches up to 1 h, the 3D positioning accuracy of GNSS RT-PPP is improved by 51.91% compared with the ultra-rapid scheme. Compare to the GPS-only kinematic PPP, the 3D positioning accuracy of GNSS kinematic PPP using CNES (Centre National d’Études Spatiales) RTS products is improved from 8.29 cm to 6.60 cm, and the mean convergence time of achieving 3D position accuracy better than 10 cm is shortened by about 44.99%.
       
  • Advanced Illumination Modeling for Data Analysis and Calibration.
           Application to the Moon.
    • Abstract: Publication date: Available online 25 August 2018Source: Advances in Space ResearchAuthor(s): Erwan Mazarico, Michael K. Barker, Joseph B. Nicholas We present a new illumination modeling tool, called IllumNG, developed at NASA Goddard Space Flight Center (GSFC). We describe its capabilities to enhance the analysis and calibration of science data collected by planetary missions. We highlight these with examples making use of lunar data, particularly the topographic and radiometric measurements collected by the Lunar Orbiter Laser Altimeter (LOLA) instrument, with applications to radiometric measurements from other LRO instruments as well. The unique features of IllumNG are its accuracy and flexibility to handle multiple types of observers and light sources, and its ability to accurately model both singly- and doubly-scattered radiation to an observer.
       
  • Contemporary Sea Level Changes from Satellite Altimetry: What have we
           learned' What are the new challenges'
    • Abstract: Publication date: Available online 25 July 2018Source: Advances in Space ResearchAuthor(s): Anny Cazenave, Hindumathi Palanisamy, Michael Ablain Since the early 1990s, high-precision multi-mission satellite altimetry has provided a 25-year-long sea level record from which global mean sea level rise and superimposed interannual and regional variability can be derived. Most recent results show that the global mean sea level is rising at a mean rate of 3.1 +/- 0.3 mm/yr since January 1993. A clear acceleration is also visible on this 25-year time span, estimated to 0.10 mm/yr2. Mapping of spatial trend patterns continue to show deviation from the global mean rise in a number of regions. However, as the altimetry record lengthens, the ratio of regional trends to the global mean rise tends to decrease, with a factor of amplification of only 2, compared to 3 to 4 some years ago. Estimates of thermal expansion from Argo and ocean mass change from GRACE show that over the GRACE and Argo time span (since 2005) the sea level budget is almost closed. Assessment of the sea level budget over the entire altimetry era (since 1993) based on estimates of individual mass components for the glaciers and the ice sheets provides some upper bound for the still poorly known contribution from water storage on land. At regional scale, ocean thermal expansion is still the main cause of the spatial trend patterns observed by satellite altimetry. However, removing the steric component reveals residual signal that still needs interpretation. In the remaining of this review, we briefly discuss future sea level changes and associated coastal impacts. Finally, we address the issue of remaining gaps in sea level studies, in particular the need for producing coastal sea level products from dedicated satellite altimetry processing of sea level data in global coastal zones.
       
  • Simulating arbitrary hyperspectral bandsets from multispectral
           observations via a generic Earth Observation-Land Data Assimilation System
           (EO-LDAS)
    • Abstract: Publication date: Available online 23 July 2018Source: Advances in Space ResearchAuthor(s): M. Chernetskiy, N. Gobron, J. Gomez-Dans, O. Morgan, M. Disney, P. Lewis, C. Schmullius This paper presents results of using multi-sensor and multi-angular constraints in the generic Earth Observation-Land Data Assimilation System (EO-LDAS) for reproducing arbitrary bandsets of hyperspectral reflectance at the top-of-canopy (TOC) level by merging observations from multispectral sensors with different spectral characteristics. This is demonstrated by combining Multi-angle Imaging Spectroradiometer (MISR) and Landsat Enhanced Thematic Mapper Plus (ETM+) data to simulate the Compact High Resolution Imaging Spectrometer CHRIS/PROBA hyperspectral signal over an agricultural test site, in Barrax, Spain. However, the method can be more generally applied to any combination of spectral data, providing a tool for merging EO data to any arbitrary hyperspectral bandset.Comparisons are presented using both synthetic and observed MISR and Landsat data, and retrieving surface biophysical properties. We find that when using simulated MISR and Landsat data, the CHRIS/PROBA hyperspectral signal is reproduced with RMSE 0.0001 - 0.04. LAI is retrieved with r2 from 0.97 to 0.99 and RMSE of from 0.21 to 0.38. The results based on observed MISR and Landsat data have lower performances, with RMSE for the reproduced CHRIS/PROBA hyperspectral signal varying from 0.007 to 0.2. LAI is retrievedwith r2 from 0.7 to 0.9 and RMSE from 0.7 to 1.4. We found that for the data considered here the main spectral variations in the visible and near infrared regions can be described by a limited number of parameters (3-4) that can be estimated from multispectral information. Results show that the method can be used to simulate arbitrary bandsets, which will be of importance to any application which requires combining new and existing streams of new EO data in the optical domain, particularly intercalibration of EO satellites in order to get continuous time series of surface reflectance, across programmes and sensors of different designs.
       
 
 
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