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Publisher: Elsevier   (Total: 3184 journals)

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Showing 1 - 200 of 3184 Journals sorted alphabetically
Academic Pediatrics     Hybrid Journal   (Followers: 37, SJR: 1.655, CiteScore: 2)
Academic Radiology     Hybrid Journal   (Followers: 26, SJR: 1.015, CiteScore: 2)
Accident Analysis & Prevention     Partially Free   (Followers: 100, SJR: 1.462, CiteScore: 3)
Accounting Forum     Hybrid Journal   (Followers: 28, SJR: 0.932, CiteScore: 2)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 40, SJR: 1.771, CiteScore: 3)
Achievements in the Life Sciences     Open Access   (Followers: 6)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 7)
Acta Astronautica     Hybrid Journal   (Followers: 434, SJR: 0.758, CiteScore: 2)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 2)
Acta Biomaterialia     Hybrid Journal   (Followers: 28, SJR: 1.967, CiteScore: 7)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 3)
Acta de Investigación Psicológica     Open Access   (Followers: 3)
Acta Ecologica Sinica     Open Access   (Followers: 11, SJR: 0.18, CiteScore: 1)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.661, CiteScore: 2)
Acta Materialia     Hybrid Journal   (Followers: 306, 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: 25, 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: 7, SJR: 0.19, CiteScore: 0)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 3)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 8)
Acute Pain     Full-text available via subscription   (Followers: 15, SJR: 2.671, CiteScore: 5)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.53, CiteScore: 4)
Addictive Behaviors     Hybrid Journal   (Followers: 18, SJR: 1.29, CiteScore: 3)
Addictive Behaviors Reports     Open Access   (Followers: 9, SJR: 0.755, CiteScore: 2)
Additive Manufacturing     Hybrid Journal   (Followers: 11, SJR: 2.611, CiteScore: 8)
Additives for Polymers     Full-text available via subscription   (Followers: 23)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 183, SJR: 4.09, CiteScore: 13)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 12, SJR: 1.167, CiteScore: 4)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.694, CiteScore: 3)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.277, CiteScore: 1)
Advances in Agronomy     Full-text available via subscription   (Followers: 17, SJR: 2.384, CiteScore: 5)
Advances in Anesthesia     Full-text available via subscription   (Followers: 29, 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: 11, 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: 24, SJR: 2.089, CiteScore: 5)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 15, 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: 33, SJR: 3.043, CiteScore: 6)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, 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: 5)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 14)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 29, 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: 26, SJR: 1.562, CiteScore: 3)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 20, 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: 13)
Advances in Digestive Medicine     Open Access   (Followers: 12)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 7)
Advances in Drug Research     Full-text available via subscription   (Followers: 26)
Advances in Ecological Research     Full-text available via subscription   (Followers: 43, SJR: 2.524, CiteScore: 4)
Advances in Engineering Software     Hybrid Journal   (Followers: 29, SJR: 1.159, CiteScore: 4)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 8)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 51, 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: 65, SJR: 0.591, CiteScore: 2)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 17)
Advances in Genetics     Full-text available via subscription   (Followers: 21, SJR: 1.354, CiteScore: 4)
Advances in Genome Biology     Full-text available via subscription   (Followers: 10, SJR: 12.74, CiteScore: 13)
Advances in Geophysics     Full-text available via subscription   (Followers: 7, SJR: 1.193, CiteScore: 3)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 26, SJR: 0.368, CiteScore: 1)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 11, SJR: 0.749, CiteScore: 3)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 24)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 3, 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: 10, 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: 9, 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: 8)
Advances in Marine Biology     Full-text available via subscription   (Followers: 21, SJR: 0.88, CiteScore: 2)
Advances in Mathematics     Full-text available via subscription   (Followers: 12, SJR: 3.027, CiteScore: 2)
Advances in Medical Sciences     Hybrid Journal   (Followers: 8, SJR: 0.694, CiteScore: 2)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 6)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 5, SJR: 1.158, CiteScore: 3)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 24)
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: 5)
Advances in Oncobiology     Full-text available via subscription   (Followers: 2)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 18, 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: 27, SJR: 0.461, CiteScore: 1)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 18)
Advances in Pharmacology     Full-text available via subscription   (Followers: 17, SJR: 1.536, CiteScore: 3)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 9, 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: 10)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 6)
Advances in Porous Media     Full-text available via subscription   (Followers: 5)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 19)
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: 66)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 6, SJR: 0.371, CiteScore: 1)
Advances in Radiation Oncology     Open Access   (Followers: 1, 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: 6)
Advances in Space Research     Full-text available via subscription   (Followers: 420, 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: 13, SJR: 0.555, CiteScore: 2)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 37, SJR: 2.208, CiteScore: 4)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 20)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 15)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 2.262, CiteScore: 5)
Advances in Water Resources     Hybrid Journal   (Followers: 53, SJR: 1.551, CiteScore: 3)
Aeolian Research     Hybrid Journal   (Followers: 6, SJR: 1.117, CiteScore: 3)
Aerospace Science and Technology     Hybrid Journal   (Followers: 381, 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: 12, SJR: 3.671, CiteScore: 9)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 473, SJR: 1.238, CiteScore: 3)
Agri Gene     Hybrid Journal   (Followers: 1, SJR: 0.13, CiteScore: 0)
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 18, SJR: 1.818, CiteScore: 5)
Agricultural Systems     Hybrid Journal   (Followers: 31, SJR: 1.156, CiteScore: 4)
Agricultural Water Management     Hybrid Journal   (Followers: 45, SJR: 1.272, CiteScore: 3)
Agriculture and Agricultural Science Procedia     Open Access   (Followers: 4)
Agriculture and Natural Resources     Open Access   (Followers: 3)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 58, SJR: 1.747, CiteScore: 4)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.589, CiteScore: 3)
Air Medical J.     Hybrid Journal   (Followers: 7, SJR: 0.26, CiteScore: 0)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.19, CiteScore: 0)
Alcohol     Hybrid Journal   (Followers: 12, SJR: 1.153, CiteScore: 3)
Alcoholism and Drug Addiction     Open Access   (Followers: 11)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 2, 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: 10, SJR: 0.201, CiteScore: 1)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 54, SJR: 4.66, CiteScore: 10)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6, SJR: 1.796, CiteScore: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 6, SJR: 1.108, CiteScore: 3)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 58, SJR: 3.267, CiteScore: 4)
American J. of Cardiology     Hybrid Journal   (Followers: 63, SJR: 1.93, CiteScore: 3)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 46, SJR: 0.604, CiteScore: 1)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 12)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.524, CiteScore: 3)
American J. of Human Genetics     Hybrid Journal   (Followers: 37, SJR: 7.45, CiteScore: 8)
American J. of Infection Control     Hybrid Journal   (Followers: 29, SJR: 1.062, CiteScore: 2)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 36, SJR: 2.973, CiteScore: 4)
American J. of Medicine     Hybrid Journal   (Followers: 50)
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: 248, SJR: 2.7, CiteScore: 4)
American J. of Ophthalmology     Hybrid Journal   (Followers: 66, 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: 32, 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: 39, 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: 7)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.144, CiteScore: 3)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 66, SJR: 0.138, CiteScore: 0)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 24, SJR: 0.411, CiteScore: 1)
Anales de Cirugia Vascular     Full-text available via subscription   (Followers: 1)
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: 44, SJR: 1.512, CiteScore: 5)
Analytica Chimica Acta : X     Open Access  
Analytical Biochemistry     Hybrid Journal   (Followers: 207, SJR: 0.633, CiteScore: 2)
Analytical Chemistry Research     Open Access   (Followers: 13, SJR: 0.411, CiteScore: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 14)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 2)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 25, 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: 217, SJR: 1.58, CiteScore: 3)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 6, SJR: 0.937, CiteScore: 2)
Animal Reproduction Science     Hybrid Journal   (Followers: 7, SJR: 0.704, CiteScore: 2)

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Similar Journals
Journal Cover
Advances in Space Research
Journal Prestige (SJR): 0.569
Citation Impact (citeScore): 2
Number of Followers: 420  
  Full-text available via subscription Subscription journal
ISSN (Print) 0273-1177
Published by Elsevier Homepage  [3184 journals]
  • Mapping paddy rice by the object-based random forest method using time
           series Sentinel-1/ Sentinel-2 data
    • Abstract: Publication date: Available online 13 September 2019Source: Advances in Space ResearchAuthor(s): Yaotong Cai, Hui Lin, Meng Zhang Rice is one of the world’s major staple foods, especially in China. In this study, we proposed an object-based random forest (RF) method for paddy rice mapping using time series Sentinel-1 and Sentinel-2 data. Firstly, the Robust Adaptive Spatial Temporal Fusion Model (RASTFM) was used to blend MODIS and Sentinel-2 data for achieving multi-temporal Sentinel-2 data. Subsequently, the Savitzky-Golay filter (S-G) was applied to smooth the time series Sentinel-2 NDVI data. And the phenological parameters were derived from the filtered time series NDVI using the threshold method. Then, the optimum feature combination for paddy mapping was formed on the basis of Sentinel-2 MSI images, time series Sentinel-2 NDVI, phenology data and time series Sentinel-1 SAR backscattering images by using the JBh distance. Finally, an object-based Random Forest classifier was used to extract paddy rice with the optimum feature combination. The result showed that fused Sentinel-2 NDVI time series using RASTFM has a high correlation with the original Sentinel-2 image. The overall accuracy and Kappa coefficient of the classification results are higher than 95% and 0.93, respectively, when use the optimum feature combination and object-based RF method. The proposed method can provide technology support for rice mapping in areas with a lot of cloudy and rainy weathers.
  • Near-real-time VTEC maps: new contribution for Latin America Space Weather
    • Abstract: Publication date: Available online 13 September 2019Source: Advances in Space ResearchAuthor(s): Luciano P.O. Mendoza, Amalia M. Meza, Juan Manuel Aragón Paz The development of regional services able to provide ionospheric vertical total electron content (VTEC) maps and ionospheric indexes with a high spatial resolution, and in near-real-time, are of great importance for both civilian applications and the research community. We provide here the methodologies, and an assessment, of such a system. It relies on the public Global Navigational Satellite Systems (GNSS) infrastructure in South America, incorporates data from multiple constellations (currently GPS, GLONASS, Galileo and BeiDou), employs multiple frequencies, and produces continental wide VTEC maps with a latency of just a few minutes. To assess the ability of our system to model the ionospheric behavior we performed a year-round intercomparison between our near-real-time regional VTEC maps, and VTEC maps of verified quality produced by several referent analysis centers, resulting in mean biases lower than 1 TEC units (TECU). Also, the evaluation of our products against direct and independent GNSS-based slant TEC measurements shows RMS values better than 1 TECU. In turn, ionospheric weather W-index maps were generated, for calm and disturbed geomagnetic scenarios, solely employing our quality verified VTEC maps. The spatial representation of these W-index maps reflects the state of the ionosphere, with a resolution of 0.5×0.5 degrees. Finally, we conclude that our products, computed every 15 minutes, do provide an excellent spatial representation of the regional TEC, and are able to provide the bases for the possible computation of ionospheric W-index maps, also in near-real-time.
  • Cataclysmic variable evolution and the white dwarf mass problem: A Review
    • Abstract: Publication date: Available online 13 September 2019Source: Advances in Space ResearchAuthor(s): Monica Zorotovic, Matthias R. Schreiber Although the theory of cataclysmic variable (CV) evolution is able to explain several observational aspects, strong discrepancies have existed for decades between observations and theoretical predictions of the orbital period distribution, the location of the minimum period, and the space density of CVs. Moreover, it has been shown in the last decade that the average white dwarf (WD) mass observed in CVs is significantly higher than the average mass in single WDs or in detached progenitors of CVs, and that there is an absence of helium-core WDs in CVs which is not observed in their immediate detached progenitors. This highly motivated us to revise the theory of CV formation and evolution. A new empirical model for angular momentum loss in CVs was developed in order to explain the high average WD mass observed and the absence of systems with helium-core WDs. This model seems to help, at the same time, with all of the above mentioned disagreements between theory and observations. Moreover, it also provides us with a very likely explanation for the existence of low-mass WDs without a companion. Here we will review the standard model for CV evolution and the disagreements that have existed for decades between simulations and observations with their possible solutions and/or improvements. We will also summarize the recently confirmed disagreement related to the average WD mass and the fraction of helium-core WDs among CVs, as well as the development of an empirical model that allows us to solve all the disagreements, discussing the physics that could be involved.
  • List of Referees
    • Abstract: Publication date: 15 October 2019Source: Advances in Space Research, Volume 64, Issue 8Author(s):
  • Onboard distributed autonomous orbit determination based on state caching
    • Abstract: Publication date: 15 October 2019Source: Advances in Space Research, Volume 64, Issue 8Author(s): Jun Lai, Yongbin Zhou, Yifan Zhou, Jun Yang Autonomous Orbit Determination (AOD) using inter-satellite ranging measurement can maintain the functionality of the Global Navigation Satellite System (GNSS) for a long time without the assistance of the ground facilities, even though it has the rank deficiency problem. This paper proposes an onboard distributed algorithm to implement AOD based on the extended Kalman filter. It exploits the inter-satellite ranging schedule as a priori information and maintains a cache of the estimated global states and the corresponding covariance on each satellite. Simulation results show that the mean User Range Error (URE) of a 31-satellite GPS constellation is less than 0.5 m in 120 days using our algorithm, which has a similar accuracy level as the centralized Kalman filter, and outperforms the conventional distributed algorithm. It also shows that our algorithm is robust to constellation size and ranging measurement noise level. Meanwhile, due to the distributed architecture, our algorithm does not require any additional communication among satellites. All these features make our algorithm more applicable to practical scenario compared to the existing algorithms.
  • The Micro Solar Flare Apparutus (MiSolFA) Instrument Concept
    • Abstract: Publication date: Available online 11 September 2019Source: Advances in Space ResearchAuthor(s): Erica Lastufka, Diego Casadei, Gordon Hurford, Matej Kuhar, Gabriele Torre, Säm Krucker The Micro Solar-Flare Apparatus (MiSolFA) is a compact X-ray imaging spectrometer designed for a small 6U micro-satellite. As a relatively inexpensive yet capable Earth-orbiting instrument, MiSolFA is designed to image the high-energy regions of solar flares from a different perspective than that of Solar Orbiter’s STIX, operating from a highly elliptical heliocentric orbit. Two instruments working together in this way would provide a 3-dimensional view of X-ray emitting regions and can bypass the dynamic range limitation preventing simultaneous coronal and chromospheric imaging. Stereoscopic X-ray observations would also contain valuable information about the anisotropy of the flare-accelerated electron distribution. To perform these types of observations, MiSolFA must be capable of imaging sources with energies between 10 and 100 keV, with 10 arcsec angular resolution.MiSolFA’s Imager will be the most compact X-ray imaging spectrometer in space. Scaling down the volume by a factor of ten from previous instrument designs requires special considerations. Here we present the design principles of the MiSolFA X-ray optics, discuss the necessary compromises, and evaluate the performance of the Engineering Model.
  • Dynamic modeling and multi-stage integrated control method of ultra-quiet
    • Abstract: Publication date: Available online 10 September 2019Source: Advances in Space ResearchAuthor(s): Liang Tang, Kebei Zhang, Xin Guan, Renjian Hao, Youyi Wang Space telescope ultrahigh precision pointing control requires the spacecraft platform to provide an ultra-quiet working environment. Vibration isolator rejection control and the multi-stage integrated control method is believed to be one of the best methods to improve the space telescope attitude control performance. In this paper, the fine dynamics model of multi-stage spacecraft systems is presented and the multi-stage integrated controller design techniques are provided. Effectiveness of the multi-stage integrated control approach is demonstrated by both the numerical simulation and experiment results. An integrated design and demonstrated experimental environment is developed for high-fidelity control performance assessment. The verification experiments for the space telescope attitude control and vibration control are carried out. The results show that the pointing accuracy and stability of the line-of-sight (LOS) for space telescope are improved at least one order by the multi-stage integrated control method.
  • The complications of learning from Super Soft Source X-ray spectra
    • Abstract: Publication date: Available online 10 September 2019Source: Advances in Space ResearchAuthor(s): Jan-Uwe Ness Super Soft X-ray Sources (SSS) are powered by nuclear burning on the surface of an accreting white dwarf, they are seen around 0.1-1 keV (thus in the soft X-ray regime), depending on effective temperature and the amount of intervening interstellar neutral hydrogen (NH). The most realistic model to derive physical parameters from observed SSS spectra would be an atmosphere model that simulates the radiation transport processes. However, observed SSS high-resolution grating spectra reveal highly complex details that cast doubts on the feasibility of achieving unique results from atmosphere modeling. In this article, I discuss two independent atmosphere model analyses of the same data set, leading to different results. I then show some of the details that complicate the analysis and conclude that we need to approach the interpretation of high-resolution SSS spectra differently. We need to focus more on the data than the models and to use more phenomenological approaches as is traditionally done with optical spectra.
  • Δ H +as+a+proxy+for+the+variations+of+ E × B +drift+and+plasma+irregularity+over+East+Africa&rft.title=Advances+in+Space+Research&rft.issn=0273-1177&">Δ H as a proxy for the variations of E × B drift and plasma irregularity
           over East Africa
    • Abstract: Publication date: Available online 10 September 2019Source: Advances in Space ResearchAuthor(s): Samson Tilahun, Nigussie Mezgebe This paper demonstrates that real-time, dip-equatorial, daytime, vertical E×B drift velocities can be derived from ground-based magnetometers over an understudied Eastern African longitude sector. An integrated third order periodic mean partial least square (PMPLS) technique is introduced for vertical drift estimation. The vertical drift data sets, obtained from Communication/Navigation Outage Forecasting Systems (C/NOFS) during an extended period of 2008 - 2013 on quiet geomagnetic storm conditions were used. The paper also characterizes the influence of daytime horizontal magnetic field perturbations for the vertical E×B drift velocity and therefore for the evening time plasma irregularities over Addis Ababa, Ethiopia (9.03° N, 38.7° E, dip latitude 2.09°). Linear and non-linear coefficients of the C/NOFS E×B drift variations were calculated in order to capture the trend of the variation on the temporal basis. Furthermore amplified (07:00 - 10:00 LT), saturated (10:00 - 16:00 LT) and linear (16:00 - 1900 LT) variations of vertical drift are found. Results are compared with independent vertical ion drift estimates of International Reference Ionosphere 2012 (IRI-2012) and partial least square (PLS). PMPLS performance was better in terms of capturing the daytime trends of observed C/NOFS E×B drift . Overall, PMPLS results showed better agreement with the observation C/NOFS E×B drift with maximum and minimum root-mean-square errors (RMSEs) of 12.67 m/s and 9.2 m/s during noontime and post noontimes respectively. Despite ΔH are weaker-positive for most of our observations during prereversal enhancement (PRE) hours the strength of the daytime ΔH are somewhat related to the formation of the post-sunset irregularities.
  • Large non-radial propagation of a coronal mass ejection on 2011 January 24
    • Abstract: Publication date: Available online 6 September 2019Source: Advances in Space ResearchAuthor(s): M. Cécere, M.V. Sieyra, H. Cremades, M. Mierla, A. Sahade, G. Stenborg, A. Costa, M.J. West, E. D’Huys Understanding the deflection of coronal mass ejections (CMEs) is of great interest to the space weather community because of their implications for improving the prediction of CME. This paper aims to shed light into the effects of the coronal magnetic field environment on CME trajectories. We analyze the influence of the magnetic environment on the early development of a particular CME event. On 2011 January 24 an eruptive filament was ejected in association with a CME that suffered a large deflection from its source region and expected trajectory. We characterize the 3D evolution of the prominence material using the tie-pointing/triangulation reconstruction technique on EUV and white-light images. To estimate the coordinates in 3D space of the apex of the CME we use a forward-modeling technique that reproduces the large-scale structure of the flux rope-like CME, the Graduated Cylindrical Shell model. We found that the deflection amounts to 42° in latitude and 20° in longitude and that most of it occurs at altitudes below 4R⊙. Moreover, we found a non-negligible deflection at higher altitudes. Combining images of different wavelengths with the extrapolated magnetic field obtained from a potential field source surface model we confirm the presence of two magnetic structures near the erupting event. The magnetic field environment suggests that field lines from the southern coronal hole act as a magnetic wall that produces the large latitudinal deflection; while a nearby pseudostreamer and a northward extension of the southern coronal hole may be responsible for the eastward deflection of the CME.
  • Quantification of Sq parameters in 2008 based on geomagnetic observatory
    • Abstract: Publication date: Available online 6 September 2019Source: Advances in Space ResearchAuthor(s): Anatoly Soloviev, Artem Smirnov, Alexei Gvishiani, John Karapetyan, Anahit Simonyan The paper presents an investigation of the time-dependent parameters of the solar quiet daily (Sq) variation for the minimum of the solar cycle 23/24 in 2008. We apply ”Measure of Anomalousness” algorithm to detection of the magnetically quiet days. Global distribution of Sq amplitudes of the three orthogonal magnetic field components is analyzed using one-year data from 75 INTERMAGNET geomagnetic observatories and 46 SuperMAG stations. The study reveals strong latitudinal dependence of the Sq(X) amplitudes, which is approximated by the sixth-order polynomial trend curve. Sq(Y) amplitudes also suggest latitudinal dependence, while no significant difference is found in the Sq(Z) amplitudes across all latitudes. In the equatorial region, Sq(X) amplitudes are strongly affected by the equatorial electrojet (EEJ), having maxima during equinoctial seasons in the region of the South Atlantic magnetic anomaly (SAA). Sq(Y) demonstrates clear dependence on solar activity and amount of solar illumination, as the Sq(Y) amplitudes are typically greater in the summer-hemisphere and smaller in the winter-hemisphere. We analyze equivalent Sq current system using observatory data from the Australian mainland and narrow European-African latitudinal segment. Sq current system also strongly depends on solar activity, as the current vortices in the winter-hemisphere disintegrate showing no trace of Sq current loops’ formation, while the current vortices become evident in the summer-hemisphere.
  • Long-term quality and stability assessment of CryoSat-2 Ocean Data
    • Abstract: Publication date: Available online 6 September 2019Source: Advances in Space ResearchAuthor(s): Marc Naeije, Jerome Bouffard Since 8 April 2010 ESA’s Earth Explorer mission CryoSat-2 has been measuring marine and land ice thickness variations with a dedicated altimeter. With the effects of a fast-changing climate becoming apparent, it is increasingly important to understand exactly how Earth’s ice fields are responding and regulate climate and sea level. It is therefore of utmost importance that the quality of the CryoSat-2 altimeter data meets the highest accuracy and precision level, not only over the ice caps and sea-ice surface but over the oceans as well. The SIRAL altimeter of CryoSat-2 is capable of measuring high-resolution geophysical parameters from the open ocean to the coast. In this paper, we validate the CryoSat-2 geophysical ocean product, Baseline-B (GOP). The analyses focus on long-term monitoring, validation, and cross-calibration of these ocean altimeter data with all the concurrent altimeter data in the Radar Altimeter Database System RADS and with independent in-situ tide gauge measurements from the Permanent Service for Mean Sea Level PSMSL. The objective is to evaluate the stability of the CryoSat-2 measurement system and the identification and explanation of biases and bias drifts. A persistent monitoring of these biases in time is important to establish the data’s usefulness for investigation of long-term sea level and ice topography/volume changes. The results constitute the final status of the GOP baseline-B product for use as essential climate variables. GOP ocean data has a –6.3 ±0.2 cm range bias w.r.t. to all calibrated satellites in RADS and a drift of 0.14 mm yr−1 w.r.t.Jason-2. GOP data has significant wave height and sea state biases close to that of the Jasons’, and seems to be better handling the LRM-SAR transitions than the RADS CryoSat-2 product. GOP data w.r.t. PSMSL tide gauge data has an average correlation of R=0.83, a mean st. dev. of σ = 6.30 cm, and a drift of 0.11 mm yr−1, equivalent to 40 Gt yr−1 ice sheet mass loss. It is concluded that GOP CryoSat-2 performs better than RADS CryoSat-2, which seems to suffer from a 480-day platform temperature cycle. GOP is also on a par with the altimeter data from the Jason reference missions, and well suited for ocean and climate studies.
  • Multi-Outburst Nova Modeling & Where Models Meet Observations
    • Abstract: Publication date: Available online 5 September 2019Source: Advances in Space ResearchAuthor(s): Yael Hillman, Michael Shara, Dina Prialnik, Attay Kovetz Direct determination of WD masses in CVs is extremely difficult, which is the reason very few direct determinations exist. We present a method for calculating an estimate of WD masses in CVs and of the rate at which they accrete matter from their companion, by combining results of nova simulations with cataloged observations of 92 novae. We present observed distributions of the WD mass (MWD) and accretion rate (Ṁ), and corrections of these distributions while taking into account the observation frequency of each nova. We show that WDs in RN systems are typically more massive than WDs in CN systems and their Ṁ is higher. If the Ṁ is sufficiently high, the WD will eject only a fraction of the accreted mass, resulting in the secular growth of the WD mass. We have followed the evolution of WDs of various initial masses and accretion rates through long series of nova cycles, focusing on the WD mass change, considering both hydrogen and helium accretion and addressing the consequences of helium flashes. We show the circumstances under which WDs can grow up to the Chandrasekhar mass, to become progenitors of type Ia Supernovae.
  • Design and regional assessment of an empirical tidal model based on
           FES2014 and coastal altimetry
    • Abstract: Publication date: Available online 4 September 2019Source: Advances in Space ResearchAuthor(s): G. Piccioni, D. Dettmering, C. Schwatke, M. Passaro, F. Seitz The updated Empirical Ocean Tide model (EOT19p) currently available on limited regions is presented in this paper. Its implementation is focused on improving the accuracy of tidal estimation at the coast. EOT19p is derived using circa 27 years of coast-dedicated altimetric data and the FES2014 tide model, and it is based on a multi-mission, weighted least-squares approach. In this work the performance of EOT19p is assessed with respect to state-of-the-art tide models against in situ observations. The study is performed on two critical regions: the North Sea and the Malay Archipelago. Comparisons for eight major tidal constituents show that EOT19p improves coastal results with respect to its former version, EOT11a, of 35.39% in the North Sea and 20.07% in the Malay Archipelago, with large error reduction in the English Channel and the Irish Sea. The median absolute differences (MAD) against in situ data show that EOT19p is in line with the latest models, with lowest error occurring for single tidal constituents, such as M2 (with a MAD of 1.63 cm in the Malay Archipelago). Finally, the tidal height differences of three models (EOT19p, FES2014, and DTU16) compared with those obtained of their former versions (EOT11a, FES2012, and DTU10), show an increased agreement at coastal areas with the latest versions, and the regional average difference for M2 constituent drops from 3.75 cm to 0.70 cm in the North Sea, and from 3.02 to 1.44 cm in the Malay Archipelago.
  • Injection of 40-kHz-modulated electron beam from the satellite: II.
           Excitation of electrostatic and whistler waves
    • Abstract: Publication date: Available online 3 September 2019Source: Advances in Space ResearchAuthor(s): N. Baranets, Yu. Ruzhin, V. Dokukin, M. Ciobanu, H. Rothkaehl, A. Kiraga, J. Vojta, J. Šmilauer, K. Kudela Beam-plasma interaction effects are studied during the active space experiment with electron and Xe-ion beam injections in an ionospheric plasma. Permanent 40-kHz-modulated electron beam injection occurs simultaneously with a xenon-ion beam injected by the Hall-type plasma thruster operating in a square-pulse mode (100/50 s for a job/pause duration). The unusual behavior of the background charged particle fluxes and wave activity stimulated during the beam-plasma interaction have been registered by the scientific instruments onboard Intercosmos-25 station (IK-25) and Magion-3 subsatellite. The longitudinal and electromagnetic wave instabilities and their mutual relationship are considered in order to explain the observed effects. The excitation of electrostatic waves by the electron injection has been considered for different resonance conditions near the linear stability boundary. Beam-driven electromagnetic instability is responsible for the backward-propagating whistler waves excited via cyclotron resonance. Competition of these two beam instabilities is one of the subjects of the present study.
  • Case studies: a possible mechanism for F2-lacuna formation
    • Abstract: Publication date: Available online 3 September 2019Source: Advances in Space ResearchAuthor(s): Shenggao Yang, Beichen Zhang, Yang Liu, Yaguang Zhu, Xu Yang, Chao Tian, Fulu Yue, Peikang Xu, Jianming Jiang Two cases of F2-lacuna and their simultaneous ionospheric convection and TEC variations were presented to further understand F2-lacuna formation mechanism. Both cases of F2-lacuna are accompanied by decreased electron density and increased plasma flow. Through analyzing the role of convection electric field in the formation of F2-lacuna, an explanation for F2-lacuna formation was provided. The joule heating and frictional heating ascribed to the strengthened electric field causes the increase of electron and ion temperature, which subsequently, causes the enhancements of the recombination rate and the upflow of the O+ density resulting in decreased O+ density in F2 region.
  • Detection statistics of the RadioAstron AGN survey
    • Abstract: Publication date: Available online 3 September 2019Source: Advances in Space ResearchAuthor(s): Y.Y. Kovalev, N.S. Kardashev, K.V. Sokolovsky, P.A. Voitsik, T. An, J.M. Anderson, A.S. Andrianov, V.Yu. Avdeev, N. Bartel, H.E. Bignall, M.S. Burgin, P.G. Edwards, S.P. Ellingsen, S. Frey, C. García-Miró, M.P. Gawroński, F.D. Ghigo, T. Ghosh, G. Giovannini, I.A. Girin The largest Key Science Program of the RadioAstron space VLBI mission is a survey of active galactic nuclei (AGN). The main goal of the survey is to measure and study the brightness of AGN cores in order to better understand the physics of their emission while taking interstellar scattering into consideration. In this paper we present detection statistics for observations on ground-space baselines of a complete sample of radio-strong AGN at the wavelengths of 18, 6, and 1.3 cm. Two-thirds of them are indeed detected by RadioAstron and are found to contain extremely compact, tens to hundreds of μas structures within their cores.
  • A New Attitude Integration Algorithm for Coning Environment
    • Abstract: Publication date: Available online 3 September 2019Source: Advances in Space ResearchAuthor(s): Lijuan Xiong, Hongtao Zhu, Weijun Wu, Bo Zhou Attitude determination of the space vehicle always plays a pivotal role in space missions. Usually, the fourth-order Runge Kutta algorithm is taken as more common attitude integration algorithm. However, more appropriate algorithms are desired in order to meet variable requirement. This paper investigates the performance of the fourth-order Runge Kutta and Taylor series algorithms in coning environment, and presents a new algorithm which takes advantages from above both. Series of simulation experiments have been conducted to verify the effect of the new algorithm. Their results show that the new algorithm outperforms the fourth-order Runge Kutta and the four-sample rotation vector algorithms over long-duration run even in complex engineering applications where the attitude change is not too fast.
  • NUCLEON-2 mission for the investigation of isotope and charge composition
           of cosmic ray ions
    • Abstract: Publication date: Available online 30 August 2019Source: Advances in Space ResearchAuthor(s): V. Bulatov, S. Fillippov, D. Karmanov, I. Kovalev, A. Kurganov, M. Panasyuk, A. Panov, D. Podorozhny, D. Polkov, L. Tkatchev, P. Tkatchev, A. Turundaevskiy, O. Vasiliev The NUCLEON-2 experiment is aimed at the investigation of isotope and charge composition of medium, heavy and ultra-heavy ions (Z
  • X-Ray properties of dwarf nova EY Cyg and the companion star using an
           XMM-Newton observation
    • Abstract: Publication date: Available online 28 August 2019Source: Advances in Space ResearchAuthor(s): Armin Nabizadeh, Sölen Balman We present the X-ray analysis of dwarf nova EY Cyg using the 45 ks XMM-Newton observatory archival data obtained in quiescence. We find orbital modulations in X-rays. We simultaneously fitted EPIC pn, MOS1 and MOS2 data using a model for interstellar medium absorption (tbabs) and a multi-temperature plasma emission model with a power-law distribution of temperatures (CEVMKL) as expected from low accretion rate quiescent dwarf novae. The XMM-Newton EPIC spectra of the source yields a maximum temperature kTmax ∼ 14.9-2.2+3.3 keV with an unabsorbed X-ray flux and luminosity of (1.8–2.0) × 10-12 ergs-1 cm-1 and (8.7–9.7) × 1031 ergs-1 , respectively, in the energy range 0.1 to 50 keV. There is 3–4 sigma excess at energies below 0.5 keV, we model the excess using MEKAL, POWERLAW and BBODY models and favor the model MEKAL which is physical. According to previous studies, the secondary in this system is thought to be a K-type star which may radiate in the soft X-ray region. The fit with an additive MEKAL model gives a temperature of kT ∼ 0.1 keV with an unabsorbed X-ray flux and luminosity of (2.7–8.8) × 10-14 ergs-1 cm-1 and (1.3–4.2) × 1030 ergs-1 , respectively, for the companion star. Based on the results from the timing and spectral analysis, we highly suggest that the secondary of EY Cyg is a K-type star.
  • The Effect of Different Phases of Severe Geomagnetic Storms on the Low
           Latitude Ionospheric Critical Frequencies
    • Abstract: Publication date: Available online 26 August 2019Source: Advances in Space ResearchAuthor(s): Erdinç Timoçin In this paper, the effect of different phases of severe geomagnetic storms on low latitude ionospheric critical frequencies (foF2) is investigated. For this purpose, hourly ionospheric critical frequency (foF2) data measured at the low latitude ionosonde station Manila during 1981 and 1991 is examined. The investigation is carried out using superposed epoch analysis method considering the disturbance storm time index Dst ≤ -100 nT hours as event times. To examine depending on local time the effect of the phases of geomagnetic storms on foF2, this analysis was conducted for separately for the day hours, night hours, and all hours during both the main and the recovery phases of the severe geomagnetic storms and the results were compared with each other. It is observed that for both 1981 and 1991, the highest change (increase or decrease) in foF2 values occurs at the event times for all hours of day during both the main and the recovery phase of severe geomagnetic storms. Also, during the main phases of severe geomagnetic storms, the foF2 values increase at day hours, while the foF2 values decrease at night hours. However, during the recovery phases of severe geomagnetic storms, the foF2 values decrease at day hours, while the foF2 values increase at night hours. For both the day and night hours, the changes in the foF2 values during the recovery phase of severe geomagnetic storms are greater than the changes in the foF2 values during the main phase of severe geomagnetic storms.
  • Sea-Level Rise and Vertical Land Motion on the Islands of Oahu and Hawaii,
    • Abstract: Publication date: Available online 26 August 2019Source: Advances in Space ResearchAuthor(s): Linqiang Yang, Oceana Puananilei Francis Sea-level rise is a highly publicized issue in the Hawaiian Islands because it is one of the main drivers for coastal hazards. In our study, multiple geodetic and in situ datasets are integrated to investigate the sea-level rise and vertical land motion on the islands of Oahu and Hawaii, Hawaii. The rates of relative sea-level changes are derived from the tide-gauge stations in the Hawaiian Islands, however the station located at Kawaihae, Hawaii presents a much higher trend than other stations. Our analysis shows that the questionable trend results from the sudden movement of the equipment on land, which is caused by a pair of earthquakes. After adjustment, we arrive at a revised and more consistent relative sea-level trend at this station. Our study shows that Oahu is vertically ‘stable’ (i.e., near-zero vertical land movement within uncertainties), and the relative sea-level change is dominated by the absolute sea-level change. However, the island of Hawaii was subsiding at -3.3±0.9 mm/year before 1973 and changed to -1.2±0.2 mm/year after 1975, which may relate to seismic activities and where relative sea-level change is attributed to both absolute sea-level change and vertical land motion. The difference in relative sea-level change between the islands of Oahu and Hawaii is due to the difference in vertical land motion rather than steric sea-level change. In addition, the ocean-mass components are the predominant factors that influence the long-term trends of absolute sea level on the islands of Oahu and Hawaii.
  • Extreme Value Statistics of Wind Speed and Wave Height of the Marmara Sea
           Based on Combined Radar Altimeter Data
    • Abstract: Publication date: Available online 26 August 2019Source: Advances in Space ResearchAuthor(s): Berguzar Oztunali Ozbahceci Both reliable and long-term wind and wave data are necessary for the design of coastal and offshore structures. Due to lack of sufficient in-situ measurement data, modeling data have been used in the limited number of wind and wave climate studies of the Marmara Sea. Satellites equipped with instruments capable of observing marine surface wind and ocean waves like Radar Altimeter can be another source for the long term wind and wave climate of the Marmara Sea. In this study, for the first time, the altimeter wind speed and the significant wave height data from different satellite missions are attempted to use in the climate and extreme value analysis of the Marmara Sea. Altimeter wind speeds and significant wave heights are compared with the in-situ measurements and it is found that while the altimeter wind speed agrees with the measurement data, the significant wave height data should be calibrated. After the calibration of the altimeter data and the inter-calibrations of earlier satellite missions, 27 years of altimeter wind speed and wave height data are obtained to use in extreme value analysis. The wind speed and the significant wave height values corresponding to different return periods are determined as a result of extreme value statistics and those values are compared with the results of the measurements and previous studies. Consistent extreme values computed in the current study indicate that the combined radar altimeter data can be used in the wind and the wave climate calculations and the extreme value analysis of the Marmara Sea.
  • Red Dwarfs as Sources of Cosmic Rays and Detection of TeV Gamma-rays from
           these Stars
    • Abstract: Publication date: Available online 26 August 2019Source: Advances in Space ResearchAuthor(s): Vera G. Sinitsyna, Vera Y. Sinitsyna, Yurii I. Stozhkov A modern paradigm on the sources of galactic cosmic rays includes supernovae and supernova remnants as the powerful ones to accelerate particles up to ∼1017 eV. Meanwhile, the recent experimental data obtained by PAMELA, AMS-02, Fermi-LAT, CALET, and DAMPE require the existence of other cosmic-ray sources located nearby the solar system, at the distances less than 1 kpc. Presence of such local sources could explain the unexpected rise of the positron fraction in cosmic rays, the observed electron fluxes with the energies more than one TeV, complex shapes of the proton and helium spectra, and anomalous low-energy cosmic rays. Here we consider active dwarf stars as possible sources of Galactic cosmic rays in the energy range up to 1014 eV. These stars are producing powerful stellar flares sometimes with energy release more than 1036 erg. Meanwhile, the generation of high-energy cosmic rays should be accompanied by the high-energy γ-ray emission, which may be observed. Here we present the results of the SHALON long-term observations of generation of γ-ray emission above 800 GeV from the active red dwarf stars.
  • Accurate estimation of relative atmospheric density error on the example
           of uncertain geomagnetic activity information
    • Abstract: Publication date: Available online 26 August 2019Source: Advances in Space ResearchAuthor(s): Fabian Schiemenz, Jens Utzmann, Hakan Kayal Errors in neutral atmospheric density are the dominant contributor to unrealistic orbital state-vector covariances in low Earth orbits (LEO). Density uncertainty is caused by model-uncertainty at spatial scales below and within the model resolution, as well as input-uncertainty of the environmental parameters supplied to the semi-empirical atmospheric model.The paper at hand provides multiple contributions. First, analytic equations are derived to estimate the relative density error due to an input parameter uncertainty in any of the environmental parameters supplied to the model. Second, it is shown on the example of uncertain geomagnetic activity information, how to compute the required inputs to facilitate the accurate estimation of the relative density error.A clamped cubic splining approach for the conversion from geomagnetic amplitude (ap) to the kp index is postulated to perform this uncertainty propagation, as other algorithms were found unsuitable for this task. Results of numerical simulations with three popular semi-empirical models are provided to validate the set of derived equations. It is found that geomagnetic input uncertainty is especially important to consider in case of low global geomagnetic activity. The findings seamlessly integrate with prior work by the authors to perform density-uncertainty considering orbit estimation.
  • List of Referees
    • Abstract: Publication date: 1 October 2019Source: Advances in Space Research, Volume 64, Issue 7Author(s):
  • A Polar Coordinate System Based on a Projection Surface for Moon-Based
           Earth Observation Images
    • Abstract: Publication date: Available online 23 August 2019Source: Advances in Space ResearchAuthor(s): Lu zhang, Huadong guo, Hui jiao, Guang liu, Guozhuang shen, Wenjin wu As a new potential platform for Earth observation, the Moon which is a natural satellite unique to the Earth has been paid more and more attention for its consistent and continuous observation capability of global-scale and macroscopic geoscience phenomena on Earth. Because of the effect of Earth curvature and the Earth–Moon geometric relationship, the geometric correction of the Moon-based Earth observation (MBEO) hemisphere images is more complex than that required for images obtained from low Earth orbit (LEO) platforms and need to be investigated, such as optical images in visible/thermal infrared frequencies or synthetic aperture radar (SAR) images in microwave frequency. In addition, it is also difficult to find the uniformly distributed geometric correction control points on the entire surface of the Earth caused by sea and cloud cover in most regions. In this paper, a polar coordinate system on a projection surface related to the sublunar point is designed to facilitate the geometric correction of MBEO hemisphere images and to try to compensate for the problems of geometrical distortion caused by the shift of the sublunar point, the curvature of the Earth and the terrain fluctuation. Through simulation analysis, the geometric error characteristics and conditions in which the proposed moon-projection polar coordinate system can be used are discussed. This involves considering the Earth model, the projection method, the offset of the sublunar point and the external error. The results show the validity and adaptation of the proposed polar coordinate system and will support the further study of the geometric correction of MEBO images.
  • Variations in the Ionosphere-Thermosphere System from Tides, Ultra-Fast
           Kelvin Waves, and Their Interactions
    • Abstract: Publication date: Available online 23 August 2019Source: Advances in Space ResearchAuthor(s): Colin C. Triplett, Thomas J. Immel, Yen-Jung Wu, Chihoko Cullens Large scale waves, such as the atmospheric tides and ultra-fast Kelvin waves (UFKW), have direct effects on the neutral wind and temperature fields of the ionosphere-thermosphere (I-T) system. In this study we examine the response of the I-T system to the atmospheric tides, one UFKW, and the secondary waves generated from their interactions using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM). We find that forcing an UFKW at the lower boundary of the TIEGCM is all that is required for it to setup in the model. We see variations around 10% in the zonal winds that lead to similar variations in the total electron content (TEC) depending on the phase of the UFKW. From these simulations, we expect the Ionospheric Connection Explorer (ICON) mission will be able to fully capture these wave interactions by observing winds and temperatures at the mesopause and above.
  • Estimating the slip rate on the north Tabriz fault (Iran) from InSAR
           measurements with tropospheric correction using 3D ray tracing technique
    • Abstract: Publication date: Available online 23 August 2019Source: Advances in Space ResearchAuthor(s): Saeid Haji-Aghajany, Behzad Voosoghi, Yazdan Amerian In this paper, interseismic deformation across the north Tabriz fault (NTF) using 17 ASAR/ENVISAT acquisitions on a single track for the period 2003–2010 have been investigated. One of the main limiting factors on the accuracy of interferometric synthetic aperture radar (InSAR) measurements comes from phase propagation delays through the troposphere. In order to retrieve millimeter velocities of interseismic deformations, it is necessary to improve the tropospheric corrections and correct interferograms. For this purpose, the 3D ray tracing technique based on eikonal equations has been used to estimate the tropospheric corrections. The corrected InSAR measurements are used to derive the interseismic displacement velocity field of the study area. The obtained velocity field has enabled us to accurately estimate the slip rate and locking depth for the NTF, using a simple elastic dislocation model. The numerical achievements show a slip rate of 5.6±0.15 mm/yr below a locking depth of 14.5±0.67 km for the NTF. Generally, the results of this paper are confirmed by the previous studies of the NTF parameters and some differences are due to this paper applied method for tropospheric corrections.
  • Estimating discharges for poorly gauged river basin using ensemble
           learning regression with satellite altimetry data and a hydrologic model
    • Abstract: Publication date: Available online 22 August 2019Source: Advances in Space ResearchAuthor(s): Donghwan Kim, Hyongki Lee, Edward Beighley, Raphael M. Tshimanga The Congo River is one of the least studied basins although it is the world’s second largest in size (∼ 3.7 million km2) and discharge (Q) (∼ 40,600 m3s-1). Using remote sensing data and a hydrologic model, previous studies have successfully estimated Q of the Congo River at Brazzaville-Kinshasa stations with an accuracy of 10 – 40 %. However, those studies depended on only a hydrologic model or estimated Q using remotely sensed data with a single rating curve. Recently, Kim et al. (2019) has also successfully applied the ensemble learning regression method, which is one of the machine learning techniques, to estimate Q (termed as ELQ) by linearly combining several rating curves over different locations. The study has estimated Q at the Brazzaville station with relative root-mean-square error (RRMSEs) of 7.17/5.53 % for training/validation datasets whose temporal resolutions are 35-day for the period from 2002 to 2010. However, ELQ still requires in-situ Q data in order to train base learners and obtain their weights. In this study, we present a study estimating daily Q by applying ELQ with satellite altimetry data and the hydrologic-hydraulic Hillslope River Routing (HRR) model for the Congo River. We parameterized our model with the HRR-derived Q (Q^HRR) in training/validation datasets without the aid of in-situ Q. ELQ-derived Q (Q^ELQ) has not been calibrated or scaled with in-situ Q data in training/validation datasets. However, the HRR model has been calibrated to mean monthly historical gauge measurements (1903 to 1990). Q^HRR showed RRMSEs of 15.72/18.00 % for training/validation datasets compared with daily in-situ Q data at the Kinshasa station spanning from November 2002 to September 2010. We used the Basic Ensemble Method (fBEM), which employs the uniformly distributed weights in ELQ process, that can provide improved estimates of Q. Q^ELQ using fBEM showed RRMSE of 11.32/9.05 % on average for training/validation datasets. Moreover, we introduced the method generating more accurate ELQ using the ensemble mean of fBEM (fBEM¯) which yielded RRMSEs of 7 – 10 %. This study demonstrates that ELQ can provide more accurate daily Q using satellite altimetry data and a hydrologic model for poorly gauged river basins.
  • Scaling Laws of Quiet-Sun Coronal Loops.
    • Abstract: Publication date: Available online 22 August 2019Source: Advances in Space ResearchAuthor(s): C. Mac Cormack, M. López Fuentes, C.H. Mandrini, D.G. Lloveras, M. Poisson, A.M. Vásquez We study a series of relations between physical parameters in coronal loops of the quiet Sun reconstructed by combining tomographic techniques and modeling of the coronal magnetic field. We use differential emission measure tomography (DEMT) to determine the three-dimensional distribution of the electron density and temperature in the corona, and we model the magnetic field with a potential-field source-surface (PFSS) extrapolation of a synoptic magnetogram. By tracing the DEMT products along the extrapolated magnetic field lines, we obtain loop-averaged electron density and temperature. Also, loop-integrated energy-related quantities are computed for each closed magnetic field line. We apply the procedure to Carrington rotation 2082, during the activity minimum between Solar Cycles 23 and 24, using data from the Extreme Ultraviolet Imager on board the Solar Terrestrial Relations Observatory (STEREO) spacecraft. We find a scaling law between the loop-average density N and loop length L,Nm∼L-0.35, but we do not find a significant relation between loop-average temperature and loop length. We confirm though the previously found result that loop-average temperatures at the equatorial latitudes are lower than at higher latitudes. We associate this behavior with the presence at the equatorial latitudes of loops with decreasing temperatures along their length (“down” loops), which are in general colder than loops with increasing temperatures (“up” loops). We also discuss the role of “down” loops in the obtained scaling laws of heating flux versus loop length for different heliographic latitudes. We find that the obtained scalings for quiet-Sun loops do not generally agree with those found in the case of AR loops from previous observational and theoretical studies. We suggest that to better understand the relations found, it is necessary to forward model the reconstructed loops using hydrodynamic codes working under the physical conditions of the quiet-Sun corona.
  • A discussion on the mode conversion from purely perpendicular upper-hybrid
           mode waves to LO mode waves in an inhomogeneous plasma
    • Abstract: Publication date: Available online 20 August 2019Source: Advances in Space ResearchAuthor(s): Mohammad Javad Kalaee, Yuto Katoh We consider the equatorial region of the magnetosphere, where the magnetic field is perpendicular (or near to perpendicular) to the density gradient and mode conversion process from UH to LO-mode waves or reverse process are expected. We review and study the mode conversion from UH (upper hybrid) to LO (left hand polarized ordinary) mode waves by a spatially two dimensional plasma fluid code. Several simulations with different initial wave vectors under the same background plasma condition have been performed. We focus on the conversion efficiency from the UH-mode waves with purely perpendicular wave normal angle to the LO-mode waves, since one of the source of generation UH wave can be Bernstein mode as the purely perpendicular electrostatic waves. For this special case, the UH wave normal is kept in perpendicular direction with respect to the magnetic field, and difficult to be in matching direction for conversion to LO mode. Simulation results show that the mode conversion efficiency in this particular case is very weak, since two branches of Z-mode wave and LO mode wave in the dispersion relation are disconnected. We present a discussion to show that for this case (purely perpendicular propagation) a special angle (except 90 degrees), between the magnetic field and the density gradient is necessary for occurrence of efficient mode conversion. For the case (purely perpendicular propagation and the magnetic field perpendicular to the density gradient), the mode conversion just occurred via the tunneling effect, where a steepness of the inhomogeneity plays an essential role.
  • Systematic Low-Thrust Trajectory Design to Mars Based on a Full Ephemeris
    • Abstract: Publication date: Available online 19 August 2019Source: Advances in Space ResearchAuthor(s): Mohammadreza Saghamanesh, Ehsan Taheri, Hexi Baoyin One of the fundamental tasks in space mission design is to choose a set of inter-disciplinary mission-critical parameters that are used for both sizing spacecraft sub-systems and designing optimal trajectories. Trajectory design and sub-system sizing are tightly coupled tasks and mission designers are interested in algorithms that not only improve fidelity of the underlying models, but also facilitate comprehensive trade-off studies using dependable algorithms. This paper presents a systematic-design/computationally-efficient framework that makes use of a recently developed hybrid optimization method, which is a fusion between homotopic approach and particle swarm optimization to perform a robust homotopic approach. A salient feature of this framework is the flexibility in altering the fidelity of the dynamical models to beyond the conventional two-body model by including perturbations due to: 1) other planets of the Solar System, 2) solar radiation pressure, and 3) the oblateness effects of the Earth. Moreover, a comprehensive study on the impact of using different types of thrusters, different hyperbolic excess velocity values, and different launch opportunities is conducted. Extensive numerical simulations are performed for a heliocentric rendezvous mission from Earth to Mars and the results are compared against those in the literature.
  • Orbit Determination of CE-4’s Relay Satellite in Earth-Moon L2
           Libration Point Orbit
    • Abstract: Publication date: Available online 19 August 2019Source: Advances in Space ResearchAuthor(s): Jianfeng Duan, Zhaokui Wang The Magpie Bridge mission is a part of the Chang’E-4 mission, it is the first Chinese spacecraft carries out Earth-Moon communication mission at Earth-Moon libration points. The Magpie Bridge operations team utilizes the Beijing Aerospace Control Center (BACC) Orbit Determination and Analysis Software (BODAS) to obtain the orbit, the measurements include range, Doppler and relay, relay-rate from China Deep Space Network (CDSN) and Very Long Baseline Interferometry (VLBI) system respectively. In order to effectively improve the accuracy of the orbit, we provided the solar radiation model with multiple characteristic surfaces. The new model is based on the structure and the real-time attitude of the satellite to solve the real-time solar pressure equivalent area. Compared with the cannon-ball model, it can calculate the solar pressure equivalent area of the satellite more accurately in orbit determination. By the analysis of the tracking measurement data, we found that the new solar radiation pressure model reduces the error of position and velocity compared to the cannon-ball model.
  • A Pseudospectral Method based Robust-Optimal Attitude Control Strategy for
    • Abstract: Publication date: Available online 16 August 2019Source: Advances in Space ResearchAuthor(s): Arunava Banerjee, Syed Muhammad Amrr, M. Nabi This paper proposes an optimal integral sliding mode control (ISMC) scheme for attitude regulation of the rigid spacecraft. This control technique is capable of handling inertial matrix uncertainties as well as external disturbances. To incorporate optimality into the robust control law, the ISMC is integrated with Legendre pseudospectral method (LPSM). The minimization of the cost function and constraint handling of the spacecraft is obtained by LPSM, while the ISMC provides disturbance rejection. LPSM is chosen for its relatively high rate of convergence and its capability of solving a wide range of challenging optimal control problems. Theoretical stability analysis of closed loop system using Lyapunov theorem guarantees the convergence of attitude states. A comparative analysis between the proposed LPSM-ISMC and Chebyshev Pseudospectral Method(CPSM) based ISMC, is also presented in this paper. The effectiveness of the proposed robust-optimal control strategy is established through simulation results.
  • Indirect robust suboptimal control of two-satellite electromagnetic
           formation reconfiguration with geomagnetic effect
    • Abstract: Publication date: Available online 16 August 2019Source: Advances in Space ResearchAuthor(s): Da-wei Qi, Le-ping Yang, Yuan-wen Zhang, Wei-wei Cai As a novel approach to control the relative motion of a satellite formation, electromagnetic formation flight (EMFF) has some prominent advantages, such as no propellant consumption and no plume contamination, and has a broad prospect of application in such fields as on-orbit detection and optical interferometry. The current paper investigates the optimal control for the reconfiguration of a two-satellite electromagnetic formation using the nonlinear quadratic optimal control technique. Specifically, the effects of the Earth’s magnetic field on the EMFF satellites are analyzed, and then the nonlinear translational dynamic model of a two-satellite electromagnetic formation is derived by utilizing the analytical mechanics theory. Considering the high nonlinearity and coupling in the dynamic model and the actuator saturation, a closed-loop robust suboptimal control strategy based on the indirect robust control scheme and the θ-D technique is proposed with robust stability and optimality. To ensure a further reduction of control input, the designed suboptimal controller is modified by applying the Tracking-Differentiator. The feasibility of the derived translational dynamics and proposed control strategy for the robust reconfiguration mission is validated through theoretical analysis and numerical simulations.
  • Dynamics Modeling and Simulation of Self-Collision of Tether-Net for Space
           Debris Removal
    • Abstract: Publication date: Available online 14 August 2019Source: Advances in Space ResearchAuthor(s): Jiyue Si, Zhaojun Pang, Zhonghua Du, Chun Cheng Tether-net is a new active removal technology for space debris, and its deployment and capture have attracted considerable attention. This study focuses on the dynamics and simulation of self-collision of tether-net. First, the mass-spring-damper method is used to model tether-net and a line–line self-collision detection algorithm is proposed according to the geometric characteristics of tether-net. Thereafter, combined with the nonlinear collision model, the self-collision process of tether-net is studied. Two simulations of the close-up of a net with or without a target are executed to show the difference between considering and not considering the self-collision of tether-net. Results reveal that the capture process of tether-net with consideration for self-collision is different from the one without self-collision, especially after the corners of the net begin to contact each other.
  • Editorial
    • Abstract: Publication date: Available online 13 August 2019Source: Advances in Space ResearchAuthor(s): Pascal Willis
  • Estimating disk parameters of black hole X-ray binary MAXI J1543-564:
           effect of disk irradiation
    • Abstract: Publication date: Available online 12 August 2019Source: Advances in Space ResearchAuthor(s): Santanu Mondal We study the central mass accretion rate and its variation with time during the outburst of X-ray transients using disk irradiation effect once the outer boundary of the disk is defined by the binary parameters. We show that the decay of the light curve and its characteristics time are well linked to the disk aspect ratio (H/R) and the binary parameters. For that we parametrize viscosity (α) parameter with H/R, assuming that there is a vertical height dependence on the energy dissipated in the disk. We derive the central accretion rate to check the sensitivity on H/R. Mass accretion rate changes notably with disk height, orbital period (P) and with binary mass function (q). For the consistency check, we apply the solution to a low mass X-ray binary (LMXRB) 4U 1543-47, whose binary parameters are dynamically measured. Finally, we estimate the unknown binary parameters of MAXI J1543-564. Using this solution for the first time we propose some predictability on P for the unknown system. The estimated value of P varies in a range from ∼10.5-15.5hr, when the companion mass is ∼0.66M⊙. Our estimated decay time scale is ∼40d with α∼0.18.
  • Study of the relative geoeffectiveness of high-speed solar wind streams of
           different speed and different durations
    • Abstract: Publication date: Available online 9 August 2019Source: Advances in Space ResearchAuthor(s): F. Mustajab, Badruddin, H. Asiri We consider high speed streams (HSS) identified from 16 years (1996-2011) of continuous solar wind plasma and field data. We compare the geomagnetic response of the HSS of different speed and different durations based on statistical distribution, the superposed epoch analysis as well as the regression analysis. We analyse the geomagnetic responses of the HSS of different speed and durations together with the solar wind plasma and field data. The observed differences in the amplitudes, time profiles and recovery characteristics of geomagnetic disturbances during the passage of the HSS of different speed and durations are compared with the differences in the simultaneous solar wind plasma/field behaviour. Implications of these results on the solar wind-magnetosphere coupling are discussed.
  • Smart-RTK: Multi-GNSS Kinematic Positioning Approach on Android Smart
    • Abstract: Publication date: Available online 7 August 2019Source: Advances in Space ResearchAuthor(s): Kaishi Zhang, Wenhai Jiao, Liang Wang, Zishen Li, Jianwen Li, Kai Zhou Global Navigation Satellite System (GNSS), once dedicated to military and geodetic applications, is entering civilian life with the development of low-cost internal multi-GNSS chips in mass-market smart devices. The recently enabled Application Programming Interface (API) to GNSS raw measurement in Android Nougat operating system, make it possible to implement precise positioning technology on Android smart devices, such as Real-Time Kinematic Positioning (RTK) and Precise Point Positioning (PPP). An optimized kinematic positioning approach on Android smart devices with Doppler-Smoothed-Code (DSC) filter and Constant Acceleration (CA) model is assessed in this paper. In this optimized approach, DSC filter is used to reduce the code measurement noise, which is extremely high on smart devices and CA model is used to accurately predict the kinematic state of smart devices. The optimized approach is named Smart-RTK for its applicability to smart devices, respectively. The performance of the Smart-RTK approach is validated by two Google/HTC Nexus 9 tablets separately under stationary, walking, and vehicular condition. The numerical experiments show the significant improvement on positioning accuracy and continuity. The positioning Root Mean Square Error (RMSE) in horizontal component reaches about 0.3 ∼ 0.6 m in stationary condition and 0.4 ∼ 0.7 m in walking condition, improved by about 85% compared with that of chipset original solutions. In the subsequent vehicular experiment, the horizontal positioning RMSE is about 0.85 m, 50% better than that of chipset solutions.
  • Invariance of conveying capacity for drilling into lunar soil simulant
    • Abstract: Publication date: Available online 7 August 2019Source: Advances in Space ResearchAuthor(s): Tao Chen, Zhen Zhao, Stephen R. Schwartz, Caishan Liu, Qi Wang In this paper, we study the conveying dynamics in the helical groove of an auger drilling into lunar simulant. We demonstrate that the stress-coupling effect of the conveyed granules by the groove of a drill auger plays a significant role on the dynamics of conveyance. For this, a discrete element method (DEM) is adopted first to uncover the motion and the stress characteristics of conveyed granules in a working auger. Then, a simplified dynamic model following the stress characteristics of DEM is established. The simplified model can not only reflect the results by the discrete element method, but can also explain well the proportional relationship between the maximum conveying rate and the rotating speed of the auger in the experiment (Zhao et al., 2019).
  • Abnormal behaviour of sporadic E-layer during the total solar eclipse of
           22 July 2009 near the crest of EIA over India
    • Abstract: Publication date: Available online 6 August 2019Source: Advances in Space ResearchAuthor(s): Prabhakar Tiwari, Navin Parihar, Adarsh Dube, Rajesh Singh, S. Sripathi In this study we present the behaviour of sporadic E - layer during a total solar eclipse (TSE) which occurred during the dawn/sunrise hours over a site located in the path of totality. A Canadian Advanced Digital Ionosonde (CADI) was operated at Allahabad (25.4° N, 81.9° E), a low latitude station located near the crest of equatorial ionization anomaly (EIA) in the Indian subcontinent to study the ionospheric effects of 22 July 2009 TSE. Corresponding to the eclipse period, a gradual increase of ftEs (top frequency of Es layer) in the 4 – 5 MHz range was seen on the control days. On 22 July (the TSE day), correlated changes in ftEs coinciding with the TSE progression was noted – (i) sharp decrease near first and second contact of TSE, (ii) an increase after first and second contact, and (iii) wavelike fluctuations in ftEs variation during eclipse hours and beyond. Much higher ftEs values were noted during the TSE hours in comparison to that seen on usual days. Strong blanketing Es layer developed during the TSE hours and persisted for slightly longer duration than its usual occurrence time. Near the TSE totality, slight lowering of the base height of Es layer was also noted.
  • A solar electron event model in near-Earth space
    • Abstract: Publication date: Available online 5 August 2019Source: Advances in Space ResearchAuthor(s): Jian-zhao Wang, Ying Wang, Shu-wu Dai, Chen Wang, Ji-nan Ma, Xiao-yu Jia, Yan-cun Li, Dai Tian, Jia-wen Qiu A new solar electron event model is developed based on Virtual Timeline Method (VTM). We study events individually by analyzing the 17-year data of 3DP instrument on WIND spacecraft. This model is established in different solar cycle phases and is based on statistics of duration, fluence, and waiting time of solar electron events. The fluences follow a log-normal distribution and logarithmic durations fit well with logarithmic fluences linearly. We prove that waiting times of events significantly deviates from the Poisson process by investigating the stationary and event independence property of Poisson distribution. After a comparison study on waiting times, we choose the Lévy distribution in solar minimum and maximum years. During solar minimum, the event frequency is much lower than that of solar maximum, but the event magnitude is independent of solar cycle period. Large events also happen in solar minimum years. In different solar cycle phases, this model can output a spectrum with confidence level and mission duration by generating many series of virtual timelines composed of many pseudo-events based on Monte Carlo method. On the other hand, spectra in solar minimum years are softer than that in solar maximum years. The fluences in solar maximum years are about one order of magnitude higher that in solar minimum years in a given mission period. We also compare this model with Interplanetary Electron Model (IEM) quantitatively and prove that this model is advanced.
  • The capability analysis of the bistatic radar system based on Tianlai
           radio array for space debris detection
    • Abstract: Publication date: Available online 5 August 2019Source: Advances in Space ResearchAuthor(s): Jiawei Li, Pengqi Gao, Ming Shen, You Zhao The bistatic radar system has been one of the effective methods to detect the space debris in low earth orbit (LEO). Tianlai radio array with cylindrical-parabolic antennas is designed for dark energy detection, which has large field of view and high sensitivity, offering a fan-beam during the observation. We propose a bistatic radar system, which consists of Tianlai radio array and an incoherent scattering radar (ISR) assumed as a transmitter in the Qujing city of China, to detect space debris. In this paper, we calculate and analyze the detection capabilities of this system. The results show the bistatic radar system has the potential to detect small space debris of less than 10 cm in LEO. We provide a space debris detection method to obtain the position of the cross-beam satisfying the observation requirement with the TLE data of the space debris. The method can solve the problem of space synchronization between the radio array and ISR. We used the long-short baseline method of the radio array to locate the space target. The relationship among positioning error, the azimuth and the elevation angle are also discussed.
  • Spectral analysis on the solar parameters and Empirical orthogonal
           functions of foF2 data obtained by Singular Value Decomposition
    • Abstract: Publication date: Available online 5 August 2019Source: Advances in Space ResearchAuthor(s): Junmi Gogoi, Kalyan Bhuyan The geomagnetic storm is an important weather issue in the earth’s ionosphere-magnetosphere system. Many linear and nonlinear systems are involved in this earth-space environment. In order to understand the nonlinearly evolving dynamical system of magnetosphere and ionosphere, Time series analysis of foF2 data, Disturbance Storm Index Dst, Geomagnetic activity Index Ap and some other parameters during various solar cycles has been carried out in this work. The hourly data of critical frequency of F2 layer (foF2) for three ionosonde stations [Townsville (TV51R) 19.7˚S, 146.9˚E; Canberra (CB53N) 35.3˚S, 149.1˚E; Juliusruh (JR055) 54.6˚N, 13.4˚E] have been noted for 4 solar cycles viz., Solar Cycle 20, 21, 22 and 23. Hourly time series analysis has been performed to achieve some functional approaches such as statistical, analytical and spectral approach etc. to examine for the presence of periodicities in the data. Time Series is a sequential set of data which can be measured over time, and since the data being used for this work had been recorded as a function of time under various conditions, the appearance of missing observations in time series data is a very common issue. Different series may require different approaches to estimate these missing values. As such, to vanquish the problem of missing data we have attempted to estimate the missing value of foF2 data for various stations using the technique of Singular Value Decomposition (SVD). Another important method, Lomb Scargle Periodogram (LSP) has been performed on the Empirical Orthogonal Functions (EOFs) u1 and u2 (that has been obtained by SVD) along with the solar parameters such as solar flux f10.7, sun spot number (SSN) etc. and geomagnetic indices such as Dst index, Kp index & Ap index etc. for the four solar cycles to find the correlation, if any. All the plots after performing LSP has been found out 99% confidence level to see how much significant the generated data with respect to the parameters is. The periodicity obtained after performing LSP are divided into three terms namely:- (a) short-term periodicity, in which 27 days periodicity is found to be prominent, (b) mid-term periodicity, in which 1.3 year periodicity is found to be very common and (c) long-term periodicity, in which 11 years periodicity is very regular in almost among all the parameters and in the EOFs.
  • Geocentric Baltic Sea level changes along the southern coastline
    • Abstract: Publication date: Available online 5 August 2019Source: Advances in Space ResearchAuthor(s): Adam Łyszkowicz, Anna Bernatowicz Sea level is a unique indicator in climate impact studies on any changes on the surface of the Earth. Traditionally, tide gauges allow observation of relative (relative to land) sea level changes at specific locations with a high resolution in time. Common method of sea level determination in XXI century is the combination of tide gauge observations with satellite observation data. So determined sea level changes are absolute changes and they are referred to the beginning of the ITRF system.Geocentric changes in the Baltic Sea level are monitored, inter alia, by the SONEL network. This network system does not include the southern coast of the Baltic Sea. The aim of this work is to fill this gap and to compute geocentric changes in the Baltic Sea at the stations: Hel, Władysławowo, Łeba, Ustka, Kołobrzeg, Świnoujście.The tide gauge data needed for the analysis were made available by the Institute of Meteorology and Water Management and the GNSS data was taken from web page Nevada Geodetic Laboratory. The analysis of the time series of tide gauge and GNSS observations was carried out using the TSAnalyzer software. We assumed that GNSS and tide gauge series have a seasonal signal (annual plus semi-annual) and a trend. First the outliers and were removed from observation, then the jumps were viewing. The trend, annual and semi-annual terms were calculated for GNSS and tide gauge series.The results of the work are calculated geocentric changes in the Baltic Sea level along southern coast and they are at a level of 0.3 mm/year except Ustka where it reach value 4.68 mm/year.
  • Designing Observation Scheme in X-ray Pulsar-Based Navigation with
           Probability Ellipsoid
    • Abstract: Publication date: Available online 5 August 2019Source: Advances in Space ResearchAuthor(s): Haoye Lin, Bo Xu, Jingxi Liu The accuracy in pulsar-based navigation system can be improved with a well-designed observation scheme. In this paper, based on the idea that minimises the size of position probability ellipsoid at each updating time, four strategies are put forward for determining observation order. As the calculation of posterior probability ellipsoid only requires a priori orbit information, the observation scheme can be designed during preliminary mission analysis. These strategies can be employed in both situations with single detector and multiple detectors. Numerical simulations show that the proposed observation strategies achieve good performance.
  • Small Satellites for Space Science
    • Abstract: Publication date: Available online 2 August 2019Source: Advances in Space ResearchAuthor(s): Robyn M. Millan, Rudolf von Steiger, Meir Ariel, Sergey Bartalev, Maurice Borgeaud, Stefano Campagnola, Julie C. Castillo-Rogez, René Fléron, Volker Gass, Anna Gregorio, David M. Klumpar, Bhavya Lal, Malcolm Macdonald, Jong Uk Park, V. Sambasiva Rao, Klaus Schilling, Graeme Stephens, Alan M. Title, Ji Wu This is a COSPAR roadmap to advance the frontiers of science through innovation and international collaboration using small satellites. The world of small satellites is evolving quickly and an opportunity exists to leverage these developments to make scientific progress. In particular, the increasing availability of low-cost launch and commercially available hardware provides an opportunity to reduce the overall cost of science missions. This in turn should increase flight rates and encourage scientists to propose more innovative concepts, leading to scientific breakthroughs. Moreover, new computer technologies and methods are changing the way data are acquired, managed, and processed. The large data sets enabled by small satellites will require a new paradigm for scientific data analysis. In this roadmap we provide several examples of long-term scientific visions that could be enabled by the small satellite revolution. For the purpose of this report, the term “small satellite” is somewhat arbitrarily defined as a spacecraft with an upper mass limit in the range of a few hundred kilograms. The mass limit is less important than the processes used to build and launch these satellites. The goal of this roadmap is to encourage the space science community to leverage developments in the small satellite industry in order to increase flight rates, and change the way small science satellites are built and managed. Five recommendations are made; one each to the science community, to space industry, to space agencies, to policy makers, and finally, to COSPAR.
  • Data-Driven Modelling of the Van Allen Belts: The 5DRBM Model for Trapped
    • Abstract: Publication date: Available online 1 August 2019Source: Advances in Space ResearchAuthor(s): Lionel Métrailler, Guillaume Bélanger, Peter Kretschmar, Erik Kuulkers, Ricardo Pérez Martínez, Jan-Uwe Ness, Pedro Rodriguez, Mauro Casale, Jorge Fauste, Timothy Finn, Celia Sanchez, Thomas Godard, Richard Southworth The magnetosphere sustained by the rotation of the Earth’s liquid iron core traps charged particles, mostly electrons and protons, into structures referred to as the Van Allen belts. These radiation belts, in which the density of charged energetic particles can be very destructive for sensitive instrumentation, have to be crossed on every orbit of satellites traveling in elliptical orbits around the Earth, as is the case for ESA’s INTEGRAL and XMM-Newton missions. This paper presents the first working version of the 5DRBM-e model, a global, data-driven model of the radiation belts for trapped electrons. The model is based on in-situ measurements of electrons by the radiation monitors on board the INTEGRAL and XMM-Newton satellites along their long elliptical orbits for respectively 16 and 19 years of operations. This model, in its present form, features the integral flux for trapped electrons within energies ranging from 0.7 to 1.75 MeV. Cross-validation of the 5DRBM-e with the well-known AE8min/max and AE9mean models for a low eccentricity GPS orbit shows excellent agreement, and demonstrates that the new model can be used to provide reliable predictions along widely different orbits around Earth for the purpose of designing, planning, and operating satellites with more accurate instrument safety margins. Future work will include extending the model based on electrons of different energies and proton radiation measurement data.
  • On-orbit Performance of the Top and Bottom Counting Detectors for the
           ISS-CREAM Experiment on the International Space Station
    • Abstract: Publication date: Available online 30 July 2019Source: Advances in Space ResearchAuthor(s): S.C. Kang, Y. Amare, T. Anderson, D. Angelaszek, N. Anthony, K. Cheryian, G.H. Choi, M. Copley, S. Coutu, L. Derome, L. Eraud, L. Hagenau, J.H. Han, H.G. Huh, Y.S. Hwang, H.J. Hyun, S. Im, H.B. Jeon, J.A. Jeon, S. Jeong The Cosmic Ray Energetics And Mass (CREAM) instrument on the International Space Station (ISS) is an experiment to study origin, propagation, acceleration and elemental composition of cosmic rays. The Top Counting Detector (TCD) and Bottom Counting Detector (BCD) are parts of the detector suite of the ISS-CREAM experiment and are designed to separate electrons and protons for studying electron and gamma-ray physics. In addition, the TCD/BCD provide a redundant trigger to that of the calorimeter and a low energy trigger to the ISS-CREAM instrument. After launching, the TCD/BCD trigger was found to be working well. Also, the TCD/BCD have been stable and their hit positions were confirmed to be well matched with other detectors on board. We present the performance and status of the TCD/BCD in flight.
  • The Atmospheric Coupling and Dynamics Across the Mesopause (ACaDAMe)
    • Abstract: Publication date: Available online 29 July 2019Source: Advances in Space ResearchAuthor(s): D. Janches, A.W. Yu, M.A. Krainak, C. Gardner, B. Kaifler, S. Etemad, D.C. Fritts, S.D. Eckermann, R.L. Collins, E.C.M. Dawkins, R.S. Lieberman, D.R. Marsh, G. Liu, W. Jarvis The Atmospheric Coupling and Dynamics Across the Mesopause (ACaDAMe) is a mission designed to uniquely address critical questions involving multi-scale wave dynamics at key space weather (SWx) “gateway altitudes” of the mesosphere and lower thermosphere (MLT) at ∼70–150 km. ACaDAMe observes with a nadir-pointing resonant lidar that utilizes the fluorescence of atomic Na present in the MLT. By tuning a laser to the Na absorption wavelength (589 nm), ACaDAMe would perform very high resolution measurements of temperature and Na densities across the mesopause during both day and night. In this manner, Na is used as tracer for observing and characterizing MLT waves generated by tropospheric weather that represent the dominant terrestrial source of energy and momentum affecting space weather and transport of mesospheric species.
  • A New Hierarchical Method for Automatic Road Centerline Extraction in
           Urban Areas using LiDAR Data
    • Abstract: Publication date: Available online 29 July 2019Source: Advances in Space ResearchAuthor(s): Sayyed Abdullah Kianezhad Tejenaki, Hamid Ebadi, Ali Mohammadzadeh Road detection and Road extraction are important and challenging issues in the fields of photogrammetry and remote sensing. Researchers have conducted wide research in this regard based on multispectral images and achieved relatively useful results. Image-data driven methods have some shortcomings such as shadows, eliminating small and long vehicles, geometric distortions, and occlusions. In recent years, in order to overcome the above limitations and complexities, several attempts have been done based on LiDAR data. The present paper proposes an automatic hierarchical road detection and extraction method. The main goal of this research is to increase the level of continuity of the road detection and extraction processes. This method includes the preprocessing of intensity data using a local minima filter, applying the Mean Shift segmentation to the refined intensity data, and finally integrating it with various nDSM-based Products. The proposed method involves not only considering both small and long vehicles as road features but also neglecting some parts of large parking lots based on the nearby neighborhood of parked vehicles as much as possible as non-road features. The next step was the process of road centerline extraction by adopting a Voronoi-diagram based approach and then removing dangle lines in several iterations. The proposed method was applied to the Vaihingen and Toronto datasets (ISPRS). The completeness of the two datasets is 95.85% and 88%, and the correctness of these datasets are 83.68% and 72.2%, respectively. The results were indicative of the great potential of the proposed method for effective road centerline extraction in urban areas.
  • Aerosol and cloud radiative forcing over various hot spot regions in India
    • Abstract: Publication date: Available online 26 July 2019Source: Advances in Space ResearchAuthor(s): C. Sivan, M.G. Manoj Twelve years of NASA CERES (Clouds and Earth’s Radiant Energy System) data have been used to examine the spatio-temporal variability of aerosol– and cloud– induced shortwave radiative forcing over selected hot spot regions in India. Four regions (northern semiarid - R1; monsoon trough - R2; densely populated urban - R3; and southern peninsula - R4) are selected with different surface characteristics and notable difference in meteorological and geographical features. The analysis shows that three out of the four regions (viz. R1, R2, and R3) experience high aerosol loading and forcing in the monsoon season followed by moderate forcing in pre-monsoon season. While all the seasons except the post-monsoon period show a positive linear relation between cloud optical depth and aerosol optical depth for all the regions, the post-monsoon season shows a negative relation. However, the relation between aerosol forcing and cloud forcing shows adequate non-linearity owing to the numerous factors that control cloud radiative effect. The estimated aerosol induced heating rate shows exponential decrease with height, but with high variability during each season. Irrespective of any region, the maximum heating rate is observed in the pre-monsoon season (2.86±0.78, 2.49±0.78, 1.89±0.57, and 0.88±0.28 K/day for R1, R2, R3, and R4, respectively). Plausible reasons for the variation in the above parameters are discussed. The results suggest that increased anthropogenic activities affect the thermodynamics and hence the dynamics through retention and exchange of heat, and it could affect the precipitation pattern adversely.
  • Model Predictive Tether-deployment Control for Precise Landing of Tethered
           Reentry Body
    • Abstract: Publication date: Available online 25 July 2019Source: Advances in Space ResearchAuthor(s): Hirohisa Kojima, Pavel M. Trivailo This paper proposes a model predictive control method for tether deployment for the precise landing of a tethered reentry body. A set of state variables for a tethered reentry system, in which the reentry body precisely lands at the target point, is numerically obtained and expressed in the form of an approximation function. The tether state is controlled by taking into consideration its deviation from the function. The effectiveness of the proposed controller for the precise landing of the reentry body is validated through numerical simulations.
  • Space Debris Observation Performance Research of CSTAR at Kunlun Station
           in Antarctica
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): Gongqiang Li, Hai jiang, Haowen Cheng, Jing Liu, Chenwei Yang, Peng Jiang Increasing space debris has seriously threatened the safety of spacecraft of various countries. The polar regions are the most densely distributed regions of Low-Earth orbit (LEO) space debris, and are ideal sites for observing LEO space debris. Through the real observation data and detection capabilities simulation, the advantages of China's Kunlun Station in Antarctica in observing LEO space debris are analyzed. Firstly, the real observation data of Chinese Small Telescope Array (CSTAR) are analyzed and compared with the space objects cataloging database (mean, which confirms the high performance and superiority of Kunlun Station in LEO space debris observation. Secondly, the space debris observation performance of CSTAR is simulated and compared with its historical observation data in the same period, to confirm the reliability of the simulation model. Finally, based on the real observation data and simulation results, some hypothesis simulations and prospects for future space debris observation facilities at Kunlun Station are made. The simulation results can provide support for future observations at Kunlun Station in Antarctica.
  • Mass composition of cosmic rays above 0.1 EeV by the Yakutsk array data
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): S. Knurenko, I. Petrov The paper presents the results of the longitudinal development of extensive air showers (Xmax) of ultra-high energies and mass composition of cosmic rays. The measurements of Xmax are based on data from observations of the Cherenkov radiation at the Yakutsk array for the period 1974-2014. The cascade curves of individual showers and the depth of maximum Xmax were reconstructed over the energy range 1016-5.7·1019 eV. It is shown that the displacement rate of the parameter dXmax / dE in the atmosphere is nonlinear and depends on the energy. Such a feature indicates a change in mass composition, which is confirmed by fluctuations of Xmax in this energy region. The composition of cosmic rays was determined by interpolation using the QGSJetII-04 model.
  • Behavior of the ionospheric F region prior to geomagnetic storms
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): A.D. Danilov, A.V. Konstantinova The problem of occurrence of disturbances of the ionospheric F2-layer parameters prior to the beginning of geomagnetic storms is discussed. It is shown that disturbances (substantial deviations from quiet conditions) of both the critical frequency foF2 and the total electron content (TEC) in an ionospheric column are found in many studies a few hours and sometimes two–three days before the SC (sudden storm commencement) moment. The amplitudes of the aforementioned disturbances are on the average 30–60%, however, in some cases they could exceed 100%. Deviations from the quiet conditions of both signs are possible, however positive pre-storm disturbances of foF2 and TEC are found more often. Some statistical results of the analysis of the pre-storm effects in foF2 according to the data of the Slough (Chilton) station are presented.
  • μ m+emission+as+observed+by+TIMED/SABER+over+Asian+sector&rft.title=Advances+in+Space+Research&rft.issn=0273-1177&">Radiative cooling due to NO at 5.3 μ m emission as observed by
           TIMED/SABER over Asian sector
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): Gaurav Bharti, M.V. Sunil Krishna, Vir Singh The effect of geomagnetic storms on the peak emission of NO Volume Emission Rate (NO VER) at 5.3 μm, in mesosphere and lower thermosphere (MLT) region, is studied over the Asian sector during 26-29 September 2011 (storm 1) and 18-21 February 2014 (storm 2). The data for peak emission of NO VER is obtained from SABER instrument onboard the NASA’s TIMED satellite. The SABER retrieved data along with the neutral densities obtained from NRLMSISE-00 model have been used to study the latitudinal and longitudinal variation of peak NO VER during the storm period. The variations induced in the peak emission of NO VER is understood with the help of fluctuations in neutral species and the resulting changes in chemistry. It has been found that the peak emission of NO VER is strongly influenced by the storm conditions. The peak emission of NO VER at 5.3 μm is found to be maximum at higher latitudes during the storms. However, the magnitude of peak NO VER gradually decreases towards the equator during the storms. The modeled atomic oxygen number density shows depletion at the higher latitudes corresponding to peak altitude of NO VER. There is a negative correlation between the peak emission of NO VER and Dst index during the main phase of the storm. The peak emission of NO VER and modeled atomic oxygen number density shows the positive correlation at the equator region, while negative correlation at the higher latitudes. At higher latitudes modeled atomic oxygen number density shows positive correlation with Dst index, while negative correlation at the equator. The correlation factors obtained between various parameters related to the storm time radiative cooling strongly support the existing understanding of the variation of NO VER during extreme space weather events.
  • Composite analysis of North Atlantic extra-tropical cyclone waves from
           satellite altimetry observations
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): S. Ponce de León, J.H. Bettencourt The north Atlantic Ocean is regularly traversed by extratropical cyclones and winter low pressure systems originated in the Western part of the basin that can potentially generate dangerous extreme sea states. In this paper we study the significant wave height distribution of extratropical cyclones using merged satellite altimetry data to produce composite maps of this sea state variable. Although there are large variations among individual cyclones, the compositing method allows obtaining general features. We find that the higher waves are in the south-eastern quadrant of the cyclone, due to the extended fetch mechanism. The highest wave heights are found during the 48h period when the cyclone’s strength is maximum. The strongest cyclones have higher waves over most of the eastern half, due to their northward propagation tendency.
  • New techniques for retrieving the [O(3P)], [O3] and [CO2] altitude
           profiles from dayglow oxygen emissions: uncertainty analysis by the Monte
           Carlo method
    • Abstract: Publication date: Available online 24 July 2019Source: Advances in Space ResearchAuthor(s): Valentine Yankovsky, Ekaterina Vorobeva, Rada Manuilova This study presents methods for retrieving the altitude profiles of atomic oxygen, [O(3P)], ozone, [O3], and carbon dioxide, [CO2], concentrations in the daytime mesosphere and lower thermosphere (MLT) in the framework of the YM2011 model of the electronic-vibrational oxygen kinetics. The emissions of singlet oxygen molecules O2(b1Σ+g, v ≤ 2), O2(a1Δg, v = 0) and the O(1D) atom are used as proxy of the [O(3P)], [O3] and [CO2]. For all the proposed techniques, we compare the uncertainty values of the retrieved [O(3P)], [O3] and [CO2], obtained by the Monte Carlo method, with estimations obtained by the sensitivity analysis method in the earlier works. For all the above mentioned methods for retrieving the [O(3P)], [O3] and [CO2] profiles, we obtained analytical expressions that include the concentrations of excited substances considered as proxies. In addition, the optimal altitude ranges for using these remote sensing methods were determined based on the results of numerical experiments by the Monte Carlo method.
  • Automated Crater Detection Algorithms from a Machine Learning Perspective
           in the Convolutional Neural Network Era
    • Abstract: Publication date: Available online 22 July 2019Source: Advances in Space ResearchAuthor(s): D.M. DeLatte, S.T. Crites, N. Guttenberg, T. Yairi Convolutional Neural Networks (CNN) offer promising opportunities to automatically glean scientifically relevant information directly from annotated images, without needing to handcraft features for detection. Crater counting started with hand counting hundreds, thousands, or even millions of craters in order to determine the age of geological units on planetary bodies of the solar system. Automated crater detection algorithms have attempted to speed up this process. Previous research has employed computer vision techniques with handcrafted features such as light and shadow patterns, circle finding, or edge detection. This research continues, but now some researchers use techniques like convolutional neural networks that enable the algorithm to develop its own features. As the field of machine learning undergoes exponential growth in terms of paper count and research methods, the crater counting application can benefit from the new research, especially when conducting joint interdisciplinary projects. Despite these advancements, the crater counting community has not yet adopted standard methods for automating the process despite decades of research. This survey enumerates challenges for both planetary geologists and machine learning researchers, looks at the recent automatic crater detection advancements using machine learning techniques (primarily in methods using CNNs), and makes recommendations for the path toward greater automation.
  • Insights from Multi-Wavelength Observations During High and Low States of
           Non-Magnetic CVs
    • Abstract: Publication date: Available online 22 July 2019Source: Advances in Space ResearchAuthor(s): Paula Szkody Close binaries containing a white dwarf accreting from a disk that receives material from a late stellar companion show an interesting variety of behaviors that depend on their accretion rates and the changes in this rate. The highest accretion rates are evident during the bright states of novalikes, as well as the superoutbursts of the shortest period dwarf novae followed by normal outbursts and the Z Cam systems. While the normal outbursts and superoutbursts of dwarf novae can be understood from the standpoint of disk and tidal instabilities, the changes in rates in novalikes when they enter low brightness states and the cause of extremely high rates for the systems with orbital periods between 3-4 hrs remain elusive. This paper highlights some recent insights and continuing problems found from X-ray, UV and optical observations of these high and low states, as well as the prospects for increased understanding from the anticipated future ground and space missions.
  • Around the world with Space VLBI: a sense of many places
    • Abstract: Publication date: Available online 22 July 2019Source: Advances in Space ResearchAuthor(s): David L. Jauncey
  • Exploring the outer emission corona spectroscopically by using Visible
           Emission Line Coronagraph (VELC) on board ADITYA–L1 mission
    • Abstract: Publication date: Available online 17 July 2019Source: Advances in Space ResearchAuthor(s): Jagdev Singh, B Raghavendra Prasad, Suresh Venkata, Amit Kumar It is very important to make the spectrographic observations of the outer emission corona in number of emission lines simultaneously in view of the results of the observations made in [Fe x] 6374 Å, [Fe xi] 7892 Å, [Fe xiv] 5303 Åand [Fe xiii] 10747 Åcoronal emission lines with the 25 cm coronagraph at Norikura Observatory in Japan. At ground based observatories, availability of number of hours of clear sky for coronagraphic observations is limited due to aerosols scattering and scattering from the internal coronagraph reflections . A space based coronagraph Visible Emission Line Coronagraph (VELC) on board ADITYA–L1 has been planned to perform spectroscopy in 3 out of the 4 emission lines mentioned above. Here, we discuss the various requirements for the parameters of the payload, given the specifications of the satellite, to observe the outer emission corona reliably with good Signal to Noise Ratio (SNR), realize the projected scientific goals and make the mission a great success.
  • Comparison-space selection to achieve efficient tracklet-to-object
    • Abstract: Publication date: Available online 17 July 2019Source: Advances in Space ResearchAuthor(s): J.A. Siminski, T. Flohrer A major challenge when maintaining a space object catalog is the proper association of new measurements to already cataloged objects. Optical observations are typically associated by comparing the modeled observation to the measured one. The modeled observation is generated from cataloged object states by propagating them to the epoch of observation and transforming them from state space, e.g. orbital elements, to the observation space, e.g. right ascension and declination angles. In addition to propagating the states, their propagated uncertainty distribution is transformed to observation space as well. Statistical distance metrics, such as the Mahalanobis distance, are then evaluated to test whether the observation originated from the cataloged object or not. These distance measures often assume that the uncertainty can be represented with a normal distribution. Assuming that the catalog state uncertainty is properly represented by a normal distribution, it can still loose this property during the propagation in time and the transformation to observation space. The uncertainty of the catalog state is typically much larger than the one from new measurements (only a few arc seconds for optical telescopes) and is therefore more affected by transformation distortions. It is therefore beneficial to perform the comparison in a space advantageous for the state representation. This study will present a projection-based transformation of tracklet information into a favorable frame around the cataloged object state. The effect of the comparison-space selection on cataloguing performance is assessed, i.e. it is systematically tested if it is beneficial to directly compare angles and angular rates, or to compare in the newly proposed projected frame.
  • Noise estimation and probability of detection in non-resolved images:
           application to space object observation
    • Abstract: Publication date: Available online 16 July 2019Source: Advances in Space ResearchAuthor(s): Francois Sanson, Carolin Frueh Charged Couple Device (CCD) technology is widely used in various scientific measurement contexts. CCD equipped cameras have revolutionized astronomy and space-related optical telescope measurements in recent years. They are also used in electroscopic measurements, e.g., in fields such as geology, biology, and medicine. The signal-to-noise ratio and the probability of detection are crucial to design experiments observation setups properly and to employ further mathematical methods for data exploitation such as, e.g. multi-target tracking methods. Previous attempts to correctly characterize the signal-to-noise ratio for star observations are revisited in this work and adapted for the application of near-Earth object observations and high precision measurements, leading to a modified CCD equation. Our formulation proposes a novel distribution of the signal noise that accurately accounts for the truncation noise and the presence of ambiguous pixels. These improvements are employed to derive the probability of detection and the SNR with significant improvements compared to existing formulations when ambiguous pixels are present.
  • Real-time clock prediction of Multi-GNSS satellites and its application in
           precise point positioning
    • Abstract: Publication date: Available online 8 July 2019Source: Advances in Space ResearchAuthor(s): Peng Yaquan, Lou Yidong, Gong Xiaopeng, Wang Yintong, Dai Xiaolei With the development of Global Navigation Satellite System (GNSS), multi-GNSS is expected to greatly benefit precise point positioning (PPP), especially during the outage of real time service (RTS). In this paper, we focus on the performance of multi-GNSS satellite clock prediction and its application in real-time PPP. Based on the statistical analysis of multi-system satellite clock products, a model consisting of polynomial and periodic terms is employed for multi-system satellite clock prediction. To evaluate the method proposed, both post-processed and real-time satellite clock products are employed in simulated real-time processing mode. The results show that the accuracy of satellite clock prediction is related to atomic clock type and satellite type. For GPS satellites, the average standard deviations (STDs) of Cs atomic clocks will reach as high as 0.65 ns while the STD of Rb atomic clocks is only about 0.15 ns. As for BDS and Galileo, the average STD of 2-hour satellite clock prediction are 0.30 ns and 0.06 ns, respectively. In addition, it is validated that real-time PPP can still achieve positioning accuracy of one to three decimeters by using products of 2-hour satellite clock prediction. Moreover, compared to the results of GPS-only PPP, multi-system can greatly enhance the accuracy of real-time PPP from 12.5% to 18.5% in different situations.
  • Seasonal variation of plasma bubbles during solar cycle 23 - 24 over the
           Brazilian equatorial region
    • Abstract: Publication date: Available online 8 July 2019Source: Advances in Space ResearchAuthor(s): Ebenezer Agyei-Yeboah, Igo Paulino, Amauri Fragaso de Medeiros, Ricardo Arlen Buriti, Ana Roberta Paulino, Patrick Essien, Solomon Otoo Lomotey, Hisao Takashi, Cristiano Max Wrasse In this study, OI 630.0 nm nightglow image data obtained from an all-sky imaging station located at Sao Joao do Cariri (7.4°S, 36.5°W), have been used to study the occurrence of equatorial plasma bubbles (EPBs) over the Brazilian equatorial region. The observations, which took place from September 2000 to December 2010 (almost eleven years), covered a significant part of solar cycle 23 (descending phase of SC23) and the very beginning of solar cycle 24 (ascending phase of SC24). There were 1337 nights of observations with 666 nights with EPB events, which translates to an occurrence rate of ∼49.8 %. Of these nights, 1290 were considered quiet (Dst ≥ -50 nT) with ∼ 50 % plasma bubbles occurrence rate. The occurrence of EPBs was studied under three solar activity phases – high solar activity phase (HSA, September 2000 – March 2004), moderate solar activity phase (MSA or descending phase, March 2004 – October 2006) and low solar activity phase (LSA, October 2006 – December 2010). The low solar activity phase is part of the peculiar solar cycle 24, considered the weakest in over a century with most sunspotless days (2008 - 2009). The maximum occurrence of bubbles, equal to 54.2 %, was found during the HSA phase, with percentages characterizing MSA and LSA being respectively 52.4 % and 45.8 %. The analysis also showed clear seasonal variation in the EPB occurrence with maximum rates in summer, spring, autumn, and the minimum rates in winter for all solar activity phases. Overall, there was observed solar cycle variation in each season with maximum occurrence in HSA followed by MSA and then LSA except in autumn where higher occurrence rate was observed in LSA phase than in MSA phase.
  • Downshifted peak features of stimulated electromagnetic emissions during a
           two-pump wave heating experiment
    • Abstract: Publication date: Available online 4 July 2019Source: Advances in Space ResearchAuthor(s): Guanglin Ma, Lixin Guo, Qingliang Li, Jutao Yang, Libin Lv, Jing Chen, Tong Xu, Shuji Hao, Jian Wu Experimental results of the downshifted peak (DP) in stimulated electromagnetic emissions under two-pump wave ionospheric heating near the third electron gyroharmonic frequency are presented. The European Incoherent Scatter Scientific Association heating antenna array was divided into two parts, one of which worked at constant pump wave frequency f1 and the other part worked at varied pump wave frequency f2 which was not larger than f1. It was found that when the second pump wave was turned on at different frequency with f1, the f1 DP power declined by more than 10 dB with respect to the background noise level, while the downshifted maximum belonging to f1 was further enhanced. The time needed to reach a steady state for DP was shortened from approximately 10 s under cold background conditions belonging to f1, which was nearly consistent with growth time of small-scale artificially field-aligned irregularity (AFAI), to less than 1 s under the preconditioned heating belonging to f2 with pre-existing AFAI. According to the difference in DP temporal evolution under two experimental conditions, it could be deduced that AFAI plays an important role in the DP generation process. Similar to single-pump wave heating, the frequency offset of DP decreases as f2 increases toward the third electron gyroharmonic frequency. These experimental findings provide new insights into the theoretical study of ionospheric plasma nonlinearity.
  • Characterizing inter-frequency bias and signal quality for GLONASS
           satellites with triple-frequency transmissions
    • Abstract: Publication date: Available online 4 July 2019Source: Advances in Space ResearchAuthor(s): Lin Pan, Xiaohong Zhang, Fei Guo The GLONASS SVNs 702K (R09), 755 (R21) and 701K (R26) satellites currently provide G1, G2 and G3 signals. The difference between satellite clocks calculated by G1/G2 and G1/G3 ionospheric-free combinations, termed inter-frequency bias (IFB), is identified. The presence of IFB limits the application of G3 signal in precise positioning. The IFB is investigated using the datasets from 70 stations with a global distribution spanning 30 consecutive days. The epoch-wise phase-specific IFB (PIFB) estimates show periodic variations with a period of eight days and an average peak-to-peak amplitude of 0.107, 0.327 and 1.663 m for the R09, R21 and R26 satellites, respectively. The daily stable code-specific IFB (CIFB) estimates also show 8-day periodic signal. The day-to-day scattering of daily stable CIFB is 0.060–0.085 m. The estimation accuracy and prediction accuracy of PIFB are 0.025 and 0.019 m, respectively, while the corresponding statistics for the daily stable CIFB are 0.452 and 0.056 m, respectively. A modified estimation approach is developed to derive the time-varying epoch-wise CIFB. The epoch-wise CIFB and PIFB shows sub-daily periodic variations with the most notable periods of 5.625 and 11.250 h, respectively. The correction rate is 32% in terms of the prediction of the time-varying part of the epoch-wise CIFB. In addition, the signal quality is assessed from such aspects as carrier-to-noise density ratio, measurement noise and multipath errors.
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Heriot-Watt University
Edinburgh, EH14 4AS, UK
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