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Showing 1 - 200 of 3089 Journals sorted alphabetically
A Practical Logic of Cognitive Systems     Full-text available via subscription   (Followers: 7)
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 25, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 22, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 86, SJR: 1.109, h-index: 94)
Accounting Forum     Hybrid Journal   (Followers: 25, SJR: 0.612, h-index: 27)
Accounting, Organizations and Society     Hybrid Journal   (Followers: 30, SJR: 2.515, h-index: 90)
Achievements in the Life Sciences     Open Access   (Followers: 4)
Acta Anaesthesiologica Taiwanica     Open Access   (Followers: 5, SJR: 0.338, h-index: 19)
Acta Astronautica     Hybrid Journal   (Followers: 363, SJR: 0.726, h-index: 43)
Acta Automatica Sinica     Full-text available via subscription   (Followers: 3)
Acta Biomaterialia     Hybrid Journal   (Followers: 25, SJR: 2.02, h-index: 104)
Acta Colombiana de Cuidado Intensivo     Full-text available via subscription   (Followers: 1)
Acta de Investigación Psicológica     Open Access   (Followers: 2)
Acta Ecologica Sinica     Open Access   (Followers: 8, SJR: 0.172, h-index: 29)
Acta Haematologica Polonica     Free   (SJR: 0.123, h-index: 8)
Acta Histochemica     Hybrid Journal   (Followers: 3, SJR: 0.604, h-index: 38)
Acta Materialia     Hybrid Journal   (Followers: 229, SJR: 3.683, h-index: 202)
Acta Mathematica Scientia     Full-text available via subscription   (Followers: 5, SJR: 0.615, h-index: 21)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9, SJR: 0.442, h-index: 21)
Acta Oecologica     Hybrid Journal   (Followers: 10, SJR: 0.915, h-index: 53)
Acta Otorrinolaringologica (English Edition)     Full-text available via subscription   (Followers: 1)
Acta Otorrinolaringológica Española     Full-text available via subscription   (Followers: 3, SJR: 0.311, h-index: 16)
Acta Pharmaceutica Sinica B     Open Access   (Followers: 1)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 24, SJR: 1.365, h-index: 73)
Acta Sociológica     Open Access  
Acta Tropica     Hybrid Journal   (Followers: 6, SJR: 1.059, h-index: 77)
Acta Urológica Portuguesa     Open Access  
Actas Dermo-Sifiliograficas     Full-text available via subscription   (Followers: 4)
Actas Dermo-Sifiliográficas (English Edition)     Full-text available via subscription   (Followers: 3)
Actas Urológicas Españolas     Full-text available via subscription   (Followers: 4, SJR: 0.383, h-index: 19)
Actas Urológicas Españolas (English Edition)     Full-text available via subscription   (Followers: 2)
Actualites Pharmaceutiques     Full-text available via subscription   (Followers: 5, SJR: 0.141, h-index: 3)
Actualites Pharmaceutiques Hospitalieres     Full-text available via subscription   (Followers: 4, SJR: 0.112, h-index: 2)
Acupuncture and Related Therapies     Hybrid Journal   (Followers: 4)
Acute Pain     Full-text available via subscription   (Followers: 13)
Ad Hoc Networks     Hybrid Journal   (Followers: 11, SJR: 0.967, h-index: 57)
Addictive Behaviors     Hybrid Journal   (Followers: 15, SJR: 1.514, h-index: 92)
Addictive Behaviors Reports     Open Access   (Followers: 6)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Advanced Cement Based Materials     Full-text available via subscription   (Followers: 3)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 132, SJR: 5.2, h-index: 222)
Advanced Engineering Informatics     Hybrid Journal   (Followers: 11, SJR: 1.265, h-index: 53)
Advanced Powder Technology     Hybrid Journal   (Followers: 17, SJR: 0.739, h-index: 33)
Advances in Accounting     Hybrid Journal   (Followers: 9, SJR: 0.299, h-index: 15)
Advances in Agronomy     Full-text available via subscription   (Followers: 15, SJR: 2.071, h-index: 82)
Advances in Anesthesia     Full-text available via subscription   (Followers: 26, SJR: 0.169, h-index: 4)
Advances in Antiviral Drug Design     Full-text available via subscription   (Followers: 3)
Advances in Applied Mathematics     Full-text available via subscription   (Followers: 6, SJR: 1.054, h-index: 35)
Advances in Applied Mechanics     Full-text available via subscription   (Followers: 11, SJR: 0.801, h-index: 26)
Advances in Applied Microbiology     Full-text available via subscription   (Followers: 22, SJR: 1.286, h-index: 49)
Advances In Atomic, Molecular, and Optical Physics     Full-text available via subscription   (Followers: 16, SJR: 3.31, h-index: 42)
Advances in Biological Regulation     Hybrid Journal   (Followers: 4, SJR: 2.277, h-index: 43)
Advances in Botanical Research     Full-text available via subscription   (Followers: 3, SJR: 0.619, h-index: 48)
Advances in Cancer Research     Full-text available via subscription   (Followers: 25, SJR: 2.215, h-index: 78)
Advances in Carbohydrate Chemistry and Biochemistry     Full-text available via subscription   (Followers: 9, SJR: 0.9, h-index: 30)
Advances in Catalysis     Full-text available via subscription   (Followers: 5, SJR: 2.139, h-index: 42)
Advances in Cell Aging and Gerontology     Full-text available via subscription   (Followers: 4)
Advances in Cellular and Molecular Biology of Membranes and Organelles     Full-text available via subscription   (Followers: 12)
Advances in Chemical Engineering     Full-text available via subscription   (Followers: 27, SJR: 0.183, h-index: 23)
Advances in Child Development and Behavior     Full-text available via subscription   (Followers: 10, SJR: 0.665, h-index: 29)
Advances in Chronic Kidney Disease     Full-text available via subscription   (Followers: 9, SJR: 1.268, h-index: 45)
Advances in Clinical Chemistry     Full-text available via subscription   (Followers: 29, SJR: 0.938, h-index: 33)
Advances in Colloid and Interface Science     Full-text available via subscription   (Followers: 18, SJR: 2.314, h-index: 130)
Advances in Computers     Full-text available via subscription   (Followers: 16, SJR: 0.223, h-index: 22)
Advances in Dermatology     Full-text available via subscription   (Followers: 12)
Advances in Developmental Biology     Full-text available via subscription   (Followers: 11)
Advances in Digestive Medicine     Open Access   (Followers: 7)
Advances in DNA Sequence-Specific Agents     Full-text available via subscription   (Followers: 5)
Advances in Drug Research     Full-text available via subscription   (Followers: 22)
Advances in Ecological Research     Full-text available via subscription   (Followers: 45, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 26, SJR: 0.486, h-index: 10)
Advances in Experimental Biology     Full-text available via subscription   (Followers: 7)
Advances in Experimental Social Psychology     Full-text available via subscription   (Followers: 43, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Fluorine Science     Full-text available via subscription   (Followers: 8)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 51, SJR: 0.674, h-index: 38)
Advances in Fuel Cells     Full-text available via subscription   (Followers: 16)
Advances in Genetics     Full-text available via subscription   (Followers: 15, SJR: 2.558, h-index: 54)
Advances in Genome Biology     Full-text available via subscription   (Followers: 11)
Advances in Geophysics     Full-text available via subscription   (Followers: 6, SJR: 2.325, h-index: 20)
Advances in Heat Transfer     Full-text available via subscription   (Followers: 22, SJR: 0.906, h-index: 24)
Advances in Heterocyclic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 0.497, h-index: 31)
Advances in Human Factors/Ergonomics     Full-text available via subscription   (Followers: 26)
Advances in Imaging and Electron Physics     Full-text available via subscription   (Followers: 2, SJR: 0.396, h-index: 27)
Advances in Immunology     Full-text available via subscription   (Followers: 36, SJR: 4.152, h-index: 85)
Advances in Inorganic Chemistry     Full-text available via subscription   (Followers: 9, SJR: 1.132, h-index: 42)
Advances in Insect Physiology     Full-text available via subscription   (Followers: 3, SJR: 1.274, h-index: 27)
Advances in Integrative Medicine     Hybrid Journal   (Followers: 6)
Advances in Intl. Accounting     Full-text available via subscription   (Followers: 4)
Advances in Life Course Research     Hybrid Journal   (Followers: 8, SJR: 0.764, h-index: 15)
Advances in Lipobiology     Full-text available via subscription   (Followers: 2)
Advances in Magnetic and Optical Resonance     Full-text available via subscription   (Followers: 9)
Advances in Marine Biology     Full-text available via subscription   (Followers: 16, SJR: 1.645, h-index: 45)
Advances in Mathematics     Full-text available via subscription   (Followers: 10, SJR: 3.261, h-index: 65)
Advances in Medical Sciences     Hybrid Journal   (Followers: 6, SJR: 0.489, h-index: 25)
Advances in Medicinal Chemistry     Full-text available via subscription   (Followers: 5)
Advances in Microbial Physiology     Full-text available via subscription   (Followers: 4, SJR: 1.44, h-index: 51)
Advances in Molecular and Cell Biology     Full-text available via subscription   (Followers: 22)
Advances in Molecular and Cellular Endocrinology     Full-text available via subscription   (Followers: 10)
Advances in Molecular Toxicology     Full-text available via subscription   (Followers: 8, SJR: 0.324, h-index: 8)
Advances in Nanoporous Materials     Full-text available via subscription   (Followers: 4)
Advances in Oncobiology     Full-text available via subscription   (Followers: 3)
Advances in Organ Biology     Full-text available via subscription   (Followers: 2)
Advances in Organometallic Chemistry     Full-text available via subscription   (Followers: 15, SJR: 2.885, h-index: 45)
Advances in Parallel Computing     Full-text available via subscription   (Followers: 7, SJR: 0.148, h-index: 11)
Advances in Parasitology     Full-text available via subscription   (Followers: 7, SJR: 2.37, h-index: 73)
Advances in Pediatrics     Full-text available via subscription   (Followers: 24, SJR: 0.4, h-index: 28)
Advances in Pharmaceutical Sciences     Full-text available via subscription   (Followers: 13)
Advances in Pharmacology     Full-text available via subscription   (Followers: 15, SJR: 1.718, h-index: 58)
Advances in Physical Organic Chemistry     Full-text available via subscription   (Followers: 8, SJR: 0.384, h-index: 26)
Advances in Phytomedicine     Full-text available via subscription  
Advances in Planar Lipid Bilayers and Liposomes     Full-text available via subscription   (Followers: 3, SJR: 0.248, h-index: 11)
Advances in Plant Biochemistry and Molecular Biology     Full-text available via subscription   (Followers: 8)
Advances in Plant Pathology     Full-text available via subscription   (Followers: 5)
Advances in Porous Media     Full-text available via subscription   (Followers: 4)
Advances in Protein Chemistry     Full-text available via subscription   (Followers: 17)
Advances in Protein Chemistry and Structural Biology     Full-text available via subscription   (Followers: 20, SJR: 1.5, h-index: 62)
Advances in Psychology     Full-text available via subscription   (Followers: 62)
Advances in Quantum Chemistry     Full-text available via subscription   (Followers: 5, SJR: 0.478, h-index: 32)
Advances in Radiation Oncology     Open Access  
Advances in Small Animal Medicine and Surgery     Hybrid Journal   (Followers: 2, SJR: 0.1, h-index: 2)
Advances in Space Biology and Medicine     Full-text available via subscription   (Followers: 5)
Advances in Space Research     Full-text available via subscription   (Followers: 360, SJR: 0.606, h-index: 65)
Advances in Structural Biology     Full-text available via subscription   (Followers: 8)
Advances in Surgery     Full-text available via subscription   (Followers: 7, SJR: 0.823, h-index: 27)
Advances in the Study of Behavior     Full-text available via subscription   (Followers: 30, SJR: 1.321, h-index: 56)
Advances in Veterinary Medicine     Full-text available via subscription   (Followers: 16)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 44, SJR: 2.408, h-index: 94)
Aeolian Research     Hybrid Journal   (Followers: 5, SJR: 0.973, h-index: 22)
Aerospace Science and Technology     Hybrid Journal   (Followers: 331, SJR: 0.816, h-index: 49)
AEU - Intl. J. of Electronics and Communications     Hybrid Journal   (Followers: 8, SJR: 0.318, h-index: 36)
African J. of Emergency Medicine     Open Access   (Followers: 5, SJR: 0.344, h-index: 6)
Ageing Research Reviews     Hybrid Journal   (Followers: 8, SJR: 3.289, h-index: 78)
Aggression and Violent Behavior     Hybrid Journal   (Followers: 417, SJR: 1.385, h-index: 72)
Agri Gene     Hybrid Journal  
Agricultural and Forest Meteorology     Hybrid Journal   (Followers: 16, SJR: 2.18, h-index: 116)
Agricultural Systems     Hybrid Journal   (Followers: 30, SJR: 1.275, h-index: 74)
Agricultural Water Management     Hybrid Journal   (Followers: 40, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 2)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 55, SJR: 1.879, h-index: 120)
Ain Shams Engineering J.     Open Access   (Followers: 5, SJR: 0.434, h-index: 14)
Air Medical J.     Hybrid Journal   (Followers: 5, SJR: 0.234, h-index: 18)
AKCE Intl. J. of Graphs and Combinatorics     Open Access   (SJR: 0.285, h-index: 3)
Alcohol     Hybrid Journal   (Followers: 11, SJR: 0.922, h-index: 66)
Alcoholism and Drug Addiction     Open Access   (Followers: 8)
Alergologia Polska : Polish J. of Allergology     Full-text available via subscription   (Followers: 1)
Alexandria Engineering J.     Open Access   (Followers: 1, SJR: 0.436, h-index: 12)
Alexandria J. of Medicine     Open Access   (Followers: 1)
Algal Research     Partially Free   (Followers: 8, SJR: 2.05, h-index: 20)
Alkaloids: Chemical and Biological Perspectives     Full-text available via subscription   (Followers: 3)
Allergologia et Immunopathologia     Full-text available via subscription   (Followers: 1, SJR: 0.46, h-index: 29)
Allergology Intl.     Open Access   (Followers: 4, SJR: 0.776, h-index: 35)
Alpha Omegan     Full-text available via subscription   (SJR: 0.121, h-index: 9)
ALTER - European J. of Disability Research / Revue Européenne de Recherche sur le Handicap     Full-text available via subscription   (Followers: 9, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 46, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 4)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 4)
Ambulatory Pediatrics     Hybrid Journal   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 49, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 48, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 40, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 9, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 14, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 32, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 26, SJR: 1.259, h-index: 81)
American J. of Kidney Diseases     Hybrid Journal   (Followers: 32, SJR: 2.313, h-index: 172)
American J. of Medicine     Hybrid Journal   (Followers: 46, SJR: 2.023, h-index: 189)
American J. of Medicine Supplements     Full-text available via subscription   (Followers: 3)
American J. of Obstetrics and Gynecology     Hybrid Journal   (Followers: 199, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 59, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 6)
American J. of Orthodontics and Dentofacial Orthopedics     Full-text available via subscription   (Followers: 6, SJR: 1.249, h-index: 88)
American J. of Otolaryngology     Hybrid Journal   (Followers: 25, SJR: 0.59, h-index: 45)
American J. of Pathology     Hybrid Journal   (Followers: 27, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 25, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 35, SJR: 1.286, h-index: 125)
American J. of the Medical Sciences     Hybrid Journal   (Followers: 12, SJR: 0.653, h-index: 70)
Ampersand : An Intl. J. of General and Applied Linguistics     Open Access   (Followers: 6)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 58, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 12)
Anales de Cirugia Vascular     Full-text available via subscription  
Anales de Pediatría     Full-text available via subscription   (Followers: 2, SJR: 0.209, h-index: 27)
Anales de Pediatría (English Edition)     Full-text available via subscription  
Anales de Pediatría Continuada     Full-text available via subscription   (SJR: 0.104, h-index: 3)
Analytic Methods in Accident Research     Hybrid Journal   (Followers: 4, SJR: 2.577, h-index: 7)
Analytica Chimica Acta     Hybrid Journal   (Followers: 37, SJR: 1.548, h-index: 152)
Analytical Biochemistry     Hybrid Journal   (Followers: 167, SJR: 0.725, h-index: 154)
Analytical Chemistry Research     Open Access   (Followers: 8, SJR: 0.18, h-index: 2)
Analytical Spectroscopy Library     Full-text available via subscription   (Followers: 12)
Anesthésie & Réanimation     Full-text available via subscription   (Followers: 1)
Anesthesiology Clinics     Full-text available via subscription   (Followers: 22, SJR: 0.421, h-index: 40)
Angiología     Full-text available via subscription   (SJR: 0.124, h-index: 9)
Angiologia e Cirurgia Vascular     Open Access  

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Journal Cover Advances in Space Research
  [SJR: 0.606]   [H-I: 65]   [360 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 0273-1177
   Published by Elsevier Homepage  [3049 journals]
  • Satellite thermal IR and atmospheric radon anomalies associated with the
           Haripur earthquake (Oct 2010; Mw 5.2), Pakistan
    • Authors: Muhammad Awais; Adnan Barkat; Aamir Ali; Khaista Rehman; Waqar Ali Zafar; Talat Iqbal
      Pages: 2333 - 2344
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Muhammad Awais, Adnan Barkat, Aamir Ali, Khaista Rehman, Waqar Ali Zafar, Talat Iqbal
      The recent scientific progress in the context of earthquake forecasting reveals some key physical processes related to seismic activity. The lithosphere–atmosphere–ionosphere coupling model provides a comprehensive mechanism to understand the underlying key physical processes. In this study, a precursory analysis was conducted for the shallow, moderate-magnitude Haripur earthquake (Oct 2010; Mw 5.2) bounded by two major water reservoirs, highlighting its significance. This precursory analysis was performed using the land surface temperature (LST) extracted from satellite (MODIS) thermal infrared data and atmospheric radon concentration recorded at Islamabad and Murree stations using radon monitors. A significant change in LST (4–8°C) was observed in the epicentral region 6 days prior to this event. In addition, a comparison was made between daily and five-year-averaged LST that further supports our results. The radon concentration also showed anomalous behavior 3–4 days prior to this particular event with crucial meteorological indicators in the safe limit. This abnormal behavior of both precursors prior to this event proposes a possible correlation with the local seismic activity. Moreover, the higher amplitude of radon anomaly at the nearest station (Islamabad) is also validating its local cause. The results presented in this study are very encouraging and stimulate the idea of earthquake forecasting using multi-precursory approach.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.08.034
  • Mapping diffuse photosynthetically active radiation from satellite data in
    • Authors: P. Choosri; S. Janjai; M. Nunez; S. Buntoung; D. Charuchittipan
      Pages: 2345 - 2354
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): P. Choosri, S. Janjai, M. Nunez, S. Buntoung, D. Charuchittipan
      In this paper, calculation of monthly average hourly diffuse photosynthetically active radiation (PAR) using satellite data is proposed. Diffuse PAR was analyzed at four stations in Thailand. A radiative transfer model was used for calculating the diffuse PAR for cloudless sky conditions. Differences between the diffuse PAR under all sky conditions obtained from the ground-based measurements and those from the model are representative of cloud effects. Two models are developed, one describing diffuse PAR only asa function of solar zenith angle, and the second one asa multiple linear regression with solar zenith angle and satellite reflectivity acting linearly and aerosol optical depth acting in logarithmic functions. When tested with an independent data set, the multiple regression model performed best with a higher coefficient of variance R2 (0.78 vs. 0.70), lower root mean square difference (RMSD) (12.92% vs. 13.05%) and the same mean bias difference (MBD) of −2.20%. Results from the multiple regression model are used to map diffuse PAR throughout the country as monthly averages of hourly data.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.001
  • Comparison of Landsat-8, ASTER and Sentinel 1 satellite remote sensing
           data in automatic lineaments extraction: A case study of Sidi
           Flah-Bouskour inlier, Moroccan Anti Atlas
    • Authors: Zakaria Adiri; Abderrazak El Harti; Amine Jellouli; Rachid Lhissou; Lhou Maacha; Mohamed Azmi; Mohamed Zouhair; El Mostafa Bachaoui
      Pages: 2355 - 2367
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Zakaria Adiri, Abderrazak El Harti, Amine Jellouli, Rachid Lhissou, Lhou Maacha, Mohamed Azmi, Mohamed Zouhair, El Mostafa Bachaoui
      Certainly, lineament mapping occupies an important place in several studies, including geology, hydrogeology and topography etc. With the help of remote sensing techniques, lineaments can be better identified due to strong advances in used data and methods. This allowed exceeding the usual classical procedures and achieving more precise results. The aim of this work is the comparison of ASTER, Landsat-8 and Sentinel 1 data sensors in automatic lineament extraction. In addition to image data, the followed approach includes the use of the pre-existing geological map, the Digital Elevation Model (DEM) as well as the ground truth. Through a fully automatic approach consisting of a combination of edge detection algorithm and line-linking algorithm, we have found the optimal parameters for automatic lineament extraction in the study area. Thereafter, the comparison and the validation of the obtained results showed that the Sentinel 1 data are more efficient in restitution of lineaments. This indicates the performance of the radar data compared to those optical in this kind of study.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.006
  • Precipitable water vapor characterization in the coastal regions of China
           based on ground-based GPS
    • Authors: Zhaoyang Wang; Xinghua Zhou; Yanxiong Liu; Dongxu Zhou; Huayi Zhang; Weikang Sun
      Pages: 2368 - 2378
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Zhaoyang Wang, Xinghua Zhou, Yanxiong Liu, Dongxu Zhou, Huayi Zhang, Weikang Sun
      Water vapor plays an important role in climate change; thus, studying the spatial distribution and temporal variation of precipitable water vapor (PWV) in the coastal regions of China would help researchers to understand the climate characteristics of those regions. In this paper, 6-year 1-h interval PWV were derived from 27 Global Positioning System stations observations of Chinese coastal GPS observation network, surface meteorological data and European Center for Medium-Range Weather Forecasts (ERA-Interim) reanalysis products. The present study provides the use of these data to investigate the spatial-temporal variability of water vapor throughout the coastal regions of China. Latitude is the main factor affecting the spatial distribution of GPS-derived PWV; that is, PWV decreased by about 1.5mm for each 1° increase of latitude. For regions at the same latitude, a region that is relatively close to the ocean will have a higher content of PWV. The PWV in the southeastern and southwestern coastal regions of China is significantly higher in summer; this may be influenced by the southeastern and southwestern water vapor inflow corridors. The PWV obviously varies monthly, reaching a minimum in January; however, the timing of the maximum varied but usually appeared in June, July or August and was affected by the monsoons. The PWV varies largely between summer and winter with a larger gradient of change in PWV with latitude in winter than in summer. The positive correlation coefficient between PWV and the surface temperature varied in different seasons; this is related to the changes of temperature and the horizontal motion of water vapor. Use of the Fast Fourier Transform method showed that the PWV time series data have multi-scale characteristics. The amplitude and phase of the PWV time series in annual, semiannual, four month and seasonal cycles were extracted through harmonic wave analysis. The amplitude of four month and seasonal cycles did not pass significance testing. The maximum amplitude of the annual PWV cycle is located in mid-latitudes with 22.09mm, which gradually decreases towards high latitude and equator area. The peak time of annual PWV cycle occurs in July, which does not agree with the timing of the maximum monthly average PWV. The semiannual cycle amplitudes is between 0.42 and 6.32mm, with no significant correlation between their distribution and latitude. The peak time of semiannual PWV cycles is during about January–March and July–September, and the peak time gradually becomes late from north to south.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.017
  • A further contribution to the seasonal variation of weighted mean
    • Authors: Maohua Ding; Wusheng Hu
      Pages: 2414 - 2422
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Maohua Ding, Wusheng Hu
      The weighted mean temperature Tm is a variable parameter in the Global Navigation Satellite System (GNSS) meteorology and the Askne-Nordius zenith wet delay (ZWD) model. Some parameters about the Tm seasonal variation (e.g. the annual mean value, the annual range, the annual and semi-annual amplitudes, and the long-term trend) were discussed before. In this study, some additional results about the Tm seasonal variation on a global scale were found by using the Tm time series at 309 global radiosonde sites. Periodic signals of the annual and semi-annual variations were detected in these Tm time series by using the Lomb-Scargle periodogram. The annual variation is the main component of the periodic Tm in non-tropical regions, while the annual variation or the semiannual variation can be the main component of the periodic Tm in tropics. The mean annual Tm almost keeps constant with the increasing latitude in tropics, while it decreases with the increasing latitude in non-tropical regions. From a global perspective, Tm has an increasing trend of 0.22K/decade on average, which may be caused by the global warming effects. The annual phase is almost found in about January for the non-tropical regions of the Southern Hemisphere and in about July for the non-tropical regions of the Northern Hemisphere, but it has no clear symmetry in tropics. Unlike the annual phase, the geographical distributions of semi-annual phase do not follow obvious rules. In non-tropical regions, the maximum and minimum Tm of the seasonal model are usually found in respective summer and winter days while the maximum and minimum Tm are distributed over a whole year but not in any fixed seasons for tropical regions. The seasonal model errors increase with the increasing value of annual amplitude. A primary reason for the irregular seasonal variation in tropics is that Tm has rather small variations in this region.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.025
  • A novel constrained ambiguity resolution approach for Beidou attitude
    • Authors: Qingsong Li; Liang Zhang; Jie Wu; Dingjie Wang; Yi Dong
      Pages: 2423 - 2436
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Qingsong Li, Liang Zhang, Jie Wu, Dingjie Wang, Yi Dong
      This paper develops a novel approach to obtain the fixed ambiguity solution with orthonormal constraints for Beidou attitude determination. The approach extends the traditional attitude model by taking the attitude matrix elements as unknown parameters directly. The orthonormal property of the attitude matrix is used as constraints to assist in calculating the float ambiguity solution and its corresponding variance–covariance matrix. An iteration algorithm with the linearization of orthonormal constraints is developed to solve the nonlinear conditional extremum problem and a sequential filtering multi-epoch ambiguity resolution method is derived for real-time applications. Long-time static experiments with three antennas tracing Beidou signals are employed to demonstrate the reliability and effectiveness of the proposed approach. The results indicate that, compared to unconstrained ambiguity resolution, the proposed approach can improve the reliability of the integer ambiguity vectors for single epochs and can also decrease the time to fix for multiple epochs.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.027
  • Ionospheric parameters as the precursors of disturbed geomagnetic
    • Authors: D.V. Blagoveshchensky; M.A. Sergeeva; A. Kozlovsky
      Pages: 2437 - 2451
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): D.V. Blagoveshchensky, M.A. Sergeeva, A. Kozlovsky
      Geomagnetic storms and substorms are the principal elements of the disturbed Space Weather conditions. The aim of the study was to reveal the ionospheric precursors that can be used to forecast geomagnetic disturbance beginning. To study the ionospheric processes before, during and after magnetic storms and substorms data from Sodankylä Geophysical Observatory was used (geomagnetic coordinates: 64.1oN, 119.2oE). In earlier works the Main Effect (ME) was revealed for substorms. It consists of the following steps: (a) the increase of critical frequency foF2 from its quiet median before and during the substorm growth phase, four-five hours before To moment that is the moment of the expansion phase onset, (b) the foF2 decrease to the level lower than its median just after To and until Te that is the moment of the end of the expansion phase, (c) the issue “a” repeated during the recovery phase (d) two bell-shape spikes in the cutoff frequency values foEs: first spike occurs three hours before To, second spike – during the expansion phase within the interval between To and Te. In the present work it is shown that ME manifestations can be used as precursors of magnetic substorms at high-latitudes (geomagnetic latitudes 50oN–65oN). In particular, the foF2 growth some hours before To can be used asa precursor of substorm development. The first foEs bell-shaped spike also can be used for short-term forecasting, two–three hours in advance of a substorm. Furthermore, the storms between 2008 and 2012 were studied. It was revealed that the similar ME also takes place in the case of magnetic storms but within the different time scale. More specifically, the first ME maximum in foF2 values occurs one-two days before the storm beginning and can be used as its precursor. In addition, the foEs spike takes place approximately ten hours before a storm and also can be used for the prediction of the storm beginning.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.013
  • Constrained optimal multi-phase lunar landing trajectory with minimum fuel
    • Authors: S. Mathavaraj; R. Pandiyan; R. Padhi
      Pages: 2477 - 2490
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): S. Mathavaraj, R. Pandiyan, R. Padhi
      A Legendre pseudo spectral philosophy based multi-phase constrained fuel-optimal trajectory design approach is presented in this paper. The objective here is to find an optimal approach to successfully guide a lunar lander from perilune ( 18 km altitude) of a transfer orbit to a height of 100 m over a specific landing site. After attaining 100 m altitude, there is a mission critical re-targeting phase, which has very different objective (but is not critical for fuel optimization) and hence is not considered in this paper. The proposed approach takes into account various mission constraints in different phases from perilune to the landing site. These constraints include phase-1 (‘braking with rough navigation’) from 18 km altitude to 7 km altitude where navigation accuracy is poor, phase-2 (‘attitude hold’) to hold the lander attitude for 35 sec for vision camera processing for obtaining navigation error, and phase-3 (‘braking with precise navigation’) from end of phase-2 to 100 m altitude over the landing site, where navigation accuracy is good (due to vision camera navigation inputs). At the end of phase-1, there are constraints on position and attitude. In Phase-2, the attitude must be held throughout. At the end of phase-3, the constraints include accuracy in position, velocity as well as attitude orientation. The proposed optimal trajectory technique satisfies the mission constraints in each phase and provides an overall fuel-minimizing guidance command history.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.016
  • Uncertainty analysis of reachable set for planetary entry using polynomial
    • Authors: Yuechen Huang; Haiyang Li; Jin Zhang
      Pages: 2491 - 2504
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Yuechen Huang, Haiyang Li, Jin Zhang
      Reachable set (RS) is a useful tool in assessing the flight capability of the entry vehicle with the given initial entry state and the required control and path constraints. The evolution of the RS under the effects of uncertainties of some important entry parameters is also beneficial to the mission design and analysis. The objective of this paper is to investigate the RS evolution under parameter uncertainties. It would be computationally intensive to compute all the elements of the RS, and therefore only the RS boundary (RSB) extreme points, which well characterize the RS, are considered. The method of tracking drag profile is employed to generate each point of the RSB. By parameterizing the random uncertainties and introducing random parameters in uncertainties, the uncertainty analysis problem of the RSB is converted to a stochastic trajectory approximation problem, which can be solved by the polynomial chaos expansion-based method. The evolutions of the RSB under uncertainties of initial flight path angle, lift-to-drag ratio and atmospheric density are illustrated by a specific Mars entry mission. With uncertainty analysis of the RSB, the robustness of deployment site selection and the satisfaction of path constraints under uncertainties can be quantified in the entry mission design, thus enhancing the safety, reliability and accuracy of entry missions.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.028
  • Trajectory design for a rendezvous mission to Earth’s Trojan
           asteroid 2010 TK7
    • Authors: Hanlun Lei; Bo Xu; Lei Zhang
      Pages: 2505 - 2517
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Hanlun Lei, Bo Xu, Lei Zhang
      In this paper a rendezvous mission to the Earth’s Trojan asteroid 2010 TK 7 is proposed, and preliminary transfer trajectories are designed. Due to the high inclination ( ∼ 20.9°) of the target asteroid relative to the ecliptic plane, direct transfers usually require large amounts of fuel consumption, which is beyond the capacity of current technology. As gravity assist technique could effectively change the inclination of spacecraft’s trajectory, it is adopted to reduce the launch energy and rendezvous velocity maneuver. In practical computation, impulsive and low-thrust, gravity-assisted trajectories are considered. Among all the trajectories computed, the low-thrust gravity-assisted trajectory with Venus–Earth–Venus (V–E–V) swingby sequence performs the best in terms of propellant mass. For a spacecraft with initial mass of 800 kg , propellant mass of the best trajectory is 36.74 kg . Numerical results indicate that both the impulsive and low-thrust, gravity-assisted trajectories corresponding to V–E–V sequence could satisfy mission constraints, and can be applied to practical rendezvous mission.

      PubDate: 2017-10-29T09:56:27Z
      DOI: 10.1016/j.asr.2017.09.020
  • Tube dynamics and low energy Earth–Moon transfers in the 4-body
    • Authors: Kaori Onozaki; Hiroaki Yoshimura; Shane D. Ross
      Pages: 2117 - 2132
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Kaori Onozaki, Hiroaki Yoshimura, Shane D. Ross
      In this paper, we show a low energy Earth–Moon transfer in the context of the Sun–Earth–Moon–spacecraft 4-body system. We consider the 4-body system as the coupled system of the Sun–Earth–spacecraft 3-body system perturbed by the Moon (which we call the Moon-perturbed system) and the Earth–Moon–spacecraft 3-body system perturbed by the Sun (which we call the Sun-perturbed system). In both perturbed systems, analogs of the stable and unstable manifolds are computed numerically by using the notion of Lagrangian coherent structures, wherein the stable and unstable manifolds play the role of separating orbits into transit and non-transit orbits. We obtain a family of non-transit orbits departing from a low Earth orbit in the Moon-perturbed system, and a family of transit orbits arriving into a low lunar orbit in the Sun-perturbed system. Finally, we show that we can construct a low energy transfer from the Earth to the Moon by choosing appropriate trajectories from both families and patching these trajectories with a maneuver.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.07.046
  • The motion and control of a complex three-body space tethered system
    • Authors: Gefei Shi; Zhanxia Zhu; Shiyu Chen; Jianping Yuan; Biwei Tang
      Pages: 2133 - 2145
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Gefei Shi, Zhanxia Zhu, Shiyu Chen, Jianping Yuan, Biwei Tang
      This paper is mainly devoted to investigating the dynamics and stability control of a three body-tethered satellite system which contains a main satellite and two subsatellites connected by two straight, massless and inextensible tethers. Firstly, a detailed mathematical model is established in the central gravitational field. Then, the dynamic characteristics of the established system are investigated and analyzed. Based on the dynamic analysis, a novel sliding mode prediction model (SMPM) control strategy is proposed to suppress the motion of the built tethered system. The numerical results show that the proposed underactuated control law is highly effective in suppressing the attitude/libration motion of the underactuated three-body tethered system. Furthermore, cases of different target angles are also examined and analyzed. The simulation results reveal that even if the final equilibrium states differ from different selections of the target angles, the whole system can still be maintained in acceptable areas.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.004
  • Modified empirical Solar Radiation Pressure model for IRNSS constellation
    • Authors: K. Rajaiah; K. Manamohan; S. Nirmala; S.C. Ratnakara
      Pages: 2146 - 2154
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): K. Rajaiah, K. Manamohan, S. Nirmala, S.C. Ratnakara
      Navigation with Indian Constellation (NAVIC) also known as Indian Regional Navigation Satellite System (IRNSS) is India’s regional navigation system designed to provide position accuracy better than 20m over India and the region extending to 1500km around India. The reduced dynamic precise orbit estimation is utilized to determine the orbit broadcast parameters for IRNSS constellation. The estimation is mainly affected by the parameterization of dynamic models especially Solar Radiation Pressure (SRP) model which is a non-gravitational force depending on shape and attitude dynamics of the spacecraft. An empirical nine parameter solar radiation pressure model is developed for IRNSS constellation, using two-way range measurements from IRNSS C-band ranging system. The paper addresses the development of modified SRP empirical model for IRNSS (IRNSS SRP Empirical Model, ISEM). The performance of the ISEM was assessed based on overlap consistency, long term prediction, Satellite Laser Ranging (SLR) residuals and compared with ECOM9, ECOM5 and new-ECOM9 models developed by Center for Orbit Determination in Europe (CODE). For IRNSS Geostationary Earth Orbit (GEO) and Inclined Geosynchronous Orbit (IGSO) satellites, ISEM has shown promising results with overlap RMS error better than 5.3m and 3.5m respectively. Long term orbit prediction using numerical integration has improved with error better than 80%, 26% and 7.8% in comparison to ECOM9, ECOM5 and new-ECOM9 respectively. Further, SLR based orbit determination with ISEM shows 70%, 47% and 39% improvement over 10days orbit prediction in comparison to ECOM9, ECOM5 and new-ECOM9 respectively and also highlights the importance of wide baseline tracking network.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.020
  • Orbit determination of the Next-Generation Beidou satellites with
           Intersatellite link measurements and a priori orbit constraints
    • Authors: Xia Ren; Yuanxi Yang; Jun Zhu; Tianhe Xu
      Pages: 2155 - 2165
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Xia Ren, Yuanxi Yang, Jun Zhu, Tianhe Xu
      Intersatellite Link (ISL) technology helps to realize the auto update of broadcast ephemeris and clock error parameters for Global Navigation Satellite System (GNSS). ISL constitutes an important approach with which to both improve the observation geometry and extend the tracking coverage of China’s Beidou Navigation Satellite System (BDS). However, ISL-only orbit determination might lead to the constellation drift, rotation, and even lead to the divergence in orbit determination. Fortunately, predicted orbits with good precision can be used as a priori information with which to constrain the estimated satellite orbit parameters. Therefore, the precision of satellite autonomous orbit determination can be improved by consideration of a priori orbit information, and vice versa. However, the errors of rotation and translation in a priori orbit will remain in the ultimate result. This paper proposes a constrained precise orbit determination (POD) method for a sub-constellation of the new Beidou satellite constellation with only a few ISLs. The observation model of dual one-way measurements eliminating satellite clock errors is presented, and the orbit determination precision is analyzed with different data processing backgrounds. The conclusions are as follows. (1) With ISLs, the estimated parameters are strongly correlated, especially the positions and velocities of satellites. (2) The performance of determined BDS orbits will be improved by the constraints with more precise priori orbits. The POD precision is better than 45m with a priori orbit constrain of 100m precision (e.g., predicted orbits by telemetry tracking and control system), and is better than 6m with precise priori orbit constraints of 10m precision (e.g., predicted orbits by international GNSS monitoring & Assessment System (iGMAS)). (3) The POD precision is improved by additional ISLs. Constrained by a priori iGMAS orbits, the POD precision with two, three, and four ISLs is better than 6, 3, and 2m, respectively. (4) The in-plane link and out-of-plane link have different contributions to observation configuration and system observability. The POD with weak observation configuration (e.g., one in-plane link and one out-of-plane link) should be tightly constrained with a priori orbits.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.024
  • The secular analytical solution of the orbital plane using
           Lindstedt-Poincaré method
    • Authors: Shengxian Yu; Changyin Zhao; Wei Zhang
      Pages: 2166 - 2180
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Shengxian Yu, Changyin Zhao, Wei Zhang
      Nowadays, the increasing amount of space objects makes the space so crowded that the satellites in orbit endure severe environment. Hence how to efficiently search and catalog these space objects becomes an urgent problem to be solved. In the paper, in order to contribute to this problem, the secular analytical solution of the orbital plane for medium and high orbit objects is studied. For medium and high orbit objects, the Earth’s oblateness and the lunisolar gravitational perturbations are considered. The double averaging method is used to first average the system. For small to medium orbit inclinations and small eccentricities, and then the differential equations can be rewritten in an expansion form. Combining the Lindstedt-Poincaré procedure and the solution for differential equations with special coefficients, the third-order analytical solutions can be derived step by step. Finally, two kinds of comparisons are carried out. One is the comparison between the analytical solution and the results derived by integrating the simplified model. It aims to verify the validity of these methods. The other one is the comparison with the integration results of the normal model to show the accuracy of the analytical solution. Both of the two comparisons results work well. The accuracy of the analytical solution can be maintained at the order of O ( 10 - 3 ) for the duration of 200yrs.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.032
  • Electric field computation analysis for the Electric Field Detector (EFD)
           on board the China Seismic-Electromagnetic Satellite (CSES)
    • Authors: P. Diego; I. Bertello; M. Candidi; A. Mura; I. Coco; G. Vannaroni; P. Ubertini; D. Badoni
      Pages: 2206 - 2216
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): P. Diego, I. Bertello, M. Candidi, A. Mura, I. Coco, G. Vannaroni, P. Ubertini, D. Badoni
      The floating potential variability of the Electric Field Detector (EFD) probes, on board the Chinese Seismo-Electromagnetic Satellite (CSES), has been modeled, and the effects of several structural and environmental elements have been determined. The expected floating potentials of the probes are computed considering the ambient ionospheric plasma parameter variations. In addition, the ion collection variability, due to the different probe attitudes along the orbit, and its effect on each floating potential, are considered. Particular attention is given to the analysis of the shadow produced by the stubs, in order to determine the artificial electric field introduced by instrumental effects which has to be subtracted from the real measurements. The modulation of the altered electric field, due to the effect on shadowing of the ion drift, as measured by the ESA satellite Swarm A in a similar orbit, is also modeled. Such simulations are made in preparation of real EFD data analysis performed during the upcoming flight of CSES.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.005
  • An electric field penetration model for seismo-ionospheric research
    • Authors: Chen Zhou; Yi Liu; Shufan Zhao; Jing Liu; Xuemin Zhang; Jianping Huang; Xuhui Shen; Binbin Ni; Zhengyu Zhao
      Pages: 2217 - 2232
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Chen Zhou, Yi Liu, Shufan Zhao, Jing Liu, Xuemin Zhang, Jianping Huang, Xuhui Shen, Binbin Ni, Zhengyu Zhao
      We investigate the electric field penetration of the lithosphere–atmosphere–ionosphere coupling (LAIC) problem to study abnormal seismo-ionospheric disturbance. By directly solving the LAIC electric field penetration model at the high-latitude region, we find that the additional current induced at the ground surface flows into the ionosphere completely and further generates an abnormal ionospheric electric field. Therefore, we reasonably suggest that the electric field penetration of LAIC at middle- and low-latitude regions can be solved from the perspective of the ionospheric electric field model. The current from the downward atmosphere is treated as the source term. The simulation results demonstrate the following principal findings: (a) for the high-latitude region, the horizontal electric field in the ionosphere does not change with height and the vertical electric field can be neglected; (b) for the middle- and low-latitude regions, the intensity of the total horizontal electric field increases with the latitude and the vertical electric field is more obvious at low latitudes; and (c) the penetration height of the LAIC electric field in the ionosphere is lower at low latitudes than at high latitudes. We also find that according to the diurnal change of the ionospheric conductivity, the most efficient time for electric field penetration is between 00:00 and 04:00 local time.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.007
  • Interplanetary Coronal Mass Ejection effects on thermospheric density as
           inferred from International Space Station orbital data
    • Authors: T. Mendaza; J.J. Blanco-Ávalos; J. Martín-Torres
      Pages: 2233 - 2251
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): T. Mendaza, J.J. Blanco-Ávalos, J. Martín-Torres
      The solar activity induces long term and short term periodical variations in the dynamics and composition of Earth’s atmosphere. The Sun also shows non periodical (i.e., impulsive) activity that reaches the planets orbiting around it. In particular, Interplanetary Coronal Mass Ejections (ICMEs) reach Earth and interact with its magnetosphere and upper neutral atmosphere. Nevertheless, the interaction with the upper atmosphere is not well characterized because of the absence of regular and dedicated in situ measurements at high altitudes; thus, current descriptions of the thermosphere are based on semi empirical models. In this paper, we present the total neutral mass densities of the thermosphere retrieved from the orbital data of the International Space Station (ISS) using the General Perturbation Method, and we applied these densities to routinely compiled trajectories of the ISS in low Earth orbit (LEO). These data are explicitly independent of any atmospheric model. Our density values are consistent with atmospheric models, which demonstrates that our method is reliable for the inference of thermospheric density. We have inferred the thermospheric total neutral density response to impulsive solar activity forcing from 2001 to the end of 2006 and determined how solar events affect this response. Our results reveal that the ISS orbital parameters can be used to infer the thermospheric density and analyze solar effects on the thermosphere.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.016
  • Application of the IRI model to the HF propagation model with optimization
           of the ionosphere parameters to day-to-day variation
    • Authors: N.Y. Zaalov; E.V. Moskaleva; T.S. Burmakina
      Pages: 2252 - 2267
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): N.Y. Zaalov, E.V. Moskaleva, T.S. Burmakina
      The HF propagation model, North Ionospheric Model and Ray Tracing (NIM-RT) was developed and tested for a number of years by comparing measured vertical and oblique ionograms over a number of radio links (especially in high latitude area) with the simulated ionograms. The present paper extends the model in order to include: (a) Implementation of the data retrieved from the International Reference Ionosphere (IRI-2012) model into the software for radio channel modeling. (b) The algorithm for IRI data optimization to the real time condition. (c) Results of comparison between simulated and measured ionograms. Based on these updates, a new software tool called North Ionospheric Model with IRI and Ray Tracing (NIMIRI-RT) was developed, and a number of vertical ionograms corresponding to multiple ionospheric reflections was simulated. The vertical ionograms observed at various ionosondes were compared with the synthesized ionograms, generated by applying NIM-RT in conjunction with initial and optimized IRI data. The ionogram structure simulated by NIMIRI-RT based on the data retrieved from optimized IRI is more reminiscent to the observations than ionograms synthesized with the initial NIMIRI-RT without parameters optimization.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.018
  • Satellite remote sensing of fine particulate air pollutants over Indian
           mega cities
    • Authors: V. Sreekanth; B. Mahesh; K. Niranjan
      Pages: 2268 - 2276
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): V. Sreekanth, B. Mahesh, K. Niranjan
      In the backdrop of the need for high spatio-temporal resolution data on PM2.5 mass concentrations for health and epidemiological studies over India, empirical relations between Aerosol Optical Depth (AOD) and PM2.5 mass concentrations are established over five Indian mega cities. These relations are sought to predict the surface PM2.5 mass concentrations from high resolution columnar AOD datasets. Current study utilizes multi-city public domain PM2.5 data (from US Consulate and Embassy’s air monitoring program) and MODIS AOD, spanning for almost four years. PM2.5 is found to be positively correlated with AOD. Station-wise linear regression analysis has shown spatially varying regression coefficients. Similar analysis has been repeated by eliminating data from the elevated aerosol prone seasons, which has improved the correlation coefficient. The impact of the day to day variability in the local meteorological conditions on the AOD-PM2.5 relationship has been explored by performing a multiple regression analysis. A cross-validation approach for the multiple regression analysis considering three years of data as training dataset and one-year data as validation dataset yielded an R value of ∼0.63. The study was concluded by discussing the factors which can improve the relationship.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.008
  • Acceleration estimation using a single GPS receiver for airborne scalar
    • Authors: Xiaohong Zhang; Kai Zheng; Cuixian Lu; Jiakuan Wan; Zhanke Liu; Xiaodong Ren
      Pages: 2277 - 2288
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Xiaohong Zhang, Kai Zheng, Cuixian Lu, Jiakuan Wan, Zhanke Liu, Xiaodong Ren
      Kinematic acceleration estimated using the global positioning system (GPS) is significant for airborne scalar gravimetry. As the conventional approach based on the differential global positioning system (DGPS) presents several drawbacks, including additional cost or the impracticality of setting up nearby base stations in challenging environments, we introduce an alternative approach, Modified Kin-VADASE (MKin-VADASE), based on a modified Kin-VADASE approach without the requirement to have ground-base stations. In this approach, the aircraft velocities are first estimated with the modified Kin-VADASE. Then the accelerations are obtained from velocity estimates using the Taylor approximation differentiator. The impact of carrier-phase measurement noise and satellite ephemeris errors on acceleration estimates are investigated carefully in the frequency domain with the Fast Fourier Transform Algorithm (FFT). The results show that the satellite clock products have a significant impact on the acceleration estimates. Then, the performance of MKin-VADASE, PPP, and DGPS are validated using flight tests carried out in Shanxi Province, China. The accelerations are estimated using the three approaches, then used to calculate the gravity disturbances. Finally, the analysis of crossover difference and the terrestrial gravity data are used to evaluate the accuracy of gravity disturbance estimates. The results show that the performances of MKin-VADASE, PPP and DGPS are comparable, but the computational complexity of MKin-VADASE is greatly reduced with regard to PPP and DGPS. For the results of the three approaches, the RMS of crossover differences of gravity disturbance estimates is approximately 1–1.5mGal at a spatial resolution of 3.5km (half wavelength) after crossover adjustment, and the accuracy is approximately 3–4mGal with respect to terrestrial gravity data.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.038
  • Observations of Phobos by the Mars Express radar MARSIS: Description of
           the detection techniques and preliminary results
    • Authors: A. Cicchetti; C. Nenna; J.J. Plaut; D. Plettemeier; R. Noschese; M. Cartacci; R. Orosei
      Pages: 2289 - 2302
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): A. Cicchetti, C. Nenna, J.J. Plaut, D. Plettemeier, R. Noschese, M. Cartacci, R. Orosei
      The Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) (Picardi et al., 2005) is a synthetic aperture low frequency radar altimeter, onboard the ESA Mars Express orbiter, launched in June 2003. It is the first and so far the only spaceborne radar that has observed the Martian moon Phobos. Radar echoes were collected on different flyby trajectories. The primary aim of sounding Phobos is to prove the feasibility of deep sounding, into its subsurface. MARSIS is optimized for deep penetration investigations and is capable of transmitting at four different bands between 1.3MHz and 5.5MHz with a 1MHz bandwidth. Unfortunately the instrument was originally designed to operate exclusively on Mars, assuming that Phobos would not be observed. Following this assumption, a protection mechanism was implemented in the hardware (HW) to maintain a minimum time separation between transmission and reception phases of the radar. This limitation does not have any impact on Mars observation but it prevented the observation of Phobos. In order to successfully operate the instrument at Phobos, a particular configuration of the MARSIS onboard software (SW) parameters, called “Range Ambiguity,” was implemented to override the HW protection zone, ensuring at the same time a high level of safety of the instrument. This paper describes the principles of MARSIS onboard processing, and the procedure through which the parameters of the processing software were tuned to observe targets below the minimum distance allowed by hardware. Some preliminary results of data analysis will be shown, with the support of radar echo simulations. A qualitative comparison between the simulated results and the actual data, does not support the detection of subsurface reflectors.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.013
  • The analytical and numerical approaches to the theory of the Moon’s
           librations: Modern analysis and results
    • Authors: N. Petrova; A. Zagidullin; Y. Nefedyev; V. Kosulin; A. Andreev
      Pages: 2303 - 2313
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): N. Petrova, A. Zagidullin, Y. Nefedyev, V. Kosulin, A. Andreev
      Observing physical librations of celestial bodies and the Moon represents one of the astronomical methods of remotely assessing the internal structure of a celestial body without conducting expensive space experiments. The paper contains a review of recent advances in studying the Moon’s structure using various methods of obtaining and applying the lunar physical librations (LPhL) data. In this article LPhL simulation methods of assessing viscoelastic and dissipative properties of the lunar body and lunar core parameters, whose existence has been recently confirmed during the seismic data reprocessing of “Apollo” space mission, are described. Much attention is paid to physical interpretation of the free librations phenomenon and the methods for its determination. In the paper the practical application of the most accurate analytical LPhL tables (Rambaux and Williams, 2011) is discussed. The tables were built on the basis of complex analytical processing of the residual differences obtained when comparing long-term series of laser observations with the numerical ephemeris DE421. In the paper an efficiency analysis of two approaches to LPhL theory is conducted: the numerical and the analytical ones. It has been shown that in lunar investigation both approaches complement each other in various aspects: the numerical approach provides high accuracy of the theory, which is required for the proper processing of modern observations, the analytical approach allows to comprehend the essence of the phenomena in the lunar rotation, predict and interpret new effects in the observations of lunar body and lunar core parameters.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.014
  • Non-randomness of exponential distance relation in the planetary system:
           An answer to Lecar
    • Authors: Vladimir Pletser
      Pages: 2314 - 2318
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Vladimir Pletser
      One of the usual main objections against attempts in finding a physical cause for the planet distance distribution is based on the assumption that similar distance distribution could be obtained by sequences of random numbers. This assumption was stated by Lecar in a short article of 1973 that is still referred to nowadays. We show here how this assumption is incorrect.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.021
  • An innovative navigation scheme for Mars entry using dynamic pressure
    • Authors: Jianfeng Deng; Ai Gao; Hua Zong; Pingyuan Cui
      Pages: 2319 - 2331
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Jianfeng Deng, Ai Gao, Hua Zong, Pingyuan Cui
      Complete observability of dynamic system is a major concern of navigation in Mars precision landing exploration missions. It is demonstrated that, however, the current measurements used for navigation during Mars entry cannot guarantee the complete observability of the dynamic system. This paper proposes an integrated navigation scheme for Mars entry phase using the dynamic pressure and accelerations from inertial measurement unit (IMU). The dynamic pressure derived from the Mars Entry Atmospheric Data System (MEADS), and the triaxle accelerations from IMU are integrated in a filter as navigation measurements to increase the dynamic system observability and perform state estimation on-board. Afterward, the perturbation of the dynamic caused by parameter uncertainties is built. In order to address the impact of perturbation on state estimation, an adaptive estimator based on modified mixture-of-expert framework is given. Numerical simulation results demonstrate that the proposed integrated navigation scheme can ensure the complete observability of the dynamic system, and the state estimation are converged with entry time after the dynamic pressure has built up.

      PubDate: 2017-10-14T12:49:22Z
      DOI: 10.1016/j.asr.2017.08.033
  • Primary mass discrimination of high energy cosmic rays using PNN and k-NN
    • Authors: G. Rastegarzadeh; M. Nemati
      Abstract: Publication date: Available online 23 November 2017
      Source:Advances in Space Research
      Author(s): G. Rastegarzadeh, M. Nemati
      Probabilistic neural network (PNN) and k-Nearest Neighbors ( k - NN ) methods are widely used data classification techniques. In this paper, these two methods have been used to classify the Extensive Air Shower (EAS) data sets which were simulated using the CORSIKA code for three primary cosmic rays. The primaries are proton, oxygen and iron nuclei at energies of 100 TeV - 10 PeV. This study is performed in the following of the investigations into the primary cosmic ray mass sensitive observables. We propose a new approach for measuring the mass sensitive observables of EAS in order to improve the primary mass separation. In this work, the EAS observables measurement has performed locally instead of total measurements. Also the relationships between the included number of observables in the classification methods and the prediction accuracy have been investigated. We have shown that the local measurements and inclusion of more mass sensitive observables in the classification processes can improve the classifying quality and also we have shown that muons and electrons energy density can be considered as primary mass sensitive observables in primary mass classification. Also it must be noted that this study is performed for Tehran observation level without considering the details of any certain EAS detection array.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.016
  • Genetic analysis of parameters of Near Earth Asteroids for determining
           parent bodies of meteoroid streams
    • Authors: M. Sokolova; M. Sergienko; Y. Nefedyev; A. Andreev; L. Nefediev
      Abstract: Publication date: Available online 22 November 2017
      Source:Advances in Space Research
      Author(s): M. Sokolova, M. Sergienko, Y. Nefedyev, A. Andreev, L. Nefediev
      The present paper is focusing on determining genetic connections between small bodies of the Solar system and their parent bodies (PB) on the basis of analysis of Near Earth Asteroids (NEAs) parameters. In order to search for parent bodies of meteoroid streams, the asteroid groups, including Atira, Apollo, Amor and Aten, have been investigated. Currently, it is considered that surface of asteroids with elongated orbit is exposed to temperature fall: in perihelion it is heated and in aphelion it is cooled. At small orbital periods around the Sun (about 2-4 years) this may lead to formation of meteoroid clusters. On the basis of comparative analysis of orbit, size and chemical and mineralogical composition of NEAs, it is found that asteroids from Apollo group are most likely to be parent bodies of the studied meteoroid streams.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.020
  • Fundamental (f) Oscillations in a Magnetically Coupled Solar
           Interior-Atmosphere System - An Analytical Approach
    • Abstract: Publication date: Available online 22 November 2017
      Source:Advances in Space Research
      Author(s): Balázs Pintér, R. Erdélyi
      Solar fundamental (f) acoustic mode oscillations are investigated analytically in a magnetohydrodynamic (MHD) model. The model consists of three layers in planar geometry, representing the solar interior, the magnetic atmosphere, and a transitional layer sandwiched between them. Since we focus on the fundamental mode here, we assume the plasma is incompressible. A horizontal, canopy-like, magnetic field is introduced to the atmosphere, in which degenerated slow MHD waves can exist. The global (f-mode) oscillations can couple to local atmospheric Alfvén waves, resulting, e.g., in a frequency shift of the oscillations. The dispersion relation of theglobal oscillation mode is derived, and is solved analytically for the thin-transitional layer approximation and for the weak-field approximation. Analytical formulae are also provided for the frequency shifts due to the presence of a thin transitional layer and a weak atmospheric magnetic field. The analytical results generally indicate that, compared to the fundamental value ( ω = gk ), the mode frequency is reduced by the presence of an atmosphere by a few per cent. A thin transitional layer reduces the eigen-frequencies further by about an additional hundred microhertz. Finally, a weak atmospheric magnetic field can slightly, by a few percent, increase the frequency of the eigen-mode. Stronger magnetic fields, however, can increase the f-mode frequency by even up to ten per cent, which cannot be seen in observed data. The presence of a magnetic atmosphere in the three-layer model also introduces non-permitted propagation windows in the frequency spectrum; here, f-mode oscillations cannot exist with certain values of the harmonic degree. The eigen-frequencies can be sensitive to the background physical parameters, such as an atmospheric density scale-height or the rate of the plasma density drop at the photosphere. Such information, if ever observed with high-resolution instrumentation and inverted, could help to gain further insight into solar magnetic structures by means of solar magneto-seismology, and could provide further insight into the role of magnetism in solar oscillations.

      PubDate: 2017-11-24T14:10:13Z
  • Effect of Matching Between the Magnetic Field and Channel Length on the
           Performance of Low Sputtering Hall Thrusters
    • Authors: Yongjie Ding; Jia Boyang; Hezhi Sun; Liqiu Wei; Wuji Peng; Peng Li; Daren Yu
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): Yongjie Ding, Jia Boyang, Hezhi Sun, Liqiu Wei, Wuji Peng, Peng Li, Daren Yu
      Discharge characteristics of a non-wall-loss Hall thruster were studied under different channel lengths using a design based on pushing a magnetic field through a double permanent magnet ring. The effect of different magnetic field intensities and channel lengths on ionization, efficiency, and plume divergence angle were studied. The experimental results show that propellant utilization is improved for optimal matching between the magnetic field and channel length. While matching the magnetic field and channel length, the ionization position of the neutral gas changes. The ion flow is effectively controlled, allowing the thrust force, specific impulse, and efficiency to be improved. Our study shows that the channel length is an important design parameter to consider for improving the performance of non-wall-loss Hall thrusters.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.003
  • Neural network-based sliding mode control for atmospheric-actuated
           spacecraft formation using switching strategy
    • Authors: Ran Sun; Jihe Wang; Dexin Zhang; Xiaowei Shao
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): Ran Sun, Jihe Wang, Dexin Zhang, Xiaowei Shao
      This paper presents an adaptive neural networks-based control method for spacecraft formation with coupled translational and rotational dynamics using only aerodynamic forces. It is assumed that each spacecraft is equipped with several large flat plates. A coupled orbit-attitude dynamic model is considered based on the specific configuration of atmospheric-based actuators. For this model, a neural network-based adaptive sliding mode controller is implemented, accounting for system uncertainties and external perturbations. To avoid invalidation of the neural networks destroying stability of the system, a switching control strategy is proposed which combines an adaptive neural networks controller dominating in its active region and an adaptive sliding mode controller outside the neural active region. An optimal process is developed to determine the control commands for the plates system. The stability of the closed-loop system is proved by a Lyapunov-based method. Comparative results through numerical simulations illustrate the effectiveness of executing attitude control while maintaining the relative motion, and higher control accuracy can be achieved by using the proposed neural-based switching control scheme than using only adaptive sliding mode controller.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.011
  • Automated and Dynamic Scheduling for Geodetic VLBI - A Simulation Study
           for AuScope and Global Networks
    • Authors: E.J. Iles; L. McCallum; J.E.J. Lovell; J.N. McCallum
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): E.J. Iles, L. McCallum, J.E.J. Lovell, J.N. McCallum
      As we move into the next era of geodetic VLBI, the scheduling process is one focus for improvement in terms of increased flexibility and the ability to react with changing conditions. A range of simulations were conducted to ascertain the impact of scheduling on geodetic results such as Earth Orientation Parameters (EOPs) and station coordinates. The potential capabilities of new automated scheduling modes were also simulated, using the so-called ‘dynamic scheduling’ technique. The primary aim was to improve efficiency for both cost and time without losing geodetic precision, particularly to maximise the uses of the Australian AuScope VLBI array. We show that short breaks in observation will not significantly degrade the results of a typical 24 hour experiment, whereas simply shortening observing time degrades precision exponentially. We also confirm the new automated, dynamic scheduling mode is capable of producing the same standard of result as a traditional schedule, with close to real-time flexibility. Further, it is possible to use the dynamic scheduler to augment the 3 station Australian AuScope array and thereby attain EOPs of the current global precision with only intermittent contribution from 2 additional stations. We thus confirm automated, dynamic scheduling bears great potential for flexibility and automation in line with aims for future continuous VLBI operations.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.012
  • A deformation model of flexible, HAMR objects for accurate propagation
           under perturbations and the self-shadowing effects
    • Authors: Sittiporn Channumsin; Matteo Ceriotti; Gianmarco Radice
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): Sittiporn Channumsin, Matteo Ceriotti, Gianmarco Radice
      A new type of space debris in near geosynchronous orbit (GEO) was recently discovered and later identified as exhibiting unique characteristics associated with high area-to-mass ratio (HAMR) objects, such as high rotation rates and high reflection properties. Observations have shown that this debris type is very sensitive to environmental disturbances, particularly solar radiation pressure, due to the fact that its motion depends on the actual effective area, orientation of that effective area, reflection properties and the area-to-mass ratio of the object is not stable over time. Previous investigations have modelled this type of debris as rigid bodies (constant area-to-mass ratios) or discrete deformed body however these simplifications will lead to inaccurate long term orbital predictions. This paper proposes a simple yet reliable model of a thin, deformable membrane based on multibody dynamics. The membrane is modelled as a series of flat plates, connected through joints, representing the flexibility of the membrane itself. The mass of the membrane, albeit low, is taken into account through lump masses at the joints. The attitude and orbital motion of this flexible membrane model is then propagated near GEO to predict its orbital evolution under the perturbations of solar radiation pressure, Earth’s gravity field (J2), third body gravitational fields (the Sun and Moon) and self-shadowing. These results are then compared to those obtained for two rigid body models (cannonball and flat rigid plate). In addition, Monte Carlo simulations of the flexible model by varying initial attitude and deformation angle (different shape) are investigated and compared with the two rigid models (cannonball and flat rigid plate) over a period of 100 days. The numerical results demonstrate that cannonball and rigid flat plate are not appropriate to capture the true dynamical evolution of these objects, at the cost of increased computational time.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.10.057
  • Event-Triggered Attitude Control of Spacecraft
    • Authors: Baolin Wu; Qiang Shen; Xibin Cao
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): Baolin Wu, Qiang Shen, Xibin Cao
      The problem of spacecraft attitude stabilization control system with limited communication and external disturbances is investigated based on an event-triggered control scheme. In the proposed scheme, information of attitude and control torque only need to be transmitted at some discrete triggered times when a defined measurement error exceeds a state-dependent threshold. The proposed control scheme not only guarantees that spacecraft attitude control errors converge toward a small invariant set containing the origin, but also ensures that there is no accumulation of triggering instants. The performance of the proposed control scheme is demonstrated through numerical simulation.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.013
  • Yarkovsky-Schach effect on space debris motion
    • Authors: M. Murawiecka; A. Lemaitre
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): M. Murawiecka, A. Lemaitre
      The Yarkovsky-Schach effect is a small perturbation affecting Earth satellites and space debris illuminated by the Sun. It was first applied to the orbit of LAGEOS satellites as an explanation of the residuals in orbital elements. In this work, we carry out several numerical integration tests taking into consideration various orbit and rotation parameters, in order to analyse this effect in a broader context. The semi-major axis variations remain small and depend on the spin axis attitude with respect to the Sun. We show that the force amplitude is maximised for orbits inclined with i ≈ 20-30°. We also observe the influence on other orbital elements, notably on the orbit inclination. However, these effects are clearly observed only on long timescales; in our simulations, we propagated the orbits for 200 y. The Yarkovsky-Schach effect is thus confirmed to have a minuscule magnitude. It should be taken into account in studies requiring high-precision orbit determination, or on expanded timescales.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.015
  • Scheduling Algorithms for Rapid Imaging using Agile Cubesat Constellations
    • Authors: Sreeja Nag; Alan S. Li; James H. Merrick
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): Sreeja Nag, Alan S. Li, James H. Merrick
      Distributed Space Missions such as formation flight and constellations, are being recognized as important Earth Observation solutions to increase measurement samples over space and time. Cubesats are increasing in size (27U, ∼40 kg in development) with increasing capabilities to host imager payloads. Given the precise attitude control systems emerging in the commercial market, Cubesats now have the ability to slew and capture images within short notice. We propose a modular framework that combines orbital mechanics, attitude control and scheduling optimization to plan the time-varying, full-body orientation of agile Cubesats in a constellation such that they maximize the number of observed images and observation time, within the constraints of Cubesat hardware specifications. The attitude control strategy combines bang-bang and PD control, with constraints such as power consumption, response time, and stability factored into the optimality computations and a possible extension to PID control to account for disturbances. Schedule optimization is performed using dynamic programming with two levels of heuristics, verified and improved upon using mixed integer linear programming. The automated scheduler is expected to run on ground station resources and the resultant schedules uplinked to the satellites for execution, however it can be adapted for onboard scheduling, contingent on Cubesat hardware and software upgrades. The framework is generalizable over small steerable spacecraft, sensor specifications, imaging objectives and regions of interest, and is demonstrated using multiple 20 kg satellites in Low Earth Orbit for two case studies – rapid imaging of Landsat’s land and coastal images and extended imaging of global, warm water coral reefs. The proposed algorithm captures up to 161% more Landsat images than nadir-pointing sensors with the same field of view, on a 2-satellite constellation over a 12-hour simulation. Integer programming was able to verify that optimality of the dynamic programming solution for single satellites was within 10%, and find up to 5% more optimal solutions. The optimality gap for constellations was found to be 22% at worst, but the dynamic programming schedules were found at nearly four orders of magnitude better computational speed than integer programming. The algorithm can integrate cloud cover predictions, ground downlink windows or any other spatial, temporal or angular constraints into the orbital module and be integrated into planning tools for agile constellations.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.010
  • CryoSat-2 swath interferometric altimetry for mapping ice elevation and
           elevation change
    • Authors: N. Gourmelen; M.J. Escorihuela; A. Shepherd; L. Foresta; A. Muir; A. Garcia-Mondejar; M. Roca; S.G. Baker; M.R. Drinkwater
      Abstract: Publication date: Available online 21 November 2017
      Source:Advances in Space Research
      Author(s): N. Gourmelen, M.J. Escorihuela, A. Shepherd, L. Foresta, A. Muir, A. Garcia-Mondejar, M. Roca, S.G. Baker, M.R. Drinkwater
      For more than 25 years, satellite radar altimetry has provided continuous information on the state of the cryosphere and on its contribution to global sea-level rise. The technique typically delivers maps of ice-sheet elevation and elevation change with 3 to 10 km spatial resolution and seasonal to monthly temporal resolution. Here we show how the interferometric mode of CryoSat-2 can be used to map broad (5 km-wide) swaths of surface elevation with fine (500 m) spatial resolution from each satellite pass, providing a step-change in the capability of satellite altimetry for glaciology. These swaths of elevation data contain up to two orders of magnitude more surface elevation measurements than standard altimeter products, which provide single elevation measurements based on the range to the Point-Of-Closest-Approach (POCA) in the vicinity of the sub-satellite ground track. The swath elevations allow a more dense, statistically robust time series of elevation change to be formed with temporal resolution of a factor 5 higher than for POCA. The mean differences between airborne altimeter and CryoSat-2 derived ice sheet elevations and elevation rates range from -0.93±1.17 m and 0.29±1.25 m a-1, respectively, at the POCA, to -1.50±1.73 m and 0.04±1.04 m a-1, respectively, across the entire swath. We demonstrate the potential of these data by creating and evaluating elevation models of: (i) the Austfonna Ice Cap (Svalbard), (ii) western Greenland, and (iii) Law Dome (East Antarctica); and maps of ice elevation change of: (iv) the Amundsen Sea sector (West Antarctica), (v) Icelandic ice caps, and (vi) above an active subglacial lake system at Thwaites Glacier (Antarctica), each at 500 m spatial posting – around 10 times finer than possible using traditional approaches based on standard altimetry products.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.014
  • Evaluation of a regional real-time precise positioning system based on
           GPS/BeiDou observations in Australia
    • Authors: Wenwu Ding; Bingfeng Tan; Yongchang Chen; Felix Norman Teferle; Yunbin Yuan
      Abstract: Publication date: Available online 20 November 2017
      Source:Advances in Space Research
      Author(s): Wenwu Ding, Bingfeng Tan, Yongchang Chen, Felix Norman Teferle, Yunbin Yuan
      The performance of real-time (RT) precise positioning can be improved by utilizing observations from multiple Global Navigation Satellite Systems (GNSS) instead of one particular system. Since the end of 2012, BeiDou, independently established by China, began to provide operational services for users in the Asia-Pacific regions. In this study, a regional RT precise positioning system is developed to evaluate the performance of GPS/BeiDou observations in Australia in providing high precision positioning services for users. Fixing three hourly updated satellite orbits, RT correction messages are generated and broadcasted by processing RT observation/navigation data streams from the national network of GNSS Continuously Operating Reference Stations in Australia (AUSCORS) at the server side. At the user side, RT PPP is realized by processing RT data streams and the RT correction messages received. RT clock offsets, for which the accuracy reached 0.07 and 0.28 ns for GPS and BeiDou, respectively, can be determined. Based on these corrections, an accuracy of 12.2, 30.0 and 45.6 cm in the North, East and Up directions was achieved for the BeiDou-only solution after 30 minutes while the GPS-only solution reached 5.1, 15.3 and 15.5 cm for the same components at the same time. A further improvement of 43.7, 36.9 and 45.0 percent in the three directions, respectively, was achieved for the combined GPS/BeiDou solution. After the initialization process, the North, East and Up positioning accuracies were 5.2, 8.1 and 17.8 cm, respectively, for the BeiDou-only solution, while 1.5, 3.0, and 4.7 cm for the GPS-only solution. However, we only noticed a 20.9% improvement in the East direction was obtained for the GPS/BeiDou solution, while no improvements in the other directions were detected. It is expected that such improvements may become bigger with the increasing accuracy of the BeiDou-only solution.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.009
  • Topological and statistical properties of nonlinear force-free fields
    • Authors: A. Mangalam; A. Prasad
      Abstract: Publication date: Available online 17 November 2017
      Source:Advances in Space Research
      Author(s): A. Mangalam, A. Prasad
      We use our semi-analytic solution of the nonlinear force-free field equation to construct three-dimensional magnetic fields that are applicable to the solar corona and study their statistical properties for estimating the degree of braiding exhibited by these fields. We present a new formula for calculating the winding number and compare it with the formula for the crossing number. The comparison is shown for a toy model of two helices and for realistic cases of nonlinear force-free fields; conceptually the formulae are nearly the same but the resulting distributions calculated for a given topology can be different. We also calculate linkages, which are useful topological quantities that are independent measures of the contribution of magnetic braiding to the total free energy and relative helicity of the field. Finally, we derive new analytical bounds for the free energy and relative helicity for the field configurations in terms of the linking number. These bounds will be of utility in estimating the braided energy available for nano-flares or for eruptions.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.007
  • Science objectives of the Magnetic Field Experiment onboard Aditya-L1
    • Authors: Vipin K. Yadav; Nandita Srivastava; S.S. Ghosh; P.T. Srikar; K. Subhalakshmi
      Abstract: Publication date: Available online 16 November 2017
      Source:Advances in Space Research
      Author(s): Vipin K. Yadav, Nandita Srivastava, S.S. Ghosh, P.T. Srikar, K. Subhalakshmi
      The Aditya-L1 is first Indian solar mission scheduled to be placed in a halo orbit around the first Lagrangian point (L1) of Sun-Earth system in the year 2018-19. The approved scientific payloads onboard Aditya-L1 spacecraft includes a Fluxgate Digital Magnetometer (FGM) to measure the local magnetic field which is necessary to supplement the outcome of other scientific experiments onboard. The in-situ vector magnetic field data at L1 is essential for better understanding of the data provided by the particle and plasma analysis experiments, onboard Aditya-L1 mission. Also, the dynamics of Coronal Mass Ejections (CMEs) can be better understood with the help of in-situ magnetic field data at the L1 point region. This data will also serve as crucial input for the short lead-time space weather forecasting models. The proposed FGM is a dual range magnetic sensor on a 6 m long boom mounted on the Sun viewing panel deck and configured to deploy along the negative roll direction of the spacecraft. Two sets of sensors (tri-axial each) are proposed to be mounted, one at the tip of boom (6 m from the spacecraft) and other, midway (3 m from the spacecraft). The main science objective of this experiment is to measure the magnitude and nature of the interplanetary magnetic field (IMF) locally and to study the disturbed magnetic conditions and extreme solar events by detecting the CME from Sun as a transient event. The proposed secondary science objectives are to study the impact of interplanetary structures and shock solar wind interaction on geo-space environment and to detect low frequency plasma waves emanating from the solar corona at L1 point. This will provide a better understanding on how the Sun affects interplanetary space. In this paper, we shall give the main scientific objectives of the magnetic field experiment and brief technical details of the FGM onboard Aditya-1 spacecraft.

      PubDate: 2017-11-24T14:10:13Z
      DOI: 10.1016/j.asr.2017.11.008
  • Examining the importance of endmember class and spectra variability in
           unmixing analysis for mapping urban impervious surfaces
    • Authors: Wenliang
      Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11
      Author(s): Wenliang Li
      Impervious surface is considered asa key indicator for evaluating urbanization intensity and environmental quality. For mapping impervious surfaces, spectral mixture analysis has been widely applied because of its effectiveness in addressing the mixed pixel problem. For spectral mixture analysis, endmember class and spectra variability have been recognized as profound error sources. In order to address these challenging problems, many techniques have been developed in recent years. While the proposed methods have proven valuable for mapping impervious surface fractions, the importance of endmember class and spectra variability in unmixing analysis is still not clear yet. In this study, I implemented five typical temporal mixture analysis models with different considerations of endmember class and endmember spectra variability. In particular, I evaluated the modelling performance of all five temporal mixture analysis models through visual examination and quantitative analysis. Furthermore, a detailed modelling performance comparison has been conducted for the overall area and both developed and less developed areas to examine the importance of endmember class and endmember spectral variability in unmixing analysis for mapping impervious surfaces. Analysis results suggest that all five proposed temporal mixture analysis models have achieved a promising performance for mapping impervious surfaces. Moreover, the performance comparison results show that the endmember class variability is more important for less developed areas and the endmember spectra variability is more important for developed areas.

      PubDate: 2017-10-29T09:56:27Z
  • List of Referees
    • Abstract: Publication date: 1 December 2017
      Source:Advances in Space Research, Volume 60, Issue 11

      PubDate: 2017-10-29T09:56:27Z
  • Revisiting the fuel-optimal four-impulse rendezvous problem near circular
    • Authors: Jing
      Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10
      Author(s): Jing Li
      This paper takes a revisit of the fuel-optimal four-impulse rendezvous problem near circular orbits. For coplanar impulsive rendezvous based on the Hill-Clohessy-Wiltshire (HCW) equations, the primer vector hodograph for an optimal four-impulse rendezvous is symmetric about the rendezvous time halfway and can be expressed as an analytical function of the third impulse time. By utilizing the associated necessary and sufficient conditions of optimality, the third and fourth impulse times are numerically determined. For practical applications, relations between the third and fourth impulse times can be well approximated as polynomial functions, which enable analytical formulas to obtain fuel-optimal four-impulse solutions. It is shown that analysis and derivations based on the HCW equations can be directly extended to the J 2 -perturbed fuel-optimal four-impulse rendezvous. Finally, numerical examples are given to illustrate and validate the obtained results.

      PubDate: 2017-10-14T12:49:22Z
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