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Showing 1 - 200 of 3043 Journals sorted alphabetically
AASRI Procedia     Open Access   (Followers: 15)
Academic Pediatrics     Hybrid Journal   (Followers: 22, SJR: 1.402, h-index: 51)
Academic Radiology     Hybrid Journal   (Followers: 21, SJR: 1.008, h-index: 75)
Accident Analysis & Prevention     Partially Free   (Followers: 84, 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: 352, 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: 235, 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: 2)
Acta Poética     Open Access   (Followers: 4)
Acta Psychologica     Hybrid Journal   (Followers: 23, 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: 5)
Additive Manufacturing     Hybrid Journal   (Followers: 7, SJR: 1.039, h-index: 5)
Additives for Polymers     Full-text available via subscription   (Followers: 21)
Advanced Drug Delivery Reviews     Hybrid Journal   (Followers: 135, 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: 25, 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 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: 26, 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: 6)
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: 41, SJR: 3.25, h-index: 43)
Advances in Engineering Software     Hybrid Journal   (Followers: 25, 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: 41, SJR: 5.465, h-index: 64)
Advances in Exploration Geophysics     Full-text available via subscription   (Followers: 3)
Advances in Food and Nutrition Research     Full-text available via subscription   (Followers: 50, 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 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: 35, 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 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: 7, 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 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: 61)
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: 3, SJR: 0.1, h-index: 2)
Advances in Space Research     Full-text available via subscription   (Followers: 353, 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: 17)
Advances in Veterinary Science and Comparative Medicine     Full-text available via subscription   (Followers: 13)
Advances in Virus Research     Full-text available via subscription   (Followers: 5, SJR: 1.878, h-index: 68)
Advances in Water Resources     Hybrid Journal   (Followers: 43, 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: 325, 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: 406, 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: 39, SJR: 1.546, h-index: 79)
Agriculture and Agricultural Science Procedia     Open Access  
Agriculture and Natural Resources     Open Access   (Followers: 1)
Agriculture, Ecosystems & Environment     Hybrid Journal   (Followers: 54, 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  
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: 8, SJR: 0.158, h-index: 9)
Alzheimer's & Dementia     Hybrid Journal   (Followers: 48, SJR: 4.289, h-index: 64)
Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring     Open Access   (Followers: 6)
Alzheimer's & Dementia: Translational Research & Clinical Interventions     Open Access   (Followers: 5)
American Heart J.     Hybrid Journal   (Followers: 49, SJR: 3.157, h-index: 153)
American J. of Cardiology     Hybrid Journal   (Followers: 47, SJR: 2.063, h-index: 186)
American J. of Emergency Medicine     Hybrid Journal   (Followers: 39, SJR: 0.574, h-index: 65)
American J. of Geriatric Pharmacotherapy     Full-text available via subscription   (Followers: 8, SJR: 1.091, h-index: 45)
American J. of Geriatric Psychiatry     Hybrid Journal   (Followers: 15, SJR: 1.653, h-index: 93)
American J. of Human Genetics     Hybrid Journal   (Followers: 31, SJR: 8.769, h-index: 256)
American J. of Infection Control     Hybrid Journal   (Followers: 25, 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: 45, 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: 233, SJR: 2.255, h-index: 171)
American J. of Ophthalmology     Hybrid Journal   (Followers: 58, SJR: 2.803, h-index: 148)
American J. of Ophthalmology Case Reports     Open Access   (Followers: 5)
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: 26, SJR: 2.653, h-index: 228)
American J. of Preventive Medicine     Hybrid Journal   (Followers: 22, SJR: 2.764, h-index: 154)
American J. of Surgery     Hybrid Journal   (Followers: 34, 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: 5)
Anaerobe     Hybrid Journal   (Followers: 4, SJR: 1.066, h-index: 51)
Anaesthesia & Intensive Care Medicine     Full-text available via subscription   (Followers: 57, SJR: 0.124, h-index: 9)
Anaesthesia Critical Care & Pain Medicine     Full-text available via subscription   (Followers: 11)
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: 11)
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  
Animal Behaviour     Hybrid Journal   (Followers: 161, SJR: 1.907, h-index: 126)
Animal Feed Science and Technology     Hybrid Journal   (Followers: 5, SJR: 1.151, h-index: 83)
Animal Reproduction Science     Hybrid Journal   (Followers: 5, SJR: 0.711, h-index: 78)
Annales d'Endocrinologie     Full-text available via subscription   (Followers: 1, SJR: 0.394, h-index: 30)
Annales d'Urologie     Full-text available via subscription  
Annales de Cardiologie et d'Angéiologie     Full-text available via subscription   (SJR: 0.177, h-index: 13)
Annales de Chirurgie de la Main et du Membre Supérieur     Full-text available via subscription  
Annales de Chirurgie Plastique Esthétique     Full-text available via subscription   (Followers: 2, SJR: 0.354, h-index: 22)
Annales de Chirurgie Vasculaire     Full-text available via subscription   (Followers: 1)

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Journal Cover Advances in Space Research
  [SJR: 0.606]   [H-I: 65]   [353 followers]  Follow
   Full-text available via subscription Subscription journal
   ISSN (Print) 0273-1177
   Published by Elsevier Homepage  [3043 journals]
  • TEC derived from some GPS stations in East African equatorial region and
           comparison with the TEC from NeQuick2 model
    • Authors: Francis Twinomugisha; Nicholausi Ssebiyonga; Florence M. D'ujanga
      Pages: 1905 - 1920
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Francis Twinomugisha, Nicholausi Ssebiyonga, Florence M. D'ujanga
      This paper investigates the capacity of NeQuick2 model in predicting the vertical Total Electron Content (vTEC) over East Africa equatorial region during solar minimum (2010) and solar maximum (2012) phases. This has been carried out by comparing the NeQuick2 vTEC and GPS vTEC from five GPS (Global Positioning System) receivers at Makerere University, University of Nairobi, Mbarara, Malindi and Addis Ababa. The diurnal, monthly and seasonal variations in the measured vTEC have been analysed and compared with the NeQuick2 modeled vTEC. Comparative analysis has shown high correlation between NeQuick2 vTEC and GPS vTEC for both years. The correlation coefficients (R2) between the predicted and measured vTEC at all the stations were in the range (0.884–0.953) and (0.881–0.910) in 2010 and 2012years respectively. NeQuick2 predicted the diurnal vTEC better for the times 01:00–03:00, Universal Time (UT) (10:00–12:00, Local Time, LT) for all the stations than for other times. There were high discrepancies between the modeled and measured vTEC values as observed between 06:00–16:00 UT (09:00–19:00 LT) over Addis Ababa during the two years in consideration. With regard to the monthly and seasonal vTEC prediction, the NeQuick2 model overestimates both the monthly and seasonal mean hourly vTEC values in almost all the stations except at Addis Ababa. The effects of geomagnetic storm on NeQuick2 model has also been investigated. NeQuick2 model did not respond to the effects associated with geomagnetic storm. There is need to include storm related parameters in the prediction of vTEC using NeQuick2 model.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.018
  • Magnetic and electric field variations during geomagnetically active days
           over Turkey
    • Authors: Emine Ceren Kalafatoğlu Eyigüler; Zerefşan Kaymaz
      Pages: 1921 - 1948
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Emine Ceren Kalafatoğlu Eyigüler, Zerefşan Kaymaz
      Currents in the magnetosphere flow into the ionosphere during geomagnetic disturbances and are detected at the ground magnetic stations as Geomagnetically Induced Currents (GICs). In this paper, magnetic and electric field characteristics of the GICs at midlatitudes were studied using electric field and magnetic field observations in Turkey during the geomagnetically active intervals. A magnetotelluric station consisting of an electrometer and a magnetometer were set up in Bozcaada, Çanakkale (37.5°N, 106°E). Several cases that showed large electric and magnetic field fluctuations during geomagnetic disturbances were selected and the effects of geomagnetic activity were studied using the time derivatives of horizontal component of the magnetic field and the deviations in the magnetic and electric field components from the quiet background. In magnetic field data, quiet day Sq variations were removed using cubic spline fits. Similarly, the magnitude of the deviations in the electric field were determined by subtracting the background electric field determined by using cubic spline. Corresponding to the strong geomagnetic activity identified using Kp and Dst indices, high frequency, strong fluctuations in the magnetic field, its derivatives, and electric field were observed. These fluctuations in horizontal magnetic and electric field were compared with those seen during a magnetically quiet day. The close association between the fluctuations of the time derivatives of the horizontal magnetic field and electric field components were demonstrated. Two types of variations in the electric and magnetic fields corresponding to the different phases of the geomagnetic activity were identified: those corresponding to the initial phase including the sudden commencement and those to the main phase of the geomagnetic storm. The fluctuations in both magnetic field and electric field corresponding to the sudden commencement and the initial phase indicate the effects of magnetopause currents driven by the large solar wind dynamic pressure as associated with the coronal mass ejection (CME) events. Each event shows increased levels of ground level magnetic and electric field fluctuations corresponding to the CME compression at the subsolar magnetopause. High frequency, large fluctuations continue subsequently during the main phase in the presence of the geomagnetic storms. The fluctuations during the main phase were found to be different than those corresponding to the sudden commencements. GIC occurrences in our latitudes were shown to be associated with the sudden commencement and main phase of the geomagnetic storm activity. The time rate of change in horizontal component of the magnetic field showed perturbations on the order of 0.5nT/s in our region. The sources of the GICs based on these observations were discussed. This study presents our preliminary results on the characteristics of the GICs over Turkey based on the simultaneous measurements of electric and magnetic field during the geomagnetic storms. It is the first study of the GICs in Eurasia region and the results contribute to the worldwide understanding and modelling efforts on the GICs.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.019
  • Analytical solution of electromagnetic radiation by a vertical electric
           dipole inside the earth and the effect of atmospheric electrical
           conductivity inhomogeneity
    • Authors: Taha Mosayebidorcheh; Fahimeh Hosseinibalam; Smaeyl Hassanzadeh
      Pages: 1949 - 1957
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Taha Mosayebidorcheh, Fahimeh Hosseinibalam, Smaeyl Hassanzadeh
      In this paper, the effect of atmospheric electrical conductivity on the electromagnetic waves radiated by a vertical electric dipole located in the earth, near the surface of the earth, is investigated. As far as electrical conductivity is concerned, the atmosphere is divided into three areas, in which the electrical conductivity changes with altitude. The Maxwell equations in these areas are investigated as well. Using the differential transform method, the differential equation is solved in a way that atmospheric electrical conductivity is variable. Solving the problem in these areas indicates that electrical conductivity in the middle and lower areas of atmosphere may be ignored. However, in the upper areas of atmosphere, the magnitude of the magnetic field in the ionosphere at a frequency of 10kHz at night is five times smaller when electrical conductivity is considered compared to when it is neglected.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.034
  • Ionospheric responses during equinox and solstice periods over Turkey
    • Authors: Secil Karatay; Ali Cinar; Feza Arikan
      Pages: 1958 - 1967
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Secil Karatay, Ali Cinar, Feza Arikan
      Ionospheric electron density is the determining variable for investigation of the spatial and temporal variations in the ionosphere. Total Electron Content (TEC) is the integral of the electron density along a ray path that indicates the total variability through the ionosphere. Global Positioning System (GPS) recordings can be utilized to estimate the TEC, thus GPS proves itself asa useful tool in monitoring the total variability of electron distribution within the ionosphere. This study focuses on the analysis of the variations of ionosphere over Turkey that can be grouped into anomalies during equinox and solstice periods using TEC estimates obtained by a regional GPS network. It is observed that noon time depletions in TEC distributions predominantly occur in winter for minimum Sun Spots Numbers (SSN) in the central regions of Turkey which also exhibit high variability due to midlatitude winter anomaly. TEC values and ionospheric variations at solstice periods demonstrate significant enhancements compared to those at equinox periods.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.038
  • Impact of receiver and constellation on high rate GNSS phase rate
           measurements to monitor ionospheric irregularities
    • Authors: Reza Ghoddousi-Fard
      Pages: 1968 - 1977
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Reza Ghoddousi-Fard
      High rate (1Hz) GPS and GLONASS phase rate measurements from the global Real Time International GNSS Service (RT-IGS) network are used to monitor ionospheric irregularities. In this paper, impact of different receiver types and satellite constellations on GNSS-derived indices are studied. Constellation dependent background phase noise is quantified at RT-IGS stations for different receiver categories. Improved sampling of the ionosphere is achieved using multiple constellations. Correlation of hourly mean values of dual constellation GNSS indices with hourly magnetic ranges at a co-located auroral magnetic observatory slightly increased compared to when single constellation is used.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.039
  • Estimation of canopy carotenoid content of winter wheat using multi-angle
           hyperspectral data
    • Authors: Weiping Kong; Wenjiang Huang; Jiangui Liu; Pengfei Chen; Qiming Qin; Huichun Ye; Dailiang Peng; Yingying Dong; A. Hugh Mortimer
      Pages: 1988 - 2000
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Weiping Kong, Wenjiang Huang, Jiangui Liu, Pengfei Chen, Qiming Qin, Huichun Ye, Dailiang Peng, Yingying Dong, A. Hugh Mortimer
      Precise estimation of carotenoid (Car) content in crops, using remote sensing data, could be helpful for agricultural resources management. Conventional methods for Car content estimation were mostly based on reflectance data acquired from nadir direction. However, reflectance acquired at this direction is highly influenced by canopy structure and soil background reflectance. Off-nadir observation is less impacted, and multi-angle viewing data are proven to contain additional information rarely exploited for crop Car content estimation. The objective of this study was to explore the potential of multi-angle observation data for winter wheat canopy Car content estimation. Canopy spectral reflectance was measured from nadir as well as from a series of off-nadir directions during different growing stages of winter wheat, with concurrent canopy Car content measurements. Correlation analyses were performed between Car content and the original and continuum removed spectral reflectance. Spectral features and previously published indices were derived from data obtained at different viewing angles and were tested for Car content estimation. Results showed that spectral features and indices obtained from backscattering directions between 20° and 40° view zenith angle had a stronger correlation with Car content than that from the nadir direction, and the strongest correlation was observed from about 30° backscattering direction. Spectral absorption depth at 500nm derived from spectral data obtained from 30° backscattering direction was found to reduce the difference induced by plant cultivars greatly. It was the most suitable for winter wheat canopy Car estimation, with a coefficient of determination 0.79 and a root mean square error of 19.03mg/m2. This work indicates the importance of taking viewing geometry effect into account when using spectral features/indices and provides new insight in the application of multi-angle remote sensing for the estimation of crop physiology.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.015
  • Spatial upscaling of green aboveground biomass derived from MODIS-based
           NDVI in arid and semiarid grasslands
    • Authors: Juanjuan Xue; Yonghui Ge; Hongrui Ren
      Pages: 2001 - 2008
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Juanjuan Xue, Yonghui Ge, Hongrui Ren
      Accurate estimation of green aboveground biomass is important for sustainable use of grassland resources in arid and semiarid grasslands. Nevertheless, it is difficult to achieve spatial upscaling of green aboveground biomass estimation using traditional spatial upscaling methods in arid and semiarid grasslands due to its inherent heterogeneity. In the study, a new spatial upscaling algorithm was proposed to estimate green aboveground biomass in the desert steppe of Inner Mongolia. The algorithm was successfully employed for spatial upscaling of green aboveground biomass estimation from MOD13Q1 NDVI (fine resolution) to MOD13A2 NDVI (coarse resolution) based on field measurements in the desert steppe. Results showed that, the correlation between distributed green aboveground biomass (obtained from fine resolution) and lumped green aboveground biomass (obtained from coarse resolution) was improved, and root mean squared error and relative error decreased after upscaling. Statistical analyses performing on the slopes and intercepts of the fitted lines between distributed green aboveground biomass and lumped green aboveground biomass demonstrated that, there was no significant difference (P >0.05) between the fitted line and the 1:1 line after upscaling, and there was significant difference (P <0.05) between the fitted line and the 1:1 line before upscaling. These indicated that, lumped green aboveground biomass after upscaling was much closer to distributed aboveground green biomass than lumped green aboveground biomass before upscaling. The algorithm proposed in the study could play an important role in large-scale green aboveground biomass investigation in arid and semiarid grasslands.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.016
  • Sliding mode control for Mars entry based on extended state observer
    • Authors: Kunfeng Lu; Yuanqing Xia; Ganghui Shen; Chunmei Yu; Liuyu Zhou; Lijun Zhang
      Pages: 2009 - 2020
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Kunfeng Lu, Yuanqing Xia, Ganghui Shen, Chunmei Yu, Liuyu Zhou, Lijun Zhang
      This paper addresses high-precision Mars entry guidance and control approach via sliding mode control (SMC) and Extended State Observer (ESO). First, differential flatness (DF) approach is applied to the dynamic equations of the entry vehicle to represent the state variables more conveniently. Then, the presented SMC law can guarantee the property of finite-time convergence of tracking error, which requires no information on high uncertainties that are estimated by ESO, and the rigorous proof of tracking error convergence is given. Finally, Monte Carlo simulation results are presented to demonstrate the effectiveness of the suggested approach.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.06.014
  • Relative tracking control of constellation satellites considering
           inter-satellite link
    • Authors: M. Fakoor; F. Amozegary; M. Bakhtiari; K. Daneshjou
      Pages: 2021 - 2046
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): M. Fakoor, F. Amozegary, M. Bakhtiari, K. Daneshjou
      In this article, two main issues related to the large-scale relative motion of satellites in the constellation are investigated to establish the Inter Satellite Link (ISL) which means the dynamic and control problems. In the section related to dynamic problems, a detailed and effective analytical solution is initially provided for the problem of satellite relative motion considering perturbations. The direct geometric method utilizing spherical coordinates is employed to achieve this solution. The evaluation of simulation shows that the solution obtained from the geometric method calculates the relative motion of the satellite with high accuracy. Thus, the proposed analytical solution will be applicable and effective. In the section related to control problems, the relative tracking control system between two satellites will be designed in order to establish a communication link between the satellites utilizing analytical solution for relative motion of satellites with respect to the reference trajectory. Sliding mode control approach is employed to develop the relative tracking control system for body to body and payload to payload tracking control. Efficiency of sliding mode control approach is compared with PID and LQR controllers. Two types of payload to payload tracking control considering with and without payload degree of freedom are designed and suitable one for practical ISL applications is introduced. Also, Fuzzy controller is utilized to eliminate the control input in the sliding mode controller.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.012
  • Consensus of satellite cluster flight using an energy-matching optimal
           control method
    • Authors: Jianjun Luo; Liang Zhou; Bo Zhang
      Pages: 2047 - 2059
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Jianjun Luo, Liang Zhou, Bo Zhang
      This paper presents an optimal control method for consensus of satellite cluster flight under a kind of energy matching condition. Firstly, the relation between energy matching and satellite periodically bounded relative motion is analyzed, and the satellite energy matching principle is applied to configure the initial conditions. Then, period-delayed errors are adopted as state variables to establish the period-delayed errors dynamics models of a single satellite and the cluster. Next a novel satellite cluster feedback control protocol with coupling gain is designed, so that the satellite cluster periodically bounded relative motion consensus problem (period-delayed errors state consensus problem) is transformed to the stability of a set of matrices with the same low dimension. Based on the consensus region theory in the research of multi-agent system consensus issues, the coupling gain can be obtained to satisfy the requirement of consensus region and decouple the satellite cluster information topology and the feedback control gain matrix, which can be determined by Linear quadratic regulator (LQR) optimal method. This method can realize the consensus of satellite cluster period-delayed errors, leading to the consistency of semi-major axes (SMA) and the energy-matching of satellite cluster. Then satellites can emerge the global coordinative cluster behavior. Finally the feasibility and effectiveness of the present energy-matching optimal consensus for satellite cluster flight is verified through numerical simulations.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.013
  • Trajectory optimization for lunar soft landing with complex constraints
    • Authors: Huiping Chu; Lin Ma; Kexin Wang; Zhijiang Shao; Zhengyu Song
      Pages: 2060 - 2076
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Huiping Chu, Lin Ma, Kexin Wang, Zhijiang Shao, Zhengyu Song
      A unified trajectory optimization framework with initialization strategies is proposed in this paper for lunar soft landing for various missions with specific requirements. Two main missions of interest are Apollo-like Landing from low lunar orbit and Vertical Takeoff Vertical Landing (a promising mobility method) on the lunar surface. The trajectory optimization is characterized by difficulties arising from discontinuous thrust, multi-phase connections, jump of attitude angle, and obstacles avoidance. Here R-function is applied to deal with the discontinuities of thrust, checkpoint constraints are introduced to connect multiple landing phases, attitude angular rate is designed to get rid of radical changes, and safeguards are imposed to avoid collision with obstacles. The resulting dynamic problems are generally with complex constraints. The unified framework based on Gauss Pseudospectral Method (GPM) and Nonlinear Programming (NLP) solver are designed to solve the problems efficiently. Advanced initialization strategies are developed to enhance both the convergence and computation efficiency. Numerical results demonstrate the adaptability of the framework for various landing missions, and the performance of successful solution of difficult dynamic problems.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.024
  • An anytime branch and bound algorithm for agile earth observation
           satellite onboard scheduling
    • Authors: Xiaogeng Chu; Yuning Chen; Yuejin Tan
      Pages: 2077 - 2090
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Xiaogeng Chu, Yuning Chen, Yuejin Tan
      To fulfill the mission of targets recognition over sea, a bi-satellite cluster composed of an autonomous low resolution satellite (LRS) leading the formation for targets detection and a trailing agile high resolution satellite (HRS) for targets recognition is considered. This paper focuses on the development of a method that is able to generate a schedule plan onboard the HRS taking into account the information received from the LRS, which amounts to solving an agile earth observation satellite (AEOS) scheduling problem. The main contributions of this paper are two folds: a mathematical model for formulating the AEOS scheduling problem, and an anytime branch and bound algorithm for problem solution. Experimental results on a set of representative scenarios show that the proposed algorithm is effective which promotes significantly the bi-satellite cluster to improve the efficiency of targets recognition over sea as opposed to traditional methods where a large number of satellites are required to work coordinately. In particular, in a scenario over a 500km×2000km sea area involving 25 targets, the performance of the bi-satellite cluster amounts to the coordination of 30 high resolution satellites.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.026
  • A fiery birth of aluminosilica analogs of refractory dust in the upper
    • Authors: F.J.M. Rietmeijer; M. Ferrari; V. Della Corte; A. Rotundi; P. Palumbo; S. De Angelis; V. Galluzzi
      Pages: 2091 - 2098
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): F.J.M. Rietmeijer, M. Ferrari, V. Della Corte, A. Rotundi, P. Palumbo, S. De Angelis, V. Galluzzi
      Following a successful dust collection flight in the upper stratosphere our DUSTER (Dust in the Upper Stratosphere Tracking Experiment and Retrieval) made a safe remote landing at its assigned location on Baffin Island during early June 2009. When the balloon payload that included DUSTER was retrieved it was found part of the payload had experienced a lithium-sparked fire while the payload was being dragged across the landing site. In this process the housing of DUSTER had developed a pin-sized hole that allowed smoke of the fire to enter the collector. Numerous smoke particles were found covering both the DUSTER collection and blank collector surfaces an indication that our experiment to collect upper stratospheric dust had failed! Both collector surfaces were covered by numerous carbon smoke and amorphous, aluminosilica nanoparticles. The compositions of vast majority of these aluminosilica nanoparticles, Al2O3 =49wt% and SiO2 =51wt%, was both surprising and unique because it was an exact match of the Deep Metastable Eutectic (DME) nanoparticles found in vapor phase condensation experiments. These vapor phase condensation experiments were conducted to explore the formation of extraterrestrial dust particles. We are not claiming an extraterrestrial origin for these particles from this DUSTER experiment. We submit that given the appropriate conditions of high temperature alumina and silica vapors and rapid quenching in a contained natural environment, DME aluminosilica nanoparticles will likely condense. This serendipitous result can be used to explore nanoparticle formation inside incandescent clouds associated with bolides and fireballs.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.030
  • Lunar regolith stratigraphy analysis based on the simulation of lunar
           penetrating radar signals
    • Authors: Jialong Lai; Yi Xu; Xiaoping Zhang; Zesheng Tang
      Pages: 2099 - 2107
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): Jialong Lai, Yi Xu, Xiaoping Zhang, Zesheng Tang
      The thickness of lunar regolith is an important index of evaluating the quantity of lunar resources such as 3He and relative geologic ages. Lunar penetrating radar (LPR) experiment of Chang’E-3 mission provided an opportunity of in situ lunar subsurface structure measurement in the northern mare imbrium area. However, prior work on analyzing LPR data obtained quite different conclusions of lunar regolith structure mainly because of the missing of clear interface reflectors in radar image. In this paper, we utilized finite-difference time-domain (FDTD) method and three models of regolith structures with different rock density, number of layers, shapes of interfaces, and etc. to simulate the LPR signals for the interpretation of radar image. The simulation results demonstrate that the scattering signals caused by numerous buried rocks in the regolith can mask the horizontal reflectors, and the die-out of radar echo does not indicate the bottom of lunar regolith layer and data processing such as migration method could recover some of the subsurface information but also result in fake signals. Based on analysis of simulation results, we conclude that LPR results uncover the subsurface layered structure containing the rework zone with multiple ejecta blankets of small crater, the ejecta blanket of Chang’E-3 crater, and the transition zone and estimate the thickness of the detected layer is about 3.25m.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.032
  • Visibility of coronal mass ejections in SOHO/LASCO coronagraphs
    • Authors: K. Bronarska; G. Michalek; S. Yashiro; S. Akiyama
      Pages: 2108 - 2115
      Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9
      Author(s): K. Bronarska, G. Michalek, S. Yashiro, S. Akiyama
      We studied the detection efficiency of coronal mass ejections (CMEs) of the Large Angle Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). For this purpose LASCO/SOHO observations are compared with these obtained by the two Solar Terrestrial Relations Observatory (STEREO) satellites in quadrature in the period of time June-November 2011. These unprecedented observations enable us to the direct detection of CMEs that are not visible in LASCO coronagraphs (invisible events). Determination of these events allowed us to evaluate the detection efficiency of LASCO coronagraphs. We found that the total visibility function is ≈ 0.80. Having source location, from associated flares or other signatures observed in the corona, longitudinal variation of the visibility function was also found. It was demonstrated that invisible-to-LASCO CMEs are narrow (average width is only 20 ° ), slow (average velocity is 328kms−1) and originate from the disk center. We have shown that the detection efficiency of the LASCO coronagraphs with typical data availability is sufficient to detect all potentially geoeffective CMEs.

      PubDate: 2017-09-30T10:29:31Z
      DOI: 10.1016/j.asr.2017.07.033
  • Studies on mesosphere, thermosphere and ionosphere from equatorial to mid
           latitudes – Recent investigations and improvements – Part 1
    • Authors: Venkatesh Kavutarapu; Michael Pezzopane
      Pages: 1583 - 1584
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): Venkatesh Kavutarapu, Michael Pezzopane

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.08.010
  • Ionospheric winter anomaly and annual anomaly observed from
           Formosat-3/COSMIC Radio Occultation observations during the ascending
           phase of solar cycle 24
    • Authors: V. Sai Gowtam; S. Tulasi Ram
      Pages: 1585 - 1593
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): V. Sai Gowtam, S. Tulasi Ram
      Ionospheric winter and annual anomalies have been investigated during the ascending phase of solar cycle 24 using high-resolution global 3D – data of the FORMOSAT – 3/COSMIC (Formosa satellite – 3/Constellation Observing System for Meterology, Ionosphere and Climate) radio occultation observations. Our detailed analysis shows that the occurrence of winter anomaly at low-latitudes is confined only to the early morning to afternoon hours, whereas, the winter anomaly at mid-latitudes is almost absent at all local times during the ascending phase of solar cycle 24. Further, in the topside ionosphere (altitudes of 400km and above), the winter anomaly is completely absent at all local times. In contrast, the ionospheric annual anomaly is consistently observed at all local times and altitudes during this ascending phase of solar cycle 24. The annual anomaly exhibits strong enhancements over southern EIA crest latitudes during day time and around Weddle Sea Anomaly (WSA) region during night times. The global mean annual asymmetry index is also computed to understand the altitudinal variation. The global mean AI maximizes around 300–500km altitudes during the low solar active periods (2008–10), whereas it extends up to 600km during moderate to high (2011) solar activity period. These findings from our study provide new insights to the current understanding of the annual anomaly.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.03.017
  • An investigation of ionospheric upper transition height variations at low
           and equatorial latitudes deduced from combined COSMIC and C/NOFS
    • Authors: Changjun Yang; Biqiang Zhao; Jie Zhu; Xinan Yue; Weixing Wan
      Pages: 1617 - 1628
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): Changjun Yang, Biqiang Zhao, Jie Zhu, Xinan Yue, Weixing Wan
      In this study we propose the combination of topside in-situ ion density data from the Communication/Navigation Outage Forecast System (C/NOFS) along with the electron density profile measurement from Constellation Observing System for Meteorology, Ionosphere & Climate (COSMIC) satellites Radio Occultation (RO) for studying the spatial and temporal variations of the ionospheric upper transition height (hT ) and the oxygen ion (O+) density scale height. The latitudinal, local time and seasonal distributions of upper transition height show more consistency between hT re-calculated by the profile of the O+ using an α-Chapman function with linearly variable scale height and that determined from direct in-situ ion composition measurements, than with constant scale height and only the COSMIC data. The discrepancy in the values of hT between the C/NOFS measurement and that derived by the combination of COSMIC and C/NOFS satellites observations with variable scale height turns larger as the solar activity decreases, which suggests that the photochemistry and the electrodynamics of the equatorial ionosphere during the extreme solar minimum period produce abnormal structures in the vertical plasma distribution. The diurnal variation of scale heights (Hm ) exhibits a minimum after sunrise and a maximum around noon near the geomagnetic equator. Further, the values of Hm exhibit a maximum in the summer hemisphere during daytime, whereas in the winter hemisphere the maximum is during night. Those features of Hm consistently indicate the prominent role of the vertical electromagnetic (E×B) drift in the equatorial ionosphere.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2016.11.024
  • Vertical and oblique HF sounding with a network of synchronised ionosondes
    • Authors: Tobias Verhulst; David Altadill; Jens Mielich; Bodo Reinisch; Ivan Galkin; Angelos Mouzakis; Anna Belehaki; Dalia Burešová; Stanimir Stankov; Estefania Blanch; Daniel Kouba
      Pages: 1644 - 1656
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): Tobias Verhulst, David Altadill, Jens Mielich, Bodo Reinisch, Ivan Galkin, Angelos Mouzakis, Anna Belehaki, Dalia Burešová, Stanimir Stankov, Estefania Blanch, Daniel Kouba
      A network of ionosondes in Europe has been established to monitor travelling ionospheric disturbances (TIDs) by simultaneously making vertical and oblique incidence HF sounding measurements. This network is the outcome of the Net-TIDE project, a collaboration between European Digisonde operators that have synchronised the sounding schedules of the Digisondes in order to record vertical and oblique ionogram traces simultaneously, and have added Digisonde-to-Digisonde (D2D) fixed frequency oblique-incidence measurements to the measurement schedule. The distances between the observatories involved in the project range from 500km to over 2000km. The technical feasibility of this network approach is explored. The challenge for the fixed-frequency D2D skymap measurements is the automatic selection of the sounding frequencies depending on the geometry of the sounding paths, the diurnal and seasonal ionospheric changes, and space weather induced events.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.06.033
  • Ionosphere VHF scintillations over Vaddeswaram (Geographic Latitude
           16.31°N, Geographic Longitude 80.30°E, Dip 18°N), a latitude Indian
           station – A case study
    • Authors: P.S. Brahmanandam; G. Uma; T.K. Pant
      Pages: 1688 - 1697
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): P.S. Brahmanandam, G. Uma, T.K. Pant
      This research reports the 250MHz amplitude ionosphere scintillations recorded at Vaddeswaram (Geographic Latitude 16.31°N, Geographic Longitude 80.30°E, Dip 18°N), a low-latitude station in India. Though amplitude scintillations were recorded for four continuous days (05–08 November 2011), the presence of intense and long-duration scintillations on 06 November 2011 instigated us to verify the ionosphere background conditions. This research, therefore, is also used important databases including, diurnal variations of h′F (virtual height of the F-layer) and the vertical drifts as measured by an advanced digital ionosonde radar located at an Indian equatorial station i.e. Trivandrum (Geographic Latitude 8.5°N, Geographic Longitude 77°E, Dip 0.5°N), equatorial Electrojet (EEJ) ground strength measured using magnetometers and the total electron content (TEC) maps provided by the International GPS Service (IGS) to study the background ionosphere conditions. The interesting observations are higher E×B drifts, the occurrence of long-duration range-type spread F signatures at Trivandrum and, thereafter, intense scintillations over Vaddeswaram. It was found a secondary peak at around 1600 LT in EEJ strength followed by a higher upward drift velocity (more than 60m/s) with a significant raise of the F region up to 470km over the magnetic equator on 06 November 2011. The possible physical mechanisms of these important observational results are discussed in the light of available literature.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.06.051
  • Modelling ionospheric scintillation under the crest of the equatorial
    • Authors: L. Alfonsi; A.W. Wernik; M. Materassi; L. Spogli
      Pages: 1698 - 1707
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): L. Alfonsi, A.W. Wernik, M. Materassi, L. Spogli
      WAM is realized making use of the plasma density data collected via the retarding potential analyser on board the Dynamics Explorer 2 spacecraft, capable to model the scintillation climatology over the northern hemisphere high latitude ionosphere. More recently, WAM has been tuned to model the ionospheric scintillations also over the equatorial latitudes. The effort has been done to support the CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project in the assessment of the scintillations climatology over Latin America. The concept of the new release of WAM is the same already adopted for the high latitudes: the in situ measurements, supplemented with an ionospheric model and with the irregularity anisotropy model, are treated to describe the morphology of scintillation, provided a suitable propagation model is used. Significant differences have been included in the low latitudes release to account for the anisotropy of the irregularities and for strong scattering regime. The paper describes the new WAM formulation and presents comparisons of the model predictions with the actual measurements collected in Brazil.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.05.021
  • Post sunset equatorial spread-F at Kwajalein and interplanetary magnetic
    • Authors: R.G. Rastogi; H. Chandra; P. Janardhan; B.W. Reinisch; Susanta Kumar Bisoi
      Pages: 1708 - 1715
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): R.G. Rastogi, H. Chandra, P. Janardhan, B.W. Reinisch, Susanta Kumar Bisoi
      We connect the time sequence of changes in the IMF-Bz to the development of spread-F at an equatorial station Kwajalein on three different nights in November 2004, one during a geomagnetic quiet period and other two during geomagnetic disturbed periods. The chosen days show clear and smooth variations of IMF-Bz without any large fluctuations thereby enabling one to correlate changes in equatorial spread-F with corresponding changes in IMF-Bz. It is shown that a slow and continuous increase in the IMF-Bz over a duration of few hours has a similar effect on the equatorial ionosphere as of a sudden northward turning of the IMF-Bz in causing an electric field through the polar region and then to the equator. We conclude that the Spread-F at equatorial and low latitudes are due to echoes from ionization irregularities that arise due to the plasma instabilities generated by an eastward electric field on the large plasma density gradient in or below the base of the F-layer during any period of the night time along with the gravity driven Rayleigh-Taylor instability.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.06.020
  • Plasma blobs associated with plasma bubbles observed in the Brazilian
    • Authors: F. Tardelli-Coelho; A.A. Pimenta; A. Tardelli; J.R. Abalde; K. Venkatesh
      Pages: 1716 - 1724
      Abstract: Publication date: 15 October 2017
      Source:Advances in Space Research, Volume 60, Issue 8
      Author(s): F. Tardelli-Coelho, A.A. Pimenta, A. Tardelli, J.R. Abalde, K. Venkatesh
      In this paper we present a case of plasma blobs associated with plasma bubbles which were observed by emission of OI 630.0nm airglow, using ground-based (all-sky images) and DMSP-F15 satellite data on 23 February 2007, over a low latitude station São José dos Campos (SJC) (23.21°S, 45.86°W; dip latitude 18.3°S) in the Brazilian sector. We calculated the zonal drift velocities of the plasma bubble and plasma blobs, and the longitudinal drift of the blobs that occurred that night using the linearization method presented by Pimenta et al. (2001). The north/south and east/west extensions of plasma blobs have also been estimated. The mean velocity of the plasma bubble is found to be 74±8m/s and the plasma blob zonal drift is 61±6m/s. The average velocity of the longitudinal drift of the plasma blob was 85±13m/s and the analyzed blobs had the mean north/south extension of 591km and east/west extension of 328 and 263km.

      PubDate: 2017-09-23T21:37:42Z
      DOI: 10.1016/j.asr.2017.06.018
  • 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
  • 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
  • List of Referees
    • Abstract: Publication date: 15 November 2017
      Source:Advances in Space Research, Volume 60, Issue 10

      PubDate: 2017-10-14T12:49:22Z
  • List of Referees
    • Abstract: Publication date: 1 November 2017
      Source:Advances in Space Research, Volume 60, Issue 9

      PubDate: 2017-09-30T10:29:31Z
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