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Advances in Space Research
Journal Prestige (SJR): 0.569
Citation Impact (citeScore): 2
Number of Followers: 419  
 
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ISSN (Print) 0273-1177
Published by Elsevier Homepage  [3183 journals]
  • Data processing center of RadioAstron space VLBI project
    • Abstract: Publication date: Available online 9 July 2019Source: Advances in Space ResearchAuthor(s): M.V. Shatskaya, A.A. Abramov, N.A. Fedorov, V.I. Kostenko, S.F. Likhachev, S.I. Seliverstov, D.A. Sychev In this paper, questions on development, implementation, and operation of RadioAstron project Data Processing Center (DPC) are reviewed. The main components of the dedicated DPC are the computer complex with 1 TFlops/s performance, storage with memory capacity of approximately 10 PB, the network infrastructure, and the corresponding communication channels. Performance enhancement methods and resolution of information storage, archiving, and process problems of space VLBI high-speed digital data flows are analyzed. It is shown that successful operation of DPC is mainly provided by optimal organization of computer system structure, storage, and networking transmission. Some of the important key features of RadioAstron project DPC and its comparative differences from the standard VLBI procedures are considered.
       
  • Real-time clock prediction of Multi-GNSS satellites and its application in
           precise point positioning
    • Abstract: Publication date: Available online 8 July 2019Source: Advances in Space ResearchAuthor(s): Peng Yaquan, Lou Yidong, Gong Xiaopeng, Wang Yintong, Dai Xiaolei With the development of Global Navigation Satellite System (GNSS), multi-GNSS is expected to greatly benefit precise point positioning (PPP), especially during the outage of real time service (RTS). In this paper, we focus on the performance of multi-GNSS satellite clock prediction and its application in real-time PPP. Based on the statistical analysis of multi-system satellite clock products, a model consisting of polynomial and periodic terms is employed for multi-system satellite clock prediction. To evaluate the method proposed, both post-processed and real-time satellite clock products are employed in simulated real-time processing mode. The results show that the accuracy of satellite clock prediction is related to atomic clock type and satellite type. For GPS satellites, the average standard deviations (STDs) of Cs atomic clocks will reach as high as 0.65 ns while the STD of Rb atomic clocks is only about 0.15 ns. As for BDS and Galileo, the average STD of 2-hour satellite clock prediction are 0.30 ns and 0.06 ns, respectively. In addition, it is validated that real-time PPP can still achieve positioning accuracy of one to three decimeters by using products of 2-hour satellite clock prediction. Moreover, compared to the results of GPS-only PPP, multi-system can greatly enhance the accuracy of real-time PPP from 12.5% to 18.5% in different situations.
       
  • Seasonal variation of plasma bubbles during solar cycle 23 - 24 over the
           Brazilian equatorial region
    • Abstract: Publication date: Available online 8 July 2019Source: Advances in Space ResearchAuthor(s): Ebenezer Agyei-Yeboah, Igo Paulino, Amauri Fragaso de Medeiros, Ricardo Arlen Buriti, Ana Roberta Paulino, Patrick Essien, Solomon Otoo Lomotey, Hisao Takashi, Cristiano Max Wrasse In this study, OI 630.0 nm nightglow image data obtained from an all-sky imaging station located at Sao Joao do Cariri (7.4°S, 36.5°W), have been used to study the occurrence of equatorial plasma bubbles (EPBs) over the Brazilian equatorial region. The observations, which took place from September 2000 to December 2010 (almost eleven years), covered a significant part of solar cycle 23 (descending phase of SC23) and the very beginning of solar cycle 24 (ascending phase of SC24). There were 1337 nights of observations with 666 nights with EPB events, which translates to an occurrence rate of ∼49.8 %. Of these nights, 1290 were considered quiet (Dst ≥ -50 nT) with ∼ 50 % plasma bubbles occurrence rate. The occurrence of EPBs was studied under three solar activity phases – high solar activity phase (HSA, September 2000 – March 2004), moderate solar activity phase (MSA or descending phase, March 2004 – October 2006) and low solar activity phase (LSA, October 2006 – December 2010). The low solar activity phase is part of the peculiar solar cycle 24, considered the weakest in over a century with most sunspotless days (2008 - 2009). The maximum occurrence of bubbles, equal to 54.2 %, was found during the HSA phase, with percentages characterizing MSA and LSA being respectively 52.4 % and 45.8 %. The analysis also showed clear seasonal variation in the EPB occurrence with maximum rates in summer, spring, autumn, and the minimum rates in winter for all solar activity phases. Overall, there was observed solar cycle variation in each season with maximum occurrence in HSA followed by MSA and then LSA except in autumn where higher occurrence rate was observed in LSA phase than in MSA phase.
       
  • Ionospheric Es Layer Scintillation Characteristics Studied with
           Hilbert-Huang Transform
    • Abstract: Publication date: Available online 8 July 2019Source: Advances in Space ResearchAuthor(s): S.-Y. Su, L.-C. Tsai, C.H. Liu, C. Nayak, R. Caton, K. Groves A coincident event of daytime ionospheric Es layer scintillation observations is analyzed with the Hilbert-Huang transform (HHT) to study its layer structure. One observation is made by a radio beacon passing through the Es layer at a slant angle received by the SCINDA (Scintillation Decision Aide) receivers located at southern Taiwan. The data indicates that the Es layer consists of scattering blocks of ∼650 to 970 meters in size as revealed in the dominant components of the HHT analysis. The time shift in the two spaced receiving antennas implies that the daytime E region westward drift is about 36 m/s. On the other hand, the same Es layer is observed by the radio occultation (RO) experiment with the L1 signal from the Global Positioning System (GPS) satellites to the FORMOSAT-3/Constellation-Observing-System-for-Meteorology (FS-3/COSMIC) satellites. The GPS L1 signal passes through the Es layer horizontally. The observed signal variations reveal a dense slab structure that blocks the L1 signal to cause a diffraction pattern. The slab thickness in the vertical direction is about 780 m. The HHT analyses of the coincident observations thus conclude that the observed daytime Es layer has a vertical dense slab structure and patches of scattering blocks in the horizontal structure.
       
  • Downshifted peak features of stimulated electromagnetic emissions during a
           two-pump wave heating experiment
    • Abstract: Publication date: Available online 4 July 2019Source: Advances in Space ResearchAuthor(s): Guanglin Ma, Lixin Guo, Qingliang Li, Jutao Yang, Libin Lv, Jing Chen, Tong Xu, Shuji Hao, Jian Wu Experimental results of the downshifted peak (DP) in stimulated electromagnetic emissions under two-pump wave ionospheric heating near the third electron gyroharmonic frequency are presented. The European Incoherent Scatter Scientific Association heating antenna array was divided into two parts, one of which worked at constant pump wave frequency f1 and the other part worked at varied pump wave frequency f2 which was not larger than f1. It was found that when the second pump wave was turned on at different frequency with f1, the f1 DP power declined by more than 10 dB with respect to the background noise level, while the downshifted maximum belonging to f1 was further enhanced. The time needed to reach a steady state for DP was shortened from approximately 10 s under cold background conditions belonging to f1, which was nearly consistent with growth time of small-scale artificially field-aligned irregularity (AFAI), to less than 1 s under the preconditioned heating belonging to f2 with pre-existing AFAI. According to the difference in DP temporal evolution under two experimental conditions, it could be deduced that AFAI plays an important role in the DP generation process. Similar to single-pump wave heating, the frequency offset of DP decreases as f2 increases toward the third electron gyroharmonic frequency. These experimental findings provide new insights into the theoretical study of ionospheric plasma nonlinearity.
       
  • Characterizing inter-frequency bias and signal quality for GLONASS
           satellites with triple-frequency transmissions
    • Abstract: Publication date: Available online 4 July 2019Source: Advances in Space ResearchAuthor(s): Lin Pan, Xiaohong Zhang, Fei Guo The GLONASS SVNs 702K (R09), 755 (R21) and 701K (R26) satellites currently provide G1, G2 and G3 signals. The difference between satellite clocks calculated by G1/G2 and G1/G3 ionospheric-free combinations, termed inter-frequency bias (IFB), is identified. The presence of IFB limits the application of G3 signal in precise positioning. The IFB is investigated using the datasets from 70 stations with a global distribution spanning 30 consecutive days. The epoch-wise phase-specific IFB (PIFB) estimates show periodic variations with a period of eight days and an average peak-to-peak amplitude of 0.107, 0.327 and 1.663 m for the R09, R21 and R26 satellites, respectively. The daily stable code-specific IFB (CIFB) estimates also show 8-day periodic signal. The day-to-day scattering of daily stable CIFB is 0.060–0.085 m. The estimation accuracy and prediction accuracy of PIFB are 0.025 and 0.019 m, respectively, while the corresponding statistics for the daily stable CIFB are 0.452 and 0.056 m, respectively. A modified estimation approach is developed to derive the time-varying epoch-wise CIFB. The epoch-wise CIFB and PIFB shows sub-daily periodic variations with the most notable periods of 5.625 and 11.250 h, respectively. The correction rate is 32% in terms of the prediction of the time-varying part of the epoch-wise CIFB. In addition, the signal quality is assessed from such aspects as carrier-to-noise density ratio, measurement noise and multipath errors.
       
  • Analysis of the Change of Orbital Elements in the Process of Gravity
           Assist
    • Abstract: Publication date: Available online 3 July 2019Source: Advances in Space ResearchAuthor(s): Jingxi Liu, Bo Xu, Lei Zhang Gravity assist is widely applied in the deep space exploration because of its reliability and practicability. There are lots of research in the literature about the nearly coplanar situations. In this work, a three-dimensional model of gravity assist model is developed in a semi-analytical manner on the basis of the geometry relationship between the parameters of spacecraft before gravity assist and the orbital elements after gravity assist. The parameters include V∞in (the hyperbolic excess velocity vector of the spacecraft before fly-by), H (the height of fly-by) and θ (the dihedral angle between approach plane and fly-by plane). These equations can be used for analyzing the change of orbital elements in the process of gravity assist, discussing the influence of different parameters on them and deriving the condition that remains the semi-major axis unchanged. Curve fitting of the feasible region boundary of Δi and contour plot of Δi are utilized to analyze the pattern of Δi changing with different parameters. This method is a valuable reference for designing gravity assist trajectories to high inclination targets in the Solar system.
       
  • Cosmic Ray Origin: Why Cosmic Ray (Astroparticle) Phenomenon is Universal
           in the Universe' What is the Main Driver of Cosmic Ray Particle
           Generation'
    • Abstract: Publication date: Available online 2 July 2019Source: Advances in Space ResearchAuthor(s): Lev Dorman During many years energetic particles generated on the Sun were called as Solar Cosmic Rays (SCR), but now increased the tendency to rename this phenomenon as Solar Energetic Particles (SEP) event. We will show that SEP, as well as energetic particles generated in magnetospheres of the Earth, Jupiter, Saturn and other planets, in interplanetary space, and in atmospheres of stars have the same nature as Galactic and Intergalactic CR: they are all runaway particles from the Maxwell-Boltzmann distribution of background plasma where they were generated. Energy of these run-away particles is much higher than average energy of background thermal particles. It is shown in this paper that the energy of all these run-away particles have the same general nature: it is always transfer energy from the Macro-objects and Macro-processes directly to Micro World (to charged runaway particles). This transfer energy is formatted in dynamic plasma with frozen in magnetic fields: really magnetic fields ’glues’ billions thermal background particles into Macro-objects and Macro-processes. So, thank to frozen in magnetic fields runaway particles can interact not only with thermal background particles (and loose energy), but also directly with Macro-objects and Macro-processes with very high macro-energy (many order higher than energy of run-away particle). Thermodynamically Macro-objects and Macro-processes have much bigger “effective temperature” than runaway particles and though the energy always transferred from Macro World to runaway particles of Micro World. We come to conclusion that main cause of origin of all types of Cosmic Rays in the Universe is the transform energy from Macro-world directly to Micro-world through frozen in magnetic fields in plasmas. At the stage when in early Universe were formatted small density plasmas objects with frozen in magnetic fields, where formatted also Cosmic Rays of different types, but these “relict” Cosmic Ray particles have now very small energy thanks to extension Universe. So, observed now CR particles of different types are generated continuously by transfer energy from Macro World to runaway charged particles of Micro World through frozen in magnetic fields (including the main sources as Supernova explosions, Supernova remnants, and some smaller sources, as stars, star’s winds, planetary magnetospheres, and others).
       
  • Secondary cosmic rays in the NUCLEON space experiment
    • Abstract: Publication date: Available online 2 July 2019Source: Advances in Space ResearchAuthor(s): V. Grebenyuk, D. Karmanov, I. Kovalev, I. Kudryashov, A. Kurganov, A. Panov, D. Podorozhny, A. Tkachenko, L. Tkachev, A. Turundaevskiy, O. Vasiliev, A. Voronin The NUCLEON space observatory is a direct cosmic ray spectrometer designed to study cosmic ray nuclei with Z=1-30 at energies 1012-1015 eV. It was launched as an additional payload onboard the Russian Resource-P No. 2 satellite in December of 2014. In this work B/C, N/O and subFe/Fe ratios are presented. The experiment has worked for half of its expected time, so the data have preliminary status, but they already give clear indications of several astrophysical phenomena, which are briefly discussed in this paper.
       
  • Evaluation of CryoSat-2 water level derived from different retracking
           scenarios over selected inland water bodies
    • Abstract: Publication date: Available online 2 July 2019Source: Advances in Space ResearchAuthor(s): Sh. Roohi, N. Sneeuw, J. Benveniste, S. Dinardo, E.A. Issawy, G. Zhang As the first satellite altimetry mission operating in sar (delay-Doppler) mode, CryoSat-2 is an interesting mission to analyze its performance for water level monitoring over inland water bodies. It offers the opportunity to make comparison of sar and conventional altimeters by a multi-mode altimeter mounted on the same platform with a long repeat orbit. This comparison gives us more knowledge about the performance of the sar altimeter. Even tough it is not possible to perform it over same objects.In this paper we analyze the CryoSat-2 performance for water level monitoring via full- and sub-waveform retracking against in-situ gauge and L2 products of other satellite altimetry missions, e.g. Envisat and Jason-2. To this end, we retrack the full-waveforms and sub-waveforms with different empirical and physical retracking algorithms such as ocog, threshold, β-parameters and samosa3. We evaluate its capability in all measurement modes, i.e. lrm, sar and sarin, over inland water bodies located in different climatic zones. We selected study areas with different shapes and sizes.Relative to in situ measurements we find a precision of the CryoSat-2 lrm mode of 15cmrms over Qinghai lake (China) and 13cm over Erie lake (usa). This is an improvement over Envisat, yielding precision of 17cm in both cases. For the sar mode over Neagh lake (Northern Ireland) and Derg lake (Ireland) we obtain 15cm and 13cm where Envisat yields 28cm and 100cm, respectively. The sarin mode’s precision is assessed over Nasser lake (Egypt) with 25cmrms and Athabasca lake (Canada) with 16cm. Over these lakes Jason-2 achieved 54cm and Envisat 19cm, respectively. The most precise results of CryoSat-2 are obtained with our retracking and sub-waveform selection scenarios. Comparing CryoSat-2 results from our retracking scenarios using L1b data with those results obtained from L2 products (data) of this mission shows an improvement of 4–17 cm. The minimum and maximum improvements belong to Erie and Derg lakes respectively, the largest and smallest lakes.From the waveform analysis over lakes with different shapes and sizes, we found that the first and the mean-all sub-waveforms (mean correction from all sub-waveforms) retracked with the threshold and samosa3 (only for sar mode) retrackers are appropriate to retrieve water level variation of small lakes and complex shaped lakes in this study. Over large lakes the full-waveform retracking leads to better results. In the case of icy-lake objects, sub-waveform retracking scenarios (the first and mean-all sub-waveforms) are more precise than the other scenarios. These are our findings over few samples, though more samples need to be analyzed to support them strongly.
       
  • Relative equilibria of an intermediary model for the roto-orbital
           dynamics. The low rotation regime
    • Abstract: Publication date: Available online 2 July 2019Source: Advances in Space ResearchAuthor(s): J.L. Zapata, F. Crespo, S. Ferrer, F.J. Molero We address the attitude dynamics of a triaxial rigid body in a circular orbit. This task is done by means of an intermediary model, which is obtained by splitting the Hamiltonian in the form H=H0+H1, where H0 is required to be a non-degenerate integrable Hamiltonian system. A numerical study is presented comparing the dynamics of the new intermediary model with the full system (MacCullagh’s truncation) and showing a competitive performance for the cases Sun-asteroid and Earth-spacecraft. This model defines a Poisson flow endowed with invariants defining a SM2×SM2 reduced space. We analyze the coupling between the orbital mean motion and rotational variables. The key role played by the moments of inertia and the value of the angular momentum is shown in detail. The analysis of the intermediary shows that, under slow rotation regime, the classic dynamics of the free rigid body is no longer maintained: bifurcations with changes of stability are displayed for several critical inclinations of the rotational angular momentum plane and for critical orientations of the body frame. Moreover, the evolution of the angular momentum plane is given by a time dependent harmonic oscillator.
       
  • Statistical analysis and modelling of sporadic E layer over Europe
    • Abstract: Publication date: Available online 1 July 2019Source: Advances in Space ResearchAuthor(s): N.Y. Zaalov, E.V. Moskaleva This paper describes a study of the daily and yearly variability of one of the main characteristics of sporadic E layers (Es), the critical frequency (foEs). Our analysis is based on ionograms recorded by GIRO network ionosondes. The study estimates the spatial and temporal variability of the Es layer parameters and generates their statistics at different seasons and phases of the solar cycle. In turn, the statistics of the Es layer parameters can provide an assessment of the capability of the HF propagation forecasting. Further, maps of the distribution of Es layer critical frequency are produced. This paper implements the “cloud” model of Es layer in HF propagation model (Northern Ionosphere Model & Ray Tracing, NIM-RT) that can accurately reproduce many features observed in experimental measurements. Within this framework, a number of vertical sounding ionograms with the presence of Es layer are simulated based on the NIM-RT software.
       
  • List of Referees
    • Abstract: Publication date: 15 August 2019Source: Advances in Space Research, Volume 64, Issue 4Author(s):
       
  • The dependence of four-peak longitudinal structure of the tropical
           electric field on the processes in the lower atmosphere and geomagnetic
           field configuration
    • Abstract: Publication date: Available online 28 June 2019Source: Advances in Space ResearchAuthor(s): V.V. Klimenko, M.V. Klimenko, F.S. Bessarab, T.V. Sukhodolov, E.V. Rozanov In this article, we estimate the influence of the atmospheric-ionospheric interaction and the differences in the location of the geographic and geomagnetic poles on the longitudinal variability of the ionospheric electric field in the vicinity of the geomagnetic equator. For the study, we applied the upper atmosphere model (GSM TIP) and the recently created entire atmosphere model (EAGLE). The simulation results confirm that the four-peak structure of the longitudinal variation and the pre-reversal enhancement of the eastward electric field at the equator are caused by the atmosphere-ionosphere coupling. The role of F-region dynamo in the formation of pre-reversal enhancement of the eastward electric field is beyond the scope of this paper. These structures appear during the minimum of solar activity periods and are formed by the longitudinal variations of the horizontal thermospheric wind and the Pedersen conductivity arising from the action of the mesospheric tides. During solar activity minimum periods, the difference in the locations of geographic and geomagnetic poles leads to some complication and smoothing of the obtained picture of longitudinal variations in the electric field. We suggest that mesospheric tides have a significant effect on the longitudinal variation of the Pedersen conductivity, while the longitudinal variation of the Hall conductivity is mainly determined by the mismatch of geographic and geomagnetic poles. The amplitudes of the equatorial electric field longitudinal variations are three to four times smaller than the amplitudes of their diurnal variations, however, they can have a significant impact on the spatial distribution of the electron density in the F region of the low-latitude ionosphere.
       
  • Attitude Control for Tethered Towing debris under Actuators and Dynamics
           Uncertainty
    • Abstract: Publication date: Available online 27 June 2019Source: Advances in Space ResearchAuthor(s): Cheng Jia, Zhongjie Meng, Panfeng Huang Tethered towing is regarded as a promising debris removal technology to decrease the population of space debris. Owing to the debris rotation, the debris and tether are vulnerable to entanglement in the towing process. After capture, the untight capture leads to relative motion between gripper and debris and changes the actuator configuration matrix inevitably. Thus, except the traditional dynamics uncertainties, it is also necessary to consider the control allocation of multi-actuators under the nonnegative unilateral magnitude constraint and configuration matrix uncertainty. To tackle these problems, a novel scheme was proposed to stabilize the attitude of debris using adaptive backstepping control with robust allocation technique. Specifically, the adaptive attitude stabilization law is designed to generate control torques in the presence of dynamics uncertainties. A robust control allocation algorithm is developed to distribute the three axis torques to redundant actuators, in which the optimal control vector of actuator is obtained by interior-point method, under the actuator configuration matrix uncertainty and saturation constraints. Finally, numerical simulation results are employed to validate the effectiveness of the proposed scheme.
       
  • Advanced Technologies for Satellite Navigation and Geodesy
    • Abstract: Publication date: Available online 27 June 2019Source: Advances in Space ResearchAuthor(s): G. Giorgi, T.D. Schmidt, C. Trainotti, R. Mata-Calvo, C. Fuchs, M.M. Hoque, J. Berdermann, J. Furthner, C. Günther, T. Schuldt, J. Sanjuan, M. Gohlke, M. Oswald, C. Braxmaier, K. Balidakis, G. Dick, F. Flechtner, M. Ge, S. Glaser, R. König This manuscript reviews recent progress in optical frequency references and optical communication systems and discusses their utilizations in global satellite navigation systems and satellite geodesy. Lasers stabilized with optical cavities or spectroscopy of molecular iodine are analyzed, and a hybrid architecture is proposed to combine both forms of stabilization with the aim of achieving a target frequency stability of 10-15 [s/s] over a wide range of sampling intervals.The synchronization between two optical frequency references in real-time is realized by means of time and frequency transfer on optical carriers. The technologies enabling coherent optical links are reviewed, and the development of an optical communication system for synchronization, ranging and data communication in space is described. An infrastructure exploiting the capabilities of both optical technologies for the realization of a modernized constellation of navigation satellites emitting highly synchronized signals is reviewed. Such infrastructure, named Kepler system, improves satellite navigation in terms intra-system synchronization, orbit determination accuracy, as well as system monitoring and integrity. The potential impact on geodetic key parameters is addressed.
       
  • Numerical modeling of cosmic-ray transport in the heliosphere and
           interpretation of the proton-to-helium ratio in Solar Cycle 24
    • Abstract: Publication date: Available online 27 June 2019Source: Advances in Space ResearchAuthor(s): Nicola Tomassetti, Fernando Barão, Bruna Bertucci, Emanuele Fiandrini, Miguel Orcinha Thanks to space-borne experiments of cosmic-ray (CR) detection, such as the AMS and PAMELA missions in low-Earth orbit, or the Voyager-1 spacecraft in the interstellar space, a large collection of multi-channel and time-resolved CR data has become available. Recently, the AMS experiment has released new precision data, on the proton and helium fluxes in CRs, measured on monthly basis during its first six years of mission. The AMS data reveal a remarkable long-term behavior in the temporal evolution of the proton-to-helium ratio at rigidity R≡p/Z≲,3 GV. As we have argued in a recent work, such a behavior may reflect the transport properties of low-rigidity CRs in the inteplanetary space. In particular, it can be caused by mass/charge dependence of the CR diffusion coefficient. In this paper, we present our developments in the numerical modeling of CR transport in the Milky Way and in the heliosphere. Within our model, and with the help of approximated analytical solutions, we describe in details the relations between the properties of CR diffusion and the time-dependent evolution of the proton-to-helium ratio.
       
  • CHAMP and GOCE thermospheric wind characterization with improved
           gas-surface interactions modelling
    • Abstract: Publication date: Available online 27 June 2019Source: Advances in Space ResearchAuthor(s): G. March, T. Visser, P.N.A.M. Visser, E.N. Doornbos The CHAMP and GOCE satellites provided high-resolution thermosphere data between 2000 and 2013, improving our knowledge of atmosphere dynamics in the thermosphere–ionosphere region. However, the currently available data sets contain inconsistencies with each other and with external data sets and models, arising to a large extent from errors in the modelling of aerodynamic forces. Improved processing of the wind data for the two satellites would benefit the further development and validation of thermosphere models and improve current understanding of atmospheric dynamics and long-term trends. The first step to remove inconsistencies has been the development of high-fidelity models of the satellite surface geometry. Next, an improved characterization of the collisions between atmospheric particles and satellite surfaces is necessary. In this article, the effect of varying the energy accommodation coefficient, which is a key parameter for describing gas-surface interactions (GSI) is investigated. For past versions of the thermosphere density and wind data from these satellites a value of the energy accommodation coefficient of αE=0.93 was selected. The satellite accelerometer measurements, from which the thermospheric data are derived, have now been reprocessed using high-fidelity geometries and a wide range of αE values. Lowering the αE value used in the processing leads to an increase in the lift over drag ratio for those satellite panels that are inclined to the flow. This changes the direction of the modelled acceleration, and therefore the interpretation of the measured acceleration in terms of wind. The wrong choice of αE therefore leads to the introduction of satellite attitude-dependent wind errors. For the CHAMP and GOCE satellites, we have found that values of the energy accommodation coefficient significantly lower than 0.93 (0.85 for CHAMP and 0.82 for GOCE) result in increased consistency of the wind data. A comparison between the two missions and an overview of the influence on the results of filtering for solar activity and seasonal and diurnal variations is presented.
       
  • InfraRed Astronomy Satellite Swarm Interferometry (IRASSI): Overview and
           Study Results
    • Abstract: Publication date: Available online 27 June 2019Source: Advances in Space ResearchAuthor(s): Hendrik Linz, Divya Bhatia, Luisa Buinhas, Matthias Lezius, Eloi Ferrer, Roger Förstner, Kathrin Frankl, Mathias Philips-Blum, Meiko Steen, Ulf Bestmann, Wolfgang Hänsel, Ronald Holzwarth, Oliver Krause, Thomas Pany The far-infrared (FIR) regime is one of the few wavelength ranges where no astronomical data with sub-arcsecond spatial resolution exist yet. Neither of the medium-term satellite projects like SPICA, Millimetron or OST will resolve this malady. For many research areas, however, information at high spatial and spectral resolution in the FIR, taken from atomic fine-structure lines, from highly excited carbon monoxide (CO) and especially from water lines would open the door for transformative science. These demands call for interferometric concepts. We present here first results of our feasibility study IRASSI (Infrared Astronomy Satellite Swarm Interferometry) for an FIR space interferometer. Extending on the principal concept of the previous study ESPRIT, it features heterodyne interferometry within a swarm of five satellite elements. The satellites can drift in and out within a range of several hundred meters, thereby achieving spatial resolutions of
       
  • Spin-to-Spin Slew Maneuvers Under Spherically Constrained Angular
           Acceleration
    • Abstract: Publication date: Available online 26 June 2019Source: Advances in Space ResearchAuthor(s): Donghun Lee, Young-Joo Song This paper addresses a three-axis time-optimal attitude-control problem of rigid spacecraft. In this problem, an angular-acceleration vector lies within a spherically constrained space, and spin-to-spin boundary conditions are considered. The problem is converted into a two-point boundary-value problem by an indirect method, which is solved numerically because non-eigen-axis slew motions do not have a general analytical solution. To solve the problem, a homotopy algorithm is applied in which a discrete continuation method, closed-form solutions for single-axis slew maneuvers, and a costate transformation method are included. Through numerical examples, the properties of the optimal solutions are analyzed, and the efficiency of the numerical algorithm is demonstrated.
       
  • List of Referees
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s):
       
  • Finite element analysis for nightside transfer function lunar
           electromagnetic induction studies
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s): H. Fuqua Haviland, G.T. Delory, I. de Pater The global electromagnetic induction response of the Moon has been solved numerically for several electrical conductivity profiles using the finite-element method. Here we demonstrate the capability and applicability in both two and three spatial dimensions for any input magnetic field time series measured at the Moon. We discuss the applicability of a vacuum approximation to the induced magnetic field response to the lunar plasma environment and the challenges of isolating geomagnetic induced fields including the interaction with the lunar wake structure. We perform three validation analyses comparing our vacuum model response to analytic solutions: (1) the time domain response to a step impulse or tangential discontinuity within the solar wind, (2) the time domain response to a ramp driving function, and (3) the broadband frequency domain response. We fit the analytic solutions to a root-mean-square error of better than 1% for all cases. We analyze the accuracy range and demonstrate our model’s capability of resolving interior structure from Apollo magnetometer data. We present the first time domain numerical solution of the induced magnetic field response of the Moon in vacuum for any driving input signal and any interior conductivity profile, building on previous Apollo era work. Lastly, we discuss the trade-offs between model accuracy and performance, which is of particular concern for large datasets and iterative optimizations. The transfer function method developed here is applicable to other airless body two-point magnetometer measurements including Apollo, ARTEMIS, and future lunar geophysical networks.
       
  • Robust foreground segmentation and image registration for optical
           detection of GEO objects
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s): Huan N. Do, Tat-Jun Chin, Nicholas Moretti, Moriba K. Jah, Matthew Tetlow With the rapid growth in space utilisation, the probability of collisions between space assets and orbital debris also increases substantially. To support the safe utilisation of space and prevent disruptions to satellite-based services, maintaining space situational awareness (SSA) is crucial. A vital first step in achieving SSA is detecting the man-made objects in orbit, such as space-crafts and debris. We focus on the surveillance of Geo-stationary (GEO) orbital band, due to the prevalence of major assets in GEO. Detecting objects in GEO is challenging, due to the objects being significantly distant (hence fainter) and slow moving relative to the observer (e.g., a ground station or an observing satellite). In this paper, we introduce a new detection technique called GP-ICP to detect GEO objects using optical sensors that is applicable for both ground and space-based observations. Our technique is based on mathematically principled methods from computer vision (robust point set registration and line fitting) and machine learning (Gaussian process regression). We demonstrate the superior performance of our technique in detecting objects in GEO.
       
  • A new multi-target tracking algorithm for a large number of orbiting
           objects
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s): E. Delande, J. Houssineau, J. Franco, C. Frueh, D. Clark, M. Jah This paper presents the filter for Hypothesised and Independent Stochastic Populations (HISP), a multi-object joint detection/tracking algorithm derived from a recent estimation framework for stochastic populations, in the context of Space Situational Awareness. Designed for multi-object estimation problems where the data association between tracks and collected observations is moderately ambiguous, the HISP filter has a linear complexity with the number of objects and the number of observations. Because of its scalable complexity, the HISP filter is a promising solution for the construction of a large-scale catalogue of Resident Space Objects. We illustrate the HISP filter on a challenging surveillance scenario built from real data for 115 satellites of PlanetLabs’ Dove constellation, and simulated observations collected from two sensors with limited coverage and measurement noise, in the presence of false positives and missed detection.
       
  • Effects of vertical accuracy of digital elevation model (DEM) data on
           automatic lineaments extraction from shaded DEM
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s): Ayman Soliman, Ling Han Remote sensing data, such as satellite images, and remote sensing derived digital elevation models (DEMs) are credited by simplifying many geological processes that require costly and laborious field work, such as lineament extraction. Furthermore, the recent increase in the availability of DEMs from many free open sources as well as their advantages over satellite imagery have promoted their wide application as remote sensing methods for lineament extraction. The quality of a DEM affects the results of its application, and this quality is controlled by its vertical accuracy and spatial resolution. The objectives of this study were to assess and verify the effects of the vertical accuracies of DEMs on lineament extraction. The area around Baoji city, Shaanxi province, China, was selected as a case study and the lineaments were automatically extracted using the LINE algorithm of PCI Geomatica from three DEMs with different vertical accuracies: tri stereo ZY3 imagery derived DEM, SRTM1V3, and ASTGDEMV2. All of these DEMs have 1″ spatial resolution (approx. 30 m). The results showed that the vertical accuracy of the applied DEM affects the number, length, and density of the extracted lineaments, where these quantities increase with increasing vertical accuracy of the DEM.
       
  • Disaggregation of modis land surface temperature in urban areas using
           improved thermal sharpening techniques
    • Abstract: Publication date: 1 August 2019Source: Advances in Space Research, Volume 64, Issue 3Author(s): Ruchi Bala, Rajendra Prasad, Vijay Pratap Yadav Applications of satellite thermal images are usually impeded by the low spatial resolution, leading to the development of various downscaling techniques. The thermal sharpening model based on the relationship between LST and Normalized Difference Vegetation Index (NDVI) was developed which shows good results in agricultural areas but may not be applicable for urban areas. Therefore, the present study focuses on determining improved downscaling techniques that shows good results in different urban regions. Hence, the performance of six different indices, namely NDVI, Enhanced Vegetation Index (EVI), Normalized Difference Built-up Index (NDBI), Urban Index (UI), Normalized Difference Soil Index (NDSI) and Normalized Difference Water Index (NDWI) were compared for thermal sharpening using Disaggregation of Radiometric Temperature (Distrad) Model over four different cities in India i.e. Bikaner, Hyderabad, Vadodara and Varanasi. LST obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) sensors (930 m) were disaggregated to the spatial resolution of Landsat 8 Thermal Infrared Sensor (TIRS) (100 m) and compared with the Landsat LST. The performance of NDBI was found better as compared to other indices in the four cities having Root Mean Square Error (RMSE) = 1.54 K, 1.24 K, 1.10 K and 1.03 K, respectively. Further, NDBI was used for disaggregation using two robust regression techniques i.e. Least Median Square Regression (LMSR) and Bi-square regression which shows better results as compared to that of Distrad model in the four study sites. Bi-square regression method shows RMSE values of 1.30 K, 1.21 K, 0.98 K and 0.97 K, respectively for the four study sites. The LMSR and Bi-square regressions are less sensitive to outliers resulting in increased accuracy of downscaled LST.
       
  • Targeting ultra-high energy neutrinos with the ARIANNA experiment
    • Abstract: Publication date: Available online 24 June 2019Source: Advances in Space ResearchAuthor(s): A. Anker, S.W. Barwick, H. Bernhoff, D.Z. Besson, Nils Bingefors, G. Gaswint, C. Glaser, A. Hallgren, J.C. Hanson, R. Lahmann, U. Latif, J. Nam, A. Novikov, S.R. Klein, S.A. Kleinfelder, A. Nelles, M.P. Paul, C. Persichilli, S.R. Shively, J. Tatar The measurement of ultra-high energy (UHE) neutrinos (E > 1016 eV) opens a new field of astronomy with the potential to reveal the sources of ultra-high energy cosmic rays especially if combined with observations in the electromagnetic spectrum and gravitational waves. The ARIANNA pilot detector explores the detection of UHE neutrinos with a surface array of independent radio detector stations in Antarctica which allows for a cost-effective instrumentation of large volumes. Twelve stations are currently operating successfully at the Moore’s Bay site (Ross Ice Shelf) in Antarctica and at the South Pole. We will review the current state of ARIANNA and its main results. We report on a newly developed wind generator that successfully operates in the harsh Antarctic conditions and powers the station for a substantial time during the dark winter months. The robust ARIANNA surface architecture, combined with environmentally friendly solar and wind power generators, can be installed at any deep ice location on the planet and operated autonomously. We report on the detector capabilities to determine the neutrino direction by reconstructing the signal arrival direction of a 800 m deep calibration pulser, and the reconstruction of the signal polarization using the more abundant cosmic-ray air showers. Finally, we describe a large-scale design – ARIA – that capitalizes on the successful experience of the ARIANNA operation and is designed sensitive enough to discover the first UHE neutrino.
       
  • Statistics of spread F characteristics across different sectors and IRI
           2016 prediction
    • Abstract: Publication date: Available online 22 June 2019Source: Advances in Space ResearchAuthor(s): A.O. Afolayan, J.S. Mandeep, M. Abdullah, S.M. Buhari The occurrence of the plasma irregularity and the related scintillation have been extensively investigated as a result of the impact on radio signal propagation. This study focused on the equatorial spread F (ESF) occurrence using ionogram data and IRI prediction taken across different longitude sectors, including the Jicamarca, Fortaleza, Ilorin, Chumphon and Kwajalein ionosonde stations. We have briefly discussed the varying range type spread F (RSF) occurrence features across these stations such as the duration, onset time and seasonal asymmetry. The largest seasonal average of the RSF occurrence percentage was recorded at the Ilorin station during the low solar activity, while the occurrence rate at the Chumphon and Kwajalein stations increases significantly with the solar flux intensity. Furthermore, we presented a comparative analysis of the observed RSF occurrence rate and the IRI model prediction. The result exhibited a significant error percentage across these longitudes. The IRI could not reproduce significant features such as the delayed RSF onset at the Kwajalein station during June solstice or the equinox asymmetry in the RSF occurrence across these longitudes. Surprisingly, the IRI model also performed poorly at the Brazilian longitude. These observations highlight the strong dynamic nature of the RSF features across the different regions. Hence, an extensive dataset of the RSF occurrence distribution selected with cognizance for the longitudinal pattern of the major factors controlling the phenomenon is considered necessary for the further improvement of the empirical model.
       
  • Accuracy Evaluation of the Latest BDGIM for BDS-3 Satellites
    • Abstract: Publication date: Available online 22 June 2019Source: Advances in Space ResearchAuthor(s): Yongxing Zhu, Shusen Tan, Qinghua Zhang, Xia Ren, Xiaolin Jia A novel model of the BeiDou Global Ionospheric delay correction Model (BDGIM) is used as the global broadcasting ionospheric correction model for the third generation of BeiDou Navigation Satellite System (BDS-3). It has been successfully implemented on five BDS-3 test satellites. The accuracy of this novel BDGIM model were evaluated using the final global ionosphere maps (GIM) products provided by the International Global Navigation Satellite System Service(IGS). Comparing with the IGS GIM final product, the root mean square (RMS) of the global correction accuracy of BDGIM was 3.57 total electron content unit (TECu) with a correction percentage of 77.2%. The average RMS at different latitudes was 3.11 TECu, with Percent of 75.2%. The mean RMS values of regions with lattilute larger than 52.5S and 62.5N were less than that of NeQuickG. Considering the distribution of the tracking stations using for calculating BDGIM coefficients , the RMS values in different regions were 3.09 TECu (Percent = 80.3%) and 3.21 TECu (Percent = 79.4%), respectively. The BDGIM coefficients was updated every two hours, comparing with NeQuickG model, the BDGIM better reflected the real changes of ionosphere. Considering that the accuracy of the non-broadcasted coefficients declines with broadcasting duration, the correction accuracy with nine broadcasted coefficients included in BDGIM was analyzed. RMS and Percent were 4.10 TECu and 72.8%, declining by about 0.53 TECu and 4.4% (maximum to 9.7%), respectively.
       
  • High-energy cosmic rays from compact galactic star clusters: particle
           fluxes and anisotropy
    • Abstract: Publication date: Available online 22 June 2019Source: Advances in Space ResearchAuthor(s): A.M. Bykov, M.E. Kalyashova, D.C. Ellison, S.M. Osipov It has been shown that supernova blast waves interacting with winds from massive stars in compact star clusters may be capable of producing cosmic-ray (CR) protons to above 1017 eV. We give a brief description of the colliding-shock-flow mechanism and look at generalizations of the diffusion of ∼100 PeV CRs in the turbulent galactic magnetic field present in the galactic disk. We calculate the temporal evolution of the CR anisotropy from a possible distribution of young compact massive star clusters assuming the sources are intermittent on time scales of a few million years, i.e., comparable to their residence time in the Milky Way. Within the confines of our model, we determine the galactic/extra-galactic fraction of high-energy CRs resulting in anisotropies consistent with observed values. We find that galactic star clusters may contribute a substantial fraction of ∼100 PeV CRs without producing anisotropies above observed limits.
       
  • RadioAstron probes the ultra-fine spatial structure in the H2O maser
           emission in the star forming region W49N
    • Abstract: Publication date: Available online 17 May 2019Source: Advances in Space ResearchAuthor(s): N.N. Shakhvorostova, A.M. Sobolev, J.M. Moran, A.V. Alakoz, H. Imai, V.Y. Avdeev H2O maser emission associated with the massive star formation region W49N were observed with the Space-VLBI mission RadioAstron. The procedure for processing of the maser spectral line data obtained in the RadioAstron observations is described. Ultra-fine spatial structures in the maser emission were detected on space-ground baselines of up to 9.6 Earth diameters. The correlated flux densities of these features range from 0.1% to 0.6% of the total flux density. These low values of correlated flux density are probably due to turbulence either in the maser itself or in the interstellar medium.
       
  • Rocket Investigation of Current Closure in the Ionosphere (RICCI): A novel
           application of CubeSats from a sounding rocket platform
    • Abstract: Publication date: Available online 15 May 2019Source: Advances in Space ResearchAuthor(s): Ian J. Cohen, Brian J. Anderson, John W. Bonnell, Robert L. Lysak, Marc R. Lessard, Robert G. Michell, Roger H. Varney The Rocket Investigation of Current Closure in the Ionosphere (RICCI) sounding rocket mission concept will use the novel deployment of multiple CubeSats as miniature sub-payloads to obtain the first direct in-situ measurement of ionospheric closure currents. These ionospheric currents are critical to understanding the nature of atmosphere-ionosphere-magnetosphere coupling and have relevance to space weather parameters such as ionospheric densities, thermospheric heating, and satellite drag. Previous attempts to measure these ionospheric closure current in-situ have been limited by poor attitude knowledge resulting in large uncertainties in the magnetic field measurement that compromise the ability to measure the gradient of the magnetic field beyond the precision necessary to resolve the current densities. To address this, RICCI uses dedicated star trackers and currently-available CubeSat subsystems to obtain the high-precision attitude knowledge necessary to directly measure these elusive currents.
       
  • Imaging strong blazars with space VLBI
    • Abstract: Publication date: Available online 13 May 2019Source: Advances in Space ResearchAuthor(s): J. Anton Zensus, Laura Vega-García, Eduardo Ros, Andrei P. Lobanov, Manel Perucho, Gabriele Bruni, Yuri Y. Kovalev The RadioAstron mission has obtained a series of detailed multi-frequency images of the brightest blazars of the radio sky concentrated in three key science programs. We present here results of the program on powerful jets in blazars. In the first two years of the mission, observations of compact relativistic jets in 0836+710, 3C 345, 3C 273, and 4C +69.21 were made at λλ 18, 6, and 1.3 cm. The resulting images have revealed compact emitting regions with brightness temperature in excess of 1013 K and a complex jet structure that can be explained by plasma instability developing in a relativistic outflow.We present here some highlights of these space-VLBI observations, designed to resolve the innermost regions in these powerful targets and address some of the still unanswered questions on their physical nature.
       
  • RadioAstron orbit determination and evaluation of its results using
           correlation of space-VLBI observations
    • Abstract: Publication date: Available online 13 May 2019Source: Advances in Space ResearchAuthor(s): M.V. Zakhvatkin, A.S. Andrianov, V.Yu. Avdeev, V.I. Kostenko, Y.Y. Kovalev, S.F. Likhachev, I.D. Litovchenko, D.A. Litvinov, A.G. Rudnitskiy, M.A. Shchurov, K.V. Sokolovsky, V.A. Stepanyants, A.G. Tuchin, P.A. Voitsik, G.S. Zaslavskiy, V.E. Zharov, V.A. Zuga A crucial part of a space mission for very-long baseline interferometery (VLBI), which is the technique capable of providing the highest resolution images in astronomy, is orbit determination of the mission’s space radio telescope(s). In order to successfully detect interference fringes that result from correlation of the signals recorded by a ground-based and a space-borne radio telescope, the propagation delays experienced in the near-Earth space by radio waves emitted by the source and the relativity effects on each telescope’s clock need to be evaluated, which requires accurate knowledge of position and velocity of the space radio telescope. In this paper we describe our approach to orbit determination (OD) of the RadioAstron spacecraft of the RadioAstron space-VLBI mission. Determining RadioAstron’s orbit is complicated due to several factors: strong solar radiation pressure, a highly eccentric orbit, and frequent orbit perturbations caused by the attitude control system. We show that in order to maintain the OD accuracy required for processing space-VLBI observations at cm-wavelengths it is required to take into account the additional data on thruster firings, reaction wheel rotation rates, and attitude of the spacecraft. We also investigate into using the unique orbit data available only for a space-VLBI spacecraft, i.e. the residual delays and delay rates that result from VLBI data processing, as a means to evaluate the achieved OD accuracy. We present the results of the first experience of OD accuracy evaluation of this kind, using more than 5000 residual values obtained as a result of space-VLBI observations performed over 7 years of the RadioAstron mission operations.
       
  • Interstellar scintillation, ISS, and intrinsic variability of radio AGN
    • Abstract: Publication date: Available online 13 May 2019Source: Advances in Space ResearchAuthor(s): David L. Jauncey, Jun Yi Koay, Hayley Bignall, Jean-Pierre Macquart, Tapio Pursimo, Marcello Giroletti, Talvikki Hovatta, Sebastian Kiehlmann, Barney Rickett, Anthony Readhead, Walter Max-Moerbeck, Harish Vedantham, Cormac Reynolds, James Lovell, Roopesh Ojha, Lucyna Kedziora-Chudczer We investigate the relationship between the 5 GHz interstellar scintillation (ISS) and the 15 GHz intrinsic variability of the compact, radio-selected active galactic nuclei (AGN) common to the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens Valley Radio Observatory blazar flux density monitoring program. As part of this investigation, we also re-examine the reported intrinsic nature of the February 1990 VLA observations of the blazar S5 0716+714. We are also examining the presence of IDV/ISS in the Owens Valley 15 GHz flux density monitoring data. We find a significant relationship between the Owens Valley 15 GHz modulation index and the MASIV modulation index. We also discuss the implications of these findings for RadioAstron.
       
  • Classification of hyperspectral imagery with a 3D convolutional neural
           network and J-M distance
    • Abstract: Publication date: Available online 10 May 2019Source: Advances in Space ResearchAuthor(s): Chunxing Wang, Nan Ma, Yanfang Ming, Quan Wang, Jinfeng Xia A three-dimensional convolutional neural network (3D-CNN) is proposed and applied to the identification of land types from hyperspectral images. Due to the advantages of the combined use of the spectral-spatial features of hyperspectral imagery, high accuracy identification of most objects can be realized. However, too many wavelengths increase information redundancy between adjacent bands and interfere with classification accuracy to some extent, complicating achievement of better results for the identification of ground objects with relatively small differences in spectral and spatial domains. To solve such problems, in this paper, the Jeffries-Matusita (J-M) distance is introduced to select effective bands to reduce the redundancy of spectral information for identifying objects with similar features. This method is based on a 3D-CNN considering pixel spectral and spatial information. The optimal band combination algorithm based on the J-M distance is first used to extract spectral features of hyperspectral data while reducing feature dimensions. Then, the 3D-CNN is applied to mine spectral and spatial features from the hyperspectral images. Finally, a Softmax classifier is used to classify land types based on the high-level features learned by the 3D-CNN. Experiments were carried out on data from an area of north-western Indiana and a Pavia university scene. In such images, some objects have very similar spectral and spatial features. The results were compared with the current 3D-CNN land type classification and show that both methods can achieve high-precision identification of most land types, but for objects with similar features, the method proposed in this article has obvious advantages.
       
  • Secondary cameras onboard the Mini-EUSO experiment: Control Software and
           Calibration
    • Abstract: Publication date: Available online 21 June 2019Source: Advances in Space ResearchAuthor(s): S. Turriziani, J. Ekelund, K. Tsuno, M. Casolino, T. Ebisuzaki Mini-EUSO is a space experiment selected to be installed inside the International Space Station. It has a compact telescope with a large field of view (44 × 44 sq. deg.) focusing light on an array of photo-multipliers tubes in order to observe UV emission coming from Earth’s atmosphere. Observations will be complemented with data recorded by some ancillary detectors. In particular, the Mini-EUSO Additional Data Acquisition System (ADS) is composed by two cameras, which will allow us to obtain data in the near infrared, and in the visible range. These will be used to monitor the observation conditions, and to acquire useful information on several scientific topics to be studied with the main instrument, such as the physics of atmosphere, meteors, and strange quark matter. Here we present the ADS control software developed to stream cameras together with the UV main instrument, in order to grab images in an automated and independent way, and we also describe the calibration activities performed on these two ancillary cameras before flight.
       
  • Polarization VLBI Observations of AGN Jets Now and into the Future
    • Abstract: Publication date: Available online 21 June 2019Source: Advances in Space ResearchAuthor(s): Denise C. Gabuzda The history of Very Long Baseline Interferometry (VLBI) observations has been characterized predominantly by an ongoing quest for increasingly high resolution and sensitivity. VLBI monitoring of relatively large samples of Active Galactic Nuclei (AGNs) with uniform quality and linear polarization sensitivity are now available at the moderately high frequencies of 15 and 43 GHz. This has enabled considerable advances in our understanding of the relativistic jets of AGNs, but gaps in the available observational material remain, which must be addressed in future VLBI polarization observations. Linear polarization observations at frequencies above 43 GHz remain non-routine, and the availability of multi-frequency and circular polarization measurements is still limited. It is of interest both to push inward toward the jet base and to study details of the jets themselves on parsec scales, such as magnetic field structures along and across the jets, which are intrinsically related to their formation, launching and propagation. Requirements for future VLBI polarization observations are considered, highlighting the key role that can be played by space VLBI observations. Unique opportunities are offered by relatively low-frequency space VLBI observations that are sensitive to effects such as Faraday rotation, opacity, and low-frequency absorption.
       
  • Quasi-Periodic Pulsations in Hard X-rays of Partially Occulted Solar
           Flares
    • Abstract: Publication date: Available online 21 June 2019Source: Advances in Space ResearchAuthor(s): Ż. Szaforz, M. Tomczak We investigated solar flares partially occulted by the solar disk observed by the Yohkoh satellite. We found that about 30–40% of them show quasi-periodic pulsations (QPPs) in hard X-rays (HXR). A lack of usually brighter footpoint sources allowed us to reconstruct coronal HXR sources with a higher quality. We analyzed 28 partially occulted flares showing the QPPs and for the first time present results for such events as a group. In our opinion, the majority of the observed HXR loop-top sources can be explained as successive compression and rarefaction of magnetic traps described in a model of oscillating magnetic traps (OMT). In this model a particular value of a ratio between the diameter of traps and the period of pulsations is postulated. In our modification of this model, different values of the ratio are possible, with the exception of a lower range, where low values of magnetic field strength and high values of electron density number can excess the plasma-β parameter above unity (ballooning instability).
       
  • Features of downshifted maximum spectra during a dual-pump ionospheric
           heating experiment
    • Abstract: Publication date: Available online 20 June 2019Source: Advances in Space ResearchAuthor(s): Libin Lv, Zhensen Wu, Qingliang Li, Shuji Hao, Guanglin Ma, JuTao Yang, Jian Ding, Jian Wu An ionospheric heating experiment was conducted using the dual-pump mode at the EISCAT/HEATING facility in Tromsø, Norway. Some new features were found in the downshifted maximum (DM) component of the stimulated electromagnetic emission (SEE) spectra. During the experiment, the DM1 generated by pump 1 was enhanced under the action of pump 2 with the peak intensity being increased by ∼4.8–9.8 dB to achieve maximum value, when the frequency of pump 2 was 4.100 MHz. The gyro resonance at the upper hybrid altitude played an important role in this phenomenon. It was also observed that the development time of DM2 generated by pump 2 was greatly shorter than that of DM1 due to the precondition provided by the artificial field-aligned irregularities (AFAIs) stimulated by pump 1. Additionally, the frequency offset and peak intensity of the DM1 spectrum showed a significant negative correlation, where the correlation coefficient reached a value of -0.91.
       
  • Impact of GPS receiver antenna GRAPHIC residual variations on
           single-frequency orbit determination of LEO satellites
    • Abstract: Publication date: Available online 19 June 2019Source: Advances in Space ResearchAuthor(s): Kai Shao, Defeng Gu, Xiao Chang, Bin Yi, Zhengming Wang Single-frequency (SF) precise orbit determination (POD) using space-borne Global Positioning System (GPS) measurements is a prerequisite for the success of many low-cost small/micro low Earth orbit (LEO) satellite missions. The first-order ionospheric effects are usually eliminated by group and phase ionospheric correction (GRAPHIC) combinations. GPS receiver antenna GRAPHIC residual variations (GRVs) are important systematic error sources in SF orbit determination. Azimuth and elevation dependent GRVs are estimated and obtained based on the GRAPHIC combination residuals in an in-flight calibration. One month of data from GRACE-A, GRACE-B, CHAMP and HY-2A satellites is used to assess the potential of receiver antenna GRVs in SF orbit determination. It is the first time to study the impact of receiver antenna GRVs on SF orbit determination for different LEO satellites, which exhibit different altitudes and data qualities. The impact of receiver antenna GRVs on SF orbit determination is significant. The use of in-flight determined receiver antenna GRVs leads to a better consistency between SF and dual-frequency POD solutions. The improvements are more obvious for GRACE-A and CHAMP satellites, whose receiver antenna GRV patterns demonstrate clear characteristics of systematic deviations. After correcting the receiver antenna GRVs, the root-mean-square of satellite laser ranging validation residuals are 3.11 cm, 2.31 cm, 2.86 cm and 5.29 cm for GRACE-A, GRACE-B, CHAMP and HY-2A satellites, respectively, which are reduced by 11.1%, 4.6%, 14.6% and 4.7%, respectively. At last, a set of a priori GDV corrections of GPS transmitter antennas are used in SF orbit determination and its effects on receiver antenna GRVs estimation and SF orbit determination are analyzed. Applying these corrections can slightly improve the SF orbit quality of GRACE-A satellite.
       

  •        ThepossibilityofestimatingtheheightoftheionosphericinhomogeneitiesbasedonTECvariationsmaps
           obtained from dense GPS network
    • Abstract: Publication date: Available online 19 June 2019Source: Advances in Space ResearchAuthor(s): Grzegorz Nykiel, Yevgen Zanimonskiy, Aleksander Koloskov, Mariusz Figurski A state of the ionosphere can be effectively studied using electromagnetic signals received from global navigation satellite systems (GNSS). Utilization of the dual frequency observations allows estimating values of the total electron content (TEC). They can be used for a number of scientific studies such as detection and monitoring of traveling ionospheric disturbances or plasma bubbles. Moreover, maps of TEC variations allow to classify ionospheric heterogeneities and to evaluate their parameters. However, most of the research describes ionospheric parameters only in 2D space and time. In this paper, we focus on the determination of the height of the ionospheric inhomogeneities. We used a dense network of GPS receivers to obtain the sequences of TEC variation maps for different heights of the ionospheric layer. For each satellite observed above 70°, we constructed separate sets of maps. For each ionospheric height, the cross-correlation function between maps corresponding to different satellites was calculated. The biggest cross-correlation coefficient value determines the height of the ionospheric irregularities. This paper describes the methodology and the results obtained for a geomagnetic storm on St. Patrick’s Day in March 2013. We have found that in quiet geomagnetic conditions the ionospheric irregularities are localized predominantly within the interval 180-220 km close to the maximum of the ionospheric F2 layer. In disturbed conditions, the height of their localization was increased up to several hundreds of kilometers. These estimations correspond to the changes in the slab thickness of the ionosphere.
       
  • On the field validation of α-μ fading coefficients estimator based on
           the autocorrelation function for ionospheric amplitude scintillation
    • Abstract: Publication date: Available online 18 June 2019Source: Advances in Space ResearchAuthor(s): Leonardo Marini-Pereira, Kelias de Oliveira, Lucas A. Salles, Alison de O. Moraes, Eurico R. de Paula, Marcio Tadeu de Assis Honorato Muella, Waldecir J. Perrella The ionosphere in low-latitude regions has intense dynamics with great variability – not only spatially but also temporally. The most critical effect found in the low-latitude region is the scintillation in phase and amplitude due to plasma bubble occurrence in the ionospheric layer. To augmentation systems like GBAS or SBAS, designed to provide Category-I (CAT I) precision approach service in low-visibility conditions, plasma bubbles can compromise the performance requirements for air navigation precision approach in a way that the service provided by the system is considered unviable. In practical terms, this is the main reason why the Brazilian Department of Airspace Control (DECEA) still has not implemented any augmentation system in Brazil. Scintillation may lead to loss of signal lock of the affected satellite. In this context, a better understanding of the scintillation pattern and its statistical properties gain particular relevance, once this is the most concerning issue for the performance of any GNSS receiver in low-latitude regions especially in the context of augmentation systems for air navigation. Previous works validated the use of the α-μ distribution to characterize amplitude scintillation. The present work is concerned with proposing a new method for the estimation of the α-μ coefficients based on the α-μ autocorrelation function. The method is validated using field data and comparing the results from empirical autocorrelation function with the results obtained from the moment-based estimator. Additionally, the efficiency of the method is proven by analyzing measurements of Level-Crossing Rate (LCR) and Average Fading Duration (AFD) with their respective theoretical formulation.
       
  • The Spörer minimum was deep
    • Abstract: Publication date: Available online 17 June 2019Source: Advances in Space ResearchAuthor(s): M.G. Ogurtsov Seventeen reconstructions of past solar activity, based on cosmogenic isotope and auroral data, were analyzed for the time interval AD 1402–1850 covering three prolonged periods of weak solar activity – the Spoerer, Maunder and Dalton minima. The information contained in these proxies has been generalized and sunspot number reconstructed. It was shown that from the point of view of solar paleoastrophysics the Spoerer minimum (15th–16th centuries) was a prolonged (ca 140 years) period of very quiet Sun with a mean solar activity level lower than that during the minimum of Maunder.
       
  • High energy interactions of cosmic rays
    • Abstract: Publication date: Available online 12 June 2019Source: Advances in Space ResearchAuthor(s): Sergey Ostapchenko A discussion of a number of important topics related to modeling of high energy cosmic ray interactions is presented. Special attention is devoted to novel theoretical approaches employed in event generators of hadronic interactions and to the impact of experimental data from the Large Hadron Collider (LHC). In relation to studies of ultra-high energy cosmic rays (UHECRs), differences between various predictions for basic characteristics of UHECR-induced extensive air showers in the atmosphere are analyzed and traced down to differences in the respective treatments of hadronic interactions. Possibilities to discriminate between the alternative approaches, based on LHC and UHECR data, are demonstrated and the relation to UHECR primary composition is outlined. Finally, in relation to direct studies of charged cosmic rays, potential improvements of the treatment of cosmic ray interactions at low and intermediate energies are discussed.
       
  • Masers: precision probes of molecular gas
    • Abstract: Publication date: Available online 11 June 2019Source: Advances in Space ResearchAuthor(s): A.M.S. Richards, A. Sobolev, A. Baudry, F. Herpin, L. Decin, M.D. Gray, S. Etoka, E.M.L. Humphreys, W. Vlemmings Maser emission from water, methanol, silicon monoxide and other molecules can reach brightness temperatures ≫1010 K. Such observations can achieve sub-pc precision for discs around black holes or sub-au scale interactions in protostellar discs and the regions where evolved star winds reach escape velocity. Ultra-high resolution maser observations also provide photon statistics, for fundamental physics experiments. RadioAstron has shown the success – and limitations – of cm-wave maser observations on scales ≪1 mas with sparse baseline coverage. ALMA, APEX and earlier single dish searches have found a wealth of mm and sub-mm masers, some of which probably also attain high brightness temperatures. Masers are ideal for high-resolution observations throughout the radio regime and we need to consider the current lessons for the best observational strategies to meet specific science cases.
       
  • Rapid determination of source parameters for the 2017 Mw 8.2 Mexico
           earthquake based on high-rate GPS data
    • Abstract: Publication date: Available online 10 June 2019Source: Advances in Space ResearchAuthor(s): Yunfei Xiang, Jianping Yue, Dongjian Cai, Hao Wang Aiming to rapidly determine source parameters (i.e., static offset, seismic wave arrival, moment magnitude, and hypocentral location) for the Mexico 8.2 earthquake, the records of 7 high-rate GPS stations are utilized. Smoothness Priors Method (SPM) is introduced to rapidly extract the static offset from GPS displacement waveforms, and the result suggests this approach is feasible. The seismic wave arrival detection is carried out with the aid of S-transform, and the propagation velocity of seismic wave detected by most GPS stations are within 4−5 km/s, implying the seismic wave captured by GPS station may be S wave or surface wave. After that, an empirical regression model is adopted to characterize the moment magnitude for this earthquake, and this empirical formula can obtain reliable magnitude in comparison with the reference magnitude. The convergence time of average moment magnitude is 298 s, suggesting that a reliable and robust magnitude (Mw 8.37) can be estimated by the 7 GPS stations with about 298 s after earthquake occurrence. Considering the influence of the spatial distribution of GPS stations, 4 nearest GPS stations evenly distributed on both sides of the fault are selected to determine the warning-magnitude for the Earthquake Early Warning (EEW). A reliable and robust moment magnitude (Mw 8.2) can be estimated by the 4 stations with about 251 s, which is 57 s ahead of 7 stations. Finally, the coordinates of 6 GPS stations and corresponding seismic wave arrival time are utilized to determine the hypocentral location, and the latitude and longitude of estimated location is 14.925°N and 93.765°W, which is 17.9 km from the reference location. The results indicate that the source parameters required for EEW can be rapidly determined based on high-rate GPS displacement waveforms, and integrating real-time GPS into a joint EEW system will be crucial going forward.
       
  • Decomposition of geodetic time series: a combined simulated annealing
           algorithm and Kalman filter approach
    • Abstract: Publication date: Available online 10 June 2019Source: Advances in Space ResearchAuthor(s): Ming Feng, Yang Yuanxi, Zeng Anmin, Zhao Bin In this paper we propose a network-based Kalman filter combined generalized simulated annealing algorithm approach to decompose a group of GPS position time series into secular trend, annual and semi-annual signals as well as noise components. This approach treats east, north and vertical components of the whole network separately and estimates network-average process-noise parameters to contrain the time variability of the seasonal signals and noise components. Each coordinate component for each station is modeled in state-space model (SSM) individually. The noise components are described as the combination of flicker noise (FN), random walk noise (RWN) and observation white noise (WN). Each component, except for the trend, is allowed to variate over the time, and their amplitudes are estimated by maximization of likelihood function using a generalized simulated annealing (GSA) algorithm. The proposed approach is applied to 10 reprocessed GPS position time series from the Tectonic and Environmental Observation Network of Mainland China (CMONOC II), and its output is compared with that of ordinary maximum likelihood estimation (MLE). The results show that the proposed approach is an effective tool for the decomposition of GPS position time series. Finally, the advantages and limitations of the proposed approach are also discussed.
       
  • Space VLBI: from first ideas to operational missions
    • Abstract: Publication date: Available online 8 June 2019Source: Advances in Space ResearchAuthor(s): Leonid I. Gurvits The operational period of the first generation of dedicated Space VLBI (SVLBI) missions commenced in 1997 with the launch of the Japan-led mission VSOP/HALCA and is coming to closure in 2019 with the completion of in-flight operations of the Russia-led mission RadioAstron. They were preceded by the SVLBI demonstration experiment with the Tracking and Data Relay Satellite System (TDRSS) in 1986–1988. While the comprehensive lessons learned from the first demonstration experiment and two dedicated SVLBI missions are still awaiting thorough attention, several preliminary conclusions can be made. This paper addresses some issues of implementation of these missions as they progressed over four decades from the original SVLBI concepts to the operational status.
       
  • The nature and origins of the day-to-day variability in Earth's surface
           magnetic field
    • Abstract: Publication date: Available online 7 June 2019Source: Advances in Space ResearchAuthor(s): Jeffrey M. Forbes, Astrid Maute, Xiaoli Zhang Numerical experiments are performed with the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM) to reveal the characteristics and origins of daytime magnetic field variations on the ground (ΔB) at planetary-wave (PW) periods (2-20 days). Simulations are performed to separate the responses to forcing in the lower atmosphere from solar-magnetospheric forcing. Lower-atmosphere forcing is specified at the 97-km lower boundary of the TIE-GCM by NCAR's Thermosphere-Ionosphere-Mesosphere Electrodynamics General Circulation Model (TIME-GCM), which itself is forced at 30 km by MERRA (Modern Era Retrospective-analysis for Research and Applications) outputs. Solar and magnetospheric inputs to the TIE-GCM are specified according to parameterizations based on F10.7 and Kp. The study focuses on latitudes 0°-65°N during October 1-31, 2009, when F10.7 (range 68-80), Kp (range 0-4), and Ap (range 0-13) are typical of quiet-time “weather”. Neutral dynamics in the dynamo region (ca. 100-150 km) during this period is dominated by winds due to PW modulated tides, where the PW include the quasi-6, 10 and 16-day westward-propagating normal modes with zonal wavenumber s = 1, and eastward-propagating ultra-fast Kelvin waves (UFKW) with s = -1 and periods between 3 and 5 days.Results and conclusions are as follows. PW-period perturbations in daytime ΔB at the ground are dominated by variability originating in the lower atmosphere. The only exception is the 45°-65° latitude regime around noon, where the ΔB variability due to lower atmospheric forcing exceeds that due to solar-magnetospheric forcing by only about 50%. Broadband zonally-symmetric oscillations also occur in ΔB due to dissipation of the tidal spectrum at PW periods in the E-region. These results raise the possibility that some level of contamination from the lower atmosphere may exist in magnetic indices such as ap, Kp, and Ap that are used as measures solar-magnetosphere-ionosphere coupling strength, under levels of geomagnetic activity similar to that characterizing October, 2009. It is also found that variations in conductivities play a minor role compared with neutral winds in producing PW-period variations in ΔB, and that there is not a robust one-to-one correspondence between spectral peaks in ΔB and those in the neutral winds. Several factors contribute to this latter result, which are explained in the text.
       
  • Chemical physics of D and E layers of the ionosphere
    • Abstract: Publication date: Available online 7 June 2019Source: Advances in Space ResearchAuthor(s): V.V. Kuverova, S.O. Adamson, A.A. Berlin, V.L. Bychkov, A.V. Dmitriev, Y.A. Dyakov, L.V. Eppelbaum, G.V. Golubkov, A.A. Lushnikov, M.I. Manzhelii, A.N. Morozov, S.S. Nabiev, V.L. Shapovalov, A.V. Suvorova, M.G. Golubkov The main chemical reactions that lead to formation of the nonequilibrium two-temperature plasma and highly excited Rydberg complexes are considered. A special attention is given to l-mixing reaction responsible for the formation of quantum resonance properties for radio wave propagation medium. A detailed analysis of the influence of Rydberg states to the behavior of GPS signals in D and E layers of the ionosphere is presented. It is shown that the transition frequencies between the excited states of orbitally degenerate Rydberg complex are resonant with respect to the carrier frequencies of GPS. That is why these states are the main cause of the GPS signal distortion. The mechanism of GPS signal delay in D and E layers is also discussed.
       
  • A new method to estimate cloud effective radius using Meteosat Second
           Generation SEVIRI over Middle East
    • Abstract: Publication date: Available online 5 June 2019Source: Advances in Space ResearchAuthor(s): Mostafa Hadizadeh, Mehdi Rahnama, Mehdi Kamali, Mona Kazemi, Ali Mohammadi The cloud particle size distribution varies with height and the phase may change from water to mixed phase to ice through the vertical profile of the cloud, giving rise to different radiative characteristics. Researchers suggested an empirical equation for an approximation of the relation between cloud-particle effective radius and reflectance of channel IR3.7 for Advanced Very High Resolution Radiometer (AVHRR) and Multi-Functional Transport Satellite (MTSAT)-1R satellites. However, when we examined this empirical equation for MSG satellites, there was no correlation between the cloud particle effective radius and those from the Terra and Aqua/MODIS (Moderate Resolution Imaging Spectrometers) products. Given the fact that this relationship is empirical and not applicable for Meteosat satellites with 3.9 µm cloud properties, we need to introduce a new nonlinear equation that is independent from other cloud properties, to retrieve the cloud effective radius from MSG satellite over Middle East. Thus, in this study, a development of the mentioned method, based on a nonlinear regression model, was introduced to estimate the water/ice-cloud particle effective radius from the 3.9 µm wavelength reflectivity of the Meteosat Second Generation Indian Ocean Data Coverage (MSG-1(IODC)) satellite over the Middle East region. For this purpose, the LibRadTran radiative transfer model was used. This approach is almost independent from other cloud properties, which makes this relationship more efficient for retrieving a cloud’s effective radius. To evaluate this approach, the results have been compared to the effective-radius product of the MODIS on board the Terra and Aqua satellites, and cloud effective radius parameter from the MSG-1satellite’s optimal cloud analysis (OCA) data. The average of correlation coefficient, standard deviation, and RMSE (root mean square error) of this retrieved algorithm method for 29 randomly selected case studies, in comparison to the corresponding MODIS product, are 0.93, 3.093, and 3.639, and compared with OCA product, 0.88, 4.015, and 4.51, respectively. Therefore, the results of analysis in the Middle East region show that the retrieved effective particle radius from Meteosat satellites corresponds strongly with MODIS data from the Terra and Aqua satellites, and also with the OCA products of the MSG-1. Furthemore, using the algorithm that is presented in this paper, a nonlinear regression relationship can be made for retrieving cloud effective radius in the intended place.
       
  • Variation of Ionospheric Range Errors for L1 Frequency GPS Users During
           the 23rd Solar Cycle Over BAHR IGS Station
    • Abstract: Publication date: Available online 4 June 2019Source: Advances in Space ResearchAuthor(s): Abdollah Masoud Darya, Muhammad Mubasshir Shaikh, Ilias Fernini Errors induced by the ionosphere on global navigation satellite systems (GNSS) signal propagation significantly affect the positioning calculation done by ground receivers. These ionospheric errors may end up reaching tens of meters in the final positioning calculation. In this study, the ionospheric range error (IRE) was monitored over the local ionosphere of BAHR, Bahrain (26.209 N, 50.608 E) during the period of the 23rd solar cycle. IRE values were obtained through observation data derived from RINEX files and compared with NeQuick 2 (NQ2) model calculations. It was found that, for the region of study, NQ2 overestimated the total electron content (TEC) values as compared to observation data, resulting in higher IRE values of up to 12 meters. However, IRE derived using GNSS observations and NQ2 follow similar trends over the course of the solar cycle. IRE values were also compared to the smoothed sunspot number (SSN) and F10.7 indexes which resulted in significant correlation between the seasonal calculation of IRE and solar activity. Throughout the 23rd solar cycle, the highest IRE values were found during the equinoxes and the lowest during solstices. The largest IRE value was observed in the vernal equinox of 2000 (19.13 m), while the lowest IRE value was observed in the winter solstice of 1998 (0.276 m).
       
  • Cut-off features in interplanetary solar radio type IV emission
    • Abstract: Publication date: Available online 4 June 2019Source: Advances in Space ResearchAuthor(s): Silja Pohjolainen, Nasrin Talebpour Sheshvan Solar radio type IV bursts can sometimes show directivity, so that no burst is observed when the source region in located far from the solar disk center. This has recently been verified also from space observations, at decameter wavelengths, using a 3D-view to the Sun with STEREO and Wind satellites. It is unclear whether the directivity is caused by the emission mechanism, by reduced radio wave formation toward certain directions, or by absorption/blocking of radio waves along the line of sight. We present here observations of three type IV burst events that occurred on 23, 25, and 29 July 2004, and originated from the same active region. The source location of the first event was near the solar disk center and in the third event near the west limb. Our analysis shows that in the last two events the type IV bursts experienced partial cut-offs in their emission, that coincided with the appearance of shock-related type II bursts. The type II bursts were formed at the flanks and leading fronts of propagating coronal mass ejections (CMEs). These events support the suggestion of absorption toward directions where the type II shock regions are located.
       
  • Experimental study on drilling basalt with small diameter drilling tools
    • Abstract: Publication date: Available online 1 June 2019Source: Advances in Space ResearchAuthor(s): Xiaogan Peng, Ting Zeng, Zhongwang Yin, Zeng Zhao, Liang Li Basalt is one of the potential hard rock targets for drilling sampling in asteroid exploration, and low sampling reaction forces are required in drilling sampling activities of an asteroid. In this paper, the experimental study of drilling basalt with small diameter cemented carbide triangular bit and diamond trepanning drill was carried out, and the drilling thrust force models of basalt drilled by cemented carbide triangular bit and diamond trepanning drill were established, respectively. The ratio of volume removal rate to drilling thrust force was proposed as the evaluation index for the primary selection of drilling tools. The test results showed that the Φ4 mm cemented carbide triangular bit was the preferred small diameter tool for drilling basalt when the minimum drilling thrust force is 40 N. The Φ8 mm electroplated diamond trepanning drill was also the preferred small diameter tool for drilling basalt, Its minimum critical drilling thrust is between 100-110N. Further analysis of the drilling thrust model of the two types of drilling tools showed that the drilling thrust force of cemented carbide triangular bit drilling basalt increased with the feed rate, and it increased with the increase of the apex angle of cemented carbide triangular bit. There was minimum and maximum critical drilling thrust force in drilling basalt with diamond trepanning drill. When the drilling thrust force was between the minimum and maximum critical drilling thrust force, the volume removal rate can be improved by increasing the rotating speed of the diamond trepanning drill. This experimental study helps to optimize the drilling tools and set the drilling thrust force and rotating speed when further studying of hard rock sampling for asteroid drilling.
       
  • A novel adaptive beamforming algorithm against impulsive noise with
           alpha-stable process for satellite navigation signal acquisition
    • Abstract: Publication date: Available online 1 June 2019Source: Advances in Space ResearchAuthor(s): Haichuan Zhang, Fangling Zeng, Daqian Lv, Huishu Wu Adaptive beamforming is an effective spatial filtering technique for overcoming the vulnerability to interference of global navigation satellite system (GNSS) receivers. Although beamforming-based satellite system has the capability of nulling electronic interference sources, the distortions to GNSS receiver induced by impulsive noises are always neglected. This paper addresses the satellite navigation signal acquisition problem in the presence of impulsive noises with alpha-stable noise using the maximum correntropy criterion in framework of the GNSS system. In addition, in order to decrease the number of active elements for avoiding overmuch energy consumption, a sparse regularization is introduced to the constraints of the novel criterion. From the analysis, the novel constraint sparse maximum correntropy (CSMC) beamforming technique that can achieve robustness against impulsive noises which uses less power is developed in this manuscript for satellite signal acquisition. The proposed CSMC, maintains the robustness against impulsive outliers and achieve better performance in conjunction with less power consumption. A mean square analysis of the CSMC algorithm is presented to verify the validity of our theory. Simulation results demonstrate the superiority of the proposed methods over other previously developed beamforming techniques in GNSS.
       
  • Optimal Transfer between Elliptic Orbits with Three Tangential Impulses
    • Abstract: Publication date: Available online 31 May 2019Source: Advances in Space ResearchAuthor(s): Andrea Caruso, Alessandro A. Quarta, Giovanni Mengali This paper introduces a mathematical model that can be used to evaluate the total velocity variation required to accomplish a given two-dimensional orbit transfer, using up to three tangential impulsive maneuvers. The problem is addressed in an optimal framework, by looking for the transfer trajectory that minimizes the total velocity variation. In particular, by exploiting the boundary nonlinear constraint equations, the total velocity variation can be calculated as a function only of the spacecraft angular position at which the impulses are applied. The small number of control variables involved in the algorithm allows the optimization problem to be solved in a simple and robust way, with a small computational effort. The algorithm is able to find the optimal transfer strategy in a generic ellipse-to-ellipse, two-dimensional, mission scenario.
       
  • Adaptive anti-windup control of post-capture combination via tethered
           space robot
    • Abstract: Publication date: Available online 29 May 2019Source: Advances in Space ResearchAuthor(s): Yingbo Lu, Panfeng Huang, Zhongjie Meng Stabilization control is an essential mission for the tethered space robot-target combination during the post-capture phase of tethered space robot (TSR). With the consideration of the space tether and the three dimensional attitude of the post-capture combination, dynamic model of the combination is derived by using Lagrange method. Considering the unknown dynamic parameters (the tether attachment point, unknown target inertia parameters) of the post-capture combination, an adaptive anti-windup control approach is presented to overcome the problem of dynamic uncertainty and control input saturation. Complete stability and performance analyses are presented and illustrative simulation results of application to the post-capture combination system verify the effectiveness of the proposed algorithm.
       
  • Safe deployment of cluster-flying nano-satellites using relative E/I
           vector separation
    • Abstract: Publication date: Available online 28 May 2019Source: Advances in Space ResearchAuthor(s): Pengfei Liu, Xiaoqian Chen, Yong Zhao Nano-satellites cluster flight has attracted an increasing interest in the domain of distributed spacecraft system in recent years. As the first phase of a cluster flight mission, on-orbit deployment process constitutes a great technical challenge, since not only safe relative trajectories, but also practical operational constraints must be considered. To deal with these issues, the concept of relative Eccentricity/Inclination (E/I) vector separation was utilized in the safety concept design and the sequent release parameters solving, as it provides direct insight into the safety characteristics of relative motion. Accordingly, a novel operational methodology for the safe deployment of cluster-flying nano-satellites is provided. It can deterministically generate deployment sequences that ensure safe relative trajectories between released satellite (RS) pairs, as well as that between the launch vehicle (LV) and RSs, for enough long time interval. Particularly, according to our methodology, no maneuver efforts are required for the LV and RSs either during the deployment process or after deployment. Moreover, the proposed methodology adheres to practical constraints from either the LV or ground station. A typical simulation scenario was setup for the deployment process of the pioneering cluster flight mission - Satellite Mission for Swarming and Geolocation (SAMSON). Results demonstrate the feasibility and efficiency of our methodology.
       
  • Equatorial and low-latitude positive ionospheric phases due to moderate
           geomagnetic storm during high solar activity in January 2013
    • Abstract: Publication date: Available online 28 May 2019Source: Advances in Space ResearchAuthor(s): B.A.G. Ribeiro, P.R. Fagundes, K. Venkatesh, A. Tardelli, V.G. Pillat, G.K. Seemala The day-to-day variability of the equatorial and low-latitude ionosphere during quiet and disturbed periods is one of the ionospheric highlighted Space Weather research topics, particularly the ionospheric electrodynamics during geomagnetic storms. This study investigates the response of ionospheric F-region from the equatorial region to beyond the Equatorial Ionization Anomaly (EIA) crest during moderate geomagnetic storm (minimum Dst = -53 nT) that took place on January 17 to 18, 2013, during the high solar activity period of solar cycle 24. The Total Electron Content (TEC) obtained through a network of 82 dual frequency GPS receivers, spanning over an area of 30° x 30° in latitude and longitude are used. Also the F-layer virtual height (h’F) and critical frequency (foF2) observations from 3 ionosondes, in the South American sector are used. Specifically, these GPS-TEC receivers and ionosondes are used to investigate how the F-layer was disturbed by two positive ionospheric phases occurred during the aforementioned disturbed period. The first positive ionospheric phase was probably due to a travelling ionospheric disturbance (TID). When this TID reached the Brazilian coast at low-latitude, the EIA crest was in the growth phase and makes it challenging to separate the spatial-temporal evolution of both phenomena. The second positive ionospheric phase was caused by an anomalous nighttime equatorial positive ionospheric cloud travelling from the east sector towards the west sector. In addition, how the EIA was disturbed by these two positive ionospheric phases in the eastern and western Brazilian sectors is also investigated.
       
  • Ionospheric scintillation impact on ambiguity resolution using ADOP in
           closed form
    • Abstract: Publication date: Available online 28 May 2019Source: Advances in Space ResearchAuthor(s): C.M. Silva, D.B.M. Alves, E.M. Souza, P.T. Setti Junior The Ambiguity Dilution of Precision (ADOP) is a well-known scalar measure that can be used to infer the strength of the Global Navigation Satellite System (GNSS) model of the carrier phase ambiguities involved in precise relative GNSS positioning. Odijk and Teunissen (2008a) derived closed-form expressions for single-baseline GNSS models that allow verifying the factors affecting the ambiguity resolution as well as the probability of its correct resolution as integer values. However, this weighted-ionosphere ADOP closed form assumes that the standard deviation of the ionosphere delay is dependent on a function associated with the baseline length. This means that a baseline of the same length at different locations around the world and in different moments in time would have the same standard deviation, which in practice is not true. This becomes even worse in regions like Brazil, where the ionospheric anomalies are more intense and frequent, especially in periods of high solar activity. In this work, a new method for calculating the ionospheric delay standard deviation that considers the ionospheric scintillation S4 index is proposed to improve the closed-form ADOP performance. Experiments with a baseline of 280m located in Presidente Prudente, Brazil (magnetic latitude of around -13⁰), were carried out. The results showed that in periods of both weak and strong ionospheric scintillation, the introduction of S4 into the ionospheric delay standard deviation was beneficial for ADOP. The average improvement of the ADOP closed form was of around 72% in the analyzed period of weak scintillation and of 35% in the period of strong scintillation. In addition, the results showed that in periods of strong scintillation, relative positioning accuracy is around 100 times worse, up to 30 meters, when compared to periods of weak ionospheric scintillation.
       
  • Operations dynamics analysis of Solar thermal propulsion for CubeSats
    • Abstract: Publication date: Available online 23 May 2019Source: Advances in Space ResearchAuthor(s): Zaynulla S. Zhumaev, Georgy A. Shcheglov This article considers operational dynamics of a solar thermal propulsion unit (STPU) with a solar energy concentrator for CubeSat nanosatellites. It was shown that for a 6U CubeSat with a 1U propulsion system, a resulting ΔV of more than 35m/s in less than 24hours is possible. This ΔV is enough to move apart two satellites to opposite points of a 600km circular orbit in less than 5days. An original scheme of the engine with a capillary feeder system and a Fresnel lens as the solar energy concentrator is proposed. A simplified mathematical model of the engine was created to make it possible to calculate hundreds of thruster operating cycles with different parameters in the chamber. The ODEs were numerically integrated using the Matlab-Simulink software package.
       
  • Calculating Risk and Payoff in Planetary Exploration and Life Detection
           Missions
    • Abstract: Publication date: Available online 23 May 2019Source: Advances in Space ResearchAuthor(s): Ralph D. Lorenz A framework for quantitative assessment of different mission architectures is described using historical data and formal (Bayesian) information value measures. The science value of the result is argued for binary questions (e.g. 'is there life on Europa') to be proportional to the logarithm of the posterior likelihood ratio of the answers, and can be derived from estimates of the false positive rates of instrumentation and of the presence (PD) of biosignatures at a given site. The expectation payoff is the product of the sought result with Markovian success probabilities of the required steps of launch, landing, sample acquisition etc., and historical planetary mission data are reviewed to derive (sometimes dismaying) estimates of these probabilities, e.g. historical landing successes rates are of the order of 66% and when landing is successful, the conditional rates of individual sample acquisition/analysis/return have similar values. The history of seafloor exploration on Earth is used as an analog, and indicates that in the absence of close reconnaissance data, PD may have rather low values of the order of 1% or less. The data acquisition success framework is demonstrated on the value of single versus multiple landers, on the choice of flyby altitudes for multiple plume fly-through missions, and on the value of surface mobility, which for small values of PD multiplies the science return by the number of sites visited. Bayesian reasoning requires encapsulation of prior information : while such estimates (of biosignature presence, false alarm rates, etc.) are inevitably subjective, the decomposition of that information onto specific factors affords transparency into their contribution to the final result and provides a basis for rational mission evaluation.
       
  • Analysis of pre-telescopic sunspots and auroras from 8th to 16th century
    • Abstract: Publication date: Available online 22 May 2019Source: Advances in Space ResearchAuthor(s): Mohamed Reda Bekli, Ilhem Chadou In this paper, we use non-parametric kernel approach to estimate the probability density function (pdf) of auroral-night and naked-eye-sunspot series over multi-century timescale. We selected the events observed in medieval epoch, and auroral records from low geographical latitude (< 45°). These astronomical phenomena are recorded mainly in the Oriental historical sources and much less in Occidental sources. The collected events are published in many recent catalogues. The density function are calculated using the Gaussian kernel, including 95% CI obtained by bootstrapping.Results confirm the existence of strong connection between auroras and sunspot activity, especially from 11th to 16th century. Indeed, a high correlation degree r=0.72 is obtained for the period AD 800 – 1500 between the two pdf of sunspots (pdfS) and auroras (pdfA) for bandwidth h=10 years, and exceed 0.8 for h>43 years. However, we notice a time-shift between the two density functions. To calculate it, we use the cross-correlation technique, and we find τ =-5.9 years, that is strangely close to the half of solar cycle period. It is very important to note that our results revealed that the high frequency of low latitude auroras occurs before the maximum of naked-eye sunspots activity, and not afterward, on contrary to what is expected.The pdf curves show multiple peaks occurring at quasi-periodic times and show clearly the three grand minima of solar activity: Oort, Wolf and Spörer. In auroral-night data, the mean period at 95% CI obtained is:T¯=61±7years. Using power spectrum analysis, we observe clearly a strong signal of 60 years period that is a new evidence of the existence of such cycle. More importantly, we identified a cycle of 262 years period in the sunspot data, and a new oscillation of 310 years in auroral-night data. These two cycles appear clearly in the pdf curves using optimized bandwidth obtained by the direct plug-in approach of Sheather and Jones.
       
  • Two-phase framework for footprint prediction of space object reentry
    • Abstract: Publication date: Available online 22 May 2019Source: Advances in Space ResearchAuthor(s): Siwoo Kim, Byeong-Un Jo, Eun-Jung Choi, Sungki Cho, Jaemyung Ahn This paper proposes a two-phase framework to predict the impact dispersion area of a reentering space object. A semi-analytic approach is developed that predicts the dispersion area by combining an analytic impact point sensitivity model with corrections to account for aerodynamic drag. The first phase of the framework (preparation phase) generates a database storing the coefficients used in the correction model; this applies the least-squares method to the results of numerical experiments on the space object reentry for various initial states (position and velocity) and aerodynamic characteristics (i.e., ballistic coefficient). The second phase (execution phase: during the reentry event) predicts the dispersion area of the falling object using the correction coefficients database generated in the preparation phase. The validity and computational efficiency of the proposed method are demonstrated through a case study.
       
  • Statistical relation of scintillation index S4 with ionospheric
           irregularity index ROTI over Indian equatorial region
    • Abstract: Publication date: Available online 21 May 2019Source: Advances in Space ResearchAuthor(s): Rajat Acharya, Saibal Majumdar Ionospheric scintillation can cause severe degradation in the GNSS services, particularly at the polar and equatorial regions, by deteriorating the positioning performance in terms of accuracy. The continuity of the GNSS service is also affected as severe scintillation may lead to the loss of lock of the receiver. In this work, the occurrence probability of amplitude scintillation index S4 has been statistically related to the ionospheric irregularity index of ROTI. Simultaneously measured S4 and TEC data from the GAGAN TEC network stations, installed across India, were used for the purpose. TEC is used for the derivation of ROTI. The distribution of the S4 observed over different finite ranges in ROTI was separately matched with standard parametric models. This was done for both quiet and disturbed geomagnetic conditions. Log-normal distribution has been found to be the best match for most of the cases. The parameters for the matched log-normal distributions were found to vary systematically with the mean ROTI values in the range. Therefore, these distribution parameters were modelled in the terms of the corresponding ROTI values. The derived model was successfully validated with independent data and the conformity was established using statistical methods. This work may find usefulness in estimating the probable scintillation strength S4 once the ionospheric irregularity is known in terms of ROTI. Moreover, given an observed value of ROTI, the probability of losing receiver lock can be determined, provided the corresponding threshold S4 that the receiver can withstand is known.
       
  • Performance of BeiDou-3 satellites: Signal Quality Analysis and Precise
           Orbit Determination
    • Abstract: Publication date: Available online 21 May 2019Source: Advances in Space ResearchAuthor(s): Bo Zhang, Xiaolin Jia, Fuping Sun, Kai Xiao, Hailiang Dai A new generation of satellites aimed for the BeiDou-3 global positioning system (BDS-3) has recently been launched. These satellites will play a crucial role in its globalization process. The performance of the BDS-3 experimental satellites has been addressed in previous works. However, performance analysis of the orbits of BDS-3 satellites is still lacking. Using the observation data of the B1I and B3I frequency signals across different stations, this paper provides quality analysis, precise orbit determination (POD), and orbit comparison. The results presented here show that the ranging accuracy of BDS-3 is superior to that of the BeiDou-2 system (BDS-2). The satellite-induced code bias of BDS-2 satellite is not obvious on BDS-3 satellite. The orbit accuracy of BDS-3 satellite is superior to the BDS-2 satellite. The average three-dimensional root-mean-square error (RMS) of two-day overlapping arcs for BDS-3 satellite orbits is within 0.1 m, and the satellite laser ranging (SLR) validation reports that the orbit radial-track is within 6 cm.
       
  • Transient nature of radio source NVSS J1957+35
    • Abstract: Publication date: Available online 18 May 2019Source: Advances in Space ResearchAuthor(s): Sabyasachi Pal, Dusmanta Patra, Monique Hollick, Sandip K. Chakrabarti We have searched for transient and variable radio sources in the field of Galactic micro-quasar Cygnus X-1 near 1.4 GHz (L band) using data from the Karl G. Jansky Very Large Array. We used twenty years of data between 1983 and 2003. We found a source NVSS J1957+35 showing transient behavior. The source was also mentioned earlier in NVSS and WENSS catalog but its transient nature was not reported earlier. The source is located 23.8 arcminutes far from Cygnus X-1. It is detected many times during the span of our study and it varied between less than 1.9 mJy (3σ) to 201 mJy. NVSS J195754+353513 also showed high intra-day variability. In one occasion, the source rose from ∼15 mJy to ∼170 mJy within 700 seconds. We detected circularly polarized emission from the source for a limited number of cases with fractional circular polarization varies between 0.14 to 0.17. 2MASS J19575420+3535152 may be the near-infrared counterpart of the source. We compared the properties of the source with other Galactic transient sources having similar properties. The nature of the source is still unknown. We discussed the possible nature of the source.
       
  • - 56+with+Suzaku&rft.title=Advances+in+Space+Research&rft.issn=0273-1177&rft.date=&rft.volume=">A study of the composite supernova remnant MSH 15 - 56 with Suzaku
    • Abstract: Publication date: Available online 17 May 2019Source: Advances in Space ResearchAuthor(s): Nergis Cesur, Aytap Sezer, Jelle de Plaa, Jacco Vink The Galactic supernova remnant (SNR) MSH 15-56 is a member of the class of composite SNRs that consists of the remnant shell and a displaced pulsar wind nebula (PWN). The earlier X-ray observations reported the comet-like morphology of the PWN and the ejecta distribution of the SNR. In this work, we present a study of MSH 15-56 using archival Suzaku data. We investigate the nature of the emission and spectral parameters of the remnant. The X-ray spectra are well fitted with a combination of a thermal and non-thermal model with temperature ∼0.6 keV and photon index ∼2.0. The slightly enhanced abundances of Ne, Mg, S and enhanced abundance of Si confirm the presence of ejected material.
       
  • Monitor link assignment for reentry users based on BeiDou inter-satellite
           links
    • Abstract: Publication date: Available online 17 May 2019Source: Advances in Space ResearchAuthor(s): Leyuan Sun, Wende Huang, Yifan Zhou, Jun Yang, Yueke Wang The BeiDou Navigation Satellite System (BDS) has equipped its new-generation satellites with inter-satellite link (ISL) payloads to improve navigation services and system operation. When the inter-satellite ranging and communication are satisfied, we analyze the exploitation of the spare ISL capability for serving atmospheric reentry users. These users can be monitored over the atmospheric reentry segment with ISL transmission, even in the absence of visibility to ground stations and escaping the blackout. We modeled the problem and proposed a link assignment method combining parallel assignment of ISLs and dynamic access of monitor links. First, ISLs were assigned for inter-satellite ranging and communication, which were quantified with the number of different links and timeslot delays respectively. Corresponding assignment algorithm operated in the stations and the computing resource was abundant. Therefore, the heuristic algorithm was used to search the shortest route and the fitness function was determined with a shortest path algorithm. Based on the ISL assignment, extended users were accessed to the ISL network dynamically without influencing performances of the constellation. Because of the uncertainty of users’ states, the monitor link assignment was implemented onboard with short-term predicted states and therefore the computing resource was scarce. Short-term predicted states conquered the deviation of satellite-user visibility. And a simple smallest delay strategy was used to determine the access nodes for users. To evaluate performances of the algorithm, link assignments were implemented for the BeiDou global constellation with 3 users. Each satellite was linked with at least 10 satellites and communicated with stations within 3 timeslots on the basis of ISL assignments. The assignment of monitor links demonstrated the user access did not influence the ranging and communication index of the ISL network and 1-, 2-, and 3-timeslot route delays of users occupy the main parts and the total ratio is larger than 95%.
       
  • Control of Nonlinear Spacecraft Attitude Motion via State Augmentation,
           Lyapunov-Floquet Transformation and Normal Forms
    • Abstract: Publication date: Available online 17 May 2019Source: Advances in Space ResearchAuthor(s): Peter M.B. Waswa, Sangram Redkar This article analyzes and controls the quasi-periodic attitude motion of a gravity-gradient stabilized spacecraft in eccentric orbit by way of system states augmentation, Lyapunov-Floquet and Normal Forms transformations. Perturbing torques in the ambient space environment can be shown to engender attitude motion represented by nonlinear dynamics coupled in the roll-yaw axes; and, uncoupled planar dynamics in the pitch axis. The non-planar dynamics equations are homogeneous and analytically solvable. However, the pitch attitude motion is nonlinear, possesses parameter-varying coefficients and is subjected to external periodic excitations. Consequently, we transform the unwieldy pitch attitude dynamics into relatively more amenable schemes for analysis and control law synthesis. Subsequently, we demonstrate the implementation of linear and nonlinear control laws (i.e. bifurcation and sliding mode control laws) on the relatively acquiescent transformed attitude dynamics. By employing a two-pronged approach, the quasi-periodic planar motion is independently shown to be stabilizable via the nonlinear control approaches.
       
 
 
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