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Journal Cover Advances in Space Research
  [SJR: 0.606]   [H-I: 65]   [348 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 0273-1177
   Published by Elsevier Homepage  [3044 journals]
  • Use of uninformative priors to initialize state estimation for dynamical
           systems
    • Authors: Johnny L. Worthy; Marcus J. Holzinger
      Pages: 1373 - 1388
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Johnny L. Worthy, Marcus J. Holzinger
      The admissible region must be expressed probabilistically in order to be used in Bayesian estimation schemes. When treated as a probability density function (PDF), a uniform admissible region can be shown to have non-uniform probability density after a transformation. An alternative approach can be used to express the admissible region probabilistically according to the Principle of Transformation Groups. This paper uses a fundamental multivariate probability transformation theorem to show that regardless of which state space an admissible region is expressed in, the probability density must remain the same under the Principle of Transformation Groups. The admissible region can be shown to be analogous to an uninformative prior with a probability density that remains constant under reparameterization. This paper introduces requirements on how these uninformative priors may be transformed and used for state estimation and the difference in results when initializing an estimation scheme via a traditional transformation versus the alternative approach.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.040
       
  • GDOP minimum in multi-GNSS positioning
    • Authors: Bi Liu; Yunlong Teng; Qi Huang
      Pages: 1400 - 1403
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Bi Liu, Yunlong Teng, Qi Huang
      In positioning, navigation and timing (PNT) applications with the Global Navigation Satellite System (GNSS), the geometric dilution of precision (GDOP) offers an important index for selecting satellites from all tracked satellites for positioning calculation. In general, the lower the GDOP values are, the more accurate the PNT solution is. Therefore, the GDOP minimum should be pursued. In this paper, we mainly focused on the GDOP minimum when the single-point positioning is based on the integration of three GNSSs. The GDOP minimum for any number of tracked satellites is theoretically derived in this paper. In addition, when the number of the satellites is equal to that of the unknown parameters, the correctness of GDOP minimum obtained has also been validated from two different perspectives.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.049
       
  • Stable orbits for lunar landing assistance
    • Authors: Ennio Condoleo; Marco Cinelli; Emiliano Ortore; Christian Circi
      Pages: 1404 - 1412
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Ennio Condoleo, Marco Cinelli, Emiliano Ortore, Christian Circi
      To improve lunar landing performances in terms of mission costs, trajectory determination and visibility the use of a single probe located over an assistance orbit around the Moon has been taken into consideration. To this end, the properties of two quasi-circular orbits characterised by a stable behaviour of semi-major axis, eccentricity and inclination have been investigated. The analysis has demonstrated the possibility of using an assistance probe, located over one of these orbits, as a relay satellite between lander and Earth, even in the case of landings on the far side of the Moon. A comparison about the accuracy in retrieving the lander’s state with respect to the use of a probe located in the Lagrangian point L2 of the Earth-Moon system has also been carried out.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.07.009
       
  • Extra-terrestrial construction processes – Advancements,
           opportunities and challenges
    • Authors: Sungwoo Lim; Vibha Levin Prabhu; Mahesh Anand; Lawrence A. Taylor
      Pages: 1413 - 1429
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Sungwoo Lim, Vibha Levin Prabhu, Mahesh Anand, Lawrence A. Taylor
      Government space agencies, including NASA and ESA, are conducting preliminary studies on building alternative space-habitat systems for deep-space exploration. Such studies include development of advanced technologies for planetary surface exploration, including an in-depth understanding of the use of local resources. Currently, NASA plans to land humans on Mars in the 2030s. Similarly, other space agencies from Europe (ESA), Canada (CSA), Russia (Roscosmos), India (ISRO), Japan (JAXA) and China (CNSA) have already initiated or announced their plans for launching a series of lunar missions over the next decade, ranging from orbiters, landers and rovers for extended stays on the lunar surface. As the Space Odyssey is one of humanity’s oldest dreams, there has been a series of research works for establishing temporary or permanent settlement on other planetary bodies, including the Moon and Mars. This paper reviews current projects developing extra-terrestrial construction, broadly categorised as: (i) ISRU-based construction materials; (ii) fabrication methods; and (iii) construction processes. It also discusses four categories of challenges to developing an appropriate construction process: (i) lunar simulants; (ii) material fabrication and curing; (iii) microwave-sintering based fabrication; and (iv) fully autonomous and scaled-up construction processes.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.038
       
  • Rapid generation of entry trajectory with multiple no-fly zone constraints
    • Authors: Rui-zhi He; Lu-hua Liu; Guo-jian Tang; Wei-min Bao
      Pages: 1430 - 1442
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Rui-zhi He, Lu-hua Liu, Guo-jian Tang, Wei-min Bao
      An entry trajectory planning algorithm that generates flyable trajectories satisfying multiple no-fly zones and other path and terminal constraints is presented. The algorithm divides the entry trajectory into initial and glide phases. In the initial phase, the maximum value of heating rate is controlled accurately as the altitude of the quasi-equilibrium glide condition (QEGC) transition point is adjusted with a nominal angle of attack and a parameterized bank angle. In the glide phase, a geometry based planning algorithm that relies on the center positions and radius of the multiple no-fly zones, is proposed to calculate the waypoints of the virtual flight path. The magnitude and reversal point of the bank angle in each sub-phase are searched based on a reduced-order lateral system with the predictor-corrector method. The altitude is designed as an analytical function of energy, and the QEGC is employed to analytically solve the remaining state variables. Finally, a linear quadratic regulator is used to test the realization of the 3D trajectory. The algorithm is tested using the common aero vehicle-H model. The results demonstrate that the algorithm can rapidly generate the entry trajectory with multiple no-fly zone constraints and achieve complex flight missions satisfying all flight constraints.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.046
       
  • Compaction of montmorillonite in ultra-dry state
    • Authors: Brian J. Chow; Tzehan Chen; Ying Zhong; Meng Wang; Yu Qiao
      Pages: 1443 - 1452
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Brian J. Chow, Tzehan Chen, Ying Zhong, Meng Wang, Yu Qiao
      The current study discovers that uniaxial compression under ambient condition can directly cause strong bonding in ultra-dry montmorillonite, which is attributed to the secondary molecular interaction other than hydrogen bonding. The strength of so-processed material is sensitive to the lateral confinement condition of loading. Similar compaction pressure produces equally strong solids between quasi-static and impact loading modes. Gas permeability of the compacted solids is comparable to those of dense rocks. These findings shed light on the study of Martian regolith and in-situ resource utilization.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.07.001
       
  • Experimental characterization of elastomeric O-rings as reusable seals for
           mass spectrometric measurements: Application to in situ K–Ar dating on
           Mars
    • Authors: Yuichiro Cho; Shingo Kameda; Mamoru Okuno; Misa Horiuchi; Kazuo Shibasaki; Ryo Wagatsuma; Yusuke Aida; Yayoi N. Miura; Kazuo Yoshioka; Ryuji Okazaki; Seiji Sugita
      Pages: 1453 - 1462
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Yuichiro Cho, Shingo Kameda, Mamoru Okuno, Misa Horiuchi, Kazuo Shibasaki, Ryo Wagatsuma, Yusuke Aida, Yayoi N. Miura, Kazuo Yoshioka, Ryuji Okazaki, Seiji Sugita
      Mass spectrometry has been widely used in lander missions to characterize the volatiles in rocks and soils on planetary surfaces. A good vacuum seal is very important for introducing such solid samples to a vacuum chamber and ejecting them. However, multiple measurements require many metal gaskets, leading to extra weight and complexity for the instruments. In this study, we investigate the capability of three kinds of elastomeric O-rings (Viton, Nexus-SLT, and Nexus-FV) as vacuum seals for mass spectrometric measurements, particularly for in situ K–Ar dating on Mars. First, thermal cycle tests revealed that low-temperature-resistant O-rings can maintain pressure <10−5 Pa at −60°C under 1bar ambient pressure, whereas Viton O-rings leaked at −25°C. Then, the amount of 40Ar due to outgassing from the O-rings and permeation under the ambient pressure of 650Pa or 3Pa was measured and compared with the amounts of 40Ar that a flight-equivalent laser would liberate from potential target Martian rocks. The measured amounts were <1% of that a target rock with 5000ppm K2O and an age of 4.2Ga would yield. These results suggest that a Viton O-ring can maintain the Ar blank low under the Mars atmospheric pressure when temperatures are higher than −25°C. A double O-ring seal using the low-temperature-resistant elastomers would be an alternative approach at lower temperatures. The elastomeric O-rings would be useful for constructing a small and light-weighted mass spectrometric instrument for in situ K–Ar dating on Mars.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.07.002
       
  • A study on predicting network corrections in PPP-RTK processing
    • Authors: Kan Wang; Amir Khodabandeh; Peter Teunissen
      Pages: 1463 - 1477
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Kan Wang, Amir Khodabandeh, Peter Teunissen
      In PPP-RTK processing, the network corrections including the satellite clocks, the satellite phase biases and the ionospheric delays are provided to the users to enable fast single-receiver integer ambiguity resolution. To solve the rank deficiencies in the undifferenced observation equations, the estimable parameters are formed to generate full-rank design matrix. In this contribution, we firstly discuss the interpretation of the estimable parameters without and with a dynamic satellite clock model incorporated in a Kalman filter during the network processing. The functionality of the dynamic satellite clock model is tested in the PPP-RTK processing. Due to the latency generated by the network processing and data transfer, the network corrections are delayed for the real-time user processing. To bridge the latencies, we discuss and compare two prediction approaches making use of the network corrections without and with the dynamic satellite clock model, respectively. The first prediction approach is based on the polynomial fitting of the estimated network parameters, while the second approach directly follows the dynamic model in the Kalman filter of the network processing and utilises the satellite clock drifts estimated in the network processing. Using 1Hz data from two networks in Australia, the influences of the two prediction approaches on the user positioning results are analysed and compared for latencies ranging from 3 to 10s. The accuracy of the positioning results decreases with the increasing latency of the network products. For a latency of 3s, the RMS of the horizontal and the vertical coordinates (with respect to the ground truth) do not show large differences applying both prediction approaches. For a latency of 10s, the prediction approach making use of the satellite clock model has generated slightly better positioning results with the differences of the RMS at mm-level. Further advantages and disadvantages of both prediction approaches are also discussed in this contribution.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.043
       
  • Real-time precise orbit determination of LEO satellites using a
           single-frequency GPS receiver: Preliminary results of Chinese SJ-9A
           satellite
    • Authors: Xiucong Sun; Chao Han; Pei Chen
      Pages: 1478 - 1487
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Xiucong Sun, Chao Han, Pei Chen
      Spaceborne Global Positioning System (GPS) receivers are widely used for orbit determination of low-Earth-orbiting (LEO) satellites. With the improvement of measurement accuracy, single-frequency receivers are recently considered for low-cost small satellite missions. In this paper, a Schmidt-Kalman filter which processes single-frequency GPS measurements and broadcast ephemerides is proposed for real-time precise orbit determination of LEO satellites. The C/A code and L1 phase are linearly combined to eliminate the first-order ionospheric effects. Systematic errors due to ionospheric delay residual, group delay variation, phase center variation, and broadcast ephemeris errors, are lumped together into a noise term, which is modeled as a first-order Gauss-Markov process. In order to reduce computational complexity, the colored noise is considered rather than estimated in the orbit determination process. This ensures that the covariance matrix accurately represents the distribution of estimation errors without increasing the dimension of the state vector. The orbit determination algorithm is tested with actual flight data from the single-frequency GPS receiver onboard China’s small satellite Shi Jian-9A (SJ-9A). Preliminary results using a 7-h data arc on October 25, 2012 show that the Schmidt-Kalman filter performs better than the standard Kalman filter in terms of accuracy.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.052
       
  • A quantitative method to evaluate the performance of topographic
           correction models used to improve land cover identification
    • Authors: Sung-Hwan Park; Hyung-Sup Jung; Jaewon Choi; Seongwoo Jeon
      Pages: 1488 - 1503
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Sung-Hwan Park, Hyung-Sup Jung, Jaewon Choi, Seongwoo Jeon
      Topographic correction methods have been widely used prior to land cover identification in sloping terrain because the topographic variation on the Earth's surface can interfere with the classifications. The topographic correction involves the normalization of brightness or surface reflectance values from the slanted to the horizontal plane. Several topographic correction models have been proposed, and a quantitative evaluation method is needed for these models because the performance can vary according to the surface cover types and spectral bands. In this study, we proposed an efficient method to evaluate the performance of topographic correction models through measuring the histogram structural similarity (HSSIM) index estimated from the sunlit and sun-shaded slope areas before and after the correction. We tested the HSSIM index by using three different land cover types derived from Landsat-8 Operational Land Imager (OLI) images and eight commonly used topographic correction models. When the proposed HSSIM index was compared with the visual analysis technique, the results matched exactly. Using the HSSIM index, the best correction methods were then determined, and the best ones included the statistical-empirical or SCS+C methods (where SCS+C refers to the sun-canopy-sensor plus C-correction) for the R, G, and B bands and the Minnaert+SCS method for the NIR, SWIR-1, and SWIR-2 bands. These results indicate that (i) the HSSIM index enables quantitative performance evaluations of topographic correction models and (ii) the HSSIM index can be used to determine the best topographic correction method for particular land cover identification applications.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.054
       
  • Ionospheric effects on repeat-pass SAR interferometry
    • Authors: Jian Feng; Weimin Zhen; Zhensen Wu
      Pages: 1504 - 1515
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Jian Feng, Weimin Zhen, Zhensen Wu
      InSAR measurements can be significantly affected by the atmosphere when the radar signal propagates through the atmosphere since it varies with space and time. Great efforts have been made in recent years to better understand the properties of the tropospheric effects and to develop methods for mitigating these effects. By using the basic principles of InSAR, the quantitative analysis of ionospheric delay effects on topography and surface deformation have been introduced for the first time. The measurement errors can be related to the vertical ionospheric total electron content (vTEC). By using the ionospheric observations, the effects of temporal ionospheric variations on InSAR have been analyzed. The results indicate that the ionospheric variations with time, season, solar cycle and geomagnetic activities can compromise the effectiveness of InSAR for both the measurement of topography and surface determination. The repeat-pass SAR interferometry errors induced by ionosphere should be corrected by actual measurements.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.019
       
  • Statistical characteristics of the polar ionospheric scale height around
           the peak height of F2 layer with observations of the ESR radar: Disturbed
           days
    • Authors: Zheng Qiao; Zhigang Yuan; Shiyong Huang; Dedong Wang
      Pages: 1516 - 1523
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Zheng Qiao, Zhigang Yuan, Shiyong Huang, Dedong Wang
      In this paper, based on observations of the European Incoherent Scatter Svalbard Radar (ESR) between 1997 and 2008, we analyzed variations of HmF2, the ionospheric scale height around the peak height of F2 layer (hmF2) at high latitude with geomagnetic activities, as well as variations of the HmF2 with the local time (LT), season and solar activity under disturbed conditions (2<Kp≤5). We found that the HmF2 shows a significant increment with enhancements of geomagnetic activities. In addition, based on a linear regression, the correlation and fitting coefficients are shown, which quantitatively describe the correlations between polar HmF2 and geomagnetic activity index Kp. The HmF2 shows a diurnal variation with a maximum early in the morning and a minimum around noon in disturbed days (2<Kp≤5), which is more complex in comparison with that in quiet days. However, in summer and autumn, the HmF2 in disturbed days shows a bulge during 06:00–11:00 LT instead of the continuous decline under quiet condition. We consider that the ESR was under the cusp region during the period so that the bulge might be related to the high-energy particles precipitating into the ionosphere resulting in changes of the electron density profile. The HmF2 has the highest seasonal magnitude in summer and the lowest seasonal magnitude in winter generally. The seasonal magnitude of the HmF2 in autumn is lower than that in spring and larger than that in winter under low solar activity, while the HmF2 shows the same seasonal variations in spring and autumn under moderate and high solar activities.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.041
       
  • Solutions of the cosmic ray velocity diffusion equation
    • Authors: J. Lasuik; A. Shalchi
      Pages: 1532 - 1546
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): J. Lasuik, A. Shalchi
      In order to describe the propagation and acceleration of cosmic rays, one usually uses a diffusive transport equation. The most fundamental equation is the pitch-angle dependent diffusion equation which is usually called the Fokker-Planck equation. In the current paper we solve the position integrated equation numerically and analytically. For a constant pitch-angle Fokker-Planck coefficient we derive an exact solution of the corresponding transport equation and compare it with numerical solutions. We show that even if the scattering coefficient is assumed to be constant, the solution behaves well. As a second example we consider the case of a linear pitch-angle Fokker-Planck coefficient. Again we solve the corresponding transport equation numerically and analytically. In all cases considered, we find similar distribution functions. We also compute the corresponding velocity correlation functions and parallel diffusion coefficients. Our results are relevant for improving analytical theories of perpendicular diffusion, for code tests, and for different astrophysical applications where a pitch-angle dependent description of the particle motion is required.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.035
       
  • Design of an adaptable Stokes polarimeter for exploring chromospheric
           magnetism
    • Authors: Rohan E. Louis; A. Raja Bayanna; Héctor Socas Navarro
      Pages: 1547 - 1556
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Rohan E. Louis, A. Raja Bayanna, Héctor Socas Navarro
      The chromosphere is a highly complex and dynamic layer of the Sun, that serves as a conduit for mass and energy supply between two, very distinct regions of the solar atmosphere, namely, the photosphere and corona. Inferring magnetic fields in the chromosphere, has thus become an important topic, that can be addressed with large-aperture solar telescopes to carry out highly sensitive polarimetric measurements. In this article, we present a design of a polarimeter for investigating the chromospheric magnetic field. The instrument consists of a number of lenses, two ferro-electric liquid crystals, a Wollaston prism, and a CCD camera. The optical design is similar to that of a commercial zoom lens which allows a variable f# while maintaining focus and aberrations well within the Airy disc. The optical design of the Adaptable ChRomOspheric POLarimeter (ACROPOL) makes use of off-the-shelf components and is described for the 70cm Vacuum Tower Telescope and the 1.5m GREGOR telescope at Observatorio del Teide, Tenerife, Spain. Our design shows that the optical train can be separated into two units where the first unit, consisting of a single lens, has to be changed while going from the VTT to the GREGOR configuration. We also discuss the tolerances within which, diffraction limited performance can be achieved with our design.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.036
       
  • Automated detection of new impact sites on Martian surface from HiRISE
           images
    • Authors: Xin Xin; Kaichang Di; Yexin Wang; Wenhui Wan; Zongyu Yue
      Pages: 1557 - 1569
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Xin Xin, Kaichang Di, Yexin Wang, Wenhui Wan, Zongyu Yue
      In this study, an automated method for Martian new impact site detection from single images is presented. It first extracts dark areas in full high resolution image, then detects new impact craters within dark areas using a cascade classifier which combines local binary pattern features and Haar-like features trained by an AdaBoost machine learning algorithm. Experimental results using 100 HiRISE images show that the overall detection rate of proposed method is 84.5%, with a true positive rate of 86.9%. The detection rate and true positive rate in the flat regions are 93.0% and 91.5%, respectively.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.044
       
  • The possible hydrogen anomalies in KREEP terrain according to the results
           of LEND and LPNS data
    • Authors: M.P. Sinitsyn
      Pages: 1570 - 1577
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): M.P. Sinitsyn
      Distribution of epithermal neutron flux and hydrogen content from equatorial surface of the Moon, obtained by neutron spectrometers LEND and LPNS is studied. The positions of spots with reduced neutron flux, so-called NSRs (Neutron Suppression Regions), in the KREEP terrain are determined. We found that typical decreasing of epithermal neutron flux is about δ = 1 – 7 % for NSRs around the equatorial lunar surface relative the comparison zone associated with crater Tycho. Mean value of neutron flux suppression for KREEP region is nearly δ = 4.6 %. This value corresponds to the average concentration of hydrogen C H = 62 ppm included in any hydrogen compounds, incorporated in the regolith layer with depth up to 1m. For all equatorial regions of the Moon ( 70 ° S – 70 ° N latitude) the average suppression factor δ = 3 % corresponds to mean value of hydrogen content nearly 55ppm. It has been recognized strong correlations between NSRs in KREEP with volcanic and impact formations, related to Mare Imbrium. The largest of the considered NSRs are located in Fra-Mauro crater ( δ = 7.2 %, C H = 127.5 ppm) and in Iridium terrain area ( δ = 6.9 %, C H = 82.2 ppm). These two hydrogen anomalies undoubtedly are related to the impact processes formed Mare Imbrium. Possible origins of epithermal neutron suppressions in KREEP, concerning both implanted solar wind protons and indigenous lunar hydrogen are discussed.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.050
       
  • The mass composition of cosmic rays according to data obtained in the
           SOKOL-2 satellite experiment
    • Authors: Andrey Turundaevskiy; Dmitry Podorozhnyi
      Pages: 1578 - 1582
      Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7
      Author(s): Andrey Turundaevskiy, Dmitry Podorozhnyi
      The mass number of cosmic-ray nuclei was obtained using the data from the SOKOL-2 satellite experiment. The mean logarithm of the mass number was determined by two independent methods – the direct method using a charge detector and indirect method using cascade shape information obtained by the ionization calorimeter. We obtained the energy dependence of the mean logarithm of the mass number in the energy range 3–200TeV. The analysis of the SOKOL-2 data showed the applicability of the indirect methods to determine the mass number. The values of the mean logarithm of the mass number obtained by different experiments are consistent.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.07.008
       
  • Formation flying for electric sails in displaced orbits. Part I:
           Geometrical analysis
    • Authors: Wei Wang; Giovanni Mengali; Alessandro A. Quarta; Jianping Yuan
      Pages: 1130 - 1147
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Wei Wang, Giovanni Mengali, Alessandro A. Quarta, Jianping Yuan
      We present a geometrical methodology for analyzing the formation flying of electric solar wind sail based spacecraft that operate in heliocentric, elliptic, displaced orbits. The spacecraft orbit is maintained by adjusting its propulsive acceleration modulus, whose value is estimated using a thrust model that takes into account a variation of the propulsive performance with the sail attitude. The properties of the relative motion of the spacecraft are studied in detail and a geometrical solution is obtained in terms of relative displaced orbital elements, assumed to be small quantities. In particular, for the small eccentricity case (i.e. for a near-circular displaced orbit), the bounds characterized by the extreme values of relative distances are analytically calculated, thus providing an useful mathematical tool for preliminary design of the spacecraft formation structure.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.017
       
  • Formation flying for electric sails in displaced orbits. Part II:
           Distributed coordinated control
    • Authors: Wei Wang; Giovanni Mengali; Alessandro A. Quarta; Jianping Yuan
      Pages: 1130 - 1147
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Wei Wang, Giovanni Mengali, Alessandro A. Quarta, Jianping Yuan
      We analyze a cooperative control framework for electric sail formation flying around a heliocentric displaced orbit, aiming at observing the polar region of a celestial body. The chief spacecraft is assumed to move along an elliptic displaced orbit, while each deputy spacecraft adjusts its thrust vector (that is, both its sail attitude and characteristic acceleration) in order to track a prescribed relative trajectory. The relative motion of the electric sail formation system is formulated in the chief rotating frame, where the control inputs of each deputy are the relative sail attitude angles and the relative lightness number with respect to those of the chief. The information exchange among the spacecraft, characterized by the communication topology, is represented by a weighted graph. Two typical cases, according to whether the communication graph is directed or undirected, are discussed. For each case, a distributed coordinated control law is designed in such a way that each deputy not only tracks the chief state, but also makes full use of information from its neighbors, thus increasing the redundancy and robustness of the formation system in case of failure among the communication links. Illustrative examples show the effectiveness of the proposed approach.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.017
       
  • Mission planning for on-orbit servicing through multiple servicing
           satellites: A new approach
    • Authors: K. Daneshjou; A.A. Mohammadi-Dehabadi; M. Bakhtiari
      Pages: 1148 - 1162
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): K. Daneshjou, A.A. Mohammadi-Dehabadi, M. Bakhtiari
      In this paper, a novel approach is proposed for the mission planning of on-orbit servicing such as visual inspection, active debris removal and refueling through multiple servicing satellites (SSs). The scheduling has been done with the aim of minimization of fuel consumption and mission duration. So a multi-objective optimization problem is dealt with here which is solved by employing particle swarm optimization algorithm. Also, Taguchi technique is employed for robust design of effective parameters of optimization problem. The day that the SSs have to leave parking orbit, transfer duration from parking orbit to final orbit, transfer duration between one target to another, and time spent for the SS on each target are the decision parameters which are obtained from the optimization problem. The raised idea is that in addition to the aforementioned decision parameters, eccentricity and inclination related to the initial orbit and also phase difference between the SSs on the initial orbit are identified by means of optimization problem, so that the designer has not much role on determining them. Furthermore, it is considered that the SS and the target rendezvous at the servicing point and the SS does not perform any phasing maneuver to reach the target. It should be noted that Lambert theorem is used for determination of the transfer orbit. The results show that the proposed approach reduces the fuel consumption and the mission duration significantly in comparison with the conventional approaches.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.05.037
       
  • Removal targets' classification: How time considerations modify the
           definition of the index
    • Authors: Mélissa Zemoura; Toshiya Hanada; Satomi Kawamoto
      Pages: 1163 - 1187
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Mélissa Zemoura, Toshiya Hanada, Satomi Kawamoto
      The growth of the near-Earth debris population since the beginning of human space activities is now a fact commonly admitted by space agencies worldwide. Numerous entities have warned about the danger that debris may have over time. Presently mitigation methods such as imposing post-mission disposal time after launch will no longer be sufficient; remediation processes seem necessary to limit the increase. In particular, this phenomenon is attributed to the generation of fragments due to more and more on-orbit collisions. Therefore, investigations on indexes to select potential removal targets were recently conducted, considering solely objects implicated in a collision course. This study also looks at the multiple fragmentation factors, including time through the altitude at time of impact (due to the behaviour of debris re-entering with time). The focal point is here to compare different criteria to select removal targets that enable scenarios in best adequacy with the future in question (long term, mid term or short term). Aware of the uncertainty of evolutionary models, this study also incorporates the simulation method as an impactful factor and tries to overcome the potential randomness of the results. Therefore, this paper presents a way to establish a selection criterion the most adequate for the time period focused on. In order to solve this issue, a “double-check” method is proposed. First, an analytical evolutionary model simulates the environment over 100years, through 100 Monte-Carlo runs. Then, among the initial population of year 2009, the objects supposed to be at the origin of the debris detected at a given time are tracked back in time into the simulations, using a collision-detecting program. The “given period” above mentioned for the presence of debris is based on a future as such that 2029 be considered a short-term scenario, 2059 a midterm scenario and 2109 a long-term scenario. This step produces three lists of targets for removal (one for each future), and simulations are run once again, through different scenarios involving the removal of particular listed targets in order to verify the appropriateness of the proposed scenarios. The analysis of the results is based both on the mean of the simulations and on the recurrence considering each run. Three studies were conducted one for each term, and a fourth one completed the work by establishing comparison between short, mid and long-term periods. As a result, three main criteria could be established: the altitude of the objects, the number of targets necessary to remove, and the phenomenon of chain collisions. According to the future that was investigated, the most adequate criterion appeared to be different, consisting in the number of objects in the long-term analysis or the ranking position at short term (linked to the close-time consideration). As a main conclusion and further perspectives, it should be more efficient to consider the collision-probability and mass product together with the time-depending generation of fragments. This would help increasing the precision in the prediction of collision impacts. Rather than pinpointing specified targets to be removed, the aim of this study is simply to understand the mechanisms at the origin of the population increase around the Earth. Also to demonstrate that a careful definition of selection criteria would enable to adopt a suitable removal process in the period of action or for the goal to be reached.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.05.046
       
  • Optimal spacecraft rendezvous by minimum velocity change and wait time
    • Authors: Snyoll Oghim; Sung-Hoon Mok; Henzeh Leeghim
      Pages: 1188 - 1200
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Snyoll Oghim, Sung-Hoon Mok, Henzeh Leeghim
      An optimization problem is investigated in this paper to obtain a minimum velocity change, sometimes called as minimum-energy, to rendezvous a target spacecraft. The problem formulation starts with known initial positions and velocity vectors of two spacecraft, so-called target and chaser, respectively. The Kepler’s time-of-flight equation in terms of the universal variables and the relationship between final position vectors of the two spacecraft are posed as constraints. Three-dimensional orbital information is obtained by using the f and g solution that called the Lagrange coefficients. One of advantages for the universal variables is that it provides total orbital information valid for all conic orbits without much numerical difficulty. The wait time concept is also employed to release the magnitude of velocity changes by minimizing the performance index. Finally, these techniques are demonstrated using numerical simulations.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.025
       
  • Stare and chase of space debris targets using real-time derived pointing
           data
    • Authors: Michael A. Steindorfer; Georg Kirchner; Franz Koidl; Peiyuan Wang; Alfredo Antón; Jaime Fernández Sánchez; Klaus Merz
      Pages: 1201 - 1209
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Michael A. Steindorfer, Georg Kirchner, Franz Koidl, Peiyuan Wang, Alfredo Antón, Jaime Fernández Sánchez, Klaus Merz
      We successfully demonstrate Stare & Chase: Space debris laser ranging to uncooperative targets has been achieved without a priori knowledge of any orbital information. An analog astronomy CCD with a standard objective, piggyback mounted on our 50cm Graz SLR receive telescope, ‘stares’ into the sky in a fixed direction. The CCD records the stellar background within a field of view of approx. 7°. From the stellar X/Y positions on the sensor a plate solving algorithm determines the pointing data of the image center with an accuracy of approx. 15 arc seconds. If a sunlit target passes through this field of view, its equatorial coordinates are calculated, stored and a Consolidated Prediction Format (CPF) file is created in near real time. The derived CPF data is used to start laser ranging (‘chase’ the object) within the same pass to retrieve highly accurate distance information. A comparison of Stare & Chase CPFs with standard TLE predictions shows the possibilities and limits of this method.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.026
       
  • Nonlinear excitations for the positron acoustic waves in auroral
           acceleration regions
    • Authors: Asit Saha; Rustam Ali; Prasanta Chatterjee
      Pages: 1220 - 1236
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Asit Saha, Rustam Ali, Prasanta Chatterjee
      Positron acoustic waves (PAWs) in an unmagnetized electron-positron-ion (e-p-i) plasma consisting of mobile cold positrons, immobile positive ions, q-nonextensive distributed electrons and hot positrons are studied. The standard reductive perturbation technique (RPT) is applied to derive the Kurteweg-de Vries (KdV) and modified Kurteweg-de Vries (mKdV) equations for PAWs. Variations of the total energy of the conservative systems corresponding to the KdV and mKdV equations are presented. Using numerical simulations, effect of the nonextensive parameter (q), temperature ratio ( σ ) of electrons to hot positrons and speed (U) of the traveling wave are discussed on the positron acoustic solitary wave solutions of the KdV and mKdV equations. Considering an external periodic perturbation, the perturbed dynamical systems corresponding to the KdV and mKdV equations are analyzed by employing phase orbit analysis, Poincare section and Lyapunov exponent. The frequency ( ω ) of the external periodic perturbation plays the role of the switching parameter in chaotic motions of the perturbed PAWs through quasiperiodic route to chaos. This work may be useful to understand the qualitative changes in the dynamics of nonlinear perturbations in auroral acceleration regions.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.012
       
  • Numerical simulation for the Gross-Pitaevskii equation based on the
           lattice Boltzmann method
    • Authors: Huimin Wang
      Pages: 1261 - 1270
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Huimin Wang
      A lattice Boltzmann model for the Gross-Pitaevskii equation is proposed in this paper. Some numerical tests for one- and two-dimensional Gross-Pitaevskii equation have been conducted. The waves of the Gross-Pitaevskii equation are simulated. Numerical results show that the lattice Boltzmann method is an effective method for the wave of the Gross-Pitaevskii equation.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.034
       
  • A random forest algorithm for nowcasting of intense precipitation events
    • Authors: Saurabh Das; Rohit Chakraborty; Animesh Maitra
      Pages: 1271 - 1282
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Saurabh Das, Rohit Chakraborty, Animesh Maitra
      Automatic nowcasting of convective initiation and thunderstorms has potential applications in several sectors including aviation planning and disaster management. In this paper, random forest based machine learning algorithm is tested for nowcasting of convective rain with a ground based radiometer. Brightness temperatures measured at 14 frequencies (7 frequencies in 22–31GHz band and 7 frequencies in 51–58GHz bands) are utilized as the inputs of the model. The lower frequency band is associated to the water vapor absorption whereas the upper frequency band relates to the oxygen absorption and hence, provide information on the temperature and humidity of the atmosphere. Synthetic minority over-sampling technique is used to balance the data set and 10-fold cross validation is used to assess the performance of the model. Results indicate that random forest algorithm with fixed alarm generation time of 30min and 60min performs quite well (probability of detection of all types of weather condition ∼90%) with low false alarms. It is, however, also observed that reducing the alarm generation time improves the threat score significantly and also decreases false alarms. The proposed model is found to be very sensitive to the boundary layer instability as indicated by the variable importance measure. The study shows the suitability of a random forest algorithm for nowcasting application utilizing a large number of input parameters from diverse sources and can be utilized in other forecasting problems.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.03.026
       
  • Evaluation on the impact of IMU grades on BDS+GPS PPP/INS tightly coupled
           integration
    • Authors: Zhouzheng Gao; Maorong Ge; Wenbin Shen; You Li; Qijin Chen; Hongping Zhang; Xiaoji Niu
      Pages: 1283 - 1299
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Zhouzheng Gao, Maorong Ge, Wenbin Shen, You Li, Qijin Chen, Hongping Zhang, Xiaoji Niu
      The unexpected observing environments in dynamic applications may lead to partial and/or complete satellite signal outages frequently, which can definitely impact on the positioning performance of the Precise Point Positioning (PPP) in terms of decreasing available satellite numbers, breaking the continuity of observations, and degrading PPP’s positioning accuracy. Generally, both the Inertial Navigation System (INS) and the multi-constellation Global Navigation Satellite System (GNSS) can be used to enhance the performance of PPP. This paper introduces the mathematical models of the multi-GNSS PPP/INS Tightly Coupled Integration (TCI), and investigates its performance from several aspects. Specifically, it covers (1) the use of the BDS/GPS PPP, PPP/INS, and their combination; (2) three positioning modes including PPP, PPP/INS TCI, and PPP/INS Loosely Coupled Integration (LCI); (3) the use of four various INS systems named navigation grade, tactical grade, auto grade, and Micro-Electro-Mechanical-Sensors (MEMS) one; (4) three PPP observation scenarios including PPP available, partially available, and fully outage. According to the statistics results, (1) the positioning performance of the PPP/INS (either TCI or LCI) mode is insignificantly depended on the grade of inertial sensor, when there are enough available satellites; (2) after the complete GNSS outages, the TCI mode expresses both higher convergence speed and more accurate positioning solutions than the LCI mode. Furthermore, in the TCI mode, using a higher grade inertial sensor is beneficial for the PPP convergence; (3) under the partial GNSS outage situations, the PPP/INS TCI mode position divergence speed is also restrained significantly; and (4) the attitude determination accuracy of the PPP/INS integration is highly correlated with the grade of inertial sensor.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.022
       
  • Development of a Cerium bromide gamma ray spectrometer for space
           applications
    • Authors: D.K. Panda; D. Banerjee; S.K. Goyal; A.R. Patel; A.D. Shukla
      Pages: 1307 - 1314
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): D.K. Panda, D. Banerjee, S.K. Goyal, A.R. Patel, A.D. Shukla
      We present the development of a CeBr3 gamma ray spectrometer with the primary objective of determining the abundance and distribution of Th, U, K, Fe, Al and Si by measuring gamma ray signals produced by radioactive decay, neutron inelastic scattering and neutron capture reactions in the energy region 0.03–8MeV. The energy resolution of the CeBr3 gamma ray spectrometer developed in-house has been measured at 662 and 1274keV to be 4.0% and 2.8% respectively. The intrinsic activity count-rate for the 1″×1″ CeBr3 gamma ray spectrometer is ∼0.03countss−1 for the 40K energy window (1400–1520keV), and ∼0.001countss−1 for the 232Th (2550–2700keV) energy window. The U concentration of a sample (3A) from a granite rock was estimated to be ∼2.1ppm and agrees with the 2.04ppm value determined using a HPGe gamma ray spectrometer. The K concentration of sample 3A was estimated to be 3.8%, and is consistent with the 3.7% value determined independently using a HPGe gamma ray spectrometer.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.016
       
  • Chang’e 3 lunar mission and upper limit on stochastic background of
           gravitational wave around the 0.01Hz band
    • Authors: Wenlin Tang; Peng Xu; Songjie Hu; Jianfeng Cao; Peng Dong; Yanlong Bu; Lue Chen; Songtao Han; Xuefei Gong; Wenxiao Li; Jinsong Ping; Yun-Kau Lau; Geshi Tang
      Pages: 1315 - 1326
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Wenlin Tang, Peng Xu, Songjie Hu, Jianfeng Cao, Peng Dong, Yanlong Bu, Lue Chen, Songtao Han, Xuefei Gong, Wenxiao Li, Jinsong Ping, Yun-Kau Lau, Geshi Tang
      The Doppler tracking data of the Chang’e 3 lunar mission is used to constrain the stochastic background of gravitational wave in cosmology within the 1mHz to 0.05Hz frequency band. Our result improves on the upper bound on the energy density of the stochastic background of gravitational wave in the 0.02–0.05Hz band obtained by the Apollo missions, with the improvement reaching almost one order of magnitude at around 0.05Hz. Detailed noise analysis of the Doppler tracking data is also presented, with the prospect that these noise sources will be mitigated in future Chinese deep space missions. A feasibility study is also undertaken to understand the scientific capability of the Chang’e 4 mission, due to be launched in 2018, in relation to the stochastic gravitational wave background around 0.01Hz. The study indicates that the upper bound on the energy density may be further improved by another order of magnitude from the Chang’e 3 mission, which will fill the gap in the frequency band from 0.02Hz to 0.1Hz in the foreseeable future.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.008
       
  • Recognition and tracking of convective flow patterns using Wollaston
           shearing interferometry
    • Authors: F. Zaussinger; A. Krebs; V. Travnikov; Ch. Egbers
      Pages: 1327 - 1344
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): F. Zaussinger, A. Krebs, V. Travnikov, Ch. Egbers
      The GeoFlow experiment on the ISS is designed to study convective flows in a spherical gap under microgravity conditions. The main challenge, however, is the visualization of the fluid flow especially under the safety requirements of the Columbus module. The Wollaston shearing interferometry unit of the Fluid Science Laboratory works by optical means alone and is therefore utilized as measurement device for temperature fluctuations. The resulting interferograms in terms of fringe patterns are the base for the presented advanced post-processing techniques. They are used to identify convective patterns, to track these structures and to reconstruct the inaccessible three-dimensional temperature field. A comparison between experimentally gained results and numerically calculated interferograms is given, too. We show that convective patterns are automatically recognized and tracked accurately in experimental images by means of the generalized structure tensor. Furthermore, generic numerical simulations are used to deduce the internal temperature distribution by comparison with interferograms from the experiment.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.028
       
  • A stowing and deployment strategy for large membrane space systems on the
           example of Gossamer-1
    • Authors: Patric Seefeldt
      Pages: 1345 - 1362
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Patric Seefeldt
      Deployment systems for innovative space applications such as solar sails require a technique for a controlled and autonomous deployment in space. The deployment process has a strong impact on the mechanism and structural design and sizing. On the example of the design implemented in the Gossamer-1 project of the German Aerospace Center (DLR), such a stowing and deployment process is analyzed. It is based on a combination of zig-zag folding and coiling of triangular sail segments spanned between crossed booms. The deployment geometry and forces introduced by the mechanism considered are explored in order to reveal how the loads are transferred through the membranes to structural components such as the booms. The folding geometry and force progressions are described by function compositions of an inverse trigonometric function with the considered trigonometric function itself. If these functions are evaluated over several periods of the trigonometric function, a non-smooth oscillating curve occurs. Depending on the trigonometric function, these are often vividly described as zig-zag or sawtooth functions. The developed functions are applied to the Gossamer-1 design. The deployment geometry reveals a tendency that the loads are transferred along the catheti of the sail segments and therefore mainly along the boom axes. The load introduced by the spool deployment mechanism is described. By combining the deployment geometry with that load, a prediction of the deployment load progression is achieved. The mathematical description of the stowing and deployment geometry, as well as the forces inflicted by the mechanism provides an understanding of how exactly the membrane deploys and through which edges the deployment forces are transferred. The mathematical analysis also gives an impression of sensitive parameters that could be influenced by manufacturing tolerances or unsymmetrical deployment of the sail segments. While the mathematical model was applied on the design of the Gossamer-1 hardware, it allows an analysis of other geometries. This is of particular interest as Gossamer-1 investigated deployment technology on a relatively small scale of 5 m × 5 m , while the currently considered solar sail missions require sails that are about one order of magnitude bigger.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.006
       
  • Wavelet-based multifractal analysis on a time series of solar activity and
           PDO climate index
    • Authors: Fumio Maruyama; Kenji Kai; Hiroshi Morimoto
      Pages: 1363 - 1372
      Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6
      Author(s): Fumio Maruyama, Kenji Kai, Hiroshi Morimoto
      There is increasing interest in finding the relation between solar activity and climate change. In general, fractal properties may be observed in the time series of the dynamics of complex systems, such as solar activity and climate. This study investigates the relations among solar activity, geomagnetic activity, and climatic regime shift by performing a multifractal analysis. To investigate the change in multifractality, we apply a wavelet transform to time series. The change in fractality of the sunspot number (SSN) correlates closely with that of the solar polar field strength. For the SSN and solar polar field strength, a weak multifractality or monofractality is present at the maximum SSN, minimum SSN, and maximum solar polar field strength. A strong multifractality is present two years before the maximum SSN. The climatic regime shift occurs when the SSN increases and the disturbance of the geomagnetic activity is large. At the climatic regime shift, the changes in the fractality of the Pacific Decadal Oscillation (PDO) index and changes in that of the solar activity indices corresponded with each other. From the fractals point of view, we clarify the relations among solar activity, geomagnetic activity, and climatic regime shift. The formation of the magnetic field of the sunspots is correlated with the solar polar field strength. The solar activity seems to influence the climatic regime shift. These findings will contribute to investigating the relation between solar activity and climate change.

      PubDate: 2017-08-27T19:37:55Z
      DOI: 10.1016/j.asr.2017.06.004
       
  • Performance analysis of PPP ambiguity resolution with UPD products
           estimated from different scales of reference station networks
    • Authors: Siyao Wang; Bofeng Li; Xingxing Li; Nan Zang
      Abstract: Publication date: Available online 14 September 2017
      Source:Advances in Space Research
      Author(s): Siyao Wang, Bofeng Li, Xingxing Li, Nan Zang
      Integer ambiguity fixing with uncalibrated phase delay (UPD) products can significantly shorten the initialization time and improve the accuracy of precise point positioning (PPP). Since the tracking arcs of satellites and the behavior of atmospheric biases can be very different for the reference networks with different scales, the qualities of corresponding UPD products may be also various. The purpose of this paper is to comparatively investigate the influence of different scales of reference station networks on UPD estimation and user ambiguity resolution. Three reference station networks with global, wide-area and local scales are used to compute the UPD products and analyze their impact on the PPP-AR. The time-to-first-fix, the unfix rate and the incorrect fix rate of PPP-AR are analyzed. Moreover, in order to further shorten the convergence time for obtaining precise positioning, a modified partial ambiguity resolution (PAR) and corresponding validation strategy are presented. In this PAR method, the ambiguity subset is determined by removing the ambiguity one by one in the order of ascending elevations. Besides, for static positioning mode, a coordinate validation strategy is employed to enhance the reliability of the fixed coordinate. The experiment results show that UPD products computed by smaller station network are more accurate and lead to a better coordinate solution; the PAR method used in this paper can shorten the convergence time and the coordinate validation strategy can improve the availability of high precision positioning.

      PubDate: 2017-09-17T15:05:38Z
      DOI: 10.1016/j.asr.2017.09.005
       
  • GNSS Global Real-time Augmentation Positioning: Real-time Precise
           Satellite Clock Estimation, Prototype System Construction and Performance
           Analysis
    • Authors: Liang CHEN; Qile ZHAO; Zhigang HU; Xinyuan JIANG; Changjiang GENG; Maorong GE; Chuang SHI
      Abstract: Publication date: Available online 9 September 2017
      Source:Advances in Space Research
      Author(s): Liang CHEN, Qile ZHAO, Zhigang HU, Xinyuan JIANG, Changjiang GENG, Maorong GE, Chuang SHI
      Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn’t appropriate for the high-frequency real-time GNSS clock estimation, like 1Hz. Mixed differenced model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS+BeiDou+Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning(RT-PPP) and real-time Standard Point Positioning(RT-SPP). The statistical analysis of the 6h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1cm to 5cm for GPS, Beidou MEO and Galileo satellites and about 10cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1 Hz). The real-time augmentation message signal-in-space ranging error(SISRE), a comprehensive accuracy of orbit and clock and effecting the users’ actual positioning performance, is introduced to evaluate and analyze the performance of GPS+BeiDou+Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4cm to 7cm for GPS, whlile 10cm for Beidou IGSO/MEO, Galileo and about 30cm for BeiDou GEO satellites. The real-time positioning results prove that the GPS+BeiDou+Galileo RT-PPP comparing to GPS-only can effectively accelerate convergence time by about 60%, improve the positioning accuracy by about 30% and obtain averaged RMS 4cm in horizontal and 6cm in vertical; additionally RT-SPP accuracy in the prototype system can realize positioning accuracy with about averaged RMS 1m in horizontal and 1.5m to 2m in vertical, which are improved by 60% and 70% to SPP based on broadcast ephemeris, respectively.

      PubDate: 2017-09-11T17:17:07Z
      DOI: 10.1016/j.asr.2017.08.037
       
  • Impact analysis of the transponder time delay on radio-tracking
           observables
    • Authors: Stefano Bertone; Christophe Le Poncin-Lafitte; Pascal Rosenblatt; Valéry Lainey; Jean-Charles Marty; Marie-Christine Angonin
      Abstract: Publication date: Available online 9 September 2017
      Source:Advances in Space Research
      Author(s): Stefano Bertone, Christophe Le Poncin-Lafitte, Pascal Rosenblatt, Valéry Lainey, Jean-Charles Marty, Marie-Christine Angonin
      Accurate tracking of probes is one of the key points of space exploration. Range and Doppler techniques are the most commonly used. In this paper we analyze the impact of the transponder delay, i . e . the processing time between reception and re-emission of a two-way tracking link at the satellite, on tracking observables and on spacecraft orbits. We show that this term, only partially accounted for in the standard formulation of computed space observables, can actually be relevant for future missions with high nominal tracking accuracies or for the re-processing of old missions. We present several applications of our formulation to Earth flybys, the NASA GRAIL and the ESA BepiColombo missions.

      PubDate: 2017-09-11T17:17:07Z
      DOI: 10.1016/j.asr.2017.09.003
       
  • Interferometry Imaging Technique for Accurate Deep-space Probe Positioning
    • Authors: Zheng Weimin; Tong Fengxian; Zhang Juan; Liu Lei; Shu Fengchun
      Abstract: Publication date: Available online 9 September 2017
      Source:Advances in Space Research
      Author(s): Zheng Weimin, Tong Fengxian, Zhang Juan, Liu Lei, Shu Fengchun
      Very long baseline interferometry (VLBI) is a radio astronomy tool with very high spatial resolution. It uses two or more radio telescopes to track the faraway object and gets its visibility. The intensity distribution image of radio source can be obtained by the inverse Fourier transformation of the visibilities sampled on UV plane perpendicular to the line of sight. Chinese VLBI Network (CVN) consists of 5 radio telescopes, and its highest spatial resolution is equivalent to that of a ∼3000km diameters single dish antenna. This paper introduces the interferometry imaging principle, the imaging results of ChangE lunar and Mars Express probes. The measured ChangE-3 (CE-3) Rover relative position accuracy is about 1 meter by this method. The 1 meter accuracy is verified by comparisons with Rover null position and the onboard stereo vision measurement results. The successful imaging of spacecraft indicates that the interferometry imaging technology can be used for accurate spacecraft positioning in the future.

      PubDate: 2017-09-11T17:17:07Z
      DOI: 10.1016/j.asr.2017.09.004
       
  • Analysis and retrieval of tropospheric corrections for CryoSat-2 over
           inland waters
    • Authors: Telmo Vieira; M. Joana Fernandes; Clara Lázaro
      Abstract: Publication date: Available online 9 September 2017
      Source:Advances in Space Research
      Author(s): Telmo Vieira, M. Joana Fernandes, Clara Lázaro
      The application of satellite altimetry over inland waters requires a proper modelling of the various error sources involved in the determination of precise surface water heights above a reference ellipsoid or above the geoid. The objectives of this study are firstly the analysis of the errors present on the dry tropospheric correction (DTC) and on the wet tropospheric correction (WTC) provided in the CryoSat-2 (CS-2) products and secondly the development of methodologies to derive improved corrections, aiming at getting improved products for CS-2. This study is conducted on selected regions of interest, such as the Amazon and Danube rivers, Titicaca and Vanern lakes and the Caspian Sea. Since CS-2 has a geodetic orbit, its ground tracks allow the retrieval of precise surface water heights over regions not covered by any other satellite. The DTC and WTC present in the CS-2 products have been compared against corrections computed from the European Centre for Medium-Range Weather Forecasts (ECMWF) operational model at various levels: i) the level of ECMWF model orography; ii) the level of the Altimetry Corrected Elevations 2 (ACE2) digital elevation model and iii) the level of mean lake/sea or river profile. An independent assessment of the corrections has also been performed by comparison with DTC derived from in situ surface pressure measurements and WTC retrieved from Global Navigation Satellite Systems (GNSS) data. Results show that the model-derived corrections present on CS-2 products seem to be referred to the model orography, except for the Caspian Sea where corrections seem to be referred to mean sea level (zero level). Model orography can depart from the mean river profile or mean lake/sea heights by hundreds of meters. Overall, ACE2 DEM is a better altimetric surface than ECMWF orography, however height errors up to hundreds of meters exist in ACE2. Height errors induce DTC errors that can reach several centimetres (11 cm in the Danube River) and WTC errors up to 2-3 cm. These errors are systematic, having always the same sign and magnitude for a given location, thus affecting the retrieval of the absolute water level. For rivers, the mean profile is the best representation of the surface height in the river basin and is also the best reference surface for use in the DTC and WTC estimations from an atmospheric model. The same happens with lakes or closed seas, where the corrections should be referred to the mean lake/sea level. Results show that, once computed at the correct mean river profile or mean lake/sea level, the DTC has a small variation, with a standard deviation going from 0.5 cm in the Amazon River to 3.0 cm in the Danube River. The DTC absolute values go from 1.48 m in Lake Titicaca to 2.32 m in the Caspian Sea. With a larger variability, once computed at mean river profile or mean lake/sea level, the standard deviation of the WTC goes from 2.7 cm in Lake Titicaca to 5-6 cm in all other regions and absolute values from only 6 cm in Lake Titicaca to 31 cm in the Amazon River. Once computed at the correct surface elevation the corresponding errors are expected to be less than 1 cm for the DTC and less than 2 cm for the WTC.

      PubDate: 2017-09-11T17:17:07Z
      DOI: 10.1016/j.asr.2017.09.002
       
  • Satellite thermal IR and atmospheric radon anomalies associated with
           Haripur earthquake (Oct 2010; Mw 5.2), Pakistan
    • Authors: Muhammad Awais; Adnan Barkat; Aamir Ali; Khaista Rehman; Waqar Ali Zafar; Talat Iqbal
      Abstract: Publication date: Available online 8 September 2017
      Source:Advances in Space Research
      Author(s): Muhammad Awais, Adnan Barkat, Aamir Ali, Khaista Rehman, Waqar Ali Zafar, Talat Iqbal
      The recent scientific progress within the context of earthquake forecasting reveals some key physical processes related with seismic activity. The Lithospheric-Atmospheric-Ionospheric Coupling model provides a comprehensive mechanism to understand the underlying key physical processes. In this study, a precursory analysis is conducted for a shallow, moderate magnitude Haripur earthquake (Oct 2010; Mw 5.2) bounded by two major water reservoirs highlighting its significance. This precursory analysis is performed with the help of Land Surface Temperature (LST) extracted from satellite (MODIS) TIR data and atmospheric radon concentration recorded at Islamabad and Murree stations using radon monitor. A significant change in LST (4-8) °C is observed in the epicentral region six days prior to this event. In addition to that, a comparison is performed between daily and five year averaged LST that further support our results. The radon concentration also shows anomalous behavior 3-4 days prior to this particular event with crucial meteorological indicators in the safe limit. This abnormal behavior of both precursors prior to this event propose a possible correlation with the local seismic activity. Moreover, the higher amplitude of radon anomaly at nearest station (Islamabad) is also validating its local cause. The results presented in this study are very encouraging and stimulate the idea of earthquake forecasting using multi-precursory approach.

      PubDate: 2017-09-11T17:17:07Z
      DOI: 10.1016/j.asr.2017.08.034
       
  • List of Referees
    • Abstract: Publication date: 1 October 2017
      Source:Advances in Space Research, Volume 60, Issue 7


      PubDate: 2017-08-27T19:37:55Z
       
  • List of Referees
    • Abstract: Publication date: 15 September 2017
      Source:Advances in Space Research, Volume 60, Issue 6


      PubDate: 2017-08-27T19:37:55Z
       
 
 
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