Journal Cover Advances in Space Research
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  • Geoeffectiveness of interplanetary shocks controlled by impact angles: A
           review
    • Authors: D.M. Oliveira; A.A. Samsonov
      Pages: 1 - 44
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): D.M. Oliveira, A.A. Samsonov
      The high variability of the Sun’s magnetic field is responsible for the generation of perturbations that propagate throughout the heliosphere. Such disturbances often drive interplanetary shocks in front of their leading regions. Strong shocks transfer momentum and energy into the solar wind ahead of them which in turn enhance the solar wind interaction with magnetic fields in its way. Shocks then eventually strike the Earth’s magnetosphere and trigger a myriad of geomagnetic effects observed not only by spacecraft in space, but also by magnetometers on the ground. Recently, it has been revealed that shocks can show different geoeffectiveness depending closely on the angle of impact. Generally, frontal shocks are more geoeffective than inclined shocks, even if the former are comparatively weaker than the latter. This review is focused on results obtained from modeling and experimental efforts in the last 15 years. Some theoretical and observational background are also provided.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.006
       
  • Improving magnetosphere in situ observations using solar sails
    • Authors: Khashayar Parsay; Hanspeter Schaub; Conrad Schiff; Trevor Williams
      Pages: 74 - 88
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Khashayar Parsay, Hanspeter Schaub, Conrad Schiff, Trevor Williams
      Past and current magnetosphere missions employ conventional spacecraft formations for in situ observations of the geomagnetic tail. Conventional spacecraft flying in inertially fixed Keplerian orbits are only aligned with the geomagnetic tail once per year, since the geomagnetic tail is always aligned with the Earth-Sun line, and therefore, rotates annually. Solar sails are able to artificially create sun-synchronous orbits such that the orbit apse line remains aligned with the geomagnetic tail line throughout the entire year. This continuous presence in the geomagnetic tail can significantly increase the science phase for magnetosphere missions. In this paper, the problem of solar sail formation design is explored using nonlinear programming to design optimal two-craft, triangle, and tetrahedron solar sail formations, in terms of formation quality and formation stability. The designed formations are directly compared to the formations used in NASA’s Magnetospheric Multi-Scale mission.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.07.045
       
  • 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
      Pages: 89 - 96
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      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: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.003
       
  • Two-segment lunar free-return trajectories design using the pseudostate
           theory
    • Authors: Changchun Bao; Jingyang Li; Hexi Baoyin
      Pages: 97 - 110
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Changchun Bao, Jingyang Li, Hexi Baoyin
      Accurate initial solutions for two-segment Earth-Moon free-return trajectories, with midcourse transfer opportunities for favorable lunar targeting, are developed analytically by using the pseudostate theory. A constrained flight-path angle quasi-Lambert problem is formulated to determine the lunar-orbiting phase of the free-return trajectory. Gradient and direct-shooting algorithms are used to correct the initial estimates of certain two-body parameters. Numerical simulations with a high-fidelity model are undertaken to verify the accuracy of the pseudostate solutions and to illustrate the efficiency of the proposed algorithm. Perilune altitude errors for the pseudostate method are less than 10% of their corresponding values for the patched conic technique. The differences between the pseudostate and the high-fidelity solutions can be eliminated rapidly.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.026
       
  • Relative equilibria in quasi-homogeneous planar three body problems
    • Authors: John A. Arredondo
      Pages: 111 - 121
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): John A. Arredondo
      In this paper we find the families of relative equilibria for the three body problem in the plane, when the interaction between the bodies is given by a quasi-homogeneous potential. The number of the relative equilibria depends on the values of the masses and on the size of the system, measured by the moment of inertia.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.035
       
  • The YORP effect on the GOES 8 and GOES 10 satellites: A case study
    • Authors: Antonella A. Albuja; Daniel J. Scheeres; Rita L. Cognion; William Ryan; Eileen V. Ryan
      Pages: 122 - 144
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Antonella A. Albuja, Daniel J. Scheeres, Rita L. Cognion, William Ryan, Eileen V. Ryan
      The Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect is a proposed explanation for the observed rotation behavior of inactive satellites in Earth orbit. This paper further explores the YORP effect for highly asymmetric inactive satellites. Satellite models are developed to represent the GOES 8 and GOES 10 satellites, both of which are currently inactive in geosynchronous Earth orbit (GEO). A simple satellite model for the GOES 8 satellite is used to analyze the short period variations of the angular velocity and obliquity as a result of the YORP effect. A more complex model for the rotational dynamics of the GOES 8 and GOES 10 satellites are developed to probe their sensitivity and to match observed spin periods and states of these satellites. The simulated rotation periods are compared to observations for both satellites. The comparison between YORP theory and observed rotation rates for both satellites show that the YORP effect could be the cause for the observed rotational behavior. The YORP model also predicts a novel state for the GOES 8 satellite, namely that it could periodically fall into a tumbling rotation state. Recent observations of this satellite are consistent with this prediction.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.002
       
  • Time synchronization of new-generation BDS satellites using
           inter-satellite link measurements
    • Authors: Junyang Pan; Xiaogong Hu; Shanshi Zhou; Chengpan Tang; Rui Guo; Lingfeng Zhu; Guifeng Tang; Guangming Hu
      Pages: 145 - 153
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Junyang Pan, Xiaogong Hu, Shanshi Zhou, Chengpan Tang, Rui Guo, Lingfeng Zhu, Guifeng Tang, Guangming Hu
      Autonomous satellite navigation is based on the ability of a Global Navigation Satellite System (GNSS), such as Beidou, to estimate orbits and clock parameters onboard satellites using Inter-Satellite Link (ISL) measurements instead of tracking data from a ground monitoring network. This paper focuses on the time synchronization of new-generation Beidou Navigation Satellite System (BDS) satellites equipped with an ISL payload. Two modes of Ka-band ISL measurements, Time Division Multiple Access (TDMA) mode and the continuous link mode, were used onboard these BDS satellites. Using a mathematical formulation for each measurement mode along with a derivation of the satellite clock offsets, geometric ranges from the dual one-way measurements were introduced. Then, pseudoranges and clock offsets were evaluated for the new-generation BDS satellites. The evaluation shows that the ranging accuracies of TDMA ISL and the continuous link are approximately 4 cm and 1 cm (root mean square, RMS), respectively. Both lead to ISL clock offset residuals of less than 0.3 ns (RMS). For further validation, time synchronization between these satellites to a ground control station keeping the systematic time in BDT was conducted using L-band Two-way Satellite Time Frequency Transfer (TWSTFT). System errors in the ISL measurements were calibrated by comparing the derived clock offsets with the TWSTFT. The standard deviations of the estimated ISL system errors are less than 0.3 ns, and the calibrated ISL clock parameters are consistent with that of the L-band TWSTFT. For the regional BDS network, the addition of ISL measurements for medium orbit (MEO) BDS satellites increased the clock tracking coverage by more than 40% for each orbital revolution. As a result, the clock predicting error for the satellite M1S was improved from 3.59 to 0.86 ns (RMS), and the predicting error of the satellite M2S was improved from 1.94 to 0.57 ns (RMS), which is a significant improvement by a factor of 3–4.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.004
       
  • Dynamics and control for contactless interaction between spacecraft and
           tumbling debris
    • Authors: Haiyang Li; Jingyang Li; Fanghua Jiang
      Pages: 154 - 166
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Haiyang Li, Jingyang Li, Fanghua Jiang
      Tumbling debris has become a great threat to orbit activities. Contactless interaction is a novel concept for active debris removal, through which the tumbling debris no longer rotates freely but is under control. The contactless interaction method aims to de-tumble the debris and then maintain desired relative states between the spacecraft and debris. The spacecraft is simultaneously stabilized through three-axis attitude control, which makes the de-tumbling and capture operation much safer, more effective and accurate. The dynamics and control for the contactless interaction have been little studied in the past years. This paper considers a generic dynamics and control problem for contactless interaction between a spacecraft and debris. A translational and rotational dynamics model of contactless interaction is proposed and the 6-DOF equations are established. The contactless interaction control law is designed with the backstepping method, and the spacecraft three-axis control law is designed with the PD control. Simulation results show that the angular momentum is transferred from the debris to the spacecraft and the debris is thus de-tumbled. The desired relative states are achieved efficiently. Significantly, the spacecraft and debris no longer rotate in the inertial frame and, hence, the safety and accuracy for capture operation are guaranteed.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.008
       
  • Uncertainty propagation for statistical impact prediction of space debris
    • Authors: R. Hoogendoorn; E. Mooij; J. Geul
      Pages: 167 - 181
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): R. Hoogendoorn, E. Mooij, J. Geul
      Predictions of the impact time and location of space debris in a decaying trajectory are highly influenced by uncertainties. The traditional Monte Carlo (MC) method can be used to perform accurate statistical impact predictions, but requires a large computational effort. A method is investigated that directly propagates a Probability Density Function (PDF) in time, which has the potential to obtain more accurate results with less computational effort. The decaying trajectory of Delta-K rocket stages was used to test the methods using a six degrees-of-freedom state model. The PDF of the state of the body was propagated in time to obtain impact-time distributions. This Direct PDF Propagation (DPP) method results in a multi-dimensional scattered dataset of the PDF of the state, which is highly challenging to process. No accurate results could be obtained, because of the structure of the DPP data and the high dimensionality. Therefore, the DPP method is less suitable for practical uncontrolled entry problems and the traditional MC method remains superior. Additionally, the MC method was used with two improved uncertainty models to obtain impact-time distributions, which were validated using observations of true impacts. For one of the two uncertainty models, statistically more valid impact-time distributions were obtained than in previous research.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.009
       
  • A holistic approach to SIM platform and its application to early-warning
           satellite system
    • Authors: Fuyu Sun; Jianping Zhou; Zheyao Xu
      Pages: 189 - 206
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Fuyu Sun, Jianping Zhou, Zheyao Xu
      This study proposes a new simulation platform named Simulation Integrated Management (SIM) for the analysis of parallel and distributed systems. The platform eases the process of designing and testing both applications and architectures. The main characteristics of SIM are flexibility, scalability, and expandability. To improve the efficiency of project development, new models of early-warning satellite system were designed based on the SIM platform. Finally, through a series of experiments, the correctness of SIM platform and the aforementioned early-warning satellite models was validated, and the systematical analyses for the orbital determination precision of the ballistic missile during its entire flight process were presented, as well as the deviation of the launch/landing point. Furthermore, the causes of deviation and prevention methods will be fully explained. The simulation platform and the models will lay the foundations for further validations of autonomy technology in space attack-defense architecture research.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.019
       
  • Motion prediction of a non-cooperative space target
    • Authors: Bang-Zhao Zhou; Guo-Ping Cai; Yun-Meng Liu; Pan Liu
      Pages: 207 - 222
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Bang-Zhao Zhou, Guo-Ping Cai, Yun-Meng Liu, Pan Liu
      Capturing a non-cooperative space target is a tremendously challenging research topic. Effective acquisition of motion information of the space target is the premise to realize target capture. In this paper, motion prediction of a free-floating non-cooperative target in space is studied and a motion prediction algorithm is proposed. In order to predict the motion of the free-floating non-cooperative target, dynamic parameters of the target must be firstly identified (estimated), such as inertia, angular momentum and kinetic energy and so on; then the predicted motion of the target can be acquired by substituting these identified parameters into the Euler’s equations of the target. Accurate prediction needs precise identification. This paper presents an effective method to identify these dynamic parameters of a free-floating non-cooperative target. This method is based on two steps, (1) the rough estimation of the parameters is computed using the motion observation data to the target, and (2) the best estimation of the parameters is found by an optimization method. In the optimization problem, the objective function is based on the difference between the observed and the predicted motion, and the interior-point method (IPM) is chosen as the optimization algorithm, which starts at the rough estimate obtained in the first step and finds a global minimum to the objective function with the guidance of objective function’s gradient. So the speed of IPM searching for the global minimum is fast, and an accurate identification can be obtained in time. The numerical results show that the proposed motion prediction algorithm is able to predict the motion of the target.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.028
       
  • An optimization tool for satellite equipment layout
    • Authors: Zheng Qin; Yan-gang Liang; Jian-ping Zhou
      Pages: 223 - 234
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Zheng Qin, Yan-gang Liang, Jian-ping Zhou
      Selection of the satellite equipment layout with performance constraints is a complex task which can be viewed as a constrained multi-objective optimization and a multiple criteria decision making problem. The layout design of a satellite cabin involves the process of locating the required equipment in a limited space, thereby satisfying various behavioral constraints of the interior and exterior environments. The layout optimization of satellite cabin in this paper includes the C.G. offset, the moments of inertia and the space debris impact risk of the system, of which the impact risk index is developed to quantify the risk to a satellite cabin of coming into contact with space debris. In this paper an optimization tool for the integration of CAD software as well as the optimization algorithms is presented, which is developed to automatically find solutions for a three-dimensional layout of equipment in satellite. The effectiveness of the tool is also demonstrated by applying to the layout optimization of a satellite platform.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.030
       
  • Examining the use of the NeQuick bottomside and topside parameterizations
           at high latitudes
    • Authors: David R. Themens; P.T. Jayachandran; Roger H. Varney
      Pages: 287 - 294
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): David R. Themens, P.T. Jayachandran, Roger H. Varney
      An examination of the high latitude performance of the bottomside and topside F-layer parameterizations of the NeQuick electron density model is presented using measurements from high latitude ionosonde and Incoherent Scatter Radar (ISR) facilities. For the bottomside, we present a comparison between modeled and measured B2Bot thickness parameter. In this comparison, it is seen that the use of the NeQuick parameterization at high latitudes results in significantly underestimated bottomside thicknesses, regularly exceeding 50%. We show that these errors can be attributed to two main issues in the NeQuick parameterization:(1) through the relationship relating foF2 and M3000F2 to the maximum derivative of F2 electron density, which is used to derive the bottomside thickness, and (2) through a fundamental inability of a constant thickness parameter, semi-Epstein shape function to fit the curvature of the high latitude F-region electron density profile. For the topside, a comparison is undertaken between the NeQuick topside thickness parameterization, using measured and CCIR-modeled ionospheric parameters, and that derived from fitting the NeQuick topside function to Incoherent Scatter Radar-measured topside electron density profiles. Through this comparison, we show that using CCIR-derived foF2 and M3000F2, used in both the NeQuick and IRI, results in significantly underestimated topside thickness during summer periods, overestimated thickness during winter periods, and an overall tendency to underestimate diurnal, seasonal, and solar cycle variability. These issues see no improvement through the use of measured foF2 and M(3000)F2 values. Such measured parameters result in a tendency for the parametrization to produce a declining trend in topside thickness with increasing solar activity, to produce damped seasonal variations, and to produce significantly overestimated topside thickness during winter periods.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.037
       
  • Ion production and ionization effect in the atmosphere during the Bastille
           day GLE 59 due to high energy SEPs
    • Authors: A.L. Mishev; P.I.Y. Velinov
      Pages: 316 - 325
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): A.L. Mishev, P.I.Y. Velinov
      The influence of high energy particles, specifically cosmic rays, on atmospheric physics and chemistry is highly discussed. In most of the proposed models the role of ionization in the atmosphere due to cosmic rays is not negligible. Moreover, effect(s) on minor constituents and aerosols are recently observed, specifically over the polar regions during strong solar particle events. According to the recent findings for such effects it is necessary an essential increase of ion production, specifically during the winter period. The galactic cosmic rays are the main source of ionization in the Earth’s stratosphere and troposphere. Occasionally, the atmospheric ionization is significantly enhanced during strong solar energetic particles events, specifically over the polar caps. During the solar cycle 23 several strong ground level enhancements were observed. One of the strongest was the Bastille day event occurred on 14 July 2000. Using a full Monte Carlo 3-D model, we compute the atmospheric ionization, considering explicitly the contribution of cosmic rays with galactic and solar origin, focusing on high energy particles. The model is based on atmospheric cascade simulation with the PLANETOCOSMICS code. The ion production rate is computed as a function of the altitude above the sea level. The ion production rate is computed on a step ranging from 10 to 30 min throughout the event, considering explicitly the spectral and angular characteristics of the high energy part of solar protons as well as their time evolution. The corresponding event averaged ionization effect relative to the average due to galactic cosmic rays is computed in lower stratosphere and upper troposphere at various altitudes, namely 20 km, 15 km, 12 km and 8 km above the sea level in a sub-polar and polar regions. The 24 h and the weekly ionization effects are also computed in the troposphere and low stratosphere. Several applications are discussed.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.023
       
  • Substorm activity during the main phase of magnetic storms induced by the
           CIR and ICME events
    • Authors: R.N. Boroyev; M.S. Vasiliev
      Pages: 348 - 354
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): R.N. Boroyev, M.S. Vasiliev
      In this work, the relation of high-latitude indices of geomagnetic activity (AE, Kp) with the rate of storm development and a solar wind electric field during the main phase of magnetic storm induced by the CIR and ICME events is investigated. 72 magnetic storms induced by CIR and ICME events have been selected. It is shown that for the CIR and ICME events the increase of average value of the Kp index (Kpaver) is observed with the growth of rate of storm development. The value of Kpaver index correlates with the magnitude of minimum value of Dst index ( Dstmin ) only for the ICME events. The analysis of average values of AE and Kp indices during the main phase of magnetic storm depending on the SW electric field has shown that for the CIR events, unlike the ICME events, the value of AEaver increases with the growth of average value of the electric field (Eswaver). The value of Kpaver correlates with the Eswaver only for the ICME events. The relation between geomagnetic indices and the maximum value of SW electric field (Eswmax) is weak. However, for the ICME events Kpaver correlates with Eswmax.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.031
       
  • Identification of seismic activity sources on the subsatellite track by
           ionospheric plasma disturbances detected with the Sich-2 onboard probes
    • Authors: Valentin A. Shuvalov; Dmitry N. Lazuchenkov; Nikolai B. Gorev; Galina S. Kochubei
      Pages: 355 - 366
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Valentin A. Shuvalov, Dmitry N. Lazuchenkov, Nikolai B. Gorev, Galina S. Kochubei
      Using a cylindrical Langmuir probe and the authors’ proprietary two-channel pressure transducer, ionospheric plasma parameter distributions along the orbit of the Sich-2 satellite (Ukraine, 2011–2012) were measured. This paper is concerned with identifying the space–time location of ionospheric plasma disturbance sources, including the epicenters of actual earthquakes (before or during the satellite flyover) and incipient earthquakes on the subsatellite track, from the measured distributions of the electron density and temperature and the neutral particle temperature along the satellite orbit. To do this, the measured ionospheric plasma parameter distributions are connected to the coordinates on the subsatellite track. It is shown that local disturbances in the electron density and temperature and neutral particle temperature distributions in the satellite orbit in the ionosphere may serve as indicators of seismic activity on the subsatellite track. The epicenters of incipient earthquakes may be set off from other plasma parameter disturbance sources associated with seismic activity using information provided by special monitoring and survey centers that monitor the current seismic situation.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.08.001
       
  • 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
      Pages: 367 - 384
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      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 1–5cm 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 1Hz). 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 4–7cm 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 1.5–2m in vertical, which are improved by 60% and 70% to SPP based on broadcast ephemeris, respectively.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.08.037
       
  • 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
      Pages: 385 - 401
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      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: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.005
       
  • A new weighted mean temperature model in China
    • Authors: Jinghong Liu; Yibin Yao; Jizhang Sang
      Pages: 402 - 412
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Jinghong Liu, Yibin Yao, Jizhang Sang
      The Global Positioning System (GPS) has been applied in meteorology to monitor the change of Precipitable Water Vapor (PWV) in atmosphere, transformed from Zenith Wet Delay (ZWD). A key factor in converting the ZWD into the PWV is the weighted mean temperature ( T m ), which has a direct impact on the accuracy of the transformation. A number of Bevis-type models, like T m - T s and T m - T s , P s type models, have been developed by statistics approaches, and are not able to clearly depict the relationship between T m and the surface temperature, T s . A new model for T m , called weighted mean temperature norm model (abbreviated as norm model), is derived as a function of T s , the lapse rate of temperature, δ, the tropopause height, h trop , and the radiosonde station height, h s . It is found that T m is better related to T s through an intermediate temperature. The small effects of lapse rate can be ignored and the tropopause height be obtained from an empirical model. Then the norm model is reduced to a simplified form, which causes fewer loss of accuracy and needs two inputs, T s and h s . In site-specific fittings, the norm model performs much better, with RMS values reduced averagely by 0.45K and the Mean of Absolute Differences (MAD) values by 0.2K. The norm model is also found more appropriate than the linear models to fit T m in a large area, not only with the RMS value reduced from 4.3K to 3.80K, correlation coefficient R 2 increased from 0.84 to 0.88, and MAD decreased from 3.24K to 2.90K, but also with the distribution of simplified model values to be more reasonable. The RMS and MAD values of the differences between reference and computed PWVs are reduced by on average 16.3% and 14.27%, respectively, when using the new norm models instead of the linear model.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.023
       
  • Validation on MERSI/FY-3A precipitable water vapor product
    • Authors: Shaoqi Gong; Daniel Fiifi Hagan; Jing Lu; Guojie Wang
      Pages: 413 - 425
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Shaoqi Gong, Daniel Fiifi Hagan, Jing Lu, Guojie Wang
      The precipitable water vapor is one of the most active gases in the atmosphere which strongly affects the climate. China's second-generation polar orbit meteorological satellite FY-3A equipped with a Medium Resolution Spectral Imager (MERSI) is able to detect atmospheric water vapor. In this paper, water vapor data from AERONET, radiosonde and MODIS were used to validate the accuracy of the MERSI water vapor product in the different seasons and climatic regions of East Asia. The results show that the values of MERSI water vapor product are relatively lower than that of the other instruments and its accuracy is generally lower. The mean bias (MB) was −0.8 to −12.7 mm, the root mean square error (RMSE) was 2.2–17.0 mm, and the mean absolute percentage error (MAPE) varied from 31.8% to 44.1%. On the spatial variation, the accuracy of MERSI water vapor product in a descending order was from North China, West China, Japan -Korea, East China, to South China, while the seasonal variation of accuracy was the best for winter, followed by spring, then in autumn and the lowest in summer. It was found that the errors of MERSI water vapor product was mainly due to the low accuracy of radiation calibration of the MERSI absorption channel, along with the inaccurate look-up table of apparent reflectance and water vapor within the water vapor retrieved algorithm. In addition, the surface reflectance, the mixed pixels of image cloud, the humidity and temperature of atmospheric vertical profile and the haze were also found to have affected the accuracy of MERSI water vapor product.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.005
       
  • Ozone chemical equilibrium in the extended mesopause under the nighttime
           conditions
    • Authors: M.V. Belikovich; M.Yu. Kulikov; M. Grygalashvyly; G.R. Sonnemann; T.S. Ermakova; A.A. Nechaev; A.M. Feigin
      Pages: 426 - 432
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): M.V. Belikovich, M.Yu. Kulikov, M. Grygalashvyly, G.R. Sonnemann, T.S. Ermakova, A.A. Nechaev, A.M. Feigin
      For retrieval of atomic oxygen and atomic hydrogen via ozone observations in the extended mesopause region (∼70–100 km) under nighttime conditions, an assumption on photochemical equilibrium of ozone is often used in research. In this work, an assumption on chemical equilibrium of ozone near mesopause region during nighttime is proofed. We examine 3D chemistry-transport model (CTM) annual calculations and determine the ratio between the correct (modeled) distributions of the O3 density and its equilibrium values depending on the altitude, latitude, and season. The results show that the retrieval of atomic oxygen and atomic hydrogen distributions using an assumption on ozone chemical equilibrium may lead to large errors below ∼81–87 km. We give simple and clear semi-empirical criterion for practical utilization of the lower boundary of the area with ozone’s chemical equilibrium near mesopause.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.010
       
  • Efficient QR sequential least square algorithm for high frequency GNSS
           precise point positioning seismic application
    • Authors: Alina L. Barbu; Julien Laurent-Varin; Felix Perosanz; Flavien Mercier; Jean-Charles Marty
      Pages: 448 - 456
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Alina L. Barbu, Julien Laurent-Varin, Felix Perosanz, Flavien Mercier, Jean-Charles Marty
      The implementation into the GINS CNES geodetic software of a more efficient filter was needed to satisfy the users who wanted to compute high-rate GNSS PPP solutions. We selected the SRI approach and a QR factorization technique including an innovative algorithm which optimizes the matrix reduction step. A full description of this algorithm is given for future users. The new capacities of the software have been tested using a set of 1 Hz data from the Japanese GEONET network including the Mw 9.0 2011 Tohoku earthquake. Station coordinates solution agreed at a sub-decimeter level with previous publications as well as with solutions we computed with the National Resource Canada software. An additional benefit from the implementation of the SRI filter is the capability to estimate high-rate tropospheric parameters too. As the CPU time to estimate a 1 Hz kinematic solution from 1 h of data is now less than 1 min we could produced series of coordinates for the full 1300 stations of the Japanese network. The corresponding movie shows the impressive co-seismic deformation as well as the wave propagation along the island. The processing was straightforward using a cluster of PCs which illustrates the new potentiality of the GINS software for massive network high rate PPP processing.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.032
       
  • New educational tools to encourage high-school students' activity in stem
    • Authors: Vera Mayorova; Dmitriy Grishko; Victor Leonov
      Pages: 457 - 465
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Vera Mayorova, Dmitriy Grishko, Victor Leonov
      Many students have to choose their future profession during their last years in the high school and therefore to choose a university where they will get proper education. That choice may define their professional life for many years ahead or probably for the rest of their lives. Bauman Moscow State Technical University conducts various events to introduce future professions to high-school students. Such activity helps them to pick specialization in line with their interests and motivates them to study key scientific subjects. The paper focuses on newly developed educational tools to encourage high school students’ interest in STEM disciplines. These tools include laboratory courses developed in the fields of physics, information technologies and mathematics. More than 2000 high school students already participated in these experimental courses. These activities are aimed at increasing the quality of STEM disciplines learning which will result in higher quality of training of future engineers.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.07.037
       
  • Feasible angular momentum of spacecraft installed with control moment
           gyros
    • Authors: Henzeh Leeghim; Jaehyun Jin; Sung-Hoon Mok
      Pages: 466 - 477
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Henzeh Leeghim, Jaehyun Jin, Sung-Hoon Mok
      In this paper, a fundamental approach to analyzing the maneuverability of spacecraft with mounted control moment gyros is addressed by searching feasible angular momentum. The geometrical array of control moment gyros considered is a roof array also known as a 2-SPEED system. Due to the simplicity of the singularity envelope of the array considered, it is reasonably practical to conduct rotational performance analysis of the spacecraft. This maneuverability analysis technique uses a unique chart developed in this work, which allows a guaranteed maximum torque output and angular momentum at any time without concern about the singularity problem of the control moment gyros. Therefore, the purpose of this paper is to provide a conservative method for maneuverability analysis of a spacecraft with installed control moment gyros by searching allowable maximum angular momentum. This method is demonstrated using an illustrative example.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.08.015
       
  • Fostering research aptitude among high school students through space
           weather competition
    • Authors: M. Abdullah; R.A. Majid; B. Bais; N.S. Bahri; M.F. Asillam
      Pages: 478 - 486
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): M. Abdullah, R.A. Majid, B. Bais, N.S. Bahri, M.F. Asillam
      Cultivating research culture at an early stage is important for capacity building in a community. The high school level is the appropriate stage for research to be introduced because of students’ competitive nature. Participation in the space weather competition is one of the ways in which research aptitude can be fostered in high school students in Malaysia. Accordingly, this paper presents how research elements were introduced to the students at the high school level through their participation in the space weather competition. The competition required the students to build a system to detect the presence of solar flares by utilizing VLF signals reflected from the ionosphere. The space weather competition started off with proposal writing for the space weather related project where the students were required to execute extensive literature review on the given topic. Additionally, the students were also required to conduct the experiments and analyse the data. Results obtained from data analysis were then validated by the students through various other observations that they had to carry out. At the end of the competition, students were expected to write a comprehensive technical report. Through this competition, the students learnt how to conduct research in accordance to the guidelines provided through the step by step approach exposed to them. Ultimately, this project revealed that the students were able to conduct research on their own with minimal guidance and that participation in the competition not only generated enjoyment in learning but also their interest in science and research.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.08.028
       
  • Geometric calibration of Colour and Stereo Surface Imaging System of
           ESA’s Trace Gas Orbiter
    • Authors: Stepan Tulyakov; Anton Ivanov; Nicolas Thomas; Victoria Roloff; Antoine Pommerol; Gabriele Cremonese; Thomas Weigel; Francois Fleuret
      Pages: 487 - 496
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Stepan Tulyakov, Anton Ivanov, Nicolas Thomas, Victoria Roloff, Antoine Pommerol, Gabriele Cremonese, Thomas Weigel, Francois Fleuret
      There are many geometric calibration methods for “standard” cameras. These methods, however, cannot be used for the calibration of telescopes with large focal lengths and complex off-axis optics. Moreover, specialized calibration methods for the telescopes are scarce in literature. We describe the calibration method that we developed for the Colour and Stereo Surface Imaging System (CaSSIS) telescope, on board of the ExoMars Trace Gas Orbiter (TGO). Although our method is described in the context of CaSSIS, with camera-specific experiments, it is general and can be applied to other telescopes. We further encourage re-use of the proposed method by making our calibration code and data available on-line.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.025
       
  • Multibody dynamical modeling for spacecraft docking process with
           spring-damper buffering device: A new validation approach
    • Authors: Kamran Daneshjou; Reza Alibakhshi
      Pages: 497 - 512
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Kamran Daneshjou, Reza Alibakhshi
      In the current manuscript, the process of spacecraft docking, as one of the main risky operations in an on-orbit servicing mission, is modeled based on unconstrained multibody dynamics. The spring-damper buffering device is utilized here in the docking probe-cone system for micro-satellites. Owing to the impact occurs inevitably during docking process and the motion characteristics of multibody systems are remarkably affected by this phenomenon, a continuous contact force model needs to be considered. Spring-damper buffering device, keeping the spacecraft stable in an orbit when impact occurs, connects a base (cylinder) inserted in the chaser satellite and the end of docking probe. Furthermore, by considering a revolute joint equipped with torsional shock absorber, between base and chaser satellite, the docking probe can experience both translational and rotational motions simultaneously. Although spacecraft docking process accompanied by the buffering mechanisms may be modeled by constrained multibody dynamics, this paper deals with a simple and efficient formulation to eliminate the surplus generalized coordinates and solve the impact docking problem based on unconstrained Lagrangian mechanics. By an example problem, first, model verification is accomplished by comparing the computed results with those recently reported in the literature. Second, according to a new alternative validation approach, which is based on constrained multibody problem, the accuracy of presented model can be also evaluated. This proposed verification approach can be applied to indirectly solve the constrained multibody problems by minimum required effort. The time history of impact force, the influence of system flexibility and physical interaction between shock absorber and penetration depth caused by impact are the issues followed in this paper. Third, the MATLAB/SIMULINK multibody dynamic analysis software will be applied to build impact docking model to validate computed results and then, investigate the trajectories of both satellites to take place the successful capture process.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.036
       
  • Radio sounding of the solar wind acceleration region with spacecraft
           signals
    • Authors: Oleg I. Yakovlev; Yuri V. Pisanko
      Pages: 552 - 566
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Oleg I. Yakovlev, Yuri V. Pisanko
      Data from coronal radio-sounding experiments carried out on various interplanetary spacecraft are used to derive the empirical radial dependence of solar wind velocity and density at heliocentric distances from 3 to 60 solar radii for heliolatitudes below 60° and for low solar activity. The radial dependencies of solar wind power and acceleration are derived from these results. Summaries of the radial behavior of characteristic parameters of the solar wind turbulence (e.g., the spectral index and the inner and outer turbulence scales), as well as the fractional density fluctuation, are also presented. These radio-sounding results provide a benchmark for models of the solar wind in its acceleration region.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.052
       
  • Alternate models to dark energy
    • Authors: Kenath Arun; S.B. Gudennavar; A. Prasad; C. Sivaram
      Pages: 567 - 570
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Kenath Arun, S.B. Gudennavar, A. Prasad, C. Sivaram
      One of the unresolved questions currently in cosmology is that of the non-linear accelerated expansion of the universe. This has been attributed to the so called Dark Energy (DE). The accelerated expansion of the universe is deduced from measurements of Type Ia supernovae. Here we propose alternate models to account for the Type Ia supernovae measurements without invoking dark energy.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.08.006
       
  • Near-infrared study of open clusters Teutsch 10 and Teutsch 25
    • Authors: D. Bisht; Shashikiran Ganesh; R.K.S. Yadav; Alok Durgapal; Geeta Rangwal
      Pages: 571 - 580
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): D. Bisht, Shashikiran Ganesh, R.K.S. Yadav, Alok Durgapal, Geeta Rangwal
      The astrophysical parameters have been estimated for two unstudied open star clusters Teutsch 10 and Teutsch 25 using the Two Micron All Sky Survey ( 2 MASS ) database. Radius is estimated as 4.5 arcmin for both clusters using radial density profiles. We have estimated proper motion values in both RA and DEC directions as 2.28 ± 0.3 and - 0.38 ± 0.11  mas yr−1 for Teutsch 10 and 0.48 ± 0.3 and 3.35 ± 0.16  mas yr−1 for Teutsch 25 using PPMXL 1 http://vizer.cfa.harvard.edu/vizbin/VizieR'-source=I/317. 1 catalog. By estimating the stellar membership probabilities, we have identified 30 and 28 most likely members for Teutsch 10 and Teutsch 25 respectively. We have estimated the reddening as E ( B - V ) = 0.96 ± 0.3  mag for Teutsch 10 and 0.58 ± 0.2  mag for Teutsch 25, while the corresponding distances are 2.4 ± 0.2 and 1.9 ± 0.1  kpc. Ages of 70 ± 10  Myr for Teutsch 10 and 900 ± 100  Myr for Teutsch 25 are estimated using the theoretical isochrones of metallicity Z = 0.019. The mass function slopes are derived as 1.23 ± 0.30 and 1.09 ± 0.35 for Teutsch 10 and Teutsch 25 respectively. Estimated mass function slope for both the clusters are close to the Salpeter value ( x = 1.35 ) within the errors. Estimated values of dynamical relaxation time are found to be less than cluster’s age for these objects. This concludes that both objects are dynamically relaxed. The possible reason for relaxation may be due to dynamical evolution or imprint of star formation or both.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.10.055
       
  • Velocity shear Kelvin-Helmholtz instability with inhomogeneous DC electric
           field in the magnetosphere of Saturn
    • Authors: Praveen Kandpal; Rajbir Kaur; R.S. Pandey
      Pages: 581 - 592
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Praveen Kandpal, Rajbir Kaur, R.S. Pandey
      In this paper parallel flow velocity shear Kelvin-Helmholtz instability has been studied in two different extended regions of the inner magnetosphere of Saturn. The method of the characteristic solution and kinetic approach has been used in the mathematical calculation of dispersion relation and growth rate of K-H waves. Effect of magnetic field (B), inhomogeneity (P/a), velocity shear scale length ( A i ), temperature anisotropy ( T ⊥ / T ), electric field (E), ratio of electron to ion temperature ( T e / T i ), density gradient ( ε n ρ i ) and angle of propagation ( θ ) on the dimensionless growth rate of K-H waves in the inner magnetosphere of Saturn has been observed with respect to k ⊥ ρ i . Calculations of this theoretical analysis have been done taking the data from the Cassini in the inner magnetosphere of Saturn in the two extended regions of Rs ∼4.60–4.01 and Rs ∼4.82–5.0. In our study velocity shear, temperature anisotropy and magnitude of the electric field are observed to be the major sources of free energy for the K-H instability in both the regions considered. The inhomogeneity of electric field, electron-ion temperature ratio, and density gradient have been observed playing stabilizing effect on K-H instability. This study also indicates the effect of the vicinity of icy moon Enceladus on the growth of K-H instability.

      PubDate: 2017-12-13T07:22:55Z
      DOI: 10.1016/j.asr.2017.09.033
       
  • Orbital Stability Close to Asteroid 624 Hektor using the Polyhedral Model
    • Authors: Yu Jiang; Hexi Baoyin; Hengnian Li
      Abstract: Publication date: Available online 26 December 2017
      Source:Advances in Space Research
      Author(s): Yu Jiang, Hexi Baoyin, Hengnian Li
      We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid’s mass center when the density increases, and the inner equilibrium point moves close to the asteroid’s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary’s equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375 d.

      PubDate: 2017-12-27T07:42:25Z
      DOI: 10.1016/j.asr.2017.12.011
       
  • Two-Phase Framework for Near-Optimal Multi-Target Lambert Rendezvous
    • Authors: Jun Bang; Jaemyung Ahn
      Abstract: Publication date: Available online 24 December 2017
      Source:Advances in Space Research
      Author(s): Jun Bang, Jaemyung Ahn
      This paper proposes a two-phase framework to obtain a near-optimal solution of multi-target Lambert rendezvous problem. The objective of the problem is to determine the minimum-cost rendezvous sequence and trajectories to visit a given set of targets within a maximum mission duration. The first phase solves a series of single-target rendezvous problems for all departure-arrival object pairs to generate the elementary solutions, which provides candidate rendezvous trajectories. The second phase formulates a variant of traveling salesman problem (TSP) using the elementary solutions prepared in the first phase and determines the final rendezvous sequence and trajectories of the multi-target rendezvous problem. The validity of the proposed optimization framework is demonstrated through an asteroid exploration case study.

      PubDate: 2017-12-27T07:42:25Z
      DOI: 10.1016/j.asr.2017.12.025
       
  • Design and Fabrication of Robotic Gripper for Grasping in Minimizing
           Contact Force
    • Authors: Hamidreza Heidari; Milad Jafary Pouria; Shahriar Sharifi; Mahmoudreza Karami
      Abstract: Publication date: Available online 24 December 2017
      Source:Advances in Space Research
      Author(s): Hamidreza Heidari, Milad Jafary Pouria, Shahriar Sharifi, Mahmoudreza Karami
      This paper presents a new method to improve the kinematics of robot gripper for grasping in unstructured environments, such as space operations. The robot gripper is inspired from the human hand and kept the hand design close to the structure of human fingers to provide successful grasping capabilities. The main goal is to improve kinematic structure of gripper to increase the grasping capability of large objects, decrease the contact forces and makes a successful grasp of various objects in unstructured environments. This research will describe the development of a self-adaptive and reconfigurable robotic hand for space operations through mechanical compliance which is versatile, robust and easy to control. Our model contains two fingers, two-link and three-link, with combining a kinematic model of thumb index. Moreover, some experimental tests are performed to examine the effectiveness of the hand-made in real, unstructured tasks. The results represent that the successful grasp range is improved about 30% and the contact forces is reduced approximately 10% for a wide range of target object size. According to the obtained results, the proposed approach provides an accommodative kinematic model which makes the better grasping capability by fingers geometries for a robot gripper.

      PubDate: 2017-12-27T07:42:25Z
      DOI: 10.1016/j.asr.2017.12.024
       
  • Solar polar magnetic field dependency of geomagnetic activity semiannual
           variation indicated in the Aa index
    • Authors: Suyeon
      Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1
      Author(s): Suyeon Oh, Yu Yi
      Three major hypotheses have been proposed to explain the well-known semiannual variation of geomagnetic activity, maxima at equinoxes and minima at solstices. This study examined whether the seasonal variation of equinoctial geomagnetic activity is different in periods of opposite solar magnetic polarity in order to understand the contribution of the interplanetary magnetic field (IMF) in the Sun-Earth connection. Solar magnetic polarity is parallel to the Earth’s polarity in solar minimum years of odd/even cycles but antiparallel in solar minimum years of even/odd cycles. The daily mean of the aa, Aa indices during each solar minimum was compared for periods when the solar magnetic polarity remained in opposite dipole conditions. The Aa index values were used for each of the three years surrounding the solar minimum years of the 14 solar cycles recorded since 1856. The Aa index reflects seasonal variation in geomagnetic activity, which is greater at the equinoxes than at the solstices. The Aa index reveals solar magnetic polarity dependency in which the geomagnetic activity is stronger in the antiparallel solar magnetic polarity condition than in the parallel one. The periodicity in semiannual variation of the Aa index is stronger in the antiparallel solar polar magnetic field period than in the parallel period. Additionally, we suggest the favorable IMF condition of the semiannual variation in geomagnetic activity. The orientation of IMF toward the Sun in spring and away from the Sun in fall mainly contributes to the semiannual variation of geomagnetic activity in both antiparallel and parallel solar minimum years.

      PubDate: 2017-12-13T07:22:55Z
       
  • List of Referees
    • Abstract: Publication date: 1 January 2018
      Source:Advances in Space Research, Volume 61, Issue 1


      PubDate: 2017-12-13T07:22:55Z
       
 
 
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