GPS掩星技术低轨卫星计划的现状及进展

主要介绍了几个国际上已经实施的GPS掩星计划（GPS／MET，Φrsted,Sunsat,SAC-C,CHAMP)和在研的（COSMIC，ACE）低轨卫星计划的现状及取得的进展。通过总结可知，下一代GPS掩星接收器应具有体积小、质量轻（几百克）、低功耗的特点；能提供实时的卫星物理状态参数；飞行器上的自主计算和控制；星上数据通信和命令解释；所有跟踪数据应符合厘米级精密定轨的要求；能提供掩星和海洋反射实验的测量。     

卫星星座与编队飞行问题综述

卫星应用的日益发展需要由多颗卫星组成的卫星系统(形成各种类型的星座)来替代单颗卫星，这就给卫星轨道力学的应用增加了一些新内容。重点阐述了卫星星座整体结构的演化、卫星星座编队飞行中的星-星相对几何构形及其保持问题，以及星座卫星定轨所涉及的测控方式和天地基网联合定轨问题。这些内容都是卫星星座轨道力学中的重要组成部分。     

针对低轨星座的空间信号测距误差投影系数确定

随着低轨星座建设的不断推进,计算卫星空间信号测距误差(signal in space range error,SISRE)的面向对象不再局限于全球卫星导航系统(Global Navigation Satellite System, GNSS)的地面用户,还包括GNSS的低轨星载用户和低轨导航系统地面用户。为更好地支持基于低轨星座SISRE的解算,根据SISRE的计算原理,分别研究了低轨星载用户和低轨卫星地面用户的SISRE误差投影系数的特征。计算结果显示,GNSS卫星对地面用户的误差投影系数并不适用于低轨星载用户及低轨导航星座地面用户。当低轨卫星轨道高度由2 000 km降低至300 km时,GNSS卫星对低轨星载接收机的轨道径向误差投影系数由0.96增加到0.98,轨道切法平面误差投影系数由0.20降低至0.15;低轨卫星对地面用户的轨道径向误差投影系数从0.72降至0.37,轨道切法平面误差投影系数从0.49增加至0.66。上述结果可为未来低轨卫星相关的空间信号测距误差分析以及低轨完好性研究提供重要参考。     

关于星—星跟踪与地面跟踪的联合定轨问题

关于航天器测轨问题,由天基网部分地代替地基网是目前航天测控的一个发展趋势,现已实现的利用全球导航系统（ＧＰＳ）和跟踪与数据中继卫星系统（ＴＤＲＳＳ）对低轨用户星的测轨手段就是如此。本文将阐述另一种类型的测轨模型和具体定轨方法,即一个中低轨卫星星座中的卫星与地面站的组合对星座中其它卫星进行定轨。     

卫星星座的结构演化

主要研究星座几何结构的演化问题，分析了在地球扁率摄动和卫星的入轨偏差影响下轨道的演化过程，以卫星的相位和升交点赤经为参数描述了星座结构演化的一般规律，又以星下点轨迹变化和星下点的相互位置关系的变化为参数描述了区域星座结构演化的地域特性．分析表明，地球扁率摄动将导致星座结构的整体漂移，而卫星的入轨偏差则会导致星座几何结构的紊乱，特别是轨道半长轴的偏差，将是影响星座几何结构稳定性的决定因素．     

区域导航卫星精密定轨研究

区域卫星导航系统采用混合星座设计,GEO(地球同步轨道)卫星是系统的重要组成部分,其精密定轨技术也是导航系统的关键技术之一。GEO卫星的高轨特性致使地面跟踪基线长度有限,定轨几何条件不佳;其静地特性致使卫星轨道与钟差存在强相关特性,对于基于伪距的GEO卫星定轨模式,需要星地与站间时间同步技术的支持。因此,如何利用区域卫星导航系统的多种测量技术实现多模式、多层次的导航卫星精密定轨,是一项值得深入研究的课题。     

日本SELENE月球探测计划和卫星间多普勒跟踪的数学模型

日本月球探测计划（SELENE）定于2004年夏季利用HIIa火箭发射一组共3颗绕月人造卫星。他们是主卫星、跟踪中断卫星和空间VLBI电波源。其主要科学目标之一是利用对绕月卫星的多普勒跟踪数据精确测定月球重力场,研究月球的起源与演化。SELENE计划中实现这个科学目标的关键技术是引入中继卫星,目的在于当处于低轨道的主卫星飞行到月球背面地面观测站无法观测时,采用卫星间跟踪方法（SST）,建立地面站与主卫星之间的联系,以得到月球背面重力场的直接测量数据。介绍了几种典型的四程卫星间多普勒跟踪模式和相应的数学模型,并针对SELENE计划中采用的特殊四程多普勒跟踪模式建立了卫星相对观测站速度与跟踪信号多普勒频移之间的转换关系。提出了利用GEODYNⅡ定轨分析软件处理SELENE多普勒跟踪数据的流程。     

精密测距测速系统地面跟踪站在上海天文台建立

精密测距测速系统可以精确测量卫星和地面站之间的距离，在介绍该测距测速系统的基础上，报道了该系统地面跟踪站在上海天台的安装、建立和运行情况。本站在第20周共获得31圈卫星通过资料，16523个观测点，测距精度为263cm，列全球所有地面跟踪站第四名。     

电离层的掩星分离假设反演法

该文首先简要介绍了无线电掩星探测技术及其发展现状和传统Abel变换方法面临的问题.为改进传统Abel变换反演方法,利用电子密度廓线的分离假设,引进了分离假设反演法.随后利用国际电离层参考模式IBI2007给出1000个掩星事件截面的模拟数据及COSMIC卫星星座的一天实测数据,进行比较计算,并对结果进行了分析,验证了分离假设反演法的有效性.文中还给出了垂直电子总量VTEC(Vertical Total Electron Content)先验场的获取途径.最后,对分离假设反演法的进一步研究的方向进行了探讨.     

依巴谷天体测量卫星的阶段成果

本文综合介绍依巴谷天体测量卫星自１９８９年１１月开始观测以来，由头两年获得的观测资料取得的空间天体测量的阶段性成果，以及空间天体测量结果与地面观测结果相互之间的比较，成功地用于解算天体测量参数的星数已达１１２４４颗，由依巴谷天体测量卫星的头两年观测资料进行归算处理，得到恒星位置，视差和年自行的预期精度分别为３、４和２ｍａｓ。由此从整体上合面地检验了依巴谷科学计划，包括观测纲要，输入星表，卫星本身及     

GPS无线电掩星数据处理系统

GPS无线电掩星技术能提供高精度、高分辨率、全球覆盖的地球电离层和中性层大气剖面。它具有全天候、低费用、无系统长期漂移等优点。从1995年4月至1997年3月,首次GPS／MET试验的成功显示了GPS掩星技术对监测全球大气能够发挥重要的作用,从而成为当前空间探测技术的研究热点之一。该文主要叙述了无线电掩星技术的数据处理系统的有关情况,并介绍了美国UCAR的掩星数据处理系统CDAAC的概况,可作为我国开展无线电掩星计划有关工作的借鉴。     

A new opportunity from space: PLATO mission

The satellite PLATO represents a new challenge for future investigations of exoplanets and oscillations of stars. It is one of the proposed missions of ESA COSMIC VISION 2015–2025 and it is scheduled for launch in 2017. The goal of the mission is a full characterization of the planet star systems with an asteroseismic analysis of the host stars. The PLATO Payload Consortium (PPLC) includes several European countries which are employed in the assessment study of the mission. Thanks to the high precision photometry, PLATO is thought to be able to detect planets and oscillations within a large sample of targets.     

DynaMICCS: The Sun as an Integrated Magnetic System

After the observations of SoHO, there is a real need to pursue global solar observations from the core to the corona and to put new constraints on the dynamical processes which act inside and outside the Sun. The DynaMICCS mission proposed to ESA in the framework of COSMIC VISION 2015–2025 has this objective. We concentrate here on the motivations to look for the magnetism of the solar radiative zone.     

On relation between mid-latitude ionospheric ionization and quasi-trapped energetic electrons during 15 December 2006 magnetic storm

We report simultaneous observations of intense fluxes of quasi-trapped energetic electrons and substantial enhancements of ionospheric electron concentration (EC) at low and middle latitudes over the Pacific region during the geomagnetic storm on 15 December 2006. Electrons with energy of tens of keV were measured at altitude of ～800–900 km by POES and DMSP satellites. Experimental data from COSMIC/FS3 satellites and global network of ground-based GPS receivers were used to determine height profiles of EC and vertical total EC, respectively. A good spatial and temporal correlation between the electron fluxes and EC enhancements was found. This fact allows us to suggest that the quasi-trapped energetic electrons can be an important source of ionospheric ionization at middle latitudes during magnetic storms.     

The Demeter microsatellite and ground segment

The Demeter program is the first application of the Myriade microsatellite program conducted by the Cnes (French Space Agency) since 1997. The Myriade objective was to benefit from the miniaturization of the technologies to develop a product with a reduced size, weight and cost able to implement either scientific missions, demonstrators or operational applications in different areas: earth observation, astronomy, fundamental physics or telecommunications, within limited financial budget.The Demeter satellite was launched in end of June 2004, from Baikonour, aboard a Dnepr launcher, on a sun synchronous orbit at 710 km altitude. Its main scientific objectives are the detection and characterization of ionosphere electrical and magnetic disturbances in connection with a seismic activity.The scientific payload has been built by French scientific institutes (LPCE, CESR, CETP) involved in external and internal geophysics and by SSD/ESTEC (ESA). It is composed of several electrical and magnetic sensors, an ion spectrometer, an energetic particle analyzer and a Langmuir probe.The Demeter platform is designed in order to offer a high level of performances in terms of power, attitude and orbit control, data storage and transmission, flexibility. For example the large amount of scientific data is transmitted to the ground station with a high data rate telemetry link in X band.This paper describes the Demeter satellite and ground segment. It focuses on the specific design adaptations of the Myriade product for Demeter and it presents the preliminary in orbit platform performances.     

A New Approach for Scientific Data Dissemination in Developing Countries: A Case of Indonesia

This short paper is a progress report on our experiences in Indonesia of collecting, integrating and disseminating both global and local scientific data across the country through the web. Our recent efforts are concentrated on improving local public access to global scientific data, and encouraging local scientific data to be more accessible for global communities. We have maintained a well-connected infrastructure and web-based information management systems to realize these objectives. This paper is especially focused on introducing the ARSIP system for mirroring global data and sharing local scientific data, and the newly developed Indonesian Scientific Index for integrating local scientific data through an automated intelligent indexing system.     

Ground facility for information reception,processing, dissemination and scientific instruments management setup in the CORONAS-PHOTON space project

This paper deals with the organizational structure of ground-based receiving, processing, and dissemination of scientific information created by the Astrophysics Institute of the Scientific Research Nuclear University, Moscow Engineering Physics Institute. Hardware structure and software features are described. The principles are given for forming sets of control commands for scientific equipment (SE) devices, and statistics data are presented on the operation of facility during flight tests of the spacecraft (SC) in the course of one year.     

Scientific data products and the data pre-processing subsystem of the Chang'e-3 mission

The Chang'e-3(CE-3) mission is China's first exploration mission on the surface of the Moon that uses a lander and a rover. Eight instruments that form the scientific payloads have the following objectives:(1) investigate the morphological features and geological structures at the landing site;(2) integrated in-situ analysis of minerals and chemical compositions;(3) integrated exploration of the structure of the lunar interior;(4) exploration of the lunar-terrestrial space environment, lunar surface environment and acquire Moon-based ultraviolet astronomical observations. The Ground Research and Application System(GRAS) is in charge of data acquisition and pre-processing, management of the payload in orbit, and managing the data products and their applications. The Data Pre-processing Subsystem(DPS) is a part of GRAS.The task of DPS is the pre-processing of raw data from the eight instruments that are part of CE-3, including channel processing, unpacking, package sorting, calibration and correction, identification of geographical location, calculation of probe azimuth angle, probe zenith angle, solar azimuth angle, and solar zenith angle and so on, and conducting quality checks. These processes produce Level 0, Level 1 and Level 2data. The computing platform of this subsystem is comprised of a high-performance computing cluster, including a real-time subsystem used for processing Level 0 data and a post-time subsystem for generating Level 1 and Level 2 data. This paper describes the CE-3 data pre-processing method, the data pre-processing subsystem, data classification, data validity and data products that are used for scientific studies.