Venus Express: Scientific goals, instrumentation, and scenario of the mission

The first European mission to Venus (Venus Express) is described. It is based on a repeated use of the Mars Express design with minor modifications dictated in the main by more severe thermal environment at Venus. The main scientific task of the mission is global exploration of the Venusian atmosphere, circumplanetary plasma, and the planet surface from an orbiting spacecraft. The Venus Express payload includes seven instruments, five of which are inherited from the missions Mars Express and Rosetta. Two instruments were specially designed for Venus Express. The advantages of Venus Express in comparison with previous missions are in using advanced instrumentation and methods of remote sounding, as well as a spacecraft with a broad spectrum of capabilities of orbital observations.     

Updating the Local Model of the TEC during the Solar Eclipse on August 11, 1999

A total solar eclipse with the locations and times of the pass well-known in advance can be used to update the local model of the TEC for these particular circumstances. The observations using GPS receivers at the Warsaw and Borowiec stations and the ionosonde in Warsaw were analyzed in order to justify the results given by the IRI theoretical predictions. The IRI program with this updating creates a useful tool for preparation of the corrections for the process of network adjustment using the GPS technique and for navigation using single frequency receivers.     

Mining Spatial Associations with Limited Sensory Information

Abstract

Human navigation in an unknown environment requires an understanding of the spatial relationships of the terrain. For example, a soldier who is on a reconnaissance mission in a new city needs to “know” the spatial layout of the surroundings with high confidence. Oftentimes, this understanding must be acquired within a very short amount of time and with limited sensory inputs. The soldier would benefit from a digital avatar that draws inferences about the spatial layout of the city based on an initial set of observations and guides the soldier either in further exploring the environment or in making decisions based on these inferences. In this paper, we present and evaluate an inductive approach to learning spatial associations using sensory data that is available from the simulation environment of a computer game, Unreal Tournament. We study two kinds of spatial relationships between nodes on a level of a game map: nodes that are placed near each other to satisfy some spatial requirement and nodes that are placed near each other to satisfy the design preferences of a level architect. We show that we can infer both kinds of relationships using an association rule mining algorithm. Furthermore, we show how to use an ontology to distinguish between these relationships in order to discover different types of spatial arrangements on a specific map. We discuss how the inferred associations can be used to control an avatar that makes recommendations for navigating unexplored areas on a map. We conclude with some thoughts on the applicability of our methods to scenarios in the real world, beyond the simulation environment of a game, and on how the learned associations can be represented and queried by a simple question-answer type system.     

Surface error estimation and correction of a space antenna based on antenna gainanalyses

Novel methods for the estimation and correction of antenna surface deformations are developed and investigated. Surface adjustment mechanisms, which are used for a reconfigurable antenna system, are used to estimate and correct surface errors. Relations between antenna surface errors and changes in antenna gains caused by intentional deformations are derived from the Ruze equation. In these methods, an antenna surface is deformed using the surface adjustment mechanisms, and the changes in the gains caused by the intentional deformations are measured. On the basis of the information regarding the intentional deformations and the resultant changes in the antenna gains, original deformation of the antenna surface is estimated. The deformation is corrected using the surface adjustment mechanisms. Some numerical simulations are carried out to investigate the feasibility of these methods. The results of these simulations show that the antenna deformations are estimated and corrected adequately using these methods.     

精密定轨中三类经验加速度的有效建模方法

根据瞬时速度脉冲、逐段常量经验加速度和周期性摄动加速度模型的特点,分别给出敏感矩阵的有效计算方法,以及最小二乘批处理的设计矩阵和法方程矩阵的分块结构。该建模方法将灵敏度矩阵数值积分规模和存储规模降为O(n),而传统方法为O(n 2)。应用GRACE-A星载GPS观测数据对法方程的计算效率测试,结果表明：对于瞬时速度脉冲和逐段常量经验加速度模型,当采用伪距观测量时,法方程构建效率提高1倍;当采用伪距加载波相位观测量时,效率提高3.5倍。对于周期性摄动加速度模型,效率没有明显提高,主要原因在于模型参数较少,矩阵分块建模方法的优越性尚未体现。     

An information fusion algorithm for integrated autonomous orbit determination of navigation satellites

This paper focuses on the information fusion problem of integrated autonomous orbit determination using the observations from inter-satellite-link (ISL), X-ray pulsars and star sensors. A step Kalman filter structure is proposed to solve the information fusion problem of multiple subsystems that have greatly different filtering precision. The subsystems are grouped according to their measurement accuracy and the state parameters and covariance matrix of a group can be calculated using the federated filter structure and propagated to the next group step-by-step. Simulation results show that the mean user range error (URE) of the constellation will be less than 1.5 m in 60 days using the step Kalman filter structure for information fusion. And it has better performance than the federated structure in dealing with information fusion of the astronomical observations and the ISL ranging measurements in integrated autonomous orbit determination.     

UKF参数估计在航天器气动辅助变轨问题中的应用

为快速精确地求解气动辅助变轨问题,提出一种基于无损卡尔曼滤波(UKF)参数估计的数值求解方法。首先,针对气动辅助变轨问题,利用极大值原理将其转化为对应的两点边值问题;然后,以协态变量的初值作为估计参数,以末端条件为期望观测值,将该两点边值问题转化为参数估计问题,并应用UKF滤波算法求解。该算法基于估计理论,避免了计算传统数值方法所需要的梯度矩阵,同时克服了猜测协态变量初值的困难,降低了求解气动辅助变轨问题的难度。数值仿真表明,该算法结构简单,求解效率高,具有良好的鲁棒性。     

导航星座的任务重构技术研究

以COMPASS卫星导航星座为对象,研究了导航任务的重构技术。首先,对COMPASS卫星导航星座的主要性能进行了分析和仿真;其次,分析了星座中部分卫星失效后对导航性能的影响;最后,提出了分别利用在轨运行的高、中、低轨卫星及临近空间飞行器进行任务重构的方法,并对重构后的导航性能进行了仿真。仿真结果表明：提出的任务重构方法对于保证导航星座的正常运行是有效的。同时,对于研究飞行器应急测控技术具有借鉴意义。     

Aladdin mission concept

Aladdin, one of five Concept Study winners for NASA's Discovery AO98-OSS-04, was a mission to obtain samples from the two Martian moons using several unique mission design and sample collection techniques. The mission design enabled sample return from two bodies at the relatively low cost of a Discovery-class mission. It featured a phasing orbit, multiple flybys of the Martian moons, and a short overall mission duration. The phasing orbit greatly reduced the post-launch Δv requirement, thus permitting the use of a Delta II launch vehicle. Multiple moon flybys provided ample opportunities for sample collection and science observations. The short overall mission duration reduced program costs. Aladdin's sample collection, unlike traditional sample collection methods, used a “launch-and-catch” technique to obtain samples. Projectiles would be launched to the moon's surface during a close flyby and the ejected particles gathered for Earth return and analysis. This innovative technique, the Aladdin mission, and the possible extension of the technique to other bodies are described.     

Time delays in the nonthermal radiation of solar flares according to observations of the <Emphasis Type="Italic">CORONAS-F</Emphasis> satellite

In 2001–2003, the X-ray and microwave observations of ten solar flares of M- and X-classes were carried out by the CORONAS-F orbital station, the RSTN Sun service, and Nobeyama radio polarimeters. Based on these observations, a correlation analysis of time profiles of nonthermal radiation was performed. On average, hard X-ray radiation outstrips the microwave radiation in 9 events, i.e., time delays are positive. The appearance of negative delays is associated with effective scattering of accelerated electrons in pitch angles, where the length of the free path of a particle is less than the half-length of a flare loop. The additional indications are obtained in favor of the need to account for the effect of magnetic mirrors on the dynamics of energetic particles in the coronal arches.     

The Tanaka-Enome criterion and solar activity in October–November 2003 as observed by the Large Pulkovo Radio Telescope

We present the results of spectral and polarization observations of two large sunspot groups, NOAA 0484 and NOAA 0486 + 0488, which determine high solar activity in October–November 2003. The observations are made with the Large Pulkovo Radio Telescope (LPRT) in the range 2.7–20 cm, the one-dimensional (E-W) resolution of observations being 1–6 arc min, respectively. The main characteristics of the corona radio emission above these active regions are measured, allowing us to follow their dynamics during the entire period of their existence on the solar disk with a period of one day. The analysis of the obtained results is presented from the point of view of the well-known Tanaka-Enome criterion [1–2] (on the basis of this criterion one can predict strong flares from characteristics of radio emission of an active region in quasi-quiet state). Using the activity in October–November 2003 as an example, we demonstrate the capabilities of a new method for estimating the level of solar activity. It was developed on the basis of long-term observations of the Sun by LPRT [3].Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 585–594.Original Russian Text Copyright © 2004 by Borisevich, Ilin, Korzhavin, Peterova, Topchilo, Shpitalnaya.     

运载火箭制导系统惯性器件误差补偿方法研究

提供了对运载火箭制导系统惯性器件的各项主要误差在飞行中进行实时补偿的方法，以提高运载火箭将卫星送入轨道的精度。文中以中等精度惯性器件为例，对运载火箭计算其补偿效果。     

Spacelab concept and its utilization for science

The first part of the paper is devoted to the presentation of the Spacelab concepts, for which detailed design studies are at present being carried out by ESRO. The second part concentrates on the utilization of the Spacelab for the various fields of science, namely: (1) Atmospheric and space plasma physics, (2) Astronomy and astrophysics, (3) Material science and (4) Life sciences. The advantages of using the Spacelab for observations in these fields as compared to conventional automated satellites are highlighted.     

Solar Orbiter—Heat shield and system technology

Solar Orbiter will enhance our knowledge of the Sun by observations and in situ measurements as close as 0.22 AU from our star. Placed on an orbit with a period two-thirds the one of Venus, Solar Orbiter will use the many encounters with the planet to gradually incline its orbit and gain view on the Sun's poles. The permanent in situ observations will be associated to remote-sensing observations over large parts of the orbits.ESA Science Directorate has awarded in parallel two Solar Orbiter Heat Shield and System Technology contracts to industry. This paper presents the achievements of Thales Alenia Space thanks to one of these two ESA contracts.It shows how the main technical challenge brought by the heat flux of 20 solar constants has been addressed by the system and heat shield design. The design and manufacturing of a breadboard of the heat shield in view of thermal test verification is then reported. The main technological developments and residual risks are assessed, paving the way for the definition phase of the program.     

Capabilities to Control the Throw-Weight of Ballistic Missiles by the Mobile Radar Data

The methods of estimating the throw-weight of ballistic missiles are analyzed on the basis of radar observations of different phases of BM trajectory from the instant of launch to the instant of impact of detachable elements. Approximate estimations of the accuracy of resulting estimations of mass, which are achieved by modern radars obtaining the data from three main phases of the BM trajectory, are given.     

基于Lyapunov势函数的小卫星编队队形保持方法

在考虑地球非球形引力J2项摄动时,用Lyaounov势函数法推导了连续和离散两种控制方法,以保持与控制运行于椭圆轨道的小卫星编队飞行位置。建立了相应的数学模型,并证明两种控制方法均可实现系统的稳定。理论分析和仿真结果表明,两种方法均能在规定的时间内将伴随星控制到理想位置,并在相同的轨道条件下比较了两者的燃料消耗。     

Observations of auroral kilometric radio emission on the <Emphasis Type="Italic">Interball-1</Emphasis> satellite in the active Sun period 1999–2000

Results of almost two years (January 1999–October 2000) of continuous observations of auroral kilometric radio emission with the instrument AKR-X onboard the high-apogee satellite of the Earth Interball-1 are presented. The observations were conducted at the growth stage (in 1999) and in the maximum (2000) of solar activity within the 100–1500 kHz frequency band. The results of AKR detection in the vicinity of the maximum of its spectrum at a frequency of 252 kHz are presented. Both similarity (for example, the character of global directivity) and important differences from the AKR emission observed during the solar activity minimum [5] are found. Together with very high sporadicity, strong seasonal changes in the intensity are typical for the emission. It is completely absent in the spring-summer period in the Northern Hemisphere and is strongly suppressed in this period in the Southern Hemisphere. Probable nature of these features of AKR is discussed.     

强磁暴期间磁尾高速流的多卫星联合观测

使用多时空尺度的多卫星数据研究磁尾高速流,已经取得了很多重要成果。文章介绍了一次持续时间大约为3天的强磁暴期间的地磁台站和多卫星联合观测。IMAGE卫星的极光观测表明有14个孤立亚暴发生。运行在靠近磁尾的CLUSTER星簇（C1、C3卫星）和运行在靠近地球的DSP-1卫星均观测到了多次地向和尾向高速整体流。多卫星联合观测给出了不同位置处地向和尾向高速整体流的分布特征。     

基于降落图像的安全着陆点选择技术研究

深空探测中,着陆器降落过程中自主避障和自主着陆点选择是安全着陆的关键。文章主要研究了基于降落图像的星体表面障碍物识别和着陆点选择技术。首先利用着陆器高度信息和降落相机参数计算每幅降落图像的分辨率;其次对每一幅图像障碍物进行阴影检测;再次,提取障碍信息;最后选出备选的安全着陆点。文章对石头障碍进行了仿真,结果表明：这种方法能够准确、快速地为着陆器提供着陆区的安全信息,并能够为着陆器提供出备选的安全着陆点。     

Water related environment modelling on Mars

During a human Mars exploration because of the lack of time astronauts need fast methods for the interpretation of unexpected observations which give them flexibility and new, important targets. With in-situ modelling it is possible to get information on various past and present processes at the same location on a far wider spectrum than would be realized even during a long mission. This work summarizes the potential technical requirements and benefits of the modelling. Based on a simple estimation with a 300 kg package, and 1-10% of the working time of 1-2 astronauts at the same location, they can get plenty of new and important information for the whole past and present Mars. With the proposed five test groups astronauts will be able to make better and newer kinds of interpretations of observations, and find better targets and methods during the same mission.