Analysis on coverage ability of BeiDou navigation satellite system for manned spacecraft

To investigate the service ability of the BeiDou Navigation Satellite System (BDS) for manned spacecraft, both the current regional and the future-planned global constellations of BDS are introduced and simulated. The orbital parameters of the International Space Station and China׳s Tiangong-1 spacelab are used to create the simulation scenario and evaluate the performance of the BDS constellations. The number of visible satellites and the position dilution (PDOP) of precision at the spacecraft-based receiver are evaluated. Simulation and analysis show quantitative results on the coverage ability and time percentages of both the current BDS regional and future global constellations for manned-space orbits which can be a guideline to the applications and mission design of BDS receivers on manned spacecraft.     

Satellite range scheduling with the priority constraint: An improved genetic algorithm using a station ID encoding method

Satellite range scheduling with the priority constraint is one of the most important problems in the field of satellite operation.This paper proposes a station coding based genetic algorithm to solve this problem,which adopts a new chromosome encoding method that arranges tasks according to the ground station ID.The new encoding method contributes to reducing the complexity in conflict checking and resolving,and helps to improve the ability to find optimal resolutions.Three different selection operators are designed to match the new encoding strategy,namely random selection,greedy selection,and roulette selection.To demonstrate the benefits of the improved genetic algorithm,a basic genetic algorithm is designed in which two cross operators are presented,a single-point crossover and a multi-point crossover.For the purpose of algorithm test and analysis,a problem-generating program is designed,which can simulate problems by modeling features encountered in real-world problems.Based on the problem generator,computational results and analysis are made and illustrated for the scheduling of multiple ground stations.     

Validation of GOME (ERS-2) NO2 vertical column data with ground-based measurements at Issyk-Kul (Kyrgyzstan)

Here we present the results of comparison between operational NO₂ vertical column data by Global Ozone Monitoring Experiment (GOME) onboard ERS-2 satellite and ground-based measurements at Issyk-Kul station in Kyrgyzstan, northern Tien Shan. The data of GOME, taken for the period of 1996–2002, was found to be reasonably close to the results of ground-based sunrise measurements. The latter were adjusted to the time of GOME overpass nearby noon, providing direct comparison between satellite and ground-based data. According to the results, there is 0.6 × 10¹⁵ mol/cm² (18%) overestimation of NO₂ vertical column by GOME, compared to our ground-based data.     

Boundary layer aerosol retrieval from thermal infrared nadir sounding – Preliminary results

A non-empirical algorithm is presented to retrieve the optical depth in the 750–1250 cm⁻¹ spectral range, of aerosol located in the boundary layer over the ocean, from nadir high-resolution radiance spectra in the thermal infrared. The algorithm is based on a line-by-line radiative transfer forward model and used the Optimal Estimation Method for the retrieval. Its performance strongly depends on the quality of the a priori temperature and H₂O atmospheric profiles. To demonstrate the relevance of the algorithm, distributions of maritime aerosol parameters have been retrieved from IMG/ADEOS data for December 1996, using the algorithm with the LBLRTM radiative transfer code, and ERA40 (ECMWF) a priori atmospheric profiles and surface conditions.     

卫星转发器载波互调噪声比的工程计算

阐述了卫星转发器在多载波工作时载波互调噪声比的工程计算方法，并给出了一个实际的计算例子。     

滤波器的相频特性对像质影响的仿真

利用计算机仿真的方法,研究了椭圆低通滤波器和Butterworth滤波器的相频特性对像质的影响。这种影响主要有边缘退化、分辨率损失、产生新的干扰条纹和几何畸变以及多波段图像配准精度降低等。     

国际航天保险市场的理性分析

以美、俄、英等国航天保险业为例，综述了航天保险业内容、合同特征，并就国际航天保险业的发展空间提出了个人见解。     

椭圆轨道卫星编队燃料最优机动实时算法

文章针对椭圆轨道编队卫星最优燃料机动的实时计算问题进行研究。利用LGL伪谱法对问题进行快速求解。由于最优燃料控制为非连续控制,如直接采用伪谱法则只有当离散点数目很大时,才能实现较高精度的编队机动控制,而这会影响算法的实时计算效率。为了克服这方面的不足,文章提出了一种时间尺度变换策略,并结合模型预测的滚动优化方法,设计了一种编队实时机动控制算法。该算法在兼顾解的全局最优性的同时改善了解的局部精确性,最后通过数值仿真验证了所设计算法的有效性。     

The PRISMA payload optomechanical design, a high performance instrument for a new hyperspectral mission

PRISMA (PRecursore IperSpettrale della Missione Applicativa) hyperspectral instrument is an advanced hyperspectral sensor including a panchromatic camera at medium resolution. The instrument is the focus of the new Earth observation mission that a consortium of Italian companies has started developing under contract of Italian Space Agency. Key features of the instrument are the very high requirement for signal-to-noise and the high quality of data that have to be provided. To meet these demanding figures the optical system has been based on a high transmittance optical system, including a single mirror telescope and two prism spectrometers based on an innovative concept to minimize number of optical elements, while high performance detectors have been chosen for the photon detection. To provide the required data quality for the entire mission lifetime an accurate calibration unit (radiometric and spectral) will be included in the instrument optomechanical assembly. The thermo-mechanical design of the instrument is based on innovative concepts, considering that the use of prism spectrometers implies a tight control of temperature variations to guarantee the stability of all instrument features once in orbit. The presented paper describes the concepts and design principle of the optomechanical assembly of the instrument, at the present status of development.     

星载红外相机相对定标算法研究

文章针对红外相机双面镜旋转多元并扫成像方式的特点,对其相对定标算法进行了研究。首先分析了探元A／B面响应差异,然后介绍了算法原理,采用不同的定标算法获得了定标校正系数,并对定标数据和在轨图像进行了相对辐射校正,验证了算法的正确性和结果的有效性,最后在定标系数校正的基础上,进一步改进了像质。