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111.
Feasibility of performing space surveillance tasks with a proposed space-based optical architecture 总被引:1,自引:0,他引:1
T. Flohrer H. Krag H. Klinkrad T. Schildknecht 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Under ESA contract an industrial consortium including Aboa Space Research Oy (ASRO), the Astronomical Institute of the University of Bern (AIUB), and the Dutch National Aerospace Laboratory (NLR), proposed the observation concept, developed a suitable sensor architecture, and assessed the performance of a space-based optical (SBO) telescope in 2005. The goal of the SBO study was to analyse how the existing knowledge gap in the space debris population in the millimetre and centimetre regime may be closed by means of a passive optical instrument. The SBO instrument was requested to provide statistical information on the space debris population in terms of number of objects and size distribution. The SBO instrument was considered to be a cost-efficient with 20 cm aperture and 6° field-of-view and having flexible integration requirements. It should be possible to integrate the SBO instrument easily as a secondary payload on satellites launched into low-Earth orbits (LEO), or into geostationary orbit (GEO). Thus the selected mission concept only allowed for fix-mounted telescopes, and the pointing direction could be requested freely. Since 2007 ESA focuses space surveillance and tracking activities in the Space Situational Awareness (SSA) preparatory program. Ground-based radars and optical telescopes are studied for the build-up and maintenance of a catalogue of objects. In this paper we analyse how the proposed SBO architecture could contribute to the space surveillance tasks survey and tracking. We assume that the SBO instrumentation is placed into a circular sun-synchronous orbit at 800 km altitude. We discuss the observation conditions of objects at higher altitude, and select an orbit close to the terminator plane. A pointing of the sensor orthogonal to the orbital plane with optimal elevation slightly in positive direction (0° and +5°) is found optimal for accessing the entire GEO regime within one day, implying a very good coverage of controlled objects in GEO, too. Simulations using ESA’s Program for Radar and Optical Observation Forecasting (PROOF) in the version 2005 and a GEO reference population extracted from DISCOS revealed that the proposed pointing scenario provides low phase angles together with low angular velocities of the objects crossing the field-of-view. Radiometric simulations show that the optimal exposure time is 1–2 s, and that spherical objects in GEO with a diameter of below 1 m can be detected. The GEO population can be covered under proper illumination nearly completely, but seasonal drops of the coverage are possible. Subsequent observations of objects are on average at least every 1.5 days, not exceeding 3 days at maximum. A single observation arc spans 3° to 5° on average. Using a simulation environment that connects PROOF to AIUB’s program system CelMech we verify the consistency of the initial orbit determination for five selected test objects on subsequent days as a function of realistic astrometric noise levels. The initial orbit determination is possible. We define requirements for a correlator process essential for catalogue build-up and maintenance. Each single observation should provide an astrometric accuracy of at least 1”–1.5” so that the initially determined orbits are consistent within a few hundred kilometres for the semi-major axis, 0.01 for the eccentricity, and 0.1° for the inclination. 相似文献
112.
113.
针对基于星间测量的多星自主导航问题,从载荷优化和节约成本考虑,提出了一种单套敏感器切换测量的导航方案。建立了该导航方案下的系统状态空间模型,并基于扩展卡尔曼滤波方程给出了导航估计算法。基于多步卡尔曼滤波方法,将集中的滤波算法解耦为多个平行的子滤波器,使计算量降低到原算法的50%以下,并且在切换测量的导航方案下,部分解耦出的子滤波器可以只预测不更新,能够进一步地降低计算负担。给出了多步滤波算法的推导过程,证明了其与标准卡尔曼滤波的数学等价性,故算法的估计性能及计算结果与标准卡尔曼滤波一致,但计算速度有明显提升。最后,通过具体算例给出了算法的仿真验证。 相似文献
114.
J.C. Pérez A. Cerdeña A. González M. Armas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
In this work a methodology for inferring water cloud macro and microphysical properties from nighttime MODIS imagery is developed. This method is based on the inversion of a theoretical radiative transfer model that simulates the radiances detected in each of the sensor infrared bands. To accomplish this inversion, an operational technique based on Artificial Neural Networks (ANNs) is proposed, whose main characteristic is the ability to retrieve cloud properties much faster than conventional methods. Furthermore, a detailed study of input data is performed to avoid different sources of errors that appear in several MODIS infrared channels. Finally, results of applying the proposed method are compared with in-situ measurements carried out during the DYCOMS-II field experiment. 相似文献
115.
多模光纤强度调制型扰动传感器传感原理 总被引:2,自引:0,他引:2
介绍了一种采用"单模光纤-多模光纤-单模光纤"结构的强度调制型扰动传感器,传感光纤为多模光纤.以提高传感灵敏度为目的,对强度调制的传感原理进行研究,并通过仿真及实验验证原理,得出使用相干光源、阶跃折射率多模光纤、对轴熔接单模光纤和多模光纤可以得到传感灵敏度很高的扰动传感器.所述方案结构简单、传感距离长,可应用于各种扰动传感领域,如边界线、军事基地、石油管道等. 相似文献
116.
提山了一种新的光流场计算方法:首先,在几何代数域内推导了光流约束方程的新形式;然后,在速度场平滑的基础上,通过求解关于初值问题的热传导方程求解光流场;最后,给出光流场的数值解和仿真结果。实验证明此方法是有效的。 相似文献
117.
对谐振式科里奥利质量流量计的基本敏感机理进行了论述.基于典型的U型管敏感结构,建立了谐振式直接质量流量计的数学模型,给出了检测质量流量的信号解算模型,设计了一种信号解算电路并研制了相应的样机.实测结果表明:所研制的信号检测电路的测量误差小于0.1%,具有一定的实用价值,为样机研制提供了具有一定参考意义的理论和实验研究结果. 相似文献
118.
119.
Yong Yu Xiao-Fen Zhao Hao Luo Yin-Dun Mao Zheng-Hong Tang 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(9):2320-2327
Geosynchronous Earth Orbit (GEO) satellites are widely used because of their unique characteristics of high-orbit and remaining permanently in the same area of the sky. Precise monitoring of GEO satellites can provide a key reference for the judgment of satellite operation status, the capture and identification of targets, and the analysis of collision warning. The observation using ground-based optical telescopes plays an important role in the field of monitoring GEO targets. Different from distant celestial bodies, there is a relative movement between the GEO target and the background reference stars, which makes the conventional observation method limited for long focal length telescopes. CCD drift-scan photoelectric technique is applied on monitoring GEO targets. In the case of parking the telescope, the good round images of the background reference stars and the GEO target at the same sky region can be obtained through the alternating observation of CCD drift-scan mode and CCD stare mode, so as to improve the precision of celestial positioning for the GEO target. Observation experiments of GEO targets were carried out with 1.56-meter telescope of Shanghai Astronomical Observatory. The results show that the application of CCD drift-scan photoelectric technique makes the precision of observing the GEO target reach the level of 0.2″, which gives full play to the advantage of the long focal length of the telescope. The effect of orbit improvement based on multi-pass of observations is obvious and the prediction precision of extrapolating to 72-h is in the order of several arc seconds in azimuth and elevation. 相似文献
120.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(5):1402-1413
The present paper reports coordinated ionospheric irregularity measurements at optical as well as GPS wavelengths. Optical measurements were obtained from Tiny Ionospheric Photometer (TIP) sensors installed onboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. GPS radio signals were obtained from a dual frequency GPS receiver operational at Calcutta (22.58°N, 88.38°E geographic; geomagnetic dip: 32.96°; 13.00°N, 161.63°E geomagnetic) under the SCIntillation Network Decision Aid (SCINDA) program. Calcutta is located near the northern crest of Equatorial Ionization Anomaly (EIA) in the Indian longitude sector. The observations were conducted during the unusually low and prolonged solar minima period of 2008–2010. During this period, four cases of post-sunset GPS scintillation were observed from Calcutta. Among those cases, simultaneous fluctuations in GPS Carrier-to-Noise ratios (C/No) and measured radiances from TIP over a common ionospheric volume were observed only on February 2, 2008 and September 25, 2008. Fluctuations observed in measured radiances (maximum 0.95 Rayleigh) from TIP due to ionospheric irregularities were found to correspond well with C/N0 fluctuations on the GPS links observed from Calcutta, such effects being noted even during late evening hours of 21:00–22:00 LT from locations around 40° magnetic dip. These measurements indicate the existence of electron density irregularities of scale sizes varying over several decades from 135.6 nm to 300–400 m well beyond the northern crest of the EIA in the Indian longitude sector during late evening hours even in the unusually low solar activity conditions. 相似文献