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采用单轴双太阳帆板空间站的一种姿态定向模式 总被引:2,自引:0,他引:2
采用单轴双帆板供电和单框架控制力矩陀螺(SGCMG)作为执行机构的倾斜轨道空间站,当太阳方向与轨道面夹角较大时,帆板的光照条件不易保证,为此本文针对这种类型的空间站设计了一种姿态定向模式以保证帆板的光照条件,并通过在阴影区姿态机动,利用重力梯度力矩对SGCMG进行卸载。仿真结果表明,该姿态定向模式满足太阳帆板的光照条件,重力梯度力矩卸载方法保证了SGCMG中的角动量不超出给定的范围。 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2020,65(7):1772-1780
Doppler frequency estimation with high accuracy is very important for precise orbit determination and scientific studies in deep space exploration. In this paper, we propose a new method which implements cross correlation of only received signals from one single station to estimate Doppler frequency. The algorithm is relatively simple and it can achieve high accuracy even when signal to noise ratio (SNR) is very low. Moreover, the accuracy can be further improved by implementing frequency compensation, especially when the frequency dynamic range is high. Simulations were performed and results proved the validity of this method. X-band observations on MEX (Mars Express) and Juno were performed by a 13 m telescope of Wuhan University, which was equipped by two back ends, i.e. CDAS (Chinese Data Acquisition System) and RSR (Radio Science Receiver). Raw data recorded by the CDAS were processed by using the proposed method, and the estimated frequencies were in good agreement with the real time frequency estimation values by the RSR. What’s more, the accuracy by using cross correlation was higher than the one of RSR. 相似文献
305.
Nabeel Ahmad Samia F. Gurmani Riffat M. Qureshi Talat Iqbal 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(2):927-936
The atmospheric electric Potential Gradient (PG) variation of fair-weather days at Muzaffarabad (MZF, Northern Pakistan) station is presented for the period of January 2015–October 2017. The present investigations focus on the diurnal variation of atmospheric PG on the seasonal and annual time scale. The fair-weather seasonal and annual average PG variation has revealed two peaks, i.e. a primary maximum peak and a secondary maximum peak. The average maximum PG value found is ~410?Vm?1. The results are then compared with the well-known standard oceanic Carnegie curve. The diurnal curve of PG is found to deviate from the Carnegie curve. The seasonal PG variation at MZF shows lower values during the summer (monsoon) and autumn (post-monsoon) as compared to the winter and spring (pre-monsoon) which could be due to local aerosol concentration. Global comparison of PG (%) values of the annual mean at different longitude, with MZF observatory, shows local morning and evening peaks depicting local sunrise and sunset effects on the PG. The overall outcomes will certainly contribute to further investigate the Global Electric Circuit (GEC). 相似文献
306.
2010年我国房地产业的政策导向与发展趋势 总被引:2,自引:0,他引:2
房地产业是我国国民经济发展的支柱产业,确保房地产业健康稳定发展不仅有助于我国抵御经济危机,而且是预防通胀的重要措施.在我国经济复苏这段时期内,国家将对房地产市场进行结构优化,包括支持保障性住房的发展、遏制投机行为、科学测算用地指标、严格规范土地储备、打击"囤地"行为等,以达到房地产市场和谐稳定发展的目标. 相似文献
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Low earth orbit has become increasingly congested as the satellite population has grown over the past few decades, making orbital debris a major concern for the operational stability of space assets. This congestion was highlighted by the collision of the Iridium 33 and Cosmos 2251 satellites in 2009. This paper addresses the current state of orbital debris regulation in the United States and asks what might be done through policy change to mitigate risks in the orbital debris environment. A brief discussion of the nature of orbital debris addresses the major contributing factors including size classes, locations of population concentrations, projected satellite populations, and current challenges presented in using post-mission active debris removal to mitigate orbital debris. An overview of the current orbital debris regulatory structure of the United States reveals the fragmented nature of having six regulating bodies providing varying levels of oversight to their markets. A closer look into the regulatory policy of these agencies shows that, while they all take direction from The U.S. Government Orbital Debris Mitigation Standard Practices, this policy is a guideline with no real penalty for non-compliance. Various policy solutions to the orbital debris problem are presented, ranging from a business as usual approach to a consolidated regulation system which would encourage spacecraft operator compliance. The positive aspects of these options are presented as themes that would comprise an effective policy shift towards successful LEO conservation. Potential economic and physical limitations to this policy approach are also addressed. 相似文献
308.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014,54(2):221-240
The pace of scientific exploration of our solar system provides ever-increasing insights into potentially habitable environments, and associated concerns for their contamination by Earth organisms. Biological and organic-chemical contamination has been extensively considered by the COSPAR Panel on Planetary Protection (PPP) and has resulted in the internationally recognized regulations to which spacefaring nations adhere, and which have been in place for 40 years. The only successful Mars lander missions with system-level “sterilization” were the Viking landers in the 1970s. Since then different cleanliness requirements have been applied to spacecraft based on their destination, mission type, and scientific objectives. The Planetary Protection Subcommittee of the NASA Advisory Council has noted that a strategic Research & Technology Development (R&TD) roadmap would be very beneficial to encourage the timely availability of effective tools and methodologies to implement planetary protection requirements. New research avenues in planetary protection for ambitious future exploration missions can best be served by developing an over-arching program that integrates capability-driven developments with mission-driven implementation efforts. This paper analyzes the current status concerning microbial reduction and cleaning methods, recontamination control and bio-barriers, operational analysis methods, and addresses concepts for human exploration. Crosscutting research and support activities are discussed and a rationale for a Strategic Planetary Protection R&TD Roadmap is outlined. Such a roadmap for planetary protection provides a forum for strategic planning and will help to enable the next phases of solar system exploration. 相似文献
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The envisaged future space research programmes, whether in the field of space exploration or Earth observation are becoming more and more technically complicated and so costly that a single nation can hardly afford to realize them. Major non-European space-faring nations, China and India will progressively play an important role besides US, Russia and Japan. The Space Advisory Group of the European Commission recommended that the European Commission supports within Horizon 2020 a comprehensive Robotic Mars-Exploration Programme under European leadership that should become an essential element of a coordinated international space research programme. The International Space Station (ISS) experience shows that cooperative space programmes build links between industries and laboratories from around the world, which then further develop in non-space related activities, with positive impact on the economy and scientific research. Strategies need to be developed to mitigate the gradual increasing risks incurred by climate change. In order to lower their entry barrier to engage in space emerging and developing space nations need to be included in cooperative space programmes. We present the recommendations of the Space Advisory Group of the European Commission concerning Europe's participation to global space endeavours. 相似文献