Multi-frequency same-beam VLBI means that two explorers with a small separation angle are simultaneously observed with the main beam of receiving antennas. In the same-beam VLBI, the differential phase delay between t...Multi-frequency same-beam VLBI means that two explorers with a small separation angle are simultaneously observed with the main beam of receiving antennas. In the same-beam VLBI, the differential phase delay between two explorers and two receiving telescopes can be obtained with a small error of several picoseconds. The differential phase delay, as the observable of the same-beam VLBI, gives the separation angular information of the two explorers in the celestial sphere. The two-dimensional relative position on the plane-of-sky can thus be precisely determined with an error of less than 1 m for a distance of 3.8×105 km far away from the earth, by using the differential phase delay obtained with the four Chinese VLBI stations. The relative position of a lunar rover on the lunar surface can be determined with an error of 10 m by using the differential phase delay data and the range data for the lander when the lunar topography near the rover and the lander can be determined with an error of 10 m.展开更多
Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLB...Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLBI,the differential phase delay between the two spacecrafts and the two receiving antennas can be obtained within a small error of several picoseconds. As a successful application,the short-arc orbit determination of several hours for Rstar and Vstar,which are two small sub-spacecrafts of SELENE,has been much improved by using the same-beam VLBI data together with the Doppler and range data. The long-arc orbit determination of several days has also been accomplished within an error of about 10 m with the same-beam VLBI data incorporated. These results show the value of the same-beam VLBI for the orbit determination of multi-spacecrafts. This paper introduces the same-beam VLBI and Doppler observations of SELENE and the orbit determination results. In addition,this paper introduces how to use the same-beam VLBI for a lunar sample-return mission,which usually consists of an orbiter,a lander and a return unit. The paper also offers the design for the onboard radio sources in the lunar sample-return mission,and introduces applications of S-band multi-frequency same-beam VLBI in lunar gravity exploration and applications during all stages in the position/orbit determinations such as orbiting,landing,sampling,ascending,and docking.展开更多
The same-beam VLBI observations of Rstar and Vstar,which were two small satellites of Japanese lunar mission,SELENE,were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle b...The same-beam VLBI observations of Rstar and Vstar,which were two small satellites of Japanese lunar mission,SELENE,were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle between Rstar and Vstar was less than 0.1 deg,the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms,which was reduced by 1-2 order compared with the former VLBI results. When the separation angle was less than 0.56 deg,the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed,and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft,and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.展开更多
When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The rel...When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.展开更多
G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确...G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确定了测地VLBI和航天器VLBI观测模式下射电源流量密度的要求。在此基础上建立了2种观测模式下时延误差与深空干涉测量天线G/T之间的关系模型。最后参考目前国际国内测地VLBI观测中的通用参数设置以及月球探测任务中航天器VLBI观测的参数设置,对不同观测任务、不同观测模式下的G/T要求进行仿真分析。综合测地VLBI和航天器VLBI观测仿真分析的结果,S频段G/T建议不小于32dB/K,X频段G/T建议不小于43dB/K。仿真分析结果可以作为后续深空干涉测量天线G/T设计的参考。展开更多
基金supported by the ‘100 Talents Project’ of Chinese Academy of Sciences, China
文摘Multi-frequency same-beam VLBI means that two explorers with a small separation angle are simultaneously observed with the main beam of receiving antennas. In the same-beam VLBI, the differential phase delay between two explorers and two receiving telescopes can be obtained with a small error of several picoseconds. The differential phase delay, as the observable of the same-beam VLBI, gives the separation angular information of the two explorers in the celestial sphere. The two-dimensional relative position on the plane-of-sky can thus be precisely determined with an error of less than 1 m for a distance of 3.8×105 km far away from the earth, by using the differential phase delay obtained with the four Chinese VLBI stations. The relative position of a lunar rover on the lunar surface can be determined with an error of 10 m by using the differential phase delay data and the range data for the lander when the lunar topography near the rover and the lander can be determined with an error of 10 m.
文摘Same-beam VLBI means that two spacecrafts with small separation angles that transmit multi-frequency signals specially designed are observed simultaneously through the main beam of receiving antennas. In same-beam VLBI,the differential phase delay between the two spacecrafts and the two receiving antennas can be obtained within a small error of several picoseconds. As a successful application,the short-arc orbit determination of several hours for Rstar and Vstar,which are two small sub-spacecrafts of SELENE,has been much improved by using the same-beam VLBI data together with the Doppler and range data. The long-arc orbit determination of several days has also been accomplished within an error of about 10 m with the same-beam VLBI data incorporated. These results show the value of the same-beam VLBI for the orbit determination of multi-spacecrafts. This paper introduces the same-beam VLBI and Doppler observations of SELENE and the orbit determination results. In addition,this paper introduces how to use the same-beam VLBI for a lunar sample-return mission,which usually consists of an orbiter,a lander and a return unit. The paper also offers the design for the onboard radio sources in the lunar sample-return mission,and introduces applications of S-band multi-frequency same-beam VLBI in lunar gravity exploration and applications during all stages in the position/orbit determinations such as orbiting,landing,sampling,ascending,and docking.
基金Supported by the National Natural Science Foundation of China (Grant No. 10973031)the CAS Key Research Program (Grant No. KJCX2-YW-T13-2)
文摘The same-beam VLBI observations of Rstar and Vstar,which were two small satellites of Japanese lunar mission,SELENE,were successfully performed by using Shanghai and Urumqi 25-m telescopes. When the separation angle between Rstar and Vstar was less than 0.1 deg,the differential phase delay of the X-band signals between Rstar and Vstar on Shanghai-Urumqi baseline was obtained with a very small error of 0.15 mm rms,which was reduced by 1-2 order compared with the former VLBI results. When the separation angle was less than 0.56 deg,the differential phase delay of the S-band signals was also obtained with a very small error of several mm rms. The orbit determination for Rstar and Vstar was performed,and the accuracy was improved to a level of several meters by using VLBI and Doppler data. The high-accuracy same-beam differential VLBI technique is very useful in orbit determination for a spacecraft,and will be used in orbit determination for Mars missions of China Yinghuo-1 and Russia Phobos-grunt.
基金supported by the Hundred Talent Project(s) of Chinese Academy of Sciencesthe National Natural Science Foundation of China (Grant Nos.11073048 and 11073047)+1 种基金the Pujiang Project of Shanghai (Grant No.10PJ1411700)Shanghai Key Laboratory of Space Navigation and Position Techniques (Grant No.Y054262001)
文摘When only data transmission signals with a bandwidth of 1 MHz exist in the rover, the position can be obtained using the differential group delay data of the same-beam very long baseline interferometry (VLBI). The relative position between a lunar rover and a lander can be determined with an error of several hundreds of meters. When the guidance information of the rover is used to determine relative position, the rover's wheel skid behavior and integral movement may influence the accuracy of the determined position. This paper proposes a new method for accurately determining relative position. The differential group delay and biased differential phase delay are obtained from the same-beam VLBI observation, while the modified biased differential phase delay is obtained using the statistic mean value of the differential group delay and the biased phase delay as basis. The small bias in the modified biased phase delay is estimated together with other parameters when the relative position of the rover is calculated. The effectiveness of the proposed method is confirmed using the same-beam VLBI observation data of SELENE. The radio sources onboard the rover and the lander are designed for same-beam VLBI observations. The results of the simulations of the differential delay of the same-beam VLBI observation between the rover and the lander show that the differential delay is sensitive to relative position. An approach to solving the relative position and a strategy for tracking are also introduced. When the lunar topography data near the rover are used and the observations are scheduled properly, the determined relative position of the rover may be nearly as accurate as that solved using differential phase delay data.
文摘G/T是天线的一项重要技术指标,在综合考虑测地VLBI(Very Long Baseline Interferometry,甚长基线干涉测量)和航天器VLBI观测两者需求的基础上,提出了深空干涉测量天线的G/T指标设计方法。首先根据射电源的空间分布以及流量密度特性,确定了测地VLBI和航天器VLBI观测模式下射电源流量密度的要求。在此基础上建立了2种观测模式下时延误差与深空干涉测量天线G/T之间的关系模型。最后参考目前国际国内测地VLBI观测中的通用参数设置以及月球探测任务中航天器VLBI观测的参数设置,对不同观测任务、不同观测模式下的G/T要求进行仿真分析。综合测地VLBI和航天器VLBI观测仿真分析的结果,S频段G/T建议不小于32dB/K,X频段G/T建议不小于43dB/K。仿真分析结果可以作为后续深空干涉测量天线G/T设计的参考。
