The Potential of VSOP2
WEI ERHU, LIU JINGNAN, YAN WEI
Results and analyses
Observing time is the guarantee of baseline observation. In the simulation, the observing time of HR-7745 by VSOP2 satellite is 79501.476 seconds, accounts for 92.02% of the simulation time. The observing time and proportion of each telescope is: Beijing, 11148.078 seconds,12.90% Shanghai, 23077.354 seconds, 26.71% Guizhou, 27132.087 seconds, 31.42% Kunming, 28297.055 seconds, 32.75% Urumqi, 0 seconds, 0%. The observing time of radio telescopes in China is decreased by the increasing latitude and longitude. Especially for Urumqi radio telescope, it can’t undertake the mission of tacking radio source in south sky.
According to the observing time, there are the most 4 baselines can be formed from 1 Jun 2008 18:18:27.371 to1 Jun 2008 19:55:06.457. The observing time is 5771 seconds and accounts for 6.68% of the simulation time. The observing time and proportion of different number of baselines is listed in Table 4.
According to the results above, three observation stations’ observing time which can form baselines with the satellite is more than an orbit period in the simulation, excluding radio telescopes in Beijing and Urumqi. The observing time is long enough for observation. In the simulation, Kunming and Guizhou can form baseline with VSOP2 satellite when it is in the apogee (it is shown in Fig 6 in which VSOP2 and HR-7745 are both projection of Sub-satellite point). So the length of baseline can be longer than 31000 km. The angular resolution can achieve 0.086 seconds by calculating with a radio wave length of 13 cm. The conclusion is considerable.
The simulant results of VSOP in the same time are listed in Table 5. According to the results, the VSOP2’s ability of observing radio sources in the south sky is improved.
In the simulation, only radio telescopes in China are considered. The observing results will be better if there are more radio telescopes all over the world. According to the observing time of simulant radio source, the observing ability of radio source in the south sky is one designing purpose of VSOP2. The observation of radio sources in this area is a weakness of Chinese radio telescopes. The use of VSOP2 is hopeful to improve it.
According to the three simulations above, an elementary conclusion can be made that the ability of VSOP2 in the applications of geodetic research has been improved obviously. First, the average accuracy of OD is less than 0.5 m by GNSS system. It is achieved the requirement of applications for geodetic studies. Second, the proportion of tracking time of satellite by observation station is over 85%. It ensures the transmission of observing data and controling command. Finally, the observing ability of radio sources in the south sky is improved.
It is just considered the improvement of VSOP2’s orbit design in this paper. The improvement of satellite structure is ignored. Considering the scarcity of data and information, we believe that more successful results can be achieved in further studying.
This research is funded by the national ‘973 Project’ of China (No. 2006CB701301), and the project of university education and research of Hubei province (20053039). And most of all, this paper is to my Indian friend Prof. Madhav N.Kulkarni who, in his life time,has made tremendous contributions in the researchment on geodesy, geodynamics, and GNSS applications.
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