Methods for the Orbit Determination of Tethered Satellites in the Project QPS
- Paper number
IAC-05-C1.7.08
- Author
Dr. Yuji Sakamoto, Tohoku University, Japan
- Coauthor
Mr. Yotsumoto Kazuhiko, Kyushu University, Japan
- Coauthor
Mr. Kazunori Sameshima, Japan
- Coauthor
Prof. Masanori Nishio, Japan
- Year
2005
- Abstract
In this study, a new method for the orbit determination of tethered satellites is proposed, then the validity when supposing actual ground observatories are verified. The characteristic of method is that the center-of-mass motion of tethered satellites and the in-plane and out-of-plane librational motion can be stably determined even if the observation span is long like about one weak. In addition, the validity of method is shown for the both cases of utilizing a low-cost ground station for amateur radio satellites and utilizing a high-precision radio interferometer. Q-shu Piggyback Satellite (QPS) is the project of industry-academic-government collaboration which is composed of universities, and medium and small-sized enterprises in the Kyushu district of Japan. At the present time, the QPS is supporting the project of tethered microsatellites QTEX (Kyushu University Tethered Satellite Experiment) from financial and technological aspects. The QTEX, which total mass is less than 50 kg, is being developed under the leadership of Kyushu University. It is composed of two satellites which are connected by a 2-km tether and which have similar shape and mass. It is the peculiarity to conventional tethered satellites that each satellite has bus hardware like as a general single satellite. The verification experiment of new tether deployment technology is the primary mission, and several science missions are carried out. The completion of the QTEX is scheduled for the first half of 2006. The QPS is planning to develop the series of tethered microsatellites which is based on the QTEX. The problem for the orbit determination of tethered satellites must be solved for the project QPS. The processing algorithm of current ground observatories is supposing that the target object is moving in accordance with the Kepler's motion. In the case of tethered satellites, the target object does not accord with the Kepler's motion while the center-of-mass motion of two satellites accords with it. Therefore, the motion of tethered satellites cannot be determined by the conventional methods for the orbit determination of a single satellite. In this study, a new method for the orbit determination of tethered satellites is proposed. The characteristic of method is that the center-of-mass motion of tethered satellites and the in-plane and out-of-plane librational motion can be stably determined even if the observation span is long like about one weak. In this method, either of two tethered satellites should be observed, which observation sources are range, range-rate, or azimuth and elevation. This method can be utilized for many kinds of space tether systems. In addition, the validity when supposing actual ground observatories is verified. Kyushu University has a low-cost ground station for amateur radio satellites, and satellite orbits can be determined from the observations of beacon-signal frequency by using a low-cost spectrum analyzer. On the other hand, Kagoshima University has a high-precision radio interferometer which is composed of the three parabola antennas of 1.4-m diameter, and three antennas are perpendicularly placed at 60-m intervals. By using this system, the beacon-signal frequency and the arrival time lag at three antennas can be measured. These observatories are used for the orbit determination of the QTEX. In numerical analyses, the orbit determination is stably successful when supposing the initial condition of 30-deg in-plane and 30-deg out-of-plane librational motion. In this study, the method for the orbit determination of tethered satellites is established, which model includes out-of-plane librational motion. This fact is peculiarity to conventional papers and it is expected that this method can be utilized in actual operations with little modification. At the present time, the ability of method is being investigated for the case studies of utilizing observatories of Kyushu University and Kagoshima University. In addition, the radio interferometer in Kagoshima University is utilized not only for the orbit determination but also for the observation of atmospheric water vapor which is primary objective of this observatory. Therefore, the correlation between the orbit determination and the scientific observation are also investigated.
- Abstract document
- Manuscript document
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