Lessons Learned from FORMOSAT-2 Mission Operations

Paper number

IAC-05-B5.4.05

Author

Dr. Jeng-Shing Chern, National Space Organization, Taiwan, China

Year

2005

Abstract

FORMOSAT-2 (formerly called ROCSAT-2) is the first Earth observation satellite owned by Taiwan. It is a small satellite of 765 kg with high resolution capability of 2 m ground sampling distance (GSD) for panchromatic band and 8 m GSD for multi spectral bands. After successful launch on 20 May 2004, the checkout and commissioning of the satellite had been completed in July of the same year. Normal mission operations (MO) was then started. The National Space Organization (NSPO) of Taiwan is responsible for the operations. Up to now, 66 anomalies related to the satellite and MO have been collected. Some of them are categorized as major. The purpose of this paper is to present the lessons NSPO learned from the MO of FORMOSAT-2.
   For 6 times, the star tracker (STR) onboard has been switched off when the updating of EPOCH is completed Sunday morning. Another time the mode of STR is changed from operation to standby. On the average, one anomaly on STR occurs per month. After detailed analysis, it is found the updating of EPOCH only reduces the pointing error by 89 m. Therefore it is decided not to perform the updating activity.
   For 3 times, the innovation attitude estimator (IAE) has provided pronounced errors and caused the automatic reconfiguration order (ARO) of the satellite. Detailed investigation found that when there is star signal along the bore sight of STR, the IAE gives wrong attitude value. This phenomenon is still under investigation. 
   The most particular characteristics of FORMOSAT-2 is its daily repetitive capability. Its orbit is sun-synchronous with 891 km altitude and exactly 14 revolutions per day. At the beginning, NSPO sent commands to the satellite and received images from it once per day. It was found that re-imaging commands can only be sent the other day. The fact is that the satellite becomes bi-daily repetitive instead of daily repetitive. After analysis, NSPO changes the strategy from one time to two times for commands sending. FORMOSAT-2 has shown its complete daily repetitive capability then.
     

Abstract document

IAC-05-B5.4.05.pdf

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