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- Title
Development and Ground Evaluation of Fast Tracking Algorithm for Star Trackers.
- Authors
Yuji SATO; Toshinori KUWAHARA; Shinya FUJITA; Yuji SAKAMOTO; Kazuya YOSHIDA
- Abstract
Fast tracking algorithm discussed in this paper is applied to star trackers for improving the performance of star identification. Space Robotics Laboratory (SRL) in Tohoku University has developed star trackers for micro-satellites so far. Since it has only a lost-in-space algorithm for star identification, the attitude update rate is limited up to 1 Hz. It was implemented to the Philippines' 50 kg-class micro-satellite "DIWATA-1" released from the International Space Station on April 2016. Although on-orbit evaluation showed good results enough to output attitude autonomously, the performance of continuous attitude determination was worse than expected. Since quite a high access frequency of star catalog is required, timeout of the process for attitude calculation occurs frequently even if update rate is 1 Hz. Insufficient ground evaluation before launch is also one of the causes of operation failure. Tracking algorithm helps to calculate latest attitude faster than conventional methods by feeding back the previous attitude information. This algorithm includes two additional processes. First, future star positions on the image frame can be predicted according to the previous attitude and pre-identified star information. The sensor can find corresponding latest centroids compared to predicted star positions. Second, un-identified stars on the camera field of view (FOV) can be detected by referring to the star neighborhood catalog, which includes the list of some adjacent star IDs against each reference star. PC simulation shows that continuous attitude determination works effectively by keeping low catalog access frequency. The proposed algorithm is implemented to the real hardware. Then, ground evaluation is conducted using star simulator environment and satellite dynamics simulator. The result demonstrates that the processing speed in real situation becomes about 70 times faster compared to the previous method and it is successful to obtain much more stable 1 Hz attitude output.
- Subjects
ALGORITHMS; STAR trackers; REMOTE sensing equipment; ROTATIONAL motion; IMAGE processing
- Publication
Transactions of the Japan Society of Aeronautical & Space Sciences, Aerospace Technology Japan, 2018, Vol 16, Issue 3, p202
- ISSN
1884-0485
- Publication type
Article
- DOI
10.2322/tastj.16.202