FLIGHT RESULTS FROM THE BIRD ONBOARD NAVIGATION SYSTEM

摘要

The German small satellite BIRD carries an elaborate GPS-based Onboard Navigation System (ONS) which provides precise real-time orbit determination as well as orbit and event prediction capabilities. The ONS supports the BIRD Attitude Control System to allow for a nadir pointing of the spacecraft during payload image sessions and enables a geocoding of BIRD sensor images on-the-flight. The analysis of the BIRD ONS flight data indicates an orbit determination accuracy of 5 m for position and 0.006 m/s for velocity. In the absence of GPS data for a two hour period, the ONS predicts the BIRD position with an accuracy of better than 110m. In addition to the ONS, a Real-time Twoline Generator is operated which estimates Twoline elements from GPS data onboard the spacecraft. This enables orbit forecasts over one week with timing errors of less than 5 s.