The BIRD Satellite Mission as a Milestone Towards GPS-based Autonomous Navigation

Abstract

This paper describes the onboard navigation system (ONS) for the German BIRD (Bi-spectral InfraRed Detection) microsatellite. BIRD is a technology satellite used for autonomous detection and indentification of hot spots such as forest fires or volcanic activities. The ONS computes the instantaneous nadir and flight direction for camera pointing, as well as precise positions for real-time geocoding of image data. Using a GPS Embedded Module (GEM)-S five-channel coarse/acquisition (C/A)-code receiver and an extended Kalman filter, the system performs dynamic orbit determination and provides smooth trajectory data with a nominal accuracy of 5 m during continuous GPS data takes. A 100 m accuracy is achieved in prediction arcs of up to 30 min. In parallel, the ONS performs a real-time estimation of SGP4 mean elements, which allows an onboard forecast of ground station contracts or eclipse times, as well as the downlink of North American Aerospace Defense Command (NORAD)-compatible two-line element sets for autonomous ground station operation.