Autonomous navigation and guidance on-board earth-observation mini-satellites

In an attempt at reducing ground operation costs and ensuring a better management of onboard resources, Earth-observation mini-satellites are now relying on the autonomous onboard execution of functions that were normally performed by ground operators. The European Space Agency is currently developing technologies that will enable such onboard autonomous mission management and operation planning. These technologies will be evaluated in a real scenario on-board the PROBA mini-satellite, to be launched in the fall of 2001. The satellite is currently undergoing final integration at Verhaert Design and Development (Belgium), while the on-board guidance, navigation and control software of the Attitude Control and Navigation System (ACNS) is being developed and validated at the Universite de Sherbrooke (Canada). In addition to the demonstration of space autonomy, the PROBA spacecraft will perform an Earth remote-sensing mission with its Compact High Resolution Imaging Spectrometer (CHRIS) payload. In order to increase the imaging performance of the payload, multiple scans of the same scene need to be performed with high accuracy by the on-board ACNS. The required attitude manoeuvres are planned and executed autonomously on board, for any target-spacecraft geometries, with no support from ground operators. In a recent presentation (Ref. 1), an overview of the PROBA mission and the ACNS was described. This paper presents in detail the onboard navigation (state-determination) and guidance (attitude command generation) flight software that has been developed in support to the highly autonomous nature of the mission. Simulation results illustrate the performance of the algorithms. The techniques for on-board attitude command generation presented here can be extended to any autonomous imaging mission.