Validation of Innovative State Estimation and Control Techniques on PROBA-2

ABSTRACT PROBA-2 is an ESA technology-demonstration mission aimed at the demonstration of autonomy-enabling space technologies. This paper will describe the PROBA-2 mission, the Attitude and Orbit Control System (AOCS) software and its new features compared to its predecessor, PROBA-1. The simulations presented will also demonstrate some of the new estimation and control techniques to be validated on PROBA-2, including attitude and orbit determination using temperature, light and/or magnetic-field sensors, attitude and orbit estimation using a Square-Root Unscented Kalman Filter and the high-precision execution of large-angle maneuvers with a constrained rotation axis. 1 INTRODUCTION Although the on-board autonomy of spacecraft has already been demonstrated, its interest still remains for the international scientific community. Autonomy refers to the migration of intelligence and decision capability from the ground station to the spacecraft. The PRoject for On-Board Autonomy program (PROBA), sponsored by European Space Agency (ESA), aims at the demonstration of on-board autonomy-enabling technologies with the objectives of reducing mission-operation costs and maximizing the efficiency of spacecraft operation. The development of on-board autonomy has the potential benefits of better managing the limited on-board resources and reducing the ground station operating costs. In addition, it could benefit to future interplanetary missions where there is no Earth contact for extended duration. PROBA-2 is the second in-orbit demonstration mini-satellite developed by ESA. Following the success of PROBA-1, PROBA-2 will continue the in-flight demonstration of onboard-autonomy technologies while maintaining low development costs. PROBA-2 is an agile mini-satellite currently under development by Verhaert Space (Belgium), the Prime Contractor, supported by Spacebel informatique (Belgium) and NGC Aerospace Ltd (Canada). The launch is foreseen in early 2007. In order to fully demonstrate the technology in a real mission scenario, various payloads will be flown on PROBA-2 to exercise and validate the advanced autonomy capabilities of the spacecraft through a Sun-observation and space plasma mission. Following a brief description of the PROBA-2 mission, spacecraft and Attitude and Orbit Control System (AOCS) hardware, this paper will present the AOCS on-board software, and particularly, its new features compared to PROBA-1: large-angle rotation along a constrained axis, Earth avoidance detection and pseudo-measurements to deal with single-vector measurements. The paper will also present a progress report on new autonomy-enabling AOCS techniques, proposed by NGC Aerospace, to be validated in flight. These include the use of a Square-Root Unscented Kalman Filter (SRUKF) for attitude and orbit determination, the validation of a low-cost orbit determination based on temperature sensor and a magnetic-only orbit and attitude navigation system.