ESA GNC Conference Papers Repository

SOLAR is an external payload of the International Space Station (ISS), mounted on the Columbus External Payload Facility (CEPF) of the Columbus Attached Pressurised Module (APM). It consists of the Coarse Pointing Device (CPD), a two-axis pointing platform, which points the three science instruments mounted upon it to the Sun. SOLAR was delivered to the ISS by the Space Shuttle STS-122 mission, launched on February 7th, 2008. This paper describes the design and architecture of the CPD Pointing Control System, including a discussion of hardware and software issues. The fully autonomous Pointing Control System is designed to track the Sun with an accuracy of 1 degree and a pointing stability of 0.3 degree over 10 seconds. It predicts the position of the Sun and orientates the CPD such that the Sun may be quickly acquired at the start of each observation period, nominally 20 minutes. The Sun is tracked up to the mechanical limits of ±25 and ±40 degrees, at which point the CPD returns to its home orientation. On orbit performances will be compared with on ground tests and simulations. Lessons learnt from AIT and commissioning will be highlighted.