SUNSAT, Stellenbosch University and SA-AMSAT's Remote Sensing and Packet Communications Microsatellite

Abstract

The Engineering Model of SUNSAT, a 50 kg, 45 cm, Ariane ASAP-compatible microsatellite is scheduled for assembly in December 1993, permitting flight model completion early in 1995. Fifteen M.Eng. students, led by Computer & Control System lecturers at Stellenbosch University, began detail design in January 1992. Most prototype hardware was operating by July 1993, and assembly of the first final-sized PCB's started. A packet radio service, a 2m parrot speech transponder, and Mode A and S transponders, all defined and endorsed by SA-AMSAT, comprise the Amateur Radio communications payload. Verification of the 15-20 m pixel spacing, 3-color, 3456 pixel pushbroom imager capable of stereo imaging, is a major research goal. Data will be downlinked in S-band, or single images stored in a 64Mbyte RAM. Coarse attitude stabilization by gravity gradient and magnetorquing is improved by small reaction wheels during imaging. Continuous attitude sensing is by magnetometers. Sun sensors, visible band horizon sensors, and star sensor provide 1 mrad accuracy when imaging from the sun-synchronous orbit. Average power of 30 W enables images of South Africa to be taken on a daily basis for real time downlinking. Satisfaction of SA electronics companies on our Advisory Board with the engineering model will lead to continued student funding. Demonstration of a working engineering model will then hopefully provide the credibility we need to finalize a launch opportunity. The satellite's layout, block diagram, and expected performance of the imager, downlink, and Amateur packet communications payload are described.