Thermal design and performance of HAMSAT

HAMSAT is a micro-satellite for providing satellite-based Amateur Radio services to the national as well as the international community of Amateur Radio Operators (HAMs). Micro-satellites (less than 100 kg) are becoming increasingly utilized as an economical means of experimentation and research in orbit. The thermal control of micro-satellite presents unique challenges to the thermal engineer since the mass; power and volume available are all very limited. Regardless of these problems and the extreme environments and changing power conditions (internally and externally) of the satellites the subsystems must still be maintained within the specified temperature limits. HAMSAT spins about an axis perpendicular to orbital plane and is placed in 632 × 621 km altitude sun-synchronous orbit. The three new technologies experimented in the spacecraft are lithium-ion batteries, Bus Management Unit and multi junction gallium arsenide solar cells in LEO orbit. A purely passive thermal control system without heaters is used to control the temperature of the spacecraft. Thermal design and on-orbit temperature characteristics are presented and discussed. The spacecraft has completed one year of operation on orbit. The on orbit thermal performance of the spacecraft is good and matches well with the prediction. Impact of variation in thermal parameters on temperature is discussed.