Thermal Study of Laser Interferometer Space Antenna (Lisa)

The objective of the Laser Interferometer Space Antenna (LISA) mission is the detection of low-frequency gravitational waves. The fluctuation of the distance of test masses inside 3 spacecraft’s which are located 5·10⁶km apart is measured with an accuracy of 10⁻¹²m to achieve this. This requires very stringent temperature stability. Variations of solar constant, dissipation and the response to switching/mode changes cause temperature fluctuations that have to be suppressed.

The spacecraft thermal design relies on a solar array as a sun shield with good thermal de-coupling between the solar cells and the structure and rejection of heat from the electronics directly to space. MLI is avoided because of its potentially unstable insulation properties.

Transient analyses were performed with a temperature accuracy of 10⁻⁸ K. It was found that the fluctuations caused by the solar constant are sufficiently damped. Correlated electronic unit dissipations within the payload must be stable within about 0.2 %. Mode changes of bus units may not change dissipation by more than 0.5W.