Mariner IV used a system that was sort of like what Jacob described. Rather than an umbrella, Mariner IV had an arrangment like Venetian blinds around the exterior of the vehicle's chassis. The Venetian blinds would open or close depending upon how hot the vehicle got locally thus changing how much heat was radiated away to deep space or abosrbed. Mariner IV was three-axis stabilized with the option of spin stabilization. It was possible for parts of the vehicle to continually face the sun or deep space thus getting quite hot or cold. Mariner IV's design heritage was used in Mariner's V - IX as well as the Viking orbiters. I do not know if those vehicles used the same thermal control system. I know the Russian orbit buses were liquid cooled with big radiators. Pathfinder and MER use and used a small plutotonium based radioactive heaters (like little RTGs). The Beagle-II uses electrical resistance and liquid-solid phase change in its batteries to provide heat while on the Martian surface. As far as I know (?), Beagle-II has no active thermal control while in interplanetary space. I find it hard to believe they will have it hit the Martian atmosphere with its electronics at typical deep space cold soak temperature (-40 to -68 deg.C). The inner wall temperature of Mars Pathfinder's heat shield when it hit the Martian atmosphere was -64 deg.C. Mars Pathfinder's electronics continued to operate because they were warmed by the little plutonium heat sources (one of them is about the size of a quarter). Radical environmentalists like to fuss about these heat sources (it's the N-word afterall). Some radical environmentalists believed that one of these heat sources could end all life on the Earth if it accidently reentered our atmosphere. The lunar ascent module (Apollo vehicle) had a big plutonium RTG in its descent stage for powering the ALSEP (cooling it was an issue). A large slug of plutonium landed in the Pacific with the burned up remains of Apollo 13's LM. For some odd reason, all life on the Earth did not end as a result (maybe it was a hoax).

Gary