What thermal effect does the Sun have on spacecraft that are roughly the same distance from the Sun as the Earth?
Specifically, do spacecraft need to constantly rotate so that one side doesn't get too hot and the other too cold?
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2$\begingroup$ "in orbit around Earth" and "the same distance from the Sun as Earth" are two very different situations (for instance, you spend an lot of time on the night side of the planet when in orbit). Which of them are you asking about? $\endgroup$– SE - stop firing the good guysJul 25, 2016 at 11:00
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2$\begingroup$ @Hohmannfan "roughly" is the key word here, and considering even GEO is all of a 0.03% variation in distance from the Sun, it's a fair assumption for things like solar flux, etc.. The question title specifically says "spacecraft in orbit around the Earth", so what are you actually confused about? $\endgroup$– ChrisJul 25, 2016 at 19:02
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$\begingroup$ Good point! I wasn't specifically thinking about the times the craft was in orbit, but more for objects that were roughly the same distance from the sun as the earth is. I should have corrected the title. $\endgroup$– Matt ParkinsJul 26, 2016 at 8:48
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It depends on the spacecraft and the instruments on-board. Obviously a spacecraft in direct sunlight will be gaining thermal energy from the sun. However, as it heats up the rate at which it radiates heat will also increase. There are ways to actively or passively control the temperature of a spacecraft; these are called thermal control systems. If none of the systems on your spacecraft are particularly sensitive to heat then you may not need a thermal control system.
Rotating a spacecraft is one way to distribute the heat, but it is more common to use heat pipes containing ammonia to distribute heat from one part of the spacecraft to the other. Other methods of thermal control on spacecraft include having radiator panels (like those seen on the ISS and on RTG's), sun shields, and use of cryogenics such as liquid helium. The James Webb Space Telescope will employ both a sun shield and liquid helium to keep its instruments cold.
