Comment Re:Isn't space 'cold'? (Score 1) 153
Space doesn't really have a temperature. Temperature and conduction of heat requires particles to bump into each other. You feel something being hot because the molecules in it are moving very quickly. You feel something being cold because the molecules in it are moving slower. However in space there are (almost) no molecules.
Thus the only ways to lose and gain temperature are via radiation (not necessarily ionizing radiation), and internal heat generation. The sun is radiating energy onto the satellite and the satellite is radiating energy. However as the satellite isn't very hot, it doesn't radiate a whole lot, thus is tends to heat up.
All of the electronics on the satellite are producing heat as they work, and I suspect that this is where most of the heat of the satellite is coming from.
This isn't all that important for most satellites as they can work at higher temperatures, however the sensors on the WISE needs to be kept cold. Since the sensors on the WISE work in the infrared part of the electromagnetic spectrum, and all things radiate infrared (unless they're at absolute zero) if the sensors are too hot, they will just detect their own infrared radiation rather than the radiation from the objects in space.