In space, things tend to glow in infrared, a phenomenon called black-body radiation. So you could cover the side of the sat facing away from the sun in graphite, and the heat would dissipate naturally until it reaches equilibrium with incoming radiation. In deep space it is 2.7 degrees kelvin (colder than liquid helium), but the earth is 250 kelvin (-23 degrees Celsius). Keith Lofstrom goes into more detail at http://server-sky.com/cooling
