How do ICs work in satellites? Is the temperature in space not 3K? How does silicon gain enough energy to have sufficient free electrons at such low temperatures to behave as a semiconductor and not an insulator? Are ICs heated?
A satelite that is in direct sunlight, in earth orbit, can reach temps of +122 deg C. When in the shade it gets to -180 deg C. There are complicated heating and cooling systems to keep these things working. There are heaters to warm things up, and thermal radiators to keep things cool. Careful use of reflective foil sheets and thermal blankets help a great deal.
In many cases, the electronics are turned on at launch and not turned off (mostly ever). The heat of the electronics themselves, plus the insulating effects of the vacuum of space, might be enough by itself. Otherwise, what is used is very mission dependent.
Trivia Point: The big doors on the space shuttle cargo bay are actually thermal radiators. They are used to cool the shuttle while in orbit. They must open the doors within a certain time period after launch or the shuttle overheats.
2nd Trivia Point: The mars rovers have heaters in their batteries to keep them warm. If they get too cold, the batteries could fail and the whole thing will never power up again.
The temperature in space isn't like the temperature outside your house. In your normal experience, you lose heat through conduction and convection. In a vacuum, those don't really do much, leaving only radiation to transfer heat.
Anyways: most major components have heaters attached to their enclosures. One or two per instrument, some by the batteries, transceiver, star trackers, etc. Our earth orbiting spacecraft all float in the vicinity of normal room temperatures, when things are working ok.
The radiation environment is much more of an issue than the temperature.