You could use a thermometer.
4,500 degrees Fahrenheit
You didn't answer the question, and are still severely misunderstanding the laws of thermodynamics. So I'll do what your teachers didn't.
The temperature of any given are molecule may be up to 2,000 C, but since there are so few molecules at that height a satellite is hardly affected by them.
When two initially isolated systems in separate but nearby regions of space, each in thermodynamic equilibrium with itself but not necessarily with each other, are then allowed to interact, they will eventually reach a mutual thermodynamic equilibrium. The sum of the entropies of the initially isolated systems is less than or equal to the total entropy of the final combination.
So you are saying the sun doesn't heat up the satellites, because there is very little air in the thermosphere? Then why is it so hot up there?
Does the sun only heat up air? But not satellites?
Radiated infrared waves are not absorbed by the spacecraft (metal) at the same rate as the atmosphere (gas molecules). A few gas molecules can absorb enough infrared waves to reach a given temperature much faster than the spacecraft. Not to mention that the hot part of the spacecraft is continually radiating that heat back into space (clear when looking at orbital decay rates vs expected) as well as trying to reach equilibrium with the cold (unlit) site of the space craft.
tl;dr - the difference between radiated heat and conducted heat
(post is archived)