Satellites, for the most part, do not emit light. Instead, they reflect light. Thus, other than portions of that light that are absorbed by the various reflective surfaces of the satellite, the spectra measured will be that of the light source shining upon them.
When satellites are bright enough to be seen at night on the earth's surface, the light is usually being reflected by antennae or solar panels that act very much like mirrors without absorbing much of any of the light falling on them. We can see them because though we are standing in the dark after the terminator between daylight and dark has passed our position, the satellites in orbit above our heads are high enough to still be bathed in sunlight.
In other words, it will look pretty much like what one gets when they measure the spectrum of our sun, Sol.