It'll likely stay a few degrees below ambient. Ordinarily, that doesn't happen because the surroundings are emitting and absorbing infrared roughly in balance w

It'll likely stay a few degrees below ambient. Ordinarily, that doesn't happen because the surroundings are emitting and absorbing infrared roughly in balance with things at the same temperature, but if you can make a material that emits most of its infrared at a particular frequency that the atmosphere is nearly transparent to, its heat will leak out into space.