What thermal coatings are used on spacecraft and how are they selected?

Thermal coatings control surface radiative properties - absorptivity (alpha, solar) and emissivity (epsilon, IR). Types: White paint - low alpha (~0.2), high epsilon (~0.9), good for radiators; Black paint - high alpha, high epsilon, thermal balance surfaces; Gold/aluminum tape - low alpha, low epsilon, reflects solar and IR; Optical Solar Reflectors (OSR) - very low alpha, high epsilon, best radiator performance. Selection based on: Desired temperature (hot surfaces: low alpha; cold: high alpha), Thermal control strategy, and Degradation characteristics (UV, atomic oxygen, contamination). Second surface mirrors minimize alpha while maximizing epsilon. Solar absorber coatings used for thermal generation. Thermal coatings are first defense against space environment. End-of-life properties (typically degraded alpha) used for design margin. Testing characterizes optical properties before and after environmental exposure.