Why is thermal control critical for spacecraft?

Spacecraft experience extreme thermal environments: intense solar heating (1361 W/m2 at Earth), cold deep space (-270C), and eclipse transitions. Components have limited operating temperature ranges (electronics: -40 to +85C typical). Thermal control maintains acceptable temperatures through: Passive methods - coatings (white paint, gold foil), insulation (MLI blankets), radiators, heat pipes, and thermal mass; Active methods - heaters, louvers, heat pumps, and fluid loops. Challenges include: Large temperature swings between sun/shadow, Heat generated by electronics, Variable orientation, and Long mission life without maintenance. Proper thermal design prevents component damage, maintains performance, and ensures mission success.