How do eclipse periods affect spacecraft operations and design?

Eclipse occurs when spacecraft passes through Earth's shadow, losing solar input. Impacts: Power - Solar arrays produce zero power, batteries must supply all loads, Maximum eclipse duration drives battery sizing; Thermal - Rapid temperature drop (can be 100+ degrees), Heaters activate to prevent cold damage, Battery discharge creates less internal heat; Attitude - Sun sensors unavailable, possible thermal distortion of structures; and Communications - Possible RF blackout with certain geometries. Design considerations: Battery depth-of-discharge limits, Heater power allocation, Component cold operational limits, and Safe mode design during eclipse. Orbit effects: LEO has frequent short eclipses (up to 35 min per 90 min orbit), GEO has long eclipses near equinoxes (up to 72 min), and High elliptical orbits have variable eclipse. Dawn-dusk sun-synchronous orbits minimize or eliminate eclipse.