Terra Engineering Breakdown

Terra launched in 1999 as the flagship of NASA's Earth Observing System. Instead of treating the atmosphere, oceans, land, ice and energy budget as isolated subjects, Terra carries five instruments that observe related parts of the Earth system during the same orbital passes. Its long record has supported research on clouds, aerosols, vegetation, fires, pollution, surface temperature, radiation and environmental change. Terra greatly exceeded its original design life, turning a single spacecraft into a multidecade scientific record.

Terra carries ASTER, CERES, MISR, MODIS and MOPITT. Together they measure surface features and temperature, Earth's radiation budget, clouds and aerosols from multiple viewing angles, broad spectral imagery, and carbon monoxide in the lower atmosphere. NASA's reference orbit for Terra was approximately 705 km (438 mi) above Earth with a 99-minute period, about 14 orbits per day and a 98.5-degree inclination. Terra's orbit has changed as the mission aged, so live catalog values can differ from those original reference numbers. A Sun-synchronous orbit was designed to cross locations at nearly the same local solar time, helping scientists compare observations under similar lighting. Terra began drifting away from its original crossing time after maneuvers maintaining that geometry ended.

Terra, originally called EOS AM-1, launched on 18 December 1999 aboard an Atlas IIAS from Vandenberg Air Force Base in California. The spacecraft entered an initial orbit and was maneuvered toward its planned approximately 705-km (438-mi) Sun-synchronous polar orbit. Its five instruments were then activated and checked before routine science observations began.