Terra

Terra was designed as the flagship of NASA's Earth Observing System, bringing several complementary instruments together on one spacecraft so scientists could study how land, oceans, clouds, aerosols, atmospheric gases, radiation, and climate processes interact.

Instead of treating each part of Earth in isolation, Terra was built to support coordinated measurements across the planet and repeated observations over many years.

Terra launched on December 18, 1999, aboard an Atlas IIAS from Vandenberg Air Force Base in California.

Its sun-synchronous polar orbit was selected to provide repeatable lighting conditions for global observations, helping scientists compare measurements over time.

Terra carries a suite of instruments designed to observe different parts of the Earth system, including surface temperature, vegetation, aerosols, clouds, radiation, and atmospheric properties.

The strength of the mission comes from combining these measurements so researchers can study relationships between processes rather than isolated variables.

Terra established one of the longest continuous records from NASA's modern Earth Observing System and has supported research on climate, wildfire, land-cover change, atmospheric aerosols, ocean processes, and Earth's energy budget.

Its long operating life makes the mission especially valuable for detecting changes that only become clear across years or decades.