Overview
Terra (formerly EOS AM-1) is the flagship satellite of NASA's Earth Observing System (EOS). Launched on 18 December 1999, it crosses the equator on each orbit at approximately 10:30 AM local time (hence "AM-1"). Terra carries five instruments that together observe the atmosphere, land, ocean, and energy balance of Earth, providing a comprehensive view of our planet's climate system.
Instruments
MODIS (Moderate Resolution Imaging Spectroradiometer) — the workhorse, imaging the entire Earth every 1–2 days in 36 spectral bands. ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) — high-resolution surface imaging. CERES — Earth radiation budget. MISR — multi-angle atmospheric imaging. MOPITT — carbon monoxide and methane measurement.
Status
After more than 26 years in orbit (well beyond its 6-year design life), Terra continues to provide science data, though NASA began lowering its orbit in 2022 to enable re-entry in the 2030s. Its vast data archive is one of the most important resources in climate science.