TERRA
Country: United States · Also known as: EOS AM-1
Live Position
Ground Track · Last 90 Minutes
Upcoming Passes · Over Your Location
About This Satellite
Terra launched on December 18, 1999, as a flagship of NASA's Earth Observing System. Its purpose is to study how land, oceans, the atmosphere, and biology interact. A smoke plume, for example, is not just a land event: particles can move through the atmosphere and alter how sunlight is reflected and absorbed.
One platform, connected Earth systems
Terra's importance is the ability to put observations of different Earth processes into a shared context. Its long record supports investigations of environmental change and hazards such as fires and volcanoes. A single scene gives a snapshot; comparisons across many observations reveal behaviour that cannot be established from one overpass.
Do not freeze a mission at its original altitude
The orbit panel describes a dated tracking solution, not a promise that Terra still follows its original mapping orbit. When comparing old and new scenes, check both acquisition time and the product documentation. A change in illumination or sampling time can matter alongside a genuine change on the ground.
Mission reference: NASA: Terra mission. Editorial review: .
Five instruments with different jobs
Terra launched with ASTER, CERES, MISR, MODIS, and MOPITT. Their roles span detailed surface observations, radiation balance, multi-angle viewing, broad environmental imaging, and carbon-monoxide measurements. This is an original payload inventory, not a statement that every instrument is currently operating. The instruments should not be treated as five interchangeable cameras.
Reference: NASA Earth Observer: Terra mission history and evolution.
Why the local crossing time changes
Terra was designed for a morning equator crossing near 10:30 local time. NASA later stopped maintaining the original orbit as fuel and power constraints shaped the extended mission. The resulting drift changes the sampling geometry. The original 705 km altitude and morning schedule therefore belong to mission-design context; the dated orbital snapshot below describes the element set actually available here.
Reference: NASA Earth Observer: original orbit and later drift.
Reading this orbital snapshot
Based on TLE epoch: 2026-09-05. Estimated altitude ranges from 688 km at perigee to 691 km at apogee, a difference of 3 km. The orbital period is about 98.6 minutes. Eccentricity 0.00021 indicates a nearly circular path. In a two-body approximation, perigee speed is 1.00 times apogee speed. These are mean-element estimates, not instantaneous measurements. Distance per orbit uses an ellipse approximation.
Saved build snapshot. If a valid TLE is retrieved, this explanation and the orbit panel update together. Otherwise this dated snapshot is retained.
Ground track is not sensor coverage
An inclination of 97.94 degrees implies approximate geocentric ground-track limits of 82.1 degrees north and south. This is a retrograde orbit, moving against the direction of Earth rotation. The plotted line marks the point beneath the object. It does not represent camera coverage, radio reception, or a guaranteed visible pass.
Accuracy and missing information
The introductory record describes the build snapshot. The orbital snapshot explanation and orbit panel share any successfully retrieved TLE; check the displayed epoch. Reentered objects retain historical data only. Mission history is not rewritten by TLE updates. TLE/SGP4 positions are predictions and can change after maneuvers or updated observations. The 14-day stale-data cutoff is a display safeguard, not an accuracy guarantee. Local passes are geometric predictions, not a visibility forecast. No verified operator or mission status means unknown, not active. Do not use this catalog for collision avoidance or operational flight decisions.
Catalog sources: CelesTrak SATCAT: NORAD 25994 · GCAT: S25994 (source update 2026 Sep 4 2345:57). Supplementary metadata: SatNOGS DB, retrieved 2026-09-05T12:57:25.375Z. Page assembled 2026-09-15. GCAT phase codes describe trajectory phases, not mission health.
Learn more: TLE data · Perigee and apogee · Ground tracks · JOT (Jewawud Live Orbital Map)