Terra (satellite)
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| Terra (satellite) | |
|---|---|
| Name | Terra |
| Mission type | Earth observation satellite |
| Operator | NASA / Goddard Space Flight Center |
| COSPAR ID | 1999-068A |
| SATCAT | 25994 |
| Website | https://terra.nasa.gov/ |
| Mission duration | 5 years (planned), 24 years, 5 months, 19 days (in progress) |
| Manufacturer | Lockheed Martin |
| Launch mass | 5,190 kg (11,440 lb) |
| Power | 2.5 kW |
| Launch date | 18 December 1999, 18:57:39 UTC |
| Launch rocket | Atlas II AS |
| Launch site | Vandenberg SLC-3E |
| Orbit reference | Sun-synchronous orbit |
| Orbit regime | Low Earth orbit |
| Orbit periapsis | 702 km (436 mi) |
| Orbit apoapsis | 705 km (438 mi) |
| Orbit inclination | 98.2° |
| Orbit period | 98.8 minutes |
| Orbit repeat | 16 days |
| Apsis | gee |
Terra (satellite). Terra, formerly known as the Earth Observing System-1 (EOS-1), is a flagship Earth observation satellite launched by NASA as a cornerstone of its Earth Science enterprise. It is the first satellite in a series designed to provide long-term, comprehensive data on the state of the Earth's climate system, land surfaces, oceans, and atmosphere. Operating in a Sun-synchronous orbit, its suite of five complementary instruments has revolutionized our understanding of global climate change, deforestation, and atmospheric chemistry.
Overview
Conceived as the flagship of NASA's ambitious Earth Observing System, Terra was developed to address critical questions about global climate change and Earth system science. Managed from the Goddard Space Flight Center, the mission represents a significant international collaboration, with contributions from Japan and Canada. Its design philosophy centered on simultaneous, coordinated measurements from multiple advanced sensors, providing an unprecedented, holistic view of terrestrial and atmospheric processes.
Mission and objectives
The primary mission objective was to establish a 15-year global data set on which to base scientific investigations into climate system interactions. Specific goals included quantifying global carbon cycle dynamics, monitoring changes in Earth's radiation budget, and assessing patterns of land cover change and productivity. The data supports research into cloud and aerosol properties, snow and ice cover, and volcanic eruption impacts, forming a critical baseline for environmental policy and climate models.
Instruments and scientific payload
Terra carries five sophisticated instruments, each designed to measure specific components of the Earth system. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), provided by Japan's Ministry of Economy, Trade and Industry, creates high-resolution images of land surface temperature and elevation. The Multi-angle Imaging SpectroRadiometer (MISR) uses nine cameras at different angles to study atmospheric aerosols and cloud albedo. The Moderate Resolution Imaging Spectroradiometer (MODIS) provides broad, daily global imagery in 36 spectral bands for tracking ocean color, land vegetation, and cloud cover. The Measurements of Pollution in the Troposphere (MOPITT) sensor, contributed by the Canadian Space Agency, maps global carbon monoxide concentrations. Finally, the Clouds and the Earth's Radiant Energy System (CERES) instrument measures reflected solar radiation and emitted thermal radiation to study the Earth's total energy balance.
Launch and orbit
Terra was successfully launched on 18 December 1999 aboard an Atlas II AS rocket from Space Launch Complex 3 at Vandenberg Air Force Base in California. It was placed into a near-polar, Sun-synchronous orbit at an altitude of approximately 705 kilometers, crossing the equator at 10:30 AM local time (the "morning constellation") to optimize observations of cloud cover and surface conditions. This orbit allows for near-global coverage every one to two days, with a exact repeat cycle of 16 days.
Key scientific findings and contributions
Terra's data have been fundamental to countless discoveries, including detailed tracking of Amazon rainforest deforestation and boreal forest fires. Its instruments have precisely measured the accelerating loss of Greenland ice sheet mass and Antarctic sea ice extent. MODIS data became the global standard for monitoring phytoplankton blooms and chlorophyll concentrations in the world's oceans, while MOPITT provided the first long-term global maps of carbon monoxide transport. CERES data has been critical for refining climate models by accurately quantifying the planet's radiation budget and the role of clouds in climate feedback loops.
Mission status and legacy
Far exceeding its planned five-year mission, Terra remains operational as of 2024, though some instruments have been powered down or experienced anomalies. Its immense, freely available data archive continues to support global research and operational applications, including wildfire management and air quality forecasting. Terra's greatest legacy is establishing the paradigm for integrated Earth system observation, directly paving the way for subsequent missions like Aqua and Aura, and solidifying the foundation for the next generation of climate observatories.
Category:NASA satellites Category:Earth observation satellites Category:Spacecraft launched in 1999