|Mission type||Climate research|
|Mission duration||Elapsed: 22 years, 7 months, 16 days|
|Launch mass||4,864 kilograms (10,723 lb)|
|Start of mission|
|Launch date||December 18, 1999, 18:57:39UTC|
|Rocket||Atlas IIAS AC-141|
|Launch site||Vandenberg SLC-3E|
|Semi-major axis||7,080.0 kilometers (4,399.3 mi)|
|Perigee altitude||708.7 kilometers (440.4 mi)|
|Apogee altitude||710.6 kilometers (441.5 mi)|
|Argument of perigee||83.7699 degrees|
|Mean anomaly||276.3654 degrees|
|Epoch||25 June 2016, 02:58:27 UTC|
Terra (EOS AM-1) is a multi-national, NASA scientific research satellite in a Sun-synchronous orbit around the Earth that takes simultaneous measurements of Earth’s atmosphere, land, and water to understand how Earth is changing and to identify the consequences for life on Earth. It is the flagship of the Earth Observing System (EOS) and the first satellite of the system which was followed by Aqua (launched in 2002) and Aura (launched in 2004). Terra was launched in 1999.
The name "Terra" comes from the Latin word for Earth. A naming contest was held by NASA among U.S. high school students. The winning essay was submitted by Sasha Jones of Brentwood, Missouri. The identifier "AM-1" refers to its orbit, passing over the equator in the morning.
The satellite was launched from Vandenberg Air Force Base on December 18th, 1999, aboard an Atlas IIAS vehicle and began collecting data on February 24th, 2000. It was placed into a near-polar, sun-synchronous orbit at an altitude of 705 km (438 mi), with a 10:30am descending node.
Terra carries a payload of five remote sensors designed to monitor the state of Earth's environment and ongoing changes in its climate system:
Data from the satellite helps scientists better understand the spread of pollution around the globe. Studies have used instruments on Terra to examine trends in global carbon monoxide and aerosol pollution. The data collected by Terra will ultimately become a new, 15-year global data set.
After launch, operators observed that high energy protons like those found over the South Atlantic Anomaly or the poles could induce single-event upsets that would cause the Motor Drive Assembly (MDA) Built-In Test Equipment (BITE) to turn off the MDA. These false shut-downs occur 12-14 times a month and eventually the operations team automated the recovery to reduce the impact of these shut-downs.
Starting in 2007, increased thermal resistance in the SWIR cryocooler of the ASTER instrument caused the temperature to gradually increase. By 2008, despite frequent attempts to recycle the cryocooler the data began to significantly degrade and on January 12, 2009, ASTER managers declared the SWIR no longer functional due to anomalously high SWIR detector temperatures. Data gathered after April 2008 was declared not usable.
On October 13, 2009, Terra suffered a single battery cell failure anomaly and a battery heater control anomaly likely the result of a Micrometeoroid or Orbital Debris (MMOD) strike.
On February 27, 2020, the Terra flight operations team conducted Terra’s last inclination adjust maneuver due to the satellite's limited remaining fuel. With no more such maneuvers, Terra's mean local time has begun to drift starting in April 2021 and with it, its data quality. In October 2022, Terra is expected to reach and exceed a 10:15 AM MLT crossing which is expected to lead operators to initiate a constellation exit to a lower orbit altitude (694 km). Decommissioning would occur around 2025-26 followed by an un-controlled reentry several years later.
In June and October 2008 the spacecraft was targeted by hackers who gained unauthorized access to its command and control systems, but did not issue any commands.