Mission complete. ESA’s second European Remote Sensing (ERS-2) satellite has reentered Earth’s atmosphere over the North Pacific Ocean. The satellite returned on February 21, 2024, at 18:17 CET (17:17 UTC) between Alaska and Hawaii.
ERS-2 was launched almost 30 years ago, on April 21, 1995. Together with ERS-1, it provided invaluable long-term data on Earth’s land surfaces, ocean temperatures, ozone layer, and polar ice extent that revolutionized our understanding of the Earth system.
ERS-2’s reentry was ‘natural’. ESA used the last of its fuel, emptied its batteries, and lowered the satellite from its altitude of 785 km to 573 km. This reduced the risk of collision with other satellites and space debris. As a result, it was not possible to control ERS-2 at any point during its reentry and the only force driving its descent was unpredictable atmospheric drag.
As well as leaving a remarkable legacy of data that still continue to advance science, this outstanding mission set the stage for many of today’s satellites and ESA’s position at the forefront of Earth observation.
The ERS-2 reentry is part of ESA’s wider efforts to ensure the long-term sustainability of space activities. These include ESA’s Clean Space initiative which promotes the development of new technologies for more sustainable space missions in collaboration with the wider European space community, as well as the Zero Debris Approach, which will even further reduce the debris left in both Earth and lunar orbits by future missions.
The European Remote Sensing satellite ERS-1, launched in 1991, carried a comprehensive payload including an imaging synthetic aperture radar, a radar altimeter and other powerful instruments to measure ocean surface temperature and winds at sea. ERS-2, which overlapped with ERS-1, was launched in 1995 with an additional sensor for atmospheric ozone research.
At their time of launch, the two ERS satellites were the most sophisticated Earth observation spacecraft ever developed and launched by Europe. These highly successful ESA satellites collected a wealth of valuable data on Earth’s land surfaces, oceans, and polar caps and were called upon to monitor natural disasters such as severe flooding or earthquakes in remote parts of the world.
Both ERS satellites were built with a core payload of two specialized radars and an infrared imaging sensor. The two were designed as identical twins with one important difference: ERS-2 included an extra instrument to monitor ozone levels in the atmosphere.
Shortly after the launch of ERS-2 in 1995, ESA decided to link the two satellites in the first ‘tandem’ mission which lasted for nine months. During this time the increased frequency and level of data available to scientists offered a unique opportunity to observe changes over a very short space of time, as both satellites orbited Earth only 24 hours apart.
In March 2000, a computer and gyro control failure led to ERS-1 finally ending its operations, after far exceeding its planned lifetime.
In July 2011, ESA decided to retire also ERS-2 and the process of deorbiting the satellite began.
During their lifetime, ERS data supported over 5000 projects producing some 4000 scientific publications. Archived data still to this day provide us with a wealth of information and are maintained accessible and continuously improved in the frame of the Heritage Space Programme to build long-term data series with successor missions including Envisat, ESA’s family of Earth Explorers and the Copernicus Sentinels.
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