ERS-2 reentry – how and why is it happening?

ESA’s European Remote Sensing 2 satellite (ERS-2) will reenter Earth’s atmosphere in February 2024.  

ERS-2 launched from Europe’s spaceport in Kourou, French Guiana on 21 April 1995. The mission laid the foundations for the future of European Earth observation and collected valuable data on Earth’s land surfaces, oceans and polar caps. It was also called upon to monitor natural disasters such as severe flooding or earthquakes in remote parts of the world. 

In 2008, 13 years after ERS-2 launched, ESA adopted its first space debris mitigation policy to address the growing hazard that debris in Earth orbit poses to current and future space activities. 

Existing missions such as ERS-2 were exempt from many of the demands of the new policy, yet ESA decided to end the mission in 2011 and actively deorbit the satellite to reduce its potential impact on the space environment. At this point, ERS-2 had spent 16 years in orbit, far exceeding its planned lifetime of three years. 

Operators at ESA’s ESOC mission control in Darmstadt, Germany, planned and conducted a series of 66 deorbiting manoeuvres in July and August 2011 that used up the satellite’s remaining fuel and lowered its average altitude from 785 km to 573 km. Lowering the satellite into a denser layer of the atmosphere greatly sped up its orbital decay. 

ERS-2 was then completely ‘passivated’ in September 2011 – its batteries and pressurised systems were emptied or rendered safe. This reduced the risk of an internal malfunction causing the satellite to break up into pieces while still at an altitude used by active satellites. 

ERS-2’s reentry is described as ‘natural’ as it is no longer possible to control the satellite. The only force causing ERS-2’s orbit to decay is atmospheric drag, which is influenced by unpredictable solar activity.  

While we can forecast the reentry to within a few days, it is not possible to predict exactly when and where the satellite will reenter prior to its final few orbits. As we approach the day of reentry, we will be able to predict a time and location with increasing certainty. 

During reentry, the satellite will break up into pieces, the majority of which will burn up. The risks associated with satellite reentries are very low. 

ESA’s space debris mitigation policy has been updated multiple times since 2008, as recently as November 2023. Our missions in Earth orbit are now increasingly designed to conduct controlled reentries at the end of their life that allow operators to accurately target over which region on Earth they reenter. 

However, ESA continues to make efforts to dispose of its older satellites (such as ERS-2, Aeolus, Cluster and Integral) in more sustainable ways than were originally planned. 

Mission legacy 

At launch, ERS-2 was Europe’s most sophisticated Earth observation spacecraft. 

“The ERS-2 satellite, together with its predecessor ERS-1, changed our view of the world in which we live,” says Mirko Albani, Head of ESA’s Heritage Space Programme. 

“It provided us with new insights on our planet, the chemistry of our atmosphere, the behaviour of our oceans, and the effects of humankind’s activity on our environment.” 

ERS-2 data are still widely used today and kept accessible through ESA’s Heritage Space Programme. They serve as long-term global records from which to derive essential climate variables that help scientists monitor our changing climate. 

The satellite was also a forerunner in Synthetic Aperture Radar and Interferometry applications (InSAR), paving the way for future SAR missions, such as Copernicus Sentinel-1.  

Read more about the successes and legacy of the mission here.