- Written by Jonathan Amos
- Science Reporter
Artwork: Europe's Earth Remote Sensing satellites weighed approximately 2.5 tons at launch
A pioneering European satellite is set to fall to Earth in the coming hours.
ERS-2 was a cutting-edge observing platform when it was launched in 1995, formulating techniques that are now routinely used to monitor the planet.
The European Space Agency (ESA) says most of the two-ton satellite will burn up during its descent.
Some of the stronger parts can withstand the extreme heat generated during high-speed diving, but the chances of these fragments hitting populated areas and causing damage are small.
It could land almost anywhere in the world, but since most of the Earth's surface is covered by oceans, any debris that remains on the surface is likely to be lost to the sea.
“It is worth noting that none of the elements that may return to the atmosphere (and reach the surface) are radioactive or toxic,” said Mirko Albani of the European Space Agency's Earth Observation Division.
Sea surface temperature: Today's climate observations are indebted to ERS
The agency launched two nearly identical Earth Remote Sensing (ERS) satellites in the 1990s. They were the most sophisticated planetary observers of their time, carrying an array of instruments to track changes on land, in the oceans, and in the air.
They monitored floods, measured the temperatures of continents and ocean surfaces, tracked the movement of ice fields, and sensed the curvature of the Earth during earthquakes.
ERS-2, specifically, has provided a new capability to assess the Earth's protective ozone layer.
“Absolutely,” said Dr. Ralph Cordy. “In terms of technology, you can draw a direct line from ERS all the way to the European Copernicus/Sentinel satellites that monitor the planet today. ERS is where it all started,” Airbus' Earth Observation Business Development Director told the BBC.
ERS-2 is the first binary to return home. Originally positioned 780 kilometers above Earth, engineers used its final fuel reserves in 2011 to lower its altitude to 570 kilometres. It was expected that the upper atmosphere would drag the spacecraft toward destruction within about 15 years.
The German company Dornier (now Airbus) led the assembly of the ERS satellites
This prediction will come true on Wednesday evening GMT.
It is difficult to determine exactly when and where. Much will depend on the density of the upper atmosphere, which is affected by solar activity.
What can be said with certainty is that the return will occur between 82 degrees north and south, as this was the range of the satellite's orbit around the Earth.
Australian tracking company HEO is tracking the descent of ERS-2
Those fragments impacting the planet may include interior panels and some metal parts, such as fuel and pressure tanks.
The element likely to have the highest probability of penetrating the atmosphere in some form is the antenna of the synthetic aperture radar system, built in the United Kingdom. The antenna has a carbon fiber construction that can withstand high temperatures.
When ERS-2 was launched, space debris mitigation guidelines were more flexible. Repatriation of redundant spacecraft within 25 years of the end of operations was considered acceptable.
ESA's new “zero debris” charter. It now recommends a grace period for disposal not to exceed five years. Its future satellites will be launched with the necessary fuel and the ability to de-orbit in a short time.
The rationale is clear: with so many satellites now launched into orbit, The probability of collisions is increasing. ERS-1 suddenly failed before engineers could lower its altitude. It is still more than 700 kilometers above the ground. At this height, it could take 100 years before it falls naturally.
Hayward Fault in California: ERS was a pioneer in radar interferometry and mapping of rock movement
The US company SpaceX, which operates most of the satellites currently in orbit (more than 5,400), recently announced that it would shoot down 100 of them after discovering a fault that “may increase the probability of failure in the future.” It wants to remove the spacecraft before any problems make the mission more difficult.
“The accumulation of abandoned LEOs in LEO continues unabated, with 28% of the current long-lived LEOs left in orbit since the turn of the century,” they said.
“These clusters of uncontrollable mass represent the greatest debris generation potential for the thousands of newly deployed satellites that fuel the global space economy.”
