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- By Jonathan Amos
- scientific correspondent
Artwork: European Earth remote sensing satellites weighed around 2.5 tons at launch
A pioneering European satellite will fall to Earth in the next few hours.
ERS-2 was a cutting-edge observation platform when it launched in 1995, forging technologies that are now routinely used to monitor the planet.
The European Space Agency (ESA) says most of the two-tonne satellite will burn up during its descent.
Some more robust pieces may be able to withstand the intense heating generated during high-speed diving, but the chances of these fragments hitting populated areas and causing damage are slim.
They could land almost anywhere in the world, but since most of the Earth’s surface is covered by oceans, any debris that survives on the surface is more likely to be lost to the sea.
“And it is worth highlighting that none of the elements that could re-enter the atmosphere (and reach the surface) are radioactive or toxic,” said Mirko Albani of ESA’s Earth Observation Department.
Sea surface temperature: current climate monitoring owes a debt to the ERS program
The agency launched two nearly identical Earth Remote Sensing Satellites (ERS) in the 1990s. They were the most sophisticated planetary observers of their time, carrying a suite of instruments to track changes in the land, oceans and air.
They monitored floods, measured continental and ocean surface temperatures, tracked the movement of ice fields, and felt the flexing of the ground during earthquakes.
And ERS-2, specifically, introduced a new capability to assess Earth’s protective ozone layer.
“Absolutely,” said Dr. Ralph Cordey. “In terms of technology, you can draw a direct line from ERS to the European Copernicus/Sentinel satellites monitoring the planet today. ERS is where it all started,” Airbus’ Earth observation business development manager told BBC News .
ERS-2 is the first of the duo to return home. Originally located 780 kilometers above Earth, engineers used their last fuel reserves in 2011 to reduce its altitude to 570 kilometers. It was expected that the upper atmosphere would drag the spacecraft to its destruction in about 15 years.
The German company Dornier (now Airbus) led the assembly of the ERS satellites
This prediction will come true on Wednesday night, GMT.
It’s hard to say exactly when and where. Much will depend on the density of the upper atmosphere, something influenced by solar activity.
What can be said with certainty is that re-entry will occur between 82 degrees north and south, since that was the extent of the satellite’s orbit around the Earth.
Australian monitoring company HEO follows the descent of ERS-2
The fragments that do impact the planet could include internal panels and some metal parts, such as fuel and pressure tanks.
The item that is potentially most likely to pass through the atmosphere in some form is the synthetic aperture radar system antenna, which was built in the United Kingdom. The antenna has a carbon fiber construction that can tolerate high temperatures.
When ERS-2 was launched, the guidelines for space debris mitigation were much more relaxed. It was considered acceptable to bring home a redundant spacecraft within 25 years of the end of operations.
Esa’s new Zero Waste Charter It recommends that the disposal grace period should now not exceed five years. And its future satellites will launch with the fuel and capacity needed to propulsively deorbit in short order.
The reason is obvious: with so many satellites currently in orbit, the potential for collisions is increasing. ERS-1 suddenly failed before engineers could reduce its altitude. It is still more than 700 kilometers above Earth. At that height it could take 100 years before it falls naturally.
Hayward Fault in California: ERS pioneered radar interferometry and rock movement mapping
The American company SpaceX, which operates most of the functional satellites currently in orbit (more than 5,400), recently announced that it would shoot down 100 of them after discovering a flaw that “could increase the probability of failure in the future.” He wants to remove the spacecraft before any problems make the task difficult.
They said: “The accumulation of massive derelict objects in low Earth orbit continues unabated; 28% of current long-lived massive derelict objects have been left in orbit since the beginning of the century.
“These clumps of uncontrollable mass represent the greatest potential for debris generation for the thousands of newly deployed satellites that are powering the global space economy.”