Leonard David's INSIDE OUTER SPACE

Wait-a-Minute!
Image credit: Barbara David

There’s some interesting “wait a minute” fallout from the upcoming nose dive to Earth of the European Remote Sensing satellite, ERS-2.

According to the European Space Agency (ESA), the spent ERS-2 satellite weighing 2.3 tons is predicted to slip into Earth’s atmosphere on February 19 – with a current uncertainty of +/- 2.8 days.

“No intervention can be made from the ground, so ERS-2 will return entirely naturally – now a common occurrence as on average one spacecraft reenters Earth’s atmosphere per month,” an ESA statement explains.

The bit about “return entirely naturally” is an interesting, user-friendly substitute for “uncontrolled.”

Artwork of incoming ERS-2. Image credit: ESA

End of life

Following its launch in April 1995, ERS-2 ran for nearly 16 years of observing the Earth.

In 2011, ESA took the decision to bring the mission to an end.

That was followed by ground-activated de-orbit maneuvers. Those lowered the satellite’s average altitude and mitigated the risk of collision with other satellites or space debris, ESA notes.

The spacecraft was also “passivated” to reduce the risk of fragmentation. Passivated is getting rid of internally stored energy, like unused propellant, even de-charging batteries.

Wake-up call

All that said there are those that see the fall of ERS-2 as a calling card from space that doubles as a wake-up call – and on several fronts.

Netting of orbital debris has been studied, with ERS-2 as the catchable bait in a mix of junk-snatching ideas.
Image credit: ESA/D.Ducros

“While the ESA should be lauded for its efforts to de-orbit the ERS-2, it should be unsurprising that a 2.3-ton satellite launched into Earth orbit without any enforceable orbital debris regulation will then return to Earth’s atmosphere as orbital debris in an explosive uncontrolled reentry,” said Michael Runnels, an assistant professor of business law at California State University, Los Angeles.

“Indeed, these events highlight the continuing need for enforceable orbital debris regulation to support the sustainable exploration and scientific investigation of outer space,” Runnels told Inside Outer Space.

Someone someday

Ewan Wright is a PhD candidate at the University of British Columbia and Junior Fellow of the Outer Space Institute. He is actively focused on the sustainability of the outer space environment.

ERS-2 is a three decade old Earth Observation satellite with a mass about that of a Ford F-150, Wright said. “ERS-2 won’t burn up entirely when it reenters the atmosphere, so there is a chance that debris will hit someone on the ground, or disrupt air traffic.”

ERS-2 artwork.
Image credit: ESA

Wright told Inside Outer Space that, fortunately, the probability of someone getting hit is small. “But if we keep doing this again and again, someone someday will get hurt.”

Random reentries

Last year, 30 satellites larger than 500 kilograms uncontrollably reentered the atmosphere.

In total, in 2023, about 55 tons of satellite reentered randomly, Wright stated. ESA was responsible in lowering ERS-2’s orbit to make sure it didn’t become permanent space debris, he said.

“But in the future, all large satellites should do controlled reentries. Operators should control them to reenter over the oceans, away from people, aircraft and ships,” Wright concluded.

Minimize risk

The incoming ERS-2 is something that happens quite regularly with defunct satellites, said Leonard Schulz, a researcher at the Technische Universität Braunschweig’s Institute of Geophysics and Extraterrestrial Physics in Braunschweig, Germany.

Such falls will only increase in the future, Schulz added, due to the growing number of objects brought into low Earth orbit.

Image credit: NOAA

“I think the mass of the object stands out, probably some parts of the satellite will survive reentry,” Schulz told Inside Outer Space. “And this is the reason why people try to make satellites burn up completely in the atmosphere, to minimize the risk to people on ground.”

Atmospheric effects

Schulz said that there’s need to consider the effects on the atmosphere from spacecraft re-entry, a hot topic that ESA is evaluating.

“Today, we are lacking information on many aspects when it comes to materials released and subsequent effects on the atmosphere,” Schulz pointed out.

Satellite reentries are a good opportunity to gather observational data with measurement campaigns, Schulz advised. However, such uncontrolled reentries as with ERS-2 are extremely difficult to observe, he said, as the uncertainty of where the satellite reenters is so high.

“But controlled reentries provide great measurement opportunities,” Schulz concluded, “which should be a focus in the future!”

Taking the fall. Space hardware dives into Earth’s atmosphere with some fragments making their way to the ground.
Image credit: ESA/D.Ducros