The satellite ERS-2 is long-serving. He has been flying through space since 1995. He has observed the Earth for 16 years and, among other things, provided data on ice flows in Antarctica, sea temperatures and the Ozone layer. But he has been unemployed since 2011. And now the European space agency Esa is bringing it to its end, and very little ceremoniously: it is scheduled to crash to Earth on Wednesday afternoon. This will the satellite weighs around two tons is expected to break up in the atmosphere and most of the pieces will burn up. But not all: The European Space Operations Center (ESOC) does not rule out the possibility that some remains could still hit Earth. The probability of this is between ten and 20 percent.
It is not yet clear where exactly the parts will end up. The trajectory also depends on how strong the solar winds will be in the next few days. In terms of area, the probability is highest that the debris will end up in the ocean, because the oceans cover around 70 percent of the earth.
The Esa had itself already done in 2008Not to leave any scrap behind in space, but to take your rubbish back with you. At the end of 2023, there were more than 36,500 objects in orbit that were ten centimeters or larger. More than 11,500 tons of space debris are floating through space. The danger is that this space debris will collide with each other and damage active satellites. Also the International Space Station EAT should therefore be at the end of its life in 2030 deliberately crash over the Pacific. Point Nemo is the name of the area in the South Pacific where ancient spaceships are directed. But the re-entry of the satellite ERS-2 is not controlled; Esa just prepared him a little.
From the control center of the Esa space scrap offices in Darmstadt Engineers, physicists and mathematicians lowered the satellite from its orbit in 2011 using its last fuel reserves, from an average altitude of 785 kilometers to 573 kilometers. According to Esa, the last fuel was also used up to… to prevent a “devastating explosion”., which would have created even more space debris. The last part of the satellite is now slowed down by the Earth’s atmosphere. This cannot be controlled – “natural re-entry”, is what Esa calls it. The closer the satellite gets to re-entry, the more accurate the prediction of when and where it will crash will become.
Esa publishes updates on the landing time a blog. The last forecast from February 19 at 4:30 p.m. predicted entry on Wednesday at 4:41 p.m., although with an uncertainty window of 11.5 hours sooner or later. Over the course of 23 hours, the satellite orbits the Earth several times as it rotates beneath it. ERS-2 could therefore actually be entering the atmosphere anywhere at the moment.
Benjamin Bastida Virgili works as a systems engineer at the space debris office that monitors entry. He says: “We can only see the satellite if it flies over radar.” The ESOC uses a radar in Berkum for this purpose, and sightings from the US Space Surveillance Network and others help. The trajectory is recalculated with each new piece of information. But hours can pass between sightings.
Where “ERS-2” will enter the atmosphere also depends on the Sun
In fact, how fast and where depends on the sun ERS-2 will land. Because solar activity influences the density of the Earth’s atmosphere in the layers that slow down the satellite. But this activity is unpredictable. During the re-entry of the satellite Aeolus Last year, for example, increased solar activity accelerated the fall. The former weather satellite landed over Antarctica. Just two minutes later it would have appeared in the Atlantic. Another factor is the orientation of the satellite in the atmosphere: is it along or across the direction of flight?
Newer satellites must be designed to cause as little damage as possible when they return to Earth. During construction, care is taken to ensure that all materials burn up in the atmosphere, i.e. no titanium or steel is included. Or that they can be returned in a controlled manner. This was not the case with older satellites.
In the next few days will ERS-2 from a height of 80 kilometers sending something back to Earth for the last time: its glow as a ball of fire in the atmosphere. But on the surface, no one needs to be seriously worried. Benjamin Bastida Virgili says: “An object of this size enters the Earth’s atmosphere every week.” Even if parts of ERS-2 should fall: According to Esa, there is a risk of being hit by space debris less than one in 100 billion. And that is three times less likely than being hit by a meteorite.