Three years ago, a pallet of batteries was thrown off the ISS space station. Since then it has been orbiting the earth – and is now expected to enter the atmosphere. Questions and answers.
A spacecraft part the size of a small car is expected to enter Earth’s atmosphere on Friday evening. Most of it will burn up, but smaller pieces could also hit the ground. “Not an extraordinary event,” says the German Aerospace Center (DLR).
What exactly is hurtling through space?
According to the European Space Agency (ESA), the object is a pallet containing nine disused batteries from the International Space Station (ISS). The platform with battery packs is about the size of a car and weighs around 2.6 tons. It was detached from the ISS in March 2021 with the aim of burning up in the atmosphere years later.
Is there a danger for Germany?
Experts believe it is very unlikely that debris will fall over Germany. A DLR spokesman confirmed this again. The Federal Ministry of Economics, which is responsible for space travel, and the Federal Office for Civil Protection and Disaster Assistance (BBK) had previously made similar statements.
If there is hardly any danger to Germany, why was there an official warning?
The fact that the BBK had spread its assessment – a very low probability of debris on Germany – via several warning apps via official danger information on Thursday caused some excitement. “If the risk increases, you will receive new information,” it said. “We are concerned with transparency and sharing the information we have,” a spokeswoman for the authority explained the procedure.
What is known about the impending entry into the atmosphere?
According to current calculations (as of Friday afternoon), the object could enter the atmosphere over the Caribbean. The online site “satflare.com” specifies an eight-hour corridor around Friday evening German time as the time window. “For such cases, predictions of the time and place of re-entry are naturally associated with large uncertainties, mainly due to the difficult to predict atmospheric resistance. The closer you get to the estimated time of re-entry, the easier it is to limit the affected area geographically,” said Esa.
How does a re-entry work?
“This is happening very quickly,” said the head of the ESA space security program, Holger Krag, to the online portal of the “Tagesschau”. “It only takes ten minutes from an altitude of 100 kilometers, where re-entry takes place when the object begins to disintegrate, to the ground. However, the battery pack will not fall as a compact individual part into a very narrow area, but that “It tends to spread in a longer trail of debris. You would expect a smaller piece every 10 or 20 kilometers in the affected area.” According to DLR, a sonic boom and also a kind of shooting star could be seen near the re-entry – so most likely not in Germany.
How great is the risk for the affected areas?
“Even if some parts can reach the ground, the risk of an accident and the likelihood of a person being hit is very low,” said Esa. Europe’s former space chief Jan Wörner also considers the danger from debris to be low. “Batteries really like to burn. I assume that the package will almost completely burn up in the atmosphere,” Wörner told the dpa news agency.
What uncertainties are there?
It is an uncontrolled re-entry, so precise predictions are difficult. “The object is gradually slowed down by the atmosphere and thus loses its orbit,” Krag explained to the “Tagesschau”. “The great uncertainty comes from the fact that we cannot predict exactly how dense the atmosphere will be. It depends on many factors and is largely left to chance. In this respect, even a few hours in advance, you cannot precisely determine the location “You may be able to exclude some continents, but you definitely can’t narrow the forecast down to one country or one city.”
Does something like this happen often?
Space debris enters the atmosphere and burns up there all the time. Just a few weeks ago, the European satellite “ERS-2”, which was launched almost 30 years ago, came to such an end and was destroyed as planned. It also happens again and again that smaller debris reaches the earth’s surface. Esa writes: “Approximately every week, a large space object re-enters in an uncontrolled manner, and the majority of the associated fragments burn up before they reach the ground.” According to the US space agency NASA, an average of one known piece has fallen to Earth per day over the past 50 years. So far, no serious injuries or significant property damage have been reported as a result.
How much space debris is currently orbiting the Earth?
According to the US space agency Nasa, there are currently more than 25,000 objects with a diameter of more than ten centimeters in space, around 500,000 with a diameter between one and ten centimeters and more than 100 million particles that are larger than a millimeter. In total there are more than 9,000 tons. The origin is primarily satellite explosions and collisions.
Are there efforts to do something about it?
Many countries active in space have expressed concern and have advocated reducing the creation of further space debris as much as possible – for example by appropriately designing spaceships and satellites. Former Esa boss Wörner also called for “finally an early warning system to protect the earth”.