How big is the dead European satellite hurtling towards Earth?

Somewhere on Earth, space debris from a defunct European Space Agency satellite is falling on Wednesday, 21 February.

After being launched in 1995 and deactivated in 2011, European Remote Sensing 2 (ERS-2) has been slowly returning to Earth.

Here’s all we know about it.

When is it falling back to Earth?

The ESA’s predictions as of Tuesday afternoon are that the defunct satellite will re-enter the Earth’s atmosphere at 10.19 am ET (i.e., 8.49 pm IST) on Wednesday, plus or minus around 19 hours.

This uncertainty is due primarily to the “influence of unpredictable solar activity, which affects the density of the Earth’s atmosphere and can therefore change how much drag pulls on the satellite on its way down.”

“It’s still too early to tell where it will come down, but we’ll have a better idea as the time of re-entry gets closer,” ESA wrote.

Interestingly, the space agency predicts that very little of the satellite will actually touch down on land or in the ocean.

It says the satellite will break into pieces at about 50 miles above the Earth’s surface, and the vast majority will burn up in the atmosphere.

If any pieces make it to Earth, they will probably fall into the ocean.

How big is the dead satellite?

When compared to other space junk, the ERS-2 satellite is huge. It weighs roughly 2,268 kilogrammes (5,000 pounds) and is about the length of a city bus, as per USA Today.

The heaviest fragment that could fall to Earth or the ocean, according to Henri Laur of the ESA Earth observation mission, would weigh about 52 kilogrammes (115 pounds), or about the same as a Tesla Model X, according to Phys.org.

According to the website, ESA space debris system engineer Benjamin Bastida Virgili said during a press briefing last week, “The odds of a piece of satellite falling on someone’s head is estimated at one in a billion, (about 1.5 million times lower than the risk of being killed in an accident at home).”

What we know about the satellite

When it was first launched on 21 April 1995, the Earth-observing ERS-2 satellite was the most advanced spacecraft Europe had ever produced and deployed, reported CNN.

It employed “an imaging synthetic aperture radar, a radar altimeter, and other powerful sensors to measure ocean-surface temperature and winds at sea,” according to the ESA, along with its older sister satellite, ERS-1.

To assess atmospheric ozone, the ERS-2 also carried an additional sensor. In 29 years since its launch, the space agency said the two satellites gathered information on “diminishing polar ice, changing land surfaces, sea-level rise, warming oceans and atmospheric chemistry.”

ERS-2 was deactivated by the European Space Agency (ESA) in 2011, and its orbit was lowered from 488 miles to 356 miles above Earth in order to significantly lower the chance of collision with other spacecraft or space debris. It is now out of fuel and out of batteries.

According to NPR, the intention was to gradually bring it down and keep it from contributing to the larger issue of orbiting space debris.

How much space junk is orbiting Earth?

Space junk, or orbital debris, can include minor rocket or satellite components as well as retired spacecraft like the ERS-2. Even human faeces from astronauts on space trips may be present. The last 30 years have seen a sharp increase in the number of objects in Earth’s orbit, as per USA Today.

The vast bulk of untracked space junk, according to the ESA, is less than 0.4 inches wide.

The majority of the debris is caused by collisions and explosions of satellites. Furthermore, smaller fragments of debris may be produced when items collide with one another. Even little things can be deadly because the average impact speed is typically 22,000 metres per hour.

However, space trash isn’t limited to satellite and missile debris.

As per the report, some unusual items include a 1969 Andy Warhol drawing left behind on the Moon by the Apollo 12 mission, a spatula lost by astronaut Piers Sellers in 2005, the red Tesla and its Starman “driver” launched in space in February 2018, and a bag of tools that floated away on a maintenance spacewalk on 1 November.

How much junk is there?

Since the space age began in the 1950s, about 50,000 tonnes of material have been launched into space by humans. The space agency, citing information from the US Space Surveillance Network, estimated that some 10,000 tonnes were still in orbit.

NASA says that there are around 100 million objects one millimetre or smaller in orbit, and about 500,000 marble-sized objects. There are another 25,000 things larger than 10 centimetres.

As of December 2023, the majority of the 16,990 satellites that have been sent into space since 1957 — roughly 9,000 of them — were still whizzing around the Earth, according to the ESA.

It says an object with an equivalent mass to the ERS-2 re-enters Earth’s atmosphere once every one to two weeks on average.

With inputs from agencies