Published: Thu, January 30, 2020
Sci-tech | By Patricia Wade

Two Defunct Satellites Now Have a 5 Percent Chance of Colliding Tonight

Two Defunct Satellites Now Have a 5 Percent Chance of Colliding Tonight

Satellites in LEO, namely those below 600 kilometres, will "naturally be dragged down into Earth's atmosphere and disintegrate within 25 years", West told Gizmodo, but "25 years is a long time-too long given the intensity to which we are using this orbit and the tens of thousands of new satellites potentially being launched". The company operates three radar stations, two in the US and one in New Zealand, and it can track objects as small as 10 centimetres in diameter. Data spacecraft located at an altitude of about 900 kilometers above the planet represent the IRAS telescope and scientific payload GGSE-4.

The defunct satellites are heading towards each other at a relative speed of 14.7 kilometres per second - or 52,920 kilometres per hour (33,000MPH) - and LeoLabs said there is a one in 100 chance they will hit each other.

LeoLabs, in an update January 28, revised the probability of a collision downward, to about 1 in 1,000, estimating that the two spacecraft will pass between 13 and 87 meters of each other.

The other is called the Gravity Gradient Stabilization Experiment (GGSE-4). Worryingly, if the satellites do collide, they could create a field of "dangerous" debris that could endanger nearby spacecraft.

"In terms of normal operations satellites, one in 10,000 is considered something that you want to take a very close look at".

Space Shuttle Endeavour had a major impact on its radiator during STS-118.

The fallout from a satellite collision can be significant, resulting in thousands of pieces of space junk.

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But the potential crash highlights the long-term risk that accumulation of space debris poses to satellites used for weather forecasting and communication. According to NASA, the agency is monitoring approximately 20,000 objects as big or bigger than a baseball and 50,000 objects as big as a marble. According to the company, the two satellites are moving toward one another at speeds of about 32,800 miles per hour.

LeoLabs estimates a crash could break the satellites - each more than 10 feet in length and traveling through space at about 9.1 miles per second - into almost 300,000 separate pieces.

While such events are extremely unlikely to harm anyone on Earth, the debris from such a collision would result in a dramatic shooting star-like show in the sky near Pittsburgh. The spacecraft stopped functioning in 2012.

Because of the enormous amount of energy involved, if the satellites touch each other, a hypersonic shock wave will go through them both, reducing them to debris which is then spread out to their orbits.

The space boffins' infrared telescope has a mass of 1,090kg (2,400lb) and measures 3.6 x 3.24 x 2.05 metres (11.8 x 10.6 x 6.7 feet), whereas GGSE-4 is much smaller: it just 4.5kg (10lb), and is said to be attached to declassified NRO intelligence sat Poppy 5B, which has a mass of 86kg (190lb).

Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, said that given the size of the satellites - about the size of a auto and a rubbish bin - "a 15-to-30 metre predicted miss distance is alarming" - a sentiment echoed by LeoLabs.

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