While it’s not written in the stars, two out-of-use space satellites may collide Wednesday evening.
LeoLabs, Inc., a space debris tracking service, announced on Twitter Monday that it was monitoring a possible collision between two satellites — IRAS (13777) and GGSE-4 (2828).
IRAS (1377) is a decommissioned space telescope that was launched in 1983. It is 3.6 by 3.24 by 2.05 metres in size, and had a launch mass of 2,388 pounds.
GGSE-4 (2828) is a retired 10-pound experimental payload that was launched in 1967. GGSE-4 is attached to another satellite, Poppy 5 (aka 1967-053G), that weighs 187 pounds.
LeoLabs data predicts that at approximately 6:39 pm EST Wednesday, the two satellites will come within 15 to 30 metres of each other. According to LeoLabs’ calculations, the satellites have a near one-in-100 chance of colliding.
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Alice Gorman is a space archaeologist at Flinders University. She calls the potential collision “one of the most dangerous possible collisions that we’ve seen for some time.”
“Spacecraft have taken evasive manoeuvres to avoid things that are only within 60 kilometres. So, this is a really, really close encounter,” Gorman said in an interview with ScienceAlert. “And if this does actually come to pass, there’s potentially a large amount of debris that will be created.”
Gorman says the danger of space debris is that it could collide with functioning satellites. If the collision does occur, it poses no threat to earth because de-orbiting debris would burn up in our atmosphere.
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According to NASA, in order for a satellite to stay in orbit with the Earth, the pull of gravity must be balanced with the object’s speed. As such, the two satellites on course for collision are travelling at an extremely fast relative velocity of 14.7 kilometres per second.
“They’re going to be colliding at an incredibly high speed. And, at that speed, it’s going to probably cause the smaller satellite to break up completely into smaller fragments. And each of those fragments becomes a piece of space debris in its own right,” Gorman told ScienceAlert.
The NASA/NIVR IRAS satellite and the NRO/USN POPPY 5B satellite (aka GGSE 4) are predicted to make a close approach on Wednesday. POPPY 5B has 18-metre-long gravity gradient booms so a 15-to-30 metre predicted miss distance is alarming https://t.co/H1UckcoaAH— Jonathan McDowell (@planet4589) January 27, 2020
“Events like this highlight the need for responsible, timely deorbiting of satellites for space sustainability moving forward,” LeoLabs said in a tweet. “We will continue to monitor this event through the coming days and provide updates as available.”
Satellites colliding is not an unheard of event. In 2009 a decommissioned Russian satellite, Cosmos-2251, and an active U.S. satellite, Iridium 33, collided.