Editor's note: This story was updated 12:20 p.m. E.S.T. on Jan. 29 to reflect new information from LeoLabs about the satellites and their collision risk.
Two defunct satellites will — hopefully — zip past each other at 32,800 mph (14.7 kilometers per second) in the sky over Pittsburgh on Wednesday evening (Jan. 29).
If they did collide, "there would be thousands of pieces of new debris that would stay in orbit for decades. Those new clouds of debris would threaten any satellites operating near the collision altitude and any spacecraft transiting through on its way to other destinations. The new debris [would] spread out and form a debris belt around the Earth," Ceperley said.
LeoLabs uses its own network of ground-based radar to track orbiting objects. Still, Jonathan McDowell, a Harvard-Smithsonian Center for Astrophysics astronomer who tracks satellites using public data, said the near-miss prediction was plausible.
"I confirm there is a close approach of these two satellites around 2339 UTC Jan 29. How close isn't clear from the data I have, but it's reasonable that LEOLabs data is better," McDowell told Live Science.
(When it's 23:39 UTC it's 6:39 p.m. Eastern time, which is the time zone in Pittsburgh.)
"What's different here is that this isn't debris-on-payload but payload-on-payload," McDowell said. In other words, in this case two satellites, rather than debris and a satellite, are coming close to one another.
It's pretty common for bits of orbital debris to have near misses in orbit, Ceperley said, which usually go untracked. It's more unusual, though, for two full-size satellites to come this close in space. IRAS in particular is the size of a truck, at 11.8 feet by 10.6 feet by 6.7 feet (3.6 by 3.2 by 2.1 m).
"Events like this highlight the need for responsible, timely deorbiting of satellites for space sustainability moving forward. We will continue to monitor this event through the coming days and provide updates as available," LeoLabs said on Twitter.
It's still unlikely the two satellites will collide, and the odds are subject to change based on new information. When this article was first written, LeoLabs calculated 1 in 100 odds of a collision. They've since been revised down to 1 in 1,000, and then up to 1 in 20.
Editor's note: This story was corrected on January 28. The date Jan. 29 is a Wednesday, not a Thursday.
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Originally published on Live Science.
