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2 satellites will — hopefully — narrowly avoid colliding at 32,800 mph over Pittsburgh on Wednesday

The The Infrared Astronomical Satellite (IRAS) orbits the Earth in this illustration.
The The Infrared Astronomical Satellite (IRAS) orbits the Earth in this illustration.
(Image: © NASA)

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).

When this article was first written Tuesday morning (Jan. 28) the odds of a collision were 1 in 100. A crash has since become five times more likely, with 1 in 20 odds. If the two satellites were to collide, the debris could endanger spacecraft around the planet.

If the satellites miss as expected, it will be a near miss: LeoLabs, the satellite-tracking company that made the prediction, said they should pass about 40 feet apart (12 meters) at 6:39:35 p.m. local time. The odds of a collision went up in large part based on the information that one of the two satellites, the Gravity Gradient Stabilization Experiment (GGSE-4), had a 60 foot (18 m) boom trailing from it, according to LeoLabs. No one knows which way the boom is facing, which complicates the calculation.

One of the satellites is called the Infrared Astronomical Satellite (IRAS). Launched in 1983, it was the first infrared space telescope and operated for less than a year, according to the Jet Propulsion Laboratory. GGSE-4 was a U.S. Air Force experiment launched in 1967 to test spacecraft design principles, according to NASA. The two satellites are unlikely to actually slam into each other, said LeoLabs CEO Dan Ceperley. But predictions of the precise movements of fairly small, fast objects over vast distances is a challenge, Ceperley told Live Science. (LeoLabs' business model is selling improvements on those predictions.)

Related: How much space junk hits Earth?

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.

Originally published on Live Science.

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  • Dave345
    The articles says, "... over Pittsburgh on Thursday evening (Jan. 29)."
    Thursday is Jan. 30.
    So which is it? Thursday the 30th or Wednesday the 29th? 🤷🏻‍♂️
    Reply
  • Prograde
    They will be passing each other at a COMBINED speed of 32,800.
    Reply
  • kamikrazee
    OK, I assume that neither is in a counter-rotational orbit, so, they are both in a (general) west to east path. Does anyone know, or know where we can find out, the individual angles of inclination of these two birds with respect to the equator? We could get a rough guess of a potential impact speed if we has an impact angle. Or not.
    Reply
  • BobPixel
    kamikrazee said:
    Does anyone know, or know where we can find out, the individual angles of inclination of these two birds with respect to the equator?

    IRAS is in a polar orbit roughly 900km up. GGSE-4 is in a nearly polar orbit, so that's how you get such a high closing speed. One is going north-ish and the other south-ish.

    Info derived from https://www.heavens-above.com
    Reply
  • Prograde
    kamikrazee said:
    OK, I assume that neither is in a counter-rotational orbit, so, they are both in a (general) west to east path. Does anyone know, or know where we can find out, the individual angles of inclination of these two birds with respect to the equator? We could get a rough guess of a potential impact speed if we has an impact angle. Or not.


    The graphic on another news source shows a fairly closely aligned north/south collision course.

    My point was only to clarify they are each moving about 16,400 mph at that altitude. 32,800 mph is a combined speed.
    Reply
  • Timsnj
    admin said:
    A collision would create a debris belt that would endanger spacecraft worldwide.

    2 satellites will narrowly avoid colliding at 32,800 mph over Pittsburgh on Thursday : Read more

    I don't get it. This is what the space shuttle was designed for. Now that the space shuttle has been put on ice who protects us from all the garbage in space. Sorry but there is something wrong with trying to clean up the damage that we have done to this planet when we have so much space garbage. What is the sense of saving the planet earth without saving the space around it. God for bid we go any further than Mars or even beyond our galaxy if we keep leaving garbage every where were we go. The UN should really be on this and include it in their conquest for renewable energy that does not pollute the universe. Maybe we should include space clean up for aliens that want citizenship with the planet earth.
    Reply
  • rebreb11
    admin said:
    A collision would create a debris belt that would endanger spacecraft worldwide.

    2 satellites will narrowly avoid colliding at 32,800 mph over Pittsburgh on Thursday : Read more
    lmao get real this is to take your mind off the real issues ....satellites are fake ...NASA is a scam
    Reply
  • MacSean
    rebreb11 said:
    lmao get real this is to take your mind off the real issues ....satellites are fake ...NASA is a scam
    Yeah like searching for BIGFOOT or proving the earth is FLAT! What a shame that this satellite article is distracting 99% of the nation with it's captivating subject matter. But what, if satellites and space is fake, how could my cousin/sister have gotten abducted by aliens? OMG my brain just exploded.
    Reply
  • kamikrazee
    OK, as I write, it is about 90 minutes past the expected (potential) impact time. What happened? How close was the miss, or, how large is the debris cloud?
    Reply
  • Crimson
    Timsnj said:
    I don't get it. This is what the space shuttle was designed for. Now that the space shuttle has been put on ice who protects us from all the garbage in space. Sorry but there is something wrong with trying to clean up the damage that we have done to this planet when we have so much space garbage. What is the sense of saving the planet earth without saving the space around it. God for bid we go any further than Mars or even beyond our galaxy if we keep leaving garbage every where were we go. The UN should really be on this and include it in their conquest for renewable energy that does not pollute the universe. Maybe we should include space clean up for aliens that want citizenship with the planet earth.

    So I'm not sure if its regulated or even in a treaty but for modern satellites, its generally expected that they be set on a path that obviously wont overlap with others. More importantly, they also are expected to have a mechanism that will force it to deorbit at the end of its life cycle. When they are small enough, they burn up on reentry... otherwise I guess they crash em into the ocean. I assume the problem this time, is this wasn't really a thing for "smaller" satellites back in the 80s, which is why that old bird is causing this problem.

    As far as space junk goes, that's no where near a concern when compared to the environment inside the atmosphere. As long as we don't get a run away debris effect, (See https://en.wikipedia.org/wiki/Kessler_syndrome) or even if we do, there are technologies being developed to handle that. Even a worst case scenario is reversible, quickly by burning it with lasers, or even just waiting it out over 100s of years. Besides, I know it was a joke, but if aliens show up with a friendly interest in our planet, they will be so far advanced that fixing a debris field will be equivalent to a normal ride in their space ship. If anything, the debris field might make us easier to spot!
    Reply