spaceSpace and Physics

Two Satellites May Collide Over Pennsylvania’s Sky This Week


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

clockJan 28 2020, 13:05 UTC

Andrey VP/Shutterstock

Two decommissioned satellites will pass very close to each other on January 29 and according to satellite tracking company LeoLabs Inc there is a one-in-100 chance of the two craft colliding. While the collision is no threat to humans on Earth, these kinds of events are exacerbating the risk of dangerous debris striking crewed crafts and important satellites.

One of the satellites in question is the decommissioned Infrared Astronomical Satellite (IRAS), the first-ever infrared telescope to perform a survey of the entire sky, which operated for 10 months in 1983. It's definitely the chunkier of the two, at 3.6 meters by 3.24 meters by 2.05 meters (11.8 × 10.6 × 6.7 feet) and weighing slightly over a ton. The other object is GGSE-4, a 4.5-kilogram (10-pound) retired science satellite that was launched in 1967.


According to LeoLabs, at 11:39pm UTC the two satellites will come as close as 15 to 30 meters (50 to 100 feet) to each other, roughly 900 kilometers (560 miles) over the city of Pittsburgh, Pennsylvania. Given that both satellites are no longer in operation, there’s no way to correct their orbit and put them on a safer course.  

"Such collisions have happened in the past for sure. The thing that's really interesting about this one is that the estimated close pass within 15 to 30 metres is incredibly close," Dr Alice Gorman, a space archaeologist at Flinders University told ScienceAlert.

"Spacecraft have taken evasive maneuvers to avoid things that are only within 60 kilometers. So this is a really, really close encounter. And if this does actually come to pass, there's potentially a large amount of debris that will be created. I would say this is one of the most dangerous possible collisions that we've seen for some time."


The main concern when a collision occurs is that we are getting closer to the formation of the so-called Kessler Syndrome. A theoretical scenario, it posits collisions between space debris cause more space debris, and if the density of objects is high enough they could create even more collisions, eventually making those orbital ranges difficult to use or pass through for generations.

There are over 100 million pieces of debris orbiting in space and they are a risk to satellites and astronauts alike. There are remains of used rockets, satellite fragments, a lost camera, and for a time even a spatula. Most of the debris is moving at around 8 kilometers (5 miles) per second or faster – even a tiny speck of paint is extremely dangerous under those conditions.

[H/T: ScienceAlert]

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