If you live in Pittsburgh and happen to spot some commotion in the sky at approximately 6:39 p.m. local time, don’t freak out. It’s quite possible that you’ll be looking at two satellites colliding 560 miles above the Earth as they crash into each other at high speed while circling the Earth. (Note: At that kind of height, you’re unlikely to see anything at all.)
The possible collision was noted by space-tracking company LeoLabs. According to its latest estimates, which are based on a network of ground-level radars that are used to detect and track low-Earth-orbit objects, the chance of a possible collision between the two satellites is approximately one in 20. This would mean that, if they do not collide as speculated, the two satellites will pass one another with just 40 feet between them, the equivalent to less than half a basketball court. That’s pretty darn close.
By comparison, a recent “near miss” that took place involving a SpaceX Starlink satellite and a weather satellite belonging to the European Space Agency (ESA) had a collision probability of one in 1,000.
4/ Adjusting our calculations to account for larger object sizes (by increasing our combined Hard Body Radius from 5m to 10m), this yields an updated collision probability closer to 1 in 20.
— LeoLabs, Inc. (@LeoLabs_Space) January 29, 2020
One of the satellites in question is the Infrared Astronomical Satellite (IRAS), a space telescope commissioned by NASA and launched in January 1983. It tips the scale at 2,100 pounds and is 847 cubic feet in size. The second satellite, POPPY 5B or GGSE-4, was launched in May 1967. A comparative minnow at 190 pounds and 60 feet fully extended, it’s still not the kind of space object you want to accidentally run into while whipping around the world at 33,000 miles per hour.
The chance that both satellites collide is still relatively low (although a 5 percent chance of it happening is still significant). If they do hit one another, the result will be debris that, while not immediately threatening, is still bad news for the orbiting space junk problem.
Between the physical risk associated with space detritus and the threat that the growing number of satellites poses to fields like astronomy, there’s more reason than ever to take space sustainability seriously. The question is exactly what should be done about it. Particularly when it comes to decommissioned satellites that have been orbiting Earth for decades.