A collision of two satellites in space may happen over Pennsylvania Wednesday (January 29, 2020) evening, perhaps distributing dangerous debris if impact occurs. The two satellites, NASA’s Infrared Astronomical Satellite (IRAS) space telescope and the experimental U.S. Naval Research Lab satellite GGSE-4, will approach each other at an estimated altitude of about 559 miles in the skies above western Pennsylvania. Traveling at a speed of roughly 32,880 miles per hour, it is possible they could hit each other. If that were to happen, debris from the impact would scatter, with some potentially threatening other satellites in space, and perhaps even the International Space Station. People on Earth are safe though: it is unlikely debris would reach the Earth’s surface. While debris wouldn’t reach the Earth, the impact could be visible on earth across a large multi-state area.
LeoLabs, a company that monitors the trajectories of spacecraft in Low Earth Orbit, initially forecast that there was a 10% chance of collision, with the two satellites coming within 50 meters (150 feet) of each other. In their latest update today, they now say their calculations show a “potential miss distance of 13-87 meters” and have lowered the overall collision probability down to 1 in 1000. If their math is correct, the time that the two satellites will be closest to each other is Wednesday at 6:39pm ET. There could be some wobble with their orbits so the precise time and location isn’t perfectly known; as such, the threat of collision persists, albeit with somewhat lower odds.
“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,” tweeted Leo Labs Inc.
Even a close-call of 87 meters is too close. While these satellites were launched in an era before they could be controlled on the ground, modern day satellites typically perform special maneuvers to avoid collisions if they come within 60 kilometers of an object.
One reason for alarm is the size of the IRAS satellite. Launched in January of 1983, it became the first-ever space telescope to perform a complete survey of the night sky at infrared wavelengths. To do that over its 10 month mission, it needed to be large. It is 11.8 feet by 10.6 feet by 6.7 feet large and had a launch mass of 2,388 pounds.