Two satellites nearly collided over US city of Pittsburgh
Two well-tracked human satellites had a fair chance of colliding in space above Pittsburgh, Pennsylvania; but had a near miss. According to various media reports, the satellites missed each other with a slight distance, adding that an increasing number of satellites in space made the situation more vulnerable. The two satellites involved were -- Infrared Astronomical Satellite (IRAS), an old space telescope that was part of a joint mission between NASA, the Netherlands, and the United Kingdom; and GGSE-4 -- a part of a gravitational experiment that the United States Air Force launched in May 1967.
Reportedly, the first satellite ran out of fuel and died. It, however, continues to encircle the Earth by virtue of momentum in a near-frictionless vacuum. The second satellite too is not operational.
According to a group tracking the satellites, the satellites were expected to be at nearly 33,000 mph (53,000 km/h) and had a fair chance of collision at about 18:30 EST (23:30 GMT), some 550 miles (900km) above Pittsburgh. Giving out the information, the group also termed the situation as 'alarming.' The last time a major satellite collision occurred was in 2009.
As per what the experts had predicted, the satellites could pass within 40ft (12m) of each other. The satellites are not operational, but a collision between the two may result in debris. The impact was very likely to damage other objects in the orbit too, they had said.
The collision between the two satellites was likely because of the sizes of the two, LeoLabs -- a group that tracks space debris has said.
The satellites are nearly the size of a car and a trash bin -- "a 15-to-30 metre predicted miss distance is alarming", Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics said.
The debris resulting from the collision, however, is of no threat to Pittsburgh, experts have said. It would simply burn up in the atmosphere before it could fall to Earth. But the debris cloud that remains in orbit could threaten other satellites and this debris is potential of remaining in the orbit for decades to centuries.
When did a satellite collision happen?
The last large collision of satellites happened in 2009, when a US commercial Iridium spacecraft hit a defunct Russian satellite over Siberia, producing thousands of pieces of debris. These satellites were launched prior to the rule changes, that stated that satellites in low orbits should be removed from orbit 25 years after being decommissioned.
The situation has renewed discussions over the importance of cleaning up space debris.
"Events like this highlight the need for responsible, timely de-orbiting of satellites for space sustainability moving forward," LeoLabs said.
According to what NASA says, there are nearly 2,000 active satellites orbiting the Earth. There are also more than 23,000 pieces of debris larger than 10cm (4in) in orbit. According to data from the Union of Concerned Scientists, the US has 1,007 operating satellites, the most by far of any country. The majority are commercial.
A 2019 article in the Massachusetts Institute of Technology (MIT) Technology Review stated by 2025, there could be as many as 1,100 new satellites launching per year.
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