Two satellites might be headed for a collision — and there's no way to stop them

• There is a 1-in-100 chance that two defunct satellites — IRAS and GGSE 4 — will collide.
  
• There’s no way for scientists to stop the collision since they can’t send signals to conduct evasive manoeuvres.
  
• More than the actual collision, the resulting debris is a bigger threat.
  

Space debris in Earth’s orbit ranges from leftover rocket parts to satellites that are no longer operational. Two such defunct satellites might be headed for a collision this week.

The Infrared Astronomical Satellite (IRAS) and the Gravity Gradient Stabilisation Experiment (GGSE 4) will be travelling at over 14 kilometres per second (kph). According to LeoLabs, there’s one in 100 chance that they will collide. At best, it will be a near miss as they pass each other at a distance of 15 to 30 meters.

The satellite-tracking company predicts that the close approach will occur on Wednesday evening over Pittsburgh in the US.


Why can’t we stop them?
Since both the satellites are now defunct, there’s no way for scientists on Earth to communicate with them — or send signals for evasive manoeuvers.

It should be noted that, in the past, space agencies have conducted evasive manoeuvres even when satellites were over 60 kilometres apart. IRAS and GGSE 4 will be much closer — and one has a better chance of obliterating the other. IRAS is massive and weighs 1,083 kilos. In comparison, the GGSE 4 is only 4.5 kilos.

What happens when satellites collide?
If the two satellites do go bump in the night, the collision itself might not be the most destructive aspect of the equation.

The resulting debris from the event could linger and travel for decades to come, threatening the existence of other satellites — including ones that currently functional and play critical roles. This was the same concern expressed by experts when India conducted its first anti-satellite (ASAT) test — Mission Shakti — last year.

However, anyone who’s down here on Earth will be safe. Any debris that might fall to Earth is likely to burn up in the atmosphere upon re-entry.

The bigger concern is what this means for the future as Earth’s orbit gets more congested. For instance, the initial plans for Elon Musk’s SpaceX Starlink constellation consist of nearly 12,000 satellites — which pending proposals for another 30,000.

To put that in perspective, there are a little over 2,000 satellites in orbit right now. Taking into account other space junk and inactive satellites, the total amount of objects is still only around 23,000.

In the near future, that amount will — at minimum — double.

See also:
India doesn't trust US with measuring space debris — and so it will set up its own agency

Europe wants to use a suicidal robot to clean up space — one satellite at a time

US, Russia and China with space debris in the thousands are complaining about 49 pieces from India's A-SAT test