A discarded Russian rocket body and fragments from a 2007 Chinese anti-satellite missile test were involved in a near-miss yesterday, sending shudders down the spine of space traffic controllers worldwide.
LeoLabs, which operates a space-tracking radar in Western Australia, issued a warning after its global network assessed the objects as coming within 9.5m of each other at a combined speed of over 50,000km/h.
Given the “bubbles of uncertainty” surrounding the exact location of each object, this presented a particularly high risk of collision, says Leolabs Pacific President Terry van Haren. “This is a timely reminder of the ‘ticking timebomb’ that we have in the bad neighbourhoods of low Earth orbit (LEO).”
Making matters worse was their orbit.
They were in the busy 970km to 980km band popular among a new generation of micro and small commercial satellites.
“Since there is no debris field or evidence of a collision, then we can safely say that the event did not occur,” Saber Astronautics CEO Dr Jason Held told Cosmos.
Held says space-tracking services and companies are obliged to report any potential collision their sensors flag. This means other operators can quickly move to analyse the threat.
“NORAD did not list this as a highly likely collision, so it’s likely that their data is a bit different,” Held says. “With a small, fast-moving object, small errors in observation can get magnified. But it’s okay to be the company that cries wolf though – it’s always better to investigate than to be surprised!
“Here at the RSOC (Responsive Space Operations Centre at Lot 14, Adelaide), we’ll then use multiple sensors from multiple suppliers to verify position.”
Objects in LEO are especially hard to track, he adds, because they are moving at about 8km/sec. “This makes it hard to determine actual position. What you really get is a range. That’s why it’s tough.”
Space traffic control is still in its infancy. Held says: “It is like air traffic control was in 1922. There are a lot of barnstormers up there, and collisions do happen. But nobody talks about it.
“We have a general picture because people are tracking them, but it takes all of the combined commercial sensors on the market working the sky at the same time to come close to what is available from government sources.”
Such a collision would produce a shotgun effect of small debris. “They’ll tend to have new orbits in a similar altitude, but different directions,” says Held.
These can then cannon into other orbital objects, generating new debris fields.
And, at the LEO altitudes involved in this conjuction, it will take decades for the combined influence of solar weather and gravity to drag the debris back to Earth.
“Regardless of where we are today, we need to get a system in place within 5 years to meet the volume of debris that is flying,” Held says. “And we keep launching stuff, so the clock is ticking.”
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