NASA has managed to find a “lost” Indian spacecraft in orbit around the Moon using a novel technique that could be used to track spacecraft in the future.
Scientists at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California, used NASA’s Goldstone Deep Space Communications Complex – also in California – to send a beam of microwaves to the Moon. By recording the waves that bounced back, they were able to detect two spacecraft – one dead and one alive – in lunar orbit, 380,000 kilometers (237,000 miles) away.
The “living” spacecraft was NASA’s Lunar Reconnaissance Orbiter (LRO), which has been in lunar orbit since 2009. Its orbital characteristics are well known, so working with the team’s navigators, these scientists were able to track it down by reflecting microwaves off it.
Using this same technique, they then attempted to find India’s Chandarayaan-1 spacecraft. This was launched to the Moon in October 2008, but it was last heard from in August 2009. So finding it presented a bit more of a challenge.
"Finding LRO was relatively easy, as we were working with the mission's navigators and had precise orbit data where it was located,” said team member Marina Brozovic in a statement. “Finding India's Chandrayaan-1 required a bit more detective work because the last contact with the spacecraft was in August of 2009."
To track it down, the scientists noted the spacecraft – just half the size of a car at about 1.5 meters (5 feet) across – had been in a polar orbit around the Moon. They knew it’s orbital period, about 2 hours and 8 minutes, and also knew its altitude, about 200 kilometers (124 miles) above the surface.
So they fired their beam of microwaves 160 kilometers (100 miles) above the Moon’s north pole on July 2, 2016, to see if any would reflect off Chandrayaan-1 as it flew past on its predicted orbit. And they were in luck, with the spacecraft’s radar signature crossing the beam twice in four hours of observations.
Thus, they were able to pinpoint where it is now. They found it had shifted its orbit by about 180 degrees, or half a cycle, since 2009, but it was otherwise still swinging around the Moon in the same orbit.
Follow-up observations were done over the next three months, which included using the Arecibo Observatory in Puerto Rico, to confirm the spacecraft’s location. The team said this method could be useful for future missions to the Moon to help track their precise location.