Nasa spots two long-lost craft orbiting the moon

Nasa has located two lost spacecraft in the moon’s orbit - one that's been missing for eight years - by making several telescopes work together in a new way.

Tracking down a missing spacecraft above the lunar surface is tricky due to regions around the moon called mascons, where gravitational pull is higher than usual. This affects a spacecraft’s orbit and can even cause it to crash into our natural satellite. 

The Lunar Reconnaissance Orbiter (LRO) and the Indian Space Research Organization's Chandrayaan-1 were found after a 70m antenna at Nasa’s Goldstone Deep Space Communications Complex in California directed a powerful beam of microwaves at the moon, which were then echoed back from lunar orbit to the 100-meter Green Back Telescope in West Virginia. 

A team from the Jet Propulsion Laboratory (JPL) in Pasadena, California, used the data to update Chandrayaan-1’s orbital predictions by estimating its velocity and distance thanks to the information from the returning signal. These radar echoes were received seven more times over three months, aligning with the new orbital calculations. 

The scientists shifted the location of Chandrayaan-1 about 180 degrees, “or half a cycle from the old orbital estimates from 2009”, says Ryan Park, manager of JPL’s Solar System Dynamics group, who delivered the new orbit back to the radar team. 

"Finding LRO was relatively easy, as we were working with the mission’s navigators and had precise orbit data where it was located," says Marina Brozovic, a radar scientist at JPL. But, she adds, locating Chandrayaan-1 “required a bit more detective work”. 

Until now, the Indian probe was considered undetectable by radars. It's very small, a cube of 1.5m on each side, and is orbiting at 200km above the moon.

India launched it to map the lunar surface in high spatial resolution and to search for any signs of water.

The discovery of LRO and Chandrayaan-1 in orbit proves that ground-based radars are powerful enough to detect and track small objects in orbit, says Nasa - opening up possibilities of applications in future robotic and human missions to the moon, both as a collisional hazard assessment tool and as a navigation and communication aid for spacecraft.