NASA has found an Indian lunar orbiter that has been lost since 2009 using a new radar technology that will pave way for future missions moon.
The US space agency found India’s Chandrayaan-1 spacecraft in lunar orbit using its ground-based radar – an achievement that is particularly noteworthy for the fact that the spacecraft is very small by astronomical standards – about half the size of a smart car. The spacecraft was declared lost in August 2009 after Indians Space Research Organization (ISRO) lost contact with the spacecraft.
To locate the spacecraft NASA used Jet Propulsion Laboratory’s new radar technology. For the hunt JPL’s team used the space agency’s 70-meter (230-foot) antenna at NASA’s Goldstone Deep Space Communications Complex in California and sent out powerful beam of microwaves directed toward the moon located 237,000 miles (380,000 kilometers) away. The echoes that bounced back from the lunar orbit were received by the 100-meter (330-foot) Green Bank Telescope in West Virginia.
The team had one thing to rely on – Chandrayaan-1 is in polar orbit around the moon and so it would always cross above the lunar poles on each orbit. On July 2, 2016, the team pointed Goldstone and Green Bank at a location about 100 miles (160 kilometers) above the moon’s north pole and waited to see if the lost spacecraft crossed the radar beam. Chandrayaan-1 was predicted to complete one orbit around the moon every two hours and 8 minutes.
Something that had a radar signature of a small spacecraft did cross the beam twice during four hours of observations, and the timings between detections matched the time it would take Chandrayaan-1 to complete one orbit and return to the same position above the moon’s pole. The team used data from the return signal to estimate its velocity and the distance to the target. This information was then used to update the orbital predictions for Chandrayaan-1.
“It turns out that we needed to shift the location of Chandrayaan-1 by about 180 degrees, or half a cycle from the old orbital estimates from 2009,” said Ryan Park, the manager of JPL’s Solar System Dynamics group, who delivered the new orbit back to the radar team. “But otherwise, Chandrayaan-1’s orbit still had the shape and alignment that we expected.”
Radar echoes from the spacecraft were obtained seven more times over three months and are in perfect agreement with the new orbital predictions. Some of the follow-up observations were done with the Arecibo Observatory in Puerto Rico, which has the most powerful astronomical radar system on Earth.
The team also found NASA’s Lunar Reconnaissance Orbiter using the same technology, however, finding LRO was relatively easy says NASA as the team has been working with the mission’s navigators and had precise orbit data where it was located.