MUMBAI: Eight years after it was considered “lost”, India’s first lunar spacecraft, Chandrayaan-1, has been “re-discovered” by Nasa’s ground-based radars, the American space agency announced on March 10.
Chandrayaan-1, launched on October 22, 2008, was credited with the first discovery of water on the moon on November 14. After that, it lost communication with Isro ground stations on August 29, 2009 due to a technical problem. Speculation was rife at Isro then that it had crashed on the moon.
But nine years since its launch, a new radar technology pioneered by scientists at Nasa’s Jet Propulsion Laboratory (JPL) was put into place to trace Nasa’s Lunar Reconnaissance Orbiter and Chandrayaan-1. “This technique could assist planners of future moon missions,” Nasa said. JPL’s orbital calculations indicated that Chandrayaan-1 was still circling 200km above the lunar surface.
The father of India’s moon mission, Krishnaswamy Kasturirangan, said, “To be declared lost and then found after eight years is a great accomplishment.”
Chandrayaan-1 was our first interplanetary mission and I am delighted that it has been found.”
According to Nasa, the main challenge in detecting Chandrayaan-1 was on account of its size; the spacecraft is very small, a cube of about 1.5 meters on each side, about half the size of a smart car. It has not been transmitting signals.
According to Nasa, to find the spacecraft 3.80 lakh km away, the JPL team used its 70-metre antenna at the Goldstone Deep Space Communications Complex in California.
A powerful beam of microwaves was directed towards the moon. The radar echoes then bounced back from the lunar orbit, which were received by the 100-metre Green Bank telescope in West Virginia in the US, Nasa said.
The radar team utilized the fact that Chandrayaan-1 is in polar orbit around the moon. 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 160km above the moon’s north pole and waited to see if the Chandrayaan-1 crossed the radar beam.
Chandrayaan-1 was predicted to complete one orbit around the moon every two hours and eight minutes. Nasa said that the timing of the detections matched the time it would take for Chandrayaan-1 to complete one orbit and return to the same position above the moon’s pole.
Nasa explained that radar echoes from Chandrayaan-1 were obtained seven more times over three months and were in perfect agreement with the new orbital predictions.
“We’ve been able to detect Nasa’s lunar reconnaissance orbiter (LRO) and Isro’s Chandrayaan-1 spacecraft in lunar orbit with ground-based radar,” said Marina Brozovic, a radar scientist at JPL and principal investigator for the test project.