National Aeronautics and Space Administration has found India's Chandrayaan-2's Vikram lander, which crashed on the surface of the Moon in September, the United States space agency said on Tuesday, crediting a Chennai-based mechanical engineer for helping it trace the debris of the ambitious lunar mission by painstakingly comparing before and after images of the landing site.
NASA's confirmation came nearly three months after India's Chandrayaan-2 mission made a hard landing near the uncharted lunar south pole in the wee hours of September 7.
'The Chandrayaan-2 Vikram lander has been found by our NASA Moon mission, the Lunar Reconnaissance Orbiter. See the first mosaic of the impact site,' NASA said in a tweet sharing before and after images captured by its moon-revolving Lunar Reconnaissance Orbiter (LRO).
On September 7, the Indian Space Research Organisation (ISRO) attempted a soft landing of Vikram on the Moon.
However, ISRO lost contact with Vikram shortly before the scheduled touchdown.
NASA's Lunar Reconnaissance Orbiter Camera (LROC) team had released the first mosaic of images acquired during its September 17 flyby of the Moon.
NASA released the mosaic image of the site on September 26, inviting people to compare it with images of the same area before the crash to find signs of the lander.
The first person to come up with a positive identification was Chennai-based 33-year-old IT professional Shanmuga Subramanian, who confirmed the identification of the crashing site of Vikram by comparing before and after images.
Subramanian told PTI that it was meticulous data analysis for about eight hours daily and burning the midnight oil that helped him zero in on the crash site of the Vikram lander.
NASA said the debris first located by Shanmuga is about 750 metres northwest of the main crash site and was a single bright pixel identification in that first mosaic.
After receiving this tip, the LROC team confirmed the identification by comparing the images.
'When the images for the first mosaic were acquired the impact point was poorly illuminated and thus not easily identifiable,' NASA said in a statement, adding that two subsequent image sequences were acquired on October 14 and 15, and November 11.
The LROC team scoured the surrounding area in these new mosaics and found the impact point about 2,500 feet to the southeast of the planned touchdown site, and a spray of debris emanating outwards.
The November mosaic had the best pixel scale (0.7 metre) and lighting conditions (72 degrees incidence angle), NASA said.
'The November mosaic shows best the impact crater, ray and extensive debris field. The three largest pieces of debris are each about 2x2 pixels and cast a one pixel shadow,' the statement said.
On October 3, Subramanian tagged the twitter handles of NASA, LRO and ISRO in a tweet, asking, 'Is this Vikram lander? (1 km from the landing spot) Lander might have been buried in Lunar sand?'
On November 17, he further zeroed in on his observations and tweeted out the possible crash site of the lander.
'This might be Vikram lander's crash site (Lat:-70.8552 Lon:21.71233) & the ejecta that was thrown out of it might have landed over here … (The one on the left side was taken on July 16th & one on the right side was from Sept 17),' he said in a tweet accompanying the images.
As it turns out, Subramanian was spot on with his inferences, and now NASA has lauded him for finding the lander.
'NASA has credited me for finding Vikram Lander on Moon's surface VikramLander Chandrayaan-2,' Subramanian said in a tweet.
"Thank you for your email informing us of your discovery of debris from the Vikram lander. The LROC team confirmed that the location does exhibit changes in images taken before and after the date of the landing," said deputy project scientist Lunar Reconnaissance Orbiter mission John Keller.
"Using this information, the LROC team did additional searches in the area and located the site of the primary impact as well as other debris around the impact location and has announced the sighting on the NASA and ASU pages where you have been given credit for your observation," he said.
'I apologise for the delay in getting back to you. We needed to be certain of our interpretation of the observation as well as making sure that all stakeholders had an opportunity to comment before we could before we could announce the results.
'Congratulations for what i am sure was a lot of time and effort on your part,' Keller said in his letter to Subramanian who shared it on Twitter.
Subramanian said he had to view many gigabytes of images released by NASA over three weeks sans any high end technology or other gadgets that led him to his 'eureka moment'.
Hailing from the temple town of Madurai, he says he used two laptops to identify the site where Vikram crashed and to compare the satellite images captured before and after.
Every day after returning from work at a top IT firm, he used to analyse data between 10 pm and 2 am and again from 8 am to 10 am before going to office.
Ever since ISRO lost contact with Vikram, NASA had made several attempts to locate the Chandrayaan-2 lander with the help of its Lunar Reconnaissance Orbiter. The LRO flew over Vikram's landing site once on September 17 and next on October 14.
Chandrayaan-2 mission to the Moon launched in July. If the spacecraft had reached the surface in one piece on September 7, India would have been only the fourth country to successfully put a lander on the Moon apart from the US, Russia and China.
Photograph: Shanmuga Subramanian/Twitter