A mechanical engineer from Chennai, Shanmuga Subramanian, who spotted debris of the Chandrayaan 2 lander in images from NASA in 2019, has now sent a round of emails to the Indian Space Research Organisation, NASA and the media, claiming that the rover likely survived the hard landing. His claims were based on images from NASA's Lunar Reconnaissance Orbiter in May 2020.
Subramanian claims that the Pragyan rover left tracks, suggesting that it moved at least a few meters away from the Vikram lander after the landing, as per his email and a Twitter thread sharing his theory. In images from the NASA Lunar Reconnaissance Orbiter's (LRO) overhead pass of the Chandrayaan 2 lander's suspected crash site, Subramanian had spotted the debris of the Vikram lander.
"Previous images before impact show nothing in the area...whereas after impact the images (do) show some objects..." he said. "Debris we found might be of the other payloads...engines & skeleton lander containing (the) rover would have jumped off the impact & landed...(the) rover was designed to automatically come out after 3 hours," he added.
Debris we found might be of the other payloads,engines & skeleton lander containing rover would have jumped off the impact & landed|Rover was designed to automatically come out after 3 hours | South Pole is so tough to land & it becomes much more difficult with diff illumination
" Shan (Shanmuga Subramanian) (@Ramanean) August 1, 2020
However, more recent images from the crash site show that the rover may have survived, Subramanian claims.
"Going by 4 January images [made public in May], I think Pragyan may be intact and that it has rolled out a few metres from the lander," he told The Times of India. "We need to know how the rover may have moved and I hope ISRO is able to confirm this."
Responding to Subramanian's findings, the Chairman of ISRO said that they had not heard from NASA about the images, and are looking into the data Subramanian has sent them.
"We've heard nothing from NASA so far on the matter. But yes, the person who had identified Vikram debris earlier has sent us an email about this. Our specialists are looking into the matter, and we cannot say anything at this juncture," Dr K Sivan told TOI.
"We will have to analyse and see what may have happened. There is nothing concrete now," Sivan added.
Vikram lander's ejecta as seen be LRO's camera. Image: NASA
Based on his own investigation, Subramanian proposed that the rover's movement in the images could be explained by a one-way lapse in communication between the lander and ground stations. While ISRO was unable to communicate with the lander even before its planned soft-landing, the lander may have relayed some of the many commands that ISRO was pinging to test communications and prompt a response from the lander-rover duo after its crash.
If this was how events unfolded, ISRO may not have known that the communication was successful, Subramanian suggests.
NASA has also shared that except for some regions, the South Pole is not bathed in sunlight throughout the year. This is because of the Moon's tilt, and similar to the pattern of sunlight in the Earth's south pole, which leaves the poles either lit well or poorly for months at a time.
This, along with the long shadows cast by structures in the lunar South Pole, are likely why NASA wasn't able to spot the lander debris in the LRO's 17 September and 18 November images, the space agency had said. Subramanian, however, claims the debris is clearly visible in LRO images from 4 January and 14 March 2020.
ISRO's post-crash investigation
ISRO had said soon after the fateful hard-landing on 7 September, that ground stations had lost communication with Vikram (and the rover Praygan tucked inside it), minutes before its planned touchdown on the lunar surface.
Since then, ISRO claimed to have been making "all possible efforts" to establish a link with the lander, but said it had temporarily suspended those operations by end of September after nightfall descended on the landing site.
"Now it's not possible [since] it's night time at our landing site...power may not be there", K Sivan told PTI on 1 October 2019. "We will make efforts afterwards [during day-time on lunar surface] also."
ISRO had constituted a national level committee consisting of academics and agency experts to analyse the cause of the communication loss with the lander.
"The committee is seriously working on that, and their report will be available soon. I don't think it will take more than a month", the official said.
In November 2019, ISRO spokesperson Vivek Singh said in an interview that the report's findings will be revealed in Parliament and likely not disclosed to the general public.
"As of now, the report is unlikely to be made public, but the findings will come out in Parliament. I cannot say anything else apart from what is given in writing," Singh said, according to a Hindustan Times report.
However, in a written update to the Parliament about the Chandrayaan-2 mission on 20 November, minister of state for the Department of Space Jitendra Singh, said that the Vikram lander had "hard landed" on the moon after a problem with its braking thrusters. This was the last official update from ISRO on the landing.