On 21 September, a cold lunar night will cover the south pole of the moon, ending the last ray of hope for re-establishing communication with the Vikram lander, the efforts for which began minutes after it lost communication with the Indian Space Research Organisation (ISRO) just 2.1 km away from the lunar surface on 7 September.
In a possible indication of the end of efforts to communicate with the lander, on 17 September, ISRO had tweeted: “Thank you for standing by us. We will continue to keep going forward – propelled by the hopes and dreams of Indians across the world!”
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Again, on 19 September, when ISRO released its latest update on the Chandrayaan-2 mission, it spoke only about the orbiter conducting experiments and a national committee probing the reason for the loss of communication. There was no mention of the re-establishing communication.
So, how did ISRO try to re-establish contact with Vikram lander during the last two weeks?
Tracking the Missing Probe
At the heart of ISRO’s attempts to re-establish contact with Vikram lander was the Indian Deep Space Network (IDSN) in Byalalu, in the outskirts of Bengaluru city. IDSN is a network of large antennas and communication facilities meant to provide communication support to India’s interplanetary spacecraft missions.
In Chandrayaan’s case it was the 32-metre antenna, which was earlier supporting the Mars Orbiter Mission (MOM), that was employed to re-establish contact.
According to a senior scientist, the frequency for communicating with Vikram was already in place and since losing communication, at regular intervals commands were sent to the lander to activate the probe.
The hopes of a reply were dependent on the three transponders and a phased array antenna on the lander, meant for receiving and deciphering the commands from ISRO. Earlier news reports, based on the initial images captured by the orbiter, had suggested that the lander was in a tilted position. This was cited as a possible reason for equipment malfunction.
While ISRO has not officially confirmed whether the equipment was damaged, a scientist told The Quint, not getting a signal from the lander indicates possible damage to the communication devices.
ISRO was also trying to find if the solar panels meant for powering the lander were operational, but lack of communication with the lander left this unanswered as well.
Tracking Using the Orbiter
Apart from sending signals from Bengaluru, attempts were made to communicate with the lander using the Chandrayaan orbiter, since the orbiter and its payloads were operational. According to sources, even minutes after losing control, attempts were made to communicate with the lander using the orbiter. Although, the orbiter couldn’t communicate with the lander, it took its photographs.
US media reported that NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft snapped a series of images of Vikram's attempted landing site near the Moon's uncharted south pole during its flyby on 17 September, and the US space agency is now analysing and reviewing them.
What Caused the Loss of Communication?
ISRO has not officially released the details of what caused the loss of communication. In its latest statement, the space agency said: “National committee of academicians and ISRO experts is analysing the cause of communication loss with Vikram Lander.”
However, sources in ISRO said a hard landing on the lunar surface, because the lander failed to reduce velocity ‘may have’ resulted in the loss of communication.
According to them, at the point where the optimal landing velocity should be zero metres per second, the lander reported a vertical velocity of 59 metres per second (212 km per hour) and horizontal velocity of 48.1 metres per second (173 km per hour).
It is suspected that the lander’s reverse thrust-producing engines, which were supposed to reduce its velocity, for reasons unascertained yet, could have led to the increased velocity.
The Road Ahead
Even though ISRO is unable to communicate with the lander and the rover, the mission is still on. Out of 14 payloads of the Chandrayaan-2 mission, eight scientific instruments were on-board the orbiter, while the lander and rover had four and two instruments respectively. So despite losing communication with the lander and the rover, the eight instruments on-board the orbiter will continue the mission.
This equipment is expected to perform tasks like mapping the lunar surface, examining the presence of major elements, measuring the intensity of solar radiation and looking for water on the moon.
The current setback does not affect anything on ISRO’s agenda as the space agency has planned missions to study planets like Venus, Mars, and even the sun in the next few years. Apart from that, ISRO's first manned mission Gaganyaan will take its first flight in December 2020 and send three Indians to space by December 2021. ISRO recently completed the first phase of training astronauts for Gaganyaan.
But for now, on 21 September the attempts to communicate with the lander will come to an end, as the systems are not expected to survive the cold lunar night.
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