BENGALURU: ISRO scientists are confident of successfully ‘waking up’ Chandrayaan-3’s rover Pragyaan and lander Vikram on Friday, after being put in a ‘sleep mode’ on September 2 and 4, respectively, to survive the 14-day lunar night.
Pragyaan and Vikram have been exposed to extreme cold temperatures of about -200 degrees Celsius through the lunar night at Shiv Shakti Point near the Moon’s south pole.
The ground station at ISRO Telemetry, Tracking and Command Network will try to revive the lander and rover modules after optimum sunshine is available to adequately recharge the lithium-ion batteries.
“The chances of resurrecting the two are bright because of the extensive simulations that were carried out by ISRO before the mission launch on July 14.
During the simulation tests, Vikram and Pragyaan were exposed to lower than -180 degrees Celsius for more than 14 days, and were yet successful in restarting them,” said a scientist involved with developing and testing the batteries of the lander and rover.
‘Chances of lander, rover waking up high’
Vikram and Pragyaan were put into sleep mode with the onset of the lunar night to prevent damage. “We are hopeful that the two will wake up after attaining positive temperatures. The lander will take more time to restart because of its volume and weight. We have to wait and watch. However, it is an unknown territory. The unknown remains unknown,” he said.
According to experts, generally electronic systems do not survive such extreme cold conditions if battery wires and links are soldered, as they start cracking. But ISRO scientists, who were involved with the batteries of Vikram and Pragyaan, informed TNIE that most of the wiring was not soldered but joined through ‘crimping’ (a process of compressing a metal sleeve around two or more wires to join them) and ‘soft-welding’.
“There is no soldering inside the batteries. Instead, crimping and spot-welding were done. There’s minimum soldering and weather extremes will not matter,” the scientist informed, adding that crimping was a safer option than soldering, besides other advantages, including speed and ease of use. It does not damage the insulation or components of the wires under extreme weather conditions.
According to ISRO, the Sun rose on the Moon’s south pole on Wednesday. But the Sun’s elevation was not adequate to generate power on Vikram and Pragyan on Thursday because of their positioning.
According to sources, chances of the lander and rover waking up and restarting are “very high” despite the extreme cold they were exposed to.
Earlier, ISRO Chairman S Somanath said, “The temperature falls below -200 degrees Celsius (during the lunar nights). In such an environment, there is no guarantee that the battery or electronics will survive. But we did some tests and we get the feeling they will survive even in such harsh conditions.”
ISRO officials and scientists, however, said even in the event of the lander and rover not waking up, it would not be considered a failure. Chandrayaan-3 has achieved more than 100% of its targeted
mission of soft landing, roving and conducting in-situ experiments.
“If the lander and rover wake up it will be a bonus. The scientists will make an attempt tomorrow (Friday). If they respond, India will have an extended Chandrayaan-3 mission,” said a scientist.