As India’s Aditya-L1 heads to study the Sun, Moon mission Chandrayaan-3 to fall asleep

Within 10 days of having successfully soft-landed Chandrayaan-3 near the Lunar South Pole (and making India the first nation to do so), the Indian Space Research Organisation (ISRO) has launched a craft to study the Sun from afar. As Chandrayaan-3 nears the end of its planned operational life (14 earth days or one Lunar day) and goes to sleep soon, it is now for Aditya-L1 to stay awake and continue on its 125-day journey to the Lagrange Point 1 position, from where it will observe the sun.

Chandrayaan-3 soft-landed on August 23 and the Aditya-L1 mission was placed in its designated elliptical (egg-shaped) orbit around 1:00 pm (local time) on Saturday, August 2. Over the last 10 days, the Chandrayaan-3 lander and rover have been performing in-situ experiments with their respective payloads and sharing the data. However, the end of the Lunar day time is closing in fast on the Vikram Lander and Pragyan Rover. As the duo are solar-powered, they would not be able to function during the fortnight-long Lunar night.

“The Chandrayaan-3 Lander and Rover are functional and our payload teams are doing all th work...The Rover has traversed a distance of 100meters from the lander... In a day or two, we will start the process of putting the lander and rover to sleep, in order to withstand the lunar night (that lay ahead)” Dr S Somanath, Chairman of ISRO, said following the successful launch of the Aditya-L1 solar observatory satellite.

On average, the temperature during the Lunar day could be around 120 degrees Centigrade (For earthlings - that’s much more than the boiling point of water or more than twice the hottest recorded temperatures on Earth). Whereas the Lunar nights could get as cold as -130 degrees Centigrade (that’s almost twice the coldest temperature recorded on the Earth). At the Lunar poles, these temperatures could be even more extreme and hostile.

ISRO hinting that the Chandrayaan-3 lander and rover are to be put to sleep, shows that the Indian space agency has the possible technological means and hope to make Vikram and Pragyan survive the Lunar night. Else, if the mission were to come to an end after the Lunar day, ISRO could have mentioned bidding permanent goodbye to the lander and rover.

By switching off all the on-board equipment and going into hibernation mode and protecting itself from the cold (comparable to covering oneself using a blanket), ISRO could possibly ensure that Chandrayaan-3 survives the Lunar night.

When the Lunar dawn breaks next (around the third week of September), if and when the lander and rover survive, they could again harness the power of the Sun and charge their batteries and continue to carry out their operations. Though a possibility, this could prove a serious bonus to ISRO’s exploratory activities near the Lunar South Pole region, which India temporarily has for itself to explore. However, both the lander and rover have to survive the night for the duo to function normally.

This is because the Lander craft is the primary and direct communication link with the Earth. If the lander cannot communicate directly, it could also use the services of the Chandrayaan-2 orbiter to relay its communications to Earth and receive new commands. However, the 26-kg rover is entirely dependent on the lander to receive commands and carry out communications, and data transfer.

“We are hoping that after the Lunar night it will come back, but it is not assured. This is because, all systems will go to minus 150degrees Centigrade temperature, which is far beyond the survival limit of may materials used on the lander craft. By design it is meant to live for 14days, but if we are lucky, we may get longer,” M. Sankaran, Director of ISRO’s UR Rao Satellite Centre had told WION.

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