India’s Chandrayaan-3 spacecraft stands at the threshold of becoming the first scientific instrument to successfully survive the frigid lunar night without heating equipment.
Following a groundbreaking two-week mission, India’s lander and rover have transitioned into sleep mode in the cold darkness of the Moon’s southern pole.
India has completed its landing mission and scientific research at the Moon’s southern pole. (Photo: ISRO).
However, whether they can “wake up” when the Sun shines at the end of this lunar month remains a significant question.
Surviving the Frigid Darkness of the Moon
According to the Indian Space Research Organisation (ISRO), both the Vikram lander and the Pragyan rover of the Chandrayaan-3 mission are not equipped with conventional heating devices typically used for lunar missions.
This is an extremely risky decision, as temperatures near the Moon’s poles can drop to as low as -253°C, colder than some planets like Pluto.
The most common heating system found on spacecraft is called a Radioisotope Heating Unit (RHU), which works by passively releasing heat to keep onboard hardware functional over the long term without “freezing.”
Diagram of the Radioisotope Heating Unit. (Photo: Wikipedia).
Typically, RHUs are used in space missions to convert heat generated from the natural decay of radioactive isotopes like plutonium or polonium into electrical energy.
This process ultimately warms the spacecraft’s equipment or simply helps it survive in extremely cold temperatures.
It is known that both halves of the Moon will experience two weeks of sunlight, followed by two weeks of darkness.
The closer to the poles, the more extreme the temperatures are, due to the tilt and orbit, meaning only the highest mountains receive sunlight.
For this reason, RHUs have been used since the early lunar landing missions in the 1970s.
A Fragile Chance of Survival
Surviving the dark side of the Moon will be the next challenge for Chandrayaan-3. (Photo: NASA).
Historically, no device has survived a “cold winter” on the Moon without heating equipment. The common use of RHUs has made them a standard for space devices before they are deployed.
Lunokhod 1 (1970), Russia’s first lunar rover, traveled over 10 km in 10 months, thanks to the temperature and energy maintenance provided by a polonium-210 radioisotope heater.
Earlier, the Apollo 11 mission (1969) also used 34 grams of plutonium-238 for warmth during its lunar landing. China’s Chang’e-3 (2013) had similar mechanisms to protect its systems from the harsh lunar nights.
This mission’s rover, Yutu, survived its first night but lost mobility after the second night. In contrast, its successor, Yutu-2 (2018), has been more successful, able to wake up each time the Sun rises to continue its mission.
Russia’s Luna-25 lunar lander, launched on August 11, was also equipped with a heating system. Unfortunately, the vehicle encountered a problem during landing and could not complete its journey.
Simulation image of the Vikram lander and Pragyan rover from the Chandrayaan-3 mission. (Photo: ISRO).
To date, ISRO has not publicly discussed why radioisotope heating systems were not installed on the Vikram lander and the Pragyan rover of Chandrayaan-3. However, they have acknowledged that the duo will have to rely heavily on luck to survive the cold, dark night.
“If they cannot wake up, the Chandrayaan-3 lander will remain there as India’s lunar ambassador,” ISRO stated in a release. Nevertheless, the mission has been praised by the media as the “greatest scientific achievement” of India.
On the positive side, both devices of the Chandrayaan-3 mission have successfully completed their scientific objectives in a region that is sure to become a “hotspot” for human space exploration in the coming decade.
According to ISRO, the rover of the mission has traveled over 100 meters on the lunar surface, performing many important tasks such as chemical analysis, thermal mapping of the upper layer of regolith, and plasma measurements.
The scientific instruments of Chandrayaan-3 have also confirmed the presence of sulfur, iron, oxygen, and many other elements on the Moon.
It is expected that the Pragyan rover and Vikram lander will reactivate on September 22, coinciding with the next sunrise on the Moon’s dark side.
If successful, Chandrayaan-3 will set a new record as the first scientific instrument to survive the cold lunar night without heating equipment.