Ever since Chandrayaan-3 lander, Vikram, landed on the moon’s surface on August 23, and its Pragyan rover rolled down the ramp, explorations of the lunar south pole region have been going on full throttle. The lander and the rover have been in operation for more than ten days now. Both Vikram and Pragyan have a mission life of 14 earth days. Currently, they are more than halfway through the time allocated to them. Data is constantly being transmitted back to the earth through the Indian Space Research Organisation’s (ISRO’s) Deep Space Antenna Networks.
Vikram and Pragyan will be left on the moon’s surface after their mission life ends, and will be decommissioned. Since the lander and the rover rely on solar panels to generate power, as the mission progresses, there arise fascinating uncertainties about the lander’s ability to last for another 14 earth days (equivalent to a single lunar day).
“Following this initial 14-day phase, the moon experiences a 14-day lunar night. Throughout this nighttime period, Vikram and Pragyan go into a state of dormancy as they can only function in daylight and depend on solar power. Compounding the difficulty, the moon’s nighttime period is incredibly harsh, with temperatures dropping to a frigid -208°F (-133°C). These exceptionally cold conditions present a substantial hurdle to the effective functioning of both rover and the lander, and their scientific instruments,” said space and aerospace expert, Girish Linganna.
Chandrayaan-3 has not been programmed to return to the earth. Its lander and rover will remain on the moon’s surface. If both remain functional, as is often the case, ISRO will keep gathering data through them about the moon’s surface. “Vikram and Pragyan cannot be considered space junk after they become defunct. Since both will remain on the moon’s surface after becoming defunct, they cannot be considered ‘space debris’ as the term refers only to non-functional objects remaining in earth’s orbit, posing a risk to active spacecraft, as these objects include abandoned spacecraft, fragments from disintegration and even minuscule particles resulting from various space activities,” said Linganna.
India has been the first country to land its lander and rover on the south pole of the moon. But the US, Russia and China have also had successful lunar missions earlier. For instance, the Apollo Lunar Module (LM) from the US was the spacecraft that landed the Apollo astronauts on the moon. It consisted of two parts—a descent stage that lowered the astronauts to the surface, and an ascent stage that brought them back to the command module in orbit. The Apollo LM did not have a rover. Instead, during the Apollo missions, astronauts used the Lunar Roving Vehicle (LRV), commonly known as the ‘Moon Buggy’, to explore the lunar surface. The LRV was a specially designed electric vehicle that allowed astronauts to travel greater distances on the moon’s surface, conduct experiments, and collect samples more efficiently. It was carried to the moon on the Apollo 15, 16, and 17 missions and played a crucial role in lunar exploration during those missions.
“The engine of the Apollo 10 ascent stage was fired until it exhausted its fuel, jettisoning it far past the moon into a heliocentric orbit. The Apollo 11 ascent stage, however, was abandoned in the moon’s orbit and it eventually crashed; all subsequent ascent stages (except for Apollo 13) were purposely channeled to the moon to obtain readings from its surface seismometers,” explained Linganna.
Likewise, the first Russian lunar rover, Lunokhod 1, was launched in 1970. It was a larger, six-wheeled rover that explored the surface of the moon for 10 months. The Lunokhod 1 rover was about 2.3 metres long and 1.5 metres tall. It had eight independently powered wheels and was equipped with a variety of instruments, including cameras, spectrometers and a seismometer. The rover was also equipped with a laser reflector, used by scientists on the earth to measure the distance between the earth and the moon.
The Lunokhod 1 rover landed in the Sea of Rains on the moon, about 38 degrees north latitude and 35 degrees west longitude. It explored the surface for approximately three months (11 lunar days), traveling a total of 10.54 kilometres. The rover sent back more than 20,000 images and 200 panoramas of the lunar surface. It also conducted more than 500 soil tests. The Lunokhod 1 rover is still on the moon today, but no longer operational.
Chang’e 3 and 4 were Chinese lunar missions. Chang’e 3 mission was launched in 2013 and landed on the moon in December that year. It carried a rover called Yutu, which is still exploring the lunar surface today. Chang’e 4 mission was launched in 2018 and landed on the far side of the moon in January that year. It carried a rover called Yutu 2, which is also still exploring the lunar surface.