India’s third lunar exploration mission, Chandrayaan-3, successfully took off on Friday afternoon, at around 2:35 pm, from the second launch pad at SDSC-SHAR, in Sriharikota, on board the LVM3 heavy lift launch vehicle.
Chandrayaan-3 marks a major milestone in India’s space programme and for the Indian Space Research Organisation (Isro), 15 years on from its first lunar mission, Chandrayaan-1. The follow-on mission to Chandrayaan-2, which was launched in July 2019, the Chandrayaan-3 mission aims to demonstrate end-to-end capability in safe landing and roving on the lunar surface. The mission is also expected to help Isro’s future plans for interplanetary missions.
The propulsion module on Chandrayaan-3 will carry the lander and rover configuration till 100 km above the lunar surface. It will take Chandrayaan-3 roughly 42 days to reach the Moon. The lander is expected to separate from the propulsion module and begin its descent to the surface around 23-24 August. Only the US, Russia and China have previously achieved a controlled landing on the lunar surface.
The biggest difference between the two missions is that Chandrayaan-3 does not have an orbiter. The 3,900-kg Chandrayaan-3 spacecraft has three main components: a propulsion module (that will carry the lander from launch injection to the lunar orbit), the lander (which will attempt a soft landing on the lunar surface) and the rover (which is housed inside the lander). Once deployed, this rover will aim to carry out in-situ chemical analysis of the lunar surface during the course of its mobility, the Isro website explains.
The propulsion module is also carrying a Spectro-polarimetry of Habitable Planetary Earth (SHAPE) payload to study the spectral and polarimetric measurements of earth from the lunar orbit, according to a detailed mission brochure. The SHAPE payload is an experimental payload that will observe the light coming from Earth in the near infrared wavelength. According to Isro, this observation will help in understanding the nature of other distant planets. “It will look back on the Earth and study it from the orbit. That shows how Chandrayaan 1, 2 and 3 are very different missions,” says Somak Raychadhury, vice-chancellor, Ashoka University. “The landing is a test this time.”
Chandrayaan-1 showcased India’s ability to reach the lunar surface – while doing so, the mission also made the conclusive discovery of lunar water in 2009. Chandrayaan 2 had an orbiter, lander and rover. The lander – along with the rover - was scheduled to land on the south pole region of the moon but crashed during its final descent. Isro cited a “software glitch” as the reason behind the crash. The orbiter, however, successfully continues to function and observe the lunar surface.
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“Chandrayaan-2 did a lot more because a lot of the major instruments were on the orbiter, which continue to work. It has produced some amazing results: including the first unambiguous detection of water, which is the 3-micron absorption line in the infrared spectrum. It’s produced some very good results on the thermal properties of the moon, etc,” says Raychadhury during a video call. He adds: “In the intervening 2-3 years, they have gone and analysed a lot of data about what went wrong with the lander... Things have been chosen more carefully this time. I am more or less confident that it will be better this time. The payloads on the lander and rover this time will focus on the surface of the moon and just under the moon.”
The south polar region of the moon is a place that is relatively unexplored. If the Chandrayaan-3 lander reaches the lunar surface successfully, the scientific community could end up learning a lot more about the Moon’s surface. Establishing a permanent on the Moon has been a long-term goal for many spacefaring nations. The US, for instance, is working with four partner space agencies on the Artemis programme, which intends to reestablish a human presence on the Moon for the first time since 1972.
The lander module on Chandrayaan-3 has scientific instruments that will measure the near surface plasma (ions and electrons) density and its changes with time and carry out measurements of thermal properties of lunar surface near the polar region. A third payload, called ILSA (short for Instrument for Lunar Seismic Activity), which – as the name suggests – will measure seismicity around the landing site and delineate the structure of the lunar crust and mantle.
The rover, meanwhile, has a spectrometer and spectroscope that will study the chemical and elemental composition of the lunar surface near the landing site. This could further enhance our understanding of the Moon’s surface.
In addition to Isro’s own deep space communication antenna, the moon mission will rely on support from ground stations around the world, coordinated by US space agency Nasa and the European Space Agency.
Raychadhury says a successful landing for the Chandrayaan-3 mission would offer a lot to the scientific community worldwide. He says: “In the future, there are plans to use the moon as part of a larger space programme. If we want to go to asteroids for mining or to Mars and beyond, then you want the moon to be the first stop. If you want to establish stations there – manned or unmanned – then we need to understand the habitability of the moon, which is what missions like Chandrayaan are trying to do.”
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