ISROs phenomenal Chandrayaan 3 mission

The Chandrayaan 3 mission was launched at 2:35 hours IST on 14 July 2023, from the Second Launch Pad at the Satish Dhawan Space Centre, India’s spaceport on the barrier island of Sriharikota. The launch took place after a week of pre-launch activities which included stacking the mightiest and heaviest rocket in ISRO’s fleet, the Launch Vehicle Mark 3, with the Vikram Lander encapsulated in the nose cone, and a rehearsal of the launch. The launch took place on a clear afternoon with favourable weather conditions. ISRO delayed the launch by four seconds to avoid space debris. After a sixteen minute flight, the Chandrayaan 3 mission was released by the rocket, with its payload fairing opening up like the flowers of a petal.

Ahead of the launch, Prime Minister Narendra Modi had said, "This remarkable mission will carry the hopes and dreams of our nation”. After the rocket deployed the spacecraft, the Propulsion Module took over when it came to controlling the probe. This on-board propulsion system gradually increased the altitude of the probe over a series of burns, before executing the translunar injection manoeuvre on 1 August, 2023 bidding goodbye to the Earth forever. The Chandrayaan 3 mission successfully injected itself into lunar orbit on 5 August, 2023. The Propulsion Module then gradually lowered the altitude of the spacecraft in lunar orbit, and delivered the spacecraft to a parking orbit at an altitude of 150 kilometres on 17 August, 2023.

The Vikram lander, carrying the Pragyaan rover within it, then deboosted itself to a 30x100 kilometre orbit on 20 August, 2023. This was the orbit from which it executed the landing. The spacecraft was traveling at 1.68 kilometres per second when initiating the landing attempt. The lander used on-board systems to evaluate the terrain, and even moved away from a hazard, which might have been a boulder or a crater. At 18:03 hours IST, on 23 August, 2023, the Cahndrayaan 3 mission successfully executed a soft, controlled landing close to the Manzinus crater, about 635 kilometres from the south pole of the Moon.

The Vikram lander on the lunar surface with the payloads deployed, as captured by the Pragyan rover. (Image Credit: ISRO). 

To be clear, the touchdown did not take place on the dark side or far side of the Moon, and was not exactly in the south pole region. The lander then deployed a sensitive array of seismometers to probe the remote interior of the Moon, a surface probe loaded with sensors to measure the thermal properties of the lunar soil or regolith, and a Langmuir probe with a spherical tip to characterise the wispy atmosphere of the Moon. After waiting for about a day for the dust ejected by the landing to settle, ISRO rolled out the Pragyaan rover to explore the lunar surface.

The Pragyaan rover ended up moving 100 kilometres across the lunar surface, dodging craters and boulders on the way. The operations had to be coordinated carefully as the single flip-out solar panel of the rover had to constantly face the Sun. ISRO was able to conduct scientific experiments on all of its instruments, then conducted a surprise short hop to move the lander by just a bit, demonstrating the capabilities for vertical take off and vertical landing (VTVL). Such capabilities are required for sample return missions, providing mobility on extraterrestrial surfaces and crewed flights. The Propulsion Module also made its way back to the Earth on the remaining fuel, demonstrating in principle, all the capabilities required for a sample return mission.

The Moon captured by Chandrayaan 3. (Image Credit: ISRO). 

At the end of the 14 day lunar day, ISRO put the rover and the lander into sleep mode. Ground tests had indicated the possibility that the sensitive electronics instruments could survive the lunar night. Without the moderating influence of a thick atmosphere, the temperature variation between day and night on the lunar surface is extreme, soaring to over 200°C during the day and dropping to -180°C during the nights. Despite multiple attempts at establishing contact, ISRO was not able to revive the Chandrayaan 3 missions after the first lunar day.

The science observations by the Chandrayaan 3 mission were complementary to those of the Chandrayaan 2 mission. ISRO managed to gather a wealth of data on the Moon that will inform the planning of future missions, and drive research for decades into the future. All the data has now been made available to the scientific community. On 19 March, 2024, the International Astronomical Union (IAU) formally approved Statio Shiv Shakti as the name of the Chandrayaan 3 landing site. The seismometer was so exquisitely sensitive that it measured the rumbling caused by the tiny rover across the lunar surface, and detected over 50 natural events that could be Moonquakes or meteor impacts on the lunar surface.

The Lunar Seismic Activity (ILSA) payload was sensitive enough to register the 26 kg rover moving across the lunar surface. The spike on the right is an unknown event, that could be a meteor strike or a moonquake. (Image Credit: ISRO). 

The data gathered by Chandrayaan 3 provided additional evidence that the Moon was a hot ball of molten lava in its youth. Vikram had landed in the remnants of a massive, ancient crater formed in the infancy of the Solar System. The Chandrayaan 3 mission won the 2024 John L Swigert Jr Award from the Space Foundation, the Leif Erikson Lunar Prize by the Exploration Museum in Húsavík, Iceland, the award for the most inspirational, important and innovative space mission of 2023 at Astro Awards 2024, as well as the World Space Award for 2024 by the International Astronautical Federation (IAF). August 23 is now observed as India’s National Space Day.