Chandrayaan-3 was launched on 14 July 2023. The spacecraft entered lunar orbit on 5 August, and the lander touched down in the lunar south pole region[10] on 23 August 2023 at 12:32 UTC, making India the fourth country to successfully land on the Moon, and the first to do so near the lunar south pole.[11][12][13]
On 22 July 2019, ISRO launched Chandrayaan-2 on board a Launch Vehicle Mark-3 (LVM3)launch vehicle consisting of an orbiter, a lander and a rover.[14] The lander was scheduled to touch down on the lunar surface on 6 September 2019 to deploy the Pragyan rover. The lander ultimately crashed when it lost contact with earth (ISRO) and deviated from its intended trajectory while attempting to land near the lunar south pole.[15][16]
The lunar South Pole region holds particular interest for scientific exploration due to studies that show large amounts of ice there. Mountainous terrain and unpredictable lighting conditions not only protect the ice from melting but also make landing scientific probes there a challenging undertaking. This ice could contain solid-state compounds that would normally melt under warmer conditions elsewhere on the Moon, compounds which could provide insight into lunar, Earth, and Solar System history. Ice could also be used as a source of drinking water and hydrogen for fuel and oxygen for future crewed missions and outposts.[17][18]
ISRO's mission objectives for the Chandrayaan-3 mission were:
Getting a lander to land safely and softly on the surface of the Moon.
Observing and demonstrating the rover's driving capabilities on the Moon.
Conducting and observing experiments on the materials available on the lunar surface to better understand the composition of the Moon.[21]
On 26th August, ISRO confirmed that two out of the three mission objectives have been accomplished already, while the third, in-situ scientific experiments, is underway.[22]
Spacecraft
Design
Chandrayaan-3 comprises three main components: a propulsion module, lander, and rover.
Chandrayaan-3 encapsulated within LVM3's payload fairing
Chandrayaan-3 integrated components
Propulsion module
The propulsion module carries the lander and rover configuration to a 100 kilometres (62 mi) lunar orbit. It is a box-like structure with a large solar panel mounted on one side and a cylindrical mounting structure for the lander (the Intermodular Adapter Cone) on top.[9][8]
Propulsion module
Lander
The Vikram lander is responsible for the soft landing on the Moon. It is also box-shaped, with four landing legs and four landing thrusters capable of producing 800 newtons of thrust each. It carries the rover and various scientific instruments to perform on-site analysis.[23][24]
The lander for Chandrayaan-3 has four variable-thrust engines with slew rate changing capabilities, unlike Chandrayaan-2's lander, which had five, with the fifth one being centrally mounted and capable only of fixed thrust. One of the main reasons for Chandrayaan-2's landing failure was attitude increase during the camera coasting phase. This was removed by allowing the lander to control attitude and thrust during all phases of descent. Attitude correction rate is increased from Chandrayaan-2's 10°/s to 25°/s with Chandrayaan-3. Additionally, the Chandrayaan-3 lander is equipped with a laser Doppler velocimeter (LDV) to allow measuring attitude in three directions.[25][26] The impact legs have been made stronger compared to Chandrayaan-2 and instrumentation redundancy has been improved. It will target a more precise 4 km (2.5 mi) by 4 km (2.5 mi) landing region based on images previously provided by the Orbiter High-Resolution Camera (OHRC) onboard Chandrayaan-2's orbiter. ISRO improved the structural rigidity, increased polling in instruments, increased data frequency and transmission, and added additional multiple contingency systems to improve lander survivability in the event of failures during descent and landing.[27][26]
Lander
Rover
The Pragyan rover is a six-wheeled vehicle with a mass of 26 kilograms (57 pounds). It is 917 millimetres (3.009 ft) x 750 millimetres (2.46 ft) x 397 millimetres (1.302 ft) in size.[28]
The rover is expected to take multiple measurements to support research into the composition of the lunar surface, the presence of water ice in the lunar soil, the history of lunar impacts, and the evolution of the Moon's atmosphere.[29][10]
Spectro-polarimetry of Habitable Planet Earth (SHAPE) will study spectral and polarimetric measurements of Earth from the lunar orbit in the near-infrared (NIR) wavelength range (1–1.7 μm [3.9×10−5–6.7×10−5 in]).[9][8]
Spectro-polarimetry of Habitable Planet Earth (SHAPE)
Mission profile
Animation of Chandrayaan-3
Around the Earth – Orbit raising phase
Around the Earth
Around the Moon
Chandrayaan-3's Path· Earth· Moon
Launch
LVM3 M4, Chandrayaan-3 – Launch vehicle lifting off from the second launch pad of SDSC-SHAR, Sriharikota
On 17 August, the Vikram lander separated from the propulsion module to begin the last phase of the mission.[36]
Descent
Image of Chandrayaan-3 Lander as captured by OHRC camera aboard Chandrayaan-2 OrbiterPragyan roll out
On 23 August 2023, as the lander approached the low point of its orbit, its four engines fired as a braking manoeuvre at 30 kilometres (19 mi) above the Moon's surface. After 11.5 minutes, the lander was 7.2 km (4.5 miles) above the surface; it maintained this altitude for about 10 seconds, then stabilized itself using eight smaller thrusters and rotated from a horizontal to a vertical position while continuing its descent.
It then used two of its four engines to slow its descent to roughly 150 metres (490 ft); it hovered there for about 30 seconds and located an optimal landing spot before continuing downward and touching down at 12:32 UTC.[23][37]
Moon as captured by the Lander Position Detection Camera (LPDC) aboard Chandrayaan-3 lander on 15 August 2023
View from the Lander Imager Camera-1 (LI-1) on 17 August 2023 just after the separation of the Chandrayaan-3 Lander Module from the Propulsion Module
Chandrayaan-3 orbital manoeuvre
Mission life
Propulsion module: Carries lander and rover to 100-by-100-kilometre (62 mi × 62 mi) orbit, with operation of experimental payload for up to six months.[52]
Lander module: 1 lunar daylight period (14 Earth days)[52]
Rover module: 1 lunar daylight period (14 Earth days)[52]
In December 2019, ISRO requested the initial funding of the project, amounting to ₹75 crore (US$9.4 million), out of which ₹60 crore (US$7.5 million) would be for meeting expenditure towards machinery, equipment, and other capital expenditure, while the remaining ₹15 crore (US$1.9 million) was sought for operating expenditure.[59] Amit Sharma, CEO of an ISRO vendor, said, "With local sourcing of equipment and design elements, we are able to reduce the price considerably."[60]
Confirming the existence of the project, ISRO's former chairman K. Sivan stated that the estimated cost would be around ₹615 crore (equivalent to ₹721 crore or US$90 million in 2023).[61][62][63]
Results
Since reaching the moon's south pole, Chandrayaan-3 deployed the Pragyan rover to explore the cratered surface, harnessed integrated cameras to send back videos of its environment, and even started working on the research objectives planned for a two-week stay on the moon.[64]
The first video of the rover, posted on 25th August 2023, showed it leaving the Vikram lander on a ramp and driving onto the Moon. ISRO posted the video in a thread on X that also included footage from the lander approaching its landing site and kicking up dust as it touched down on the surface. ISRO wrote afterwards that the rover’s two scientific instruments had been turned on and that it had moved eight meters.[65]
A 4-metre-diameter (13 ft) crater, as captured by the Navigation camera onboard the rover.
On 26th August, ISRO posted a new video, shot from the lander, of the rover's drive away, moving almost out of the lander’s sight.[66] On 27th August, it published two pictures after the rover encountered a large crater positioned 3 metres (9.8 ft) ahead of its location. However, the rover safely headed on a new path afterwards.[67][68]
Temperature variation
ISRO also released a first-of-its-kind data from the observations made by ChaSTE (Chandra's Surface Thermophysical Experiment), one of the four instruments present on the lander module. ChaSTE was meant to study the heat conductivity of the Moon’s surface and measure the differences in temperatures at different points on and below the surface, with the overall objective of creating a thermal profile of the Moon.
The graph of temperature variation across the lunar topsoil at a point in the solar polar region, as measured by the ChaSTE instrument.
The first set of data released by ISRO showed a very sharp difference in temperatures just above and below the surface of the Moon. A graphical plot put out by ISRO showed that while temperatures on the surface were over 50 °C (122 °F), they dropped to nearly −10 °C (14 °F) just a few millimetres below the surface. The measurements suggested that the topsoil of the lunar surface did not conduct heat very well, and insulated the sub-surface from heat.
These measurements were consistent with what is known about the thermal profile of the Moon from previous expeditions and experiments. But this was the first 'direct measurement' of temperatures of the topsoil and the subsoil near the South Pole of the Moon.[69]
ISRO scientist BH Darukesha, while commenting on the findings, said the high range of 70-degree-Celsius (158-degree-Fahrenheit) temperature near the surface was "not expected".[70]
Detection of sulfur
On 29th August, ISRO said that the laser-induced breakdown spectroscope (LIBS) instrument onboard the Pragyan rover has "unambiguously" confirmed the presence of sulfur in the lunar surface near south pole, through "first-ever in-situ measurements".[71][72] The presence of sulfur on the Moon has been known before;[73] however, it was detected for the first time at the south pole.[74] Additionally, there was no previous direct evidence of the element.[75]
Noah Petro, a project scientist at NASA, while speaking to the BBC, described Pragyaan's findings as a "tremendous accomplishment".[76]
Apart from sulfur, the rover also detected other elements including aluminium (Al), calcium (Ca), iron (Fe), chromium (Cr), titanium (Ti), manganese (Mn), silicon (Si), and oxygen (O).[77] Additionally, the agency said the search for hydrogen (H) is also underway.[78]
Pragyan rover detected elements present on moon.
Lunar water
John Bridges, a professor of planetary science at the University of Leicester, UK,[79] told New Scientist that due to the low pressure on the moon it would be "unlikely" for Chandrayaan-3 to find liquid water near to the surface – even in areas where the temperature was above freezing point so water would not be trapped in ice – because it would boil away, although at lower depths the pressure could rise enough to allow liquid water. However, he also added that it's "too early" to interpret the readings from Chandrayaan-3. "But it's fantastic they're getting data", Bridges said. "You can't help comparing it to certain other space agencies; engineers are just getting on now and doing it. They're sort of overtaking Russia", he concluded.[80]
Domestic reactions
Congratulating the ISRO team behind the successful Chandrayaan-3 Moon Mission at ISRO Telemetry, Tracking and Command Network in Bengaluru, Prime Minister Narendra Modi announced that the touchdown point of the Vikram lander would henceforth be known as Shiv Shakti point.[81] He further declared August 23, the day the Vikram lander landed on the moon, as National Space Day.[82][83]
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Cubesats are smaller. Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
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