Chandrayaan-3

Chandrayaan-3 ( ) is the third mission in the Chandrayaan programme, a series of lunar-exploration missions developed by the Indian Space Research Organisation (ISRO). Launched on 14 July 2023, the mission consists of a lunar lander named Vikram and a lunar rover named Pragyan, similar to those launched aboard Chandrayaan-2 in 2019. 

Chandrayaan-3 was launched from Satish Dhawan Space Centre on 14 July 2023. The spacecraft entered lunar orbit on 5 August, and the lander touched down near the Lunar south pole on 23 August at 18:03 IST (12:33 UTC), making India the fourth country to successfully land on the Moon, and the first to do so near the lunar south pole. On 3 September the lander hopped and repositioned itself  from its landing site. After the completion of its mission objectives, it was hoped that the lander and rover would revive for extra tasks, on 22 September 2023, but missed the wake-up call. On September 30, the second lunar night began, eliminating hopes of revival.

Background 
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. The lander was scheduled to touch down on the lunar surface on 6 September 2019 to deploy the Pragyan rover. The lander lost contact with mission control, deviated from its intended trajectory while attempting to land near the lunar south pole, and crashed.

The lunar south pole region holds particular interest for scientific exploration. Studies show large amounts of ice there. Mountainous terrain and unpredictable lighting protect the ice from melting, but they also make landing scientific probes there a challenging undertaking. The 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. For future crewed missions and outposts, ice could also be a source of drinking water and of hydrogen for fuel and oxygen.

The European Space Tracking network (ESTRACK), operated by the European Space Agency (ESA), and Deep Space Network operated by Jet Propulsion Laboratory (JPL) of NASA are supporting the mission.
Under a new cross-support arrangement, ESA tracking support could be provided for upcoming ISRO missions such as those of India's first human spaceflight programme, Gaganyaan, and the Aditya-L1 solar research mission. In return, future ESA missions will receive similar support from ISRO's own tracking stations.

Objectives 
ISRO's mission objectives for the Chandrayaan-3 mission are:
 Engineering and implementing 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.

Spacecraft

Design 
Chandrayaan-3 comprises three main components: a propulsion module, lander, and rover.

Propulsion module 
The propulsion module carried the lander and rover configuration to a  lunar orbit. It was 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. 

A few months after the conclusion of the lander portion of the mission ,Isro officials said that the propulsion module is equipped with two radioisotope heating units (RHU) generating one watt designed and developed by BARC (Bhabha Atomic Research Centre). RHUs keep the spacecraft at their operational temperatures by the decay of radioactive meterial , leading to electricity generation to power heaters , even with solar power or using battery power . It is to be thought that National Security reasons delayed the disclosure to the media .Chandrayaan 3 project director P Veeramuthuvel  said Isro may soon use nuclear resources to maintain instruments in future rovers. Isro officials later stated  that the RHUs could not be installed on Chandrayaan 3’s Vikram lander and Pragyan rover because it would have increased their mass  which unfortunately led them to have a maximum lifespan of 14 earth days or 1 lunar day.

Vikram Lander 
The Vikram lander was 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 carried the rover and has various scientific instruments to perform on-site analysis. The lander 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 altitude 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 was 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 altitude in three directions. The impact legs were made stronger compared to Chandrayaan-2 and instrumentation redundancy was improved. It targeted a more precise  landing region based on images 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 failure during descent and landing.

Rover 
The Pragyan rover is a six-wheeled vehicle with a mass of . It is  in size. 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.

Payloads

On lander 
 Chandra's Surface Thermophysical Experiment (ChaSTE) will measure the thermal conductivity and temperature of the lunar surface.
 Instrument for Lunar Seismic Activity (ILSA) will measure the seismicity around the landing site.
 Langmuir Probe (LP) will estimate the near-surface plasma density over time.

On rover 
 An alpha particle X-ray spectrometer (APXS) will derive the chemical composition and infer the mineralogical composition of the lunar surface.
 Laser-induced breakdown spectroscopy (LIBS) will determine the elemental composition (Mg, Al, Si, K, Ca, Ti, Fe) of lunar soil and rocks around the lunar landing site.

On the propulsion module 
 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). Findings of SHAPE might aid in future exoplanet research and search for extraterrestrial life.

Mission profile

Launch 

Chandrayaan-3 was launched aboard an LVM3-M4 rocket on 14 July 2023, at 09:05 UTC from Satish Dhawan Space Centre Second Launch Pad in Sriharikota, Andhra Pradesh, India, entering an Earth parking orbit with a perigee of  and an apogee of .

Orbit 
After a series of Earth bound manoeuvres that placed Chandrayaan-3 in a trans-lunar injection orbit, ISRO performed a lunar-orbit insertion (LOI) on 5 August, successfully placing the Chandrayaan-3 spacecraft into an orbit around the Moon. The LOI operation was carried out from the ISRO Telemetry, Tracking, and Command Network (ISTRAC) in Bengaluru.

On 17 August, the Vikram lander separated from the propulsion module to begin the last phase of the mission.

Landing 

On 23 August 2023, as the lander approached the low point of its orbit, its four engines fired as a braking manoeuvre at  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 ; it hovered there for about 30 seconds and located an optimal landing spot before continuing downward and touching down at 12:33 UTC.

Surface operations 

On 3 September, the rover was put into sleep mode after it had completed all of its assignments. Its batteries were charged and receiver left on, according to ISRO, in preparation for the impending lunar night. "The rover's payloads are turned off and the data it collected has been transmitted to Earth via the lander", the statement said. Chandrayaan-3's lander and rover were expected to operate only for one lunar daylight period, or 14 Earth days, and the on-board electronics were not designed to withstand the  nighttime temperatures on the Moon. On 22 September, the lander and rover missed their wake-up calls, and by 28 September neither had responded, diminishing hopes for further surface operations.

Hop experiment 

Vikram fired its engines for a brief 'hop' on the lunar surface on 3 September, ascending  off the lunar surface and translating a similar distance laterally across the surface. The test demonstrated capabilities to be used in potential future sample return missions. The instruments and rover deployment ramp were retracted for the hop and redeployed afterwards.

Mission life 
 Propulsion module: Carries lander and rover to  orbit, with operation of experimental payload for up to six months.
 Lander module: one lunar daylight period (14 Earth days).
 Rover module: one lunar daylight period (14 Earth days).

Team 
 ISRO chairman: S. Somanath
 Mission Director: S. Mohanakumar
 Associate Mission Director: G. Narayanan
 Project Director: P. Veeramuthuvel
 Associate Project Director: Kalpana Kalahasti
 Vehicle Director: Biju C. Thomas

Funding 
In December 2019, ISRO requested the initial funding of the project, amounting to , out of which  would be for meeting expenditure towards machinery, equipment, and other capital expenditure, while the remaining  was sought for operating expenditure. Amit Sharma, CEO of an ISRO vendor, said, "With local sourcing of equipment and design elements, we are able to reduce the price considerably."

Confirming the existence of the project, ISRO's former chairman K. Sivan stated that the estimated cost would be around .

Results 
The Associated Press, while commenting on the success of the mission, said, "The successful mission showcases India's rising standing as a technology and space powerhouse and dovetails with Prime Minister Narendra Modi's desire to project an image of an ascendant country asserting its place among the global elite."

Temperature variation 
ISRO also released data from the observations made by ChaSTE (Chandra's Surface Thermophysical Experiment), one of the four instruments present on the lander module. ChaSTE was designed 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.

ISRO scientist BH Darukesha said the high range of  temperature near the surface was "not expected".

Detection of sulfur 
On 29 August, ISRO reported that the laser-induced breakdown spectroscope (LIBS) instrument on board the Pragyan rover has "unambiguously" confirmed the presence of sulfur in the lunar surface near the south pole, through "first-ever in-situ measurements". The presence of sulfur on the Moon has been known before; however, it was detected for the first time at the south pole by the rover.

Noah Petro, a project scientist at NASA, while speaking to the BBC, stated that while sulfur has been known to be in the lunar regolith from Apollo program samples, he described Pragyans findings as a "tremendous accomplishment".

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). The agency said it is also searching for hydrogen (H).

Plasma measurement 
On 31 August, ISRO released plasma density data from the RAMBHA Instrument aboard the Vikram lander. Initial assessments reported relatively low plasma densities above the lunar surface varying from 5 to 30 million electrons per m3. The evaluation pertains to early stages of the lunar day. The probe aims to explore the changes in the near-surface plasma environment throughout the duration of the lunar day.

Seismic measurements 
On the same day, ISRO released data from the ILSA payload on the lander, providing vibration measurements of the rover movement on 25 August, and a presumed natural event on 26 August. The cause of the latter event is a subject of investigation, it is suspected to be a moonquake.

Domestic reactions 
Chandrayaan-3's landing live stream on ISRO's official YouTube channel received eight million concurrent viewers, which is the highest in YouTube's history.

Congratulating the ISRO team behind the successful Chandrayaan-3 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. He further declared 23 August, the day the Vikram lander landed on the Moon, as National Space Day.

ISRO chief S. Somanath exclaimed "India is on the Moon" after the successful touchdown. "We learnt a lot from our failure and corrected it. It's now 14 days of work and we have to conduct experiments," he told India Today.

P Veeramuthuvel, the Project Director of the mission said, "It's a great moment of happiness. On behalf of the team it gives me immense satisfaction on achieving this goal as the Project Director of the mission. The entire mission operations right from launch till landing happened flawlessly as per the timeline". S. Mohana Kumar, the Mission Director, said that Chandrayaan-3 was a "team effort".

Meanwhile, former ISRO chief K Sivan, under whose tenure the Chandrayaan-2 was launched said, "We are really excited to see this grand success. For this, we have been waiting for the last four years. This success is sweet news for us and for the entire nation."

Rahul Gandhi, the leader of the opposition, also celebrated Chandrayaan-3's success, calling it a result of "tremendous ingenuity and hard work" by the country's scientific community. "Since 1962, India's space program has continued to scale new heights and inspire generations of young dreamers," he posted on X.
 
Delhi Chief Minister Arvind Kejriwal too, congratulated the scientists of ISRO on the successful landing and termed it a "historic" moment. "This is historical. It's a significant achievement for the country. It's a matter of pride for all of us. The success of Chandrayaan-3 is a result of the hard work of all citizens, ISRO scientists, engineers, and employees. Congratulations to everyone involved. Bharat Mata ki jai.", he posted on X.

DY Chandrachud, the Chief Justice of India hailed the landing as "a milestone in the onward march of our nation" and congratulated the ISRO team.

International reactions 

Josef Aschbacher, Director General of European Space Agency, said: "Incredible! Congratulations to ISRO, Chandrayaan-3, and to all the people of India!! What a way to demonstrate new technologies AND achieve India's first soft landing on another celestial body. Well done, I am thoroughly impressed."

Foreign Minister of Maldives, Abdulla Shahid  tweeted: "As a South Asian nation, and neighbour, we are proud of the successful landing of Chandrayaan 3 near the moon's south pole. This is a success for all of humanity! Opening new avenues for new areas of exploration."

NASA Administrator Bill Nelson tweeted: "Congratulations ISRO on your successful Chandrayaan-3 lunar South Pole landing and congratulations to India on being the 4th country to successfully soft-land a spacecraft on the Moon. We’re glad to be your partner on this mission".

Cyril Ramaphosa, the President of South Africa said: "This for us, as the BRICS family, is a momentous occasion and we rejoice with you. We join you in the joy of this great achievement."

Kremlin quoted Russian President Putin's message to Indian President Droupadi Murmu and Prime Minister Narendra Modi, "Please, accept my heartfelt congratulations on the occasion of the successful landing of the Indian space station Chandrayaan-3 on the Moon near its South Pole. This is a big step forward in space exploration and certainly a testament to the impressive progress made by India in the area of science and technology”. 

Nepal PM Pushpa Kamal Dahal said on X (formerly known as Twitter): "I congratulate Prime Minister Shri Narendra Modi ji and ISRO team of India on successful landing of Chandrayan-3 in the surface of the moon today and unleashing of a historic achievement in science and space technology."

See also 
 Aditya-L1 – Indian solar observation mission
 Gaganyaan – Indian crewed spacecraft project
 Indian Human Spaceflight Programme
 Indian Martian Exploration Programme
 Venus Orbiter Mission – Indian Venus exploration mission

Notes

References

External links 
 Chandrayaan – 3 ISRO official site
 Chandrayaan 3 Image Gallery- LVM3-M4 Gallery
 Orbital and Lunar Surface operation videos- Chandrayaan-3 Videos

Missions to the Moon
Lunar rovers
Indian lunar exploration programme
Space probes launched in 2023
Spacecraft launched by India in 2023
ISRO space probes
2023 on the Moon
Soft landings on the Moon