India’s Historic Moon Landing

By R Anil Kumar

• The success of the Chandrayaan-3 mission made India become the first country in the world to land near the lunar south pole

• The success of Chandrayaan-3 mission has raised the stature of the Indian Space Research Organisation (ISRO), globally

• For India, Chandrayaan-3 was not only a demonstrative mission to showcase their expertise in regards to soft landing on the Moon, but also had some scientific agenda associated with it

Bengaluru, July 14. One year ago (July 14, 2023) India’s Chandrayaan-3 mission was launched. This mission could be said to be one of the most important missions ever launched in the history of India’s space program. The success of this mission has raised the stature of the Indian Space Research Organisation (ISRO) globally.

ISRO was successful in performing a soft landing of its rover and lander system (Lander Module) on the lunar surface on August 23, 2023. Subsequently, within a few hours, the ramp in the belly of the lander had opened, and very slowly, the rover unit had come out and operated over the lunar surface. The Lander Module was designed for operation on the lunar surface for one Moon-day (14 Earth-days).

The rover, Pragyanand lander Vikram, are known to have functioned normally for one lunar day. Particularly, at the backdrop of the failure during the Chandrayaan-2 mission in respect of conducting the soft-landing of the Lander Module on the lunar surface, this achievement was praiseworthy. With the success of the Chandrayaan-3 mission, India became the first country in the world to land near the lunar south pole.

ISRO’s prestige was at stake during Chandrayaan-3 since, during the 2019 Chandrayaan-2 mission, they witnessed a last-minute failure to soft-land the lander and rover unit on the lunar surface. But in 2023, ISRO got it right. People connected with the Chandrayaan-3 project had taken major efforts for almost four years to get it correct. Learning from the experiences of Chandrayaan-2, ISRO had designed an almost fool-proof mission from their side. They had factored in all possible known failures, and the software was fed with multiple options to respond in case of any emergency.

In fact, before the launch of the mission, it was heartening to note that ISRO was beaming with a lot of confidence. For India, Chandrayaan-3 was not only a demonstrative mission to showcase their expertise in regards to soft landing on the Moon, but also had some scientific agenda associated with it.

The success of the Chandrayaan-3 mission made India the only fourth country to successfully undertake robotic landings on the Moon surface. The major powers were astonished by the sound success of India, a state from the global south and a state that still gets bracketed as a developing state.

It is important not to look at the success of the Chandrayaan-3 mission in isolation. India put in place its agenda for the Moon almost two decades ago. India undertook its first mission to the Moon, called Chandrayaan-1, during the 2008–2009 period. Astonishingly, the Moon looks to be a strong source of hydrogen atoms.

This surprise discovery was made based on the data received from the ESA-ISRO instrument SARA onboard the Chandrayaan-1 lunar orbiter. This mission helped the world realise the availability of water on the Moon’s surface. India’s Chandrayaan-2 mission was launched in 2019, and the orbiter launched during this mission is working fine even today, and it did assist the Lander module of Chandrayaan-3 in commutations.

Normally, all rover and lander systems on the lunar surface work on solar power. Hence, during the night, these units are required to be switched off. The nighttime temperatures on the lunar surface could be as low as minus 150 degrees Celsius.

The Indian system was not designed to withstand such extremely low temperatures. Still, there was some hope for ISRO that the lander module could work beyond one day. Hence, on September 3, 2023, the system was put into sleep mode. After that, ISRO did try to give wake-up calls to the rover and lander between September 22 and September 28, but luck was not on their side.

Chandrayaan-3 had important payloads (sensors) placed both on the lander and rover units. The lander was equipped with a sensor to measure the thermal conductivity and temperature of the lunar surface.

ISRO released the data received from this payload immediately. They had also shared the graph of temperature variation based on the observations taken by the lander’s payload.

Another instrument onboard the lander was meant for studying lunar seismic activity and undertaking seismic measurements. This sensor did provide the vibration measurements of the rover movement on August 25.

Possibly, there was an indication of some natural event happening on August 26. Was that a moonquake? Some observations were picked up by ISRO on August 26. But nothing is known about the analysis carried out by ISRO, or maybe there is nothing much to affirm. The lander had one more instrument for undertaking plasma measurements. The plasma density data collected revealed that there are relatively low plasma densities above the lunar surface during the early stages of the lunar day.

On the rover, there was a payload called an alpha particle X-ray spectrometer for studying the chemical composition and gathering information about the mineralogical composition of the lunar surface, as well as another instrument for determining the elemental composition of lunar soil and rocks close to the lunar landing site.

Based on the observations collected, ISRO has been able to confirm the presence of sulphur on the lunar surface. This knowledge did exist based on assessments made by satellite imagery and lunar samples collected during the Apollo missions. However, this is for the first time; the confirmation has come from the first-ever in-situ measurements undertaken on the south pole of the Moon.

The rover was also able to detect the presence of other elements like calcium, aluminium, iron, titanium, manganese, chromium, and silicon. The detection of oxygen was also there. But, for analysing the possibility of the presence of water, the most important discovery the ISRO and the entire world were looking for, was the presence of hydrogen. However, it appears that no definite inputs have been received in this regard or that ISRO is still analysing the data for finer details.

Over the years, ISRO has developed the mastery to overcome its own limitations by adopting innovative ideas. Unfortunately, so far, ISRO has not been able to develop a launch vehicle that can carry heavy satellites towards the Moon or Mars. Also, their rocket power is not strong enough to put very heavy satellites in higher orbits.

For example, Apollo 11, carrying Neil Armstrong and others, took about three days and four hours to reach the Moon and less than three days to get back. Chandrayaan-3 took over 40 days to reach the Moon orbit.

Owing to rocket limitations, Indian crafts are engaged in taking a slower and gradual trajectory (undertaking orbit-raising manoeuvres and using slingshot mechanisms) against the direct translunar injection done during the Apollo missions.

In the case of Chandrayaan-4, samples from the Moon will be brought back. ISRO is planning to undertake the mission in two parts by doing two separate launches. They would carry different parts of the spacecraft in two launches, and the spacecraft would be assembled in space before advancing towards the Moon. This becomes necessary since the weight of Chandrayaan-4 is going to be beyond the carrying capacity of rockets in ISRO’s current inventory.

For this purpose, ISRO would be developing expertise for space docking. ISRO has plans to establish a space station by 2035, and obviously, such technologies would be required for establishing the space station too.

The success of the Chandrayaan-3 mission has given a boost to ISRO’s space ambitions, and during the last year, they have already conceptualised a major agenda for the future.

Today, ISRO’s focus is on the Gaganyaan programme, and let us hope that this mission to carry Indian astronauts to space, possibly by the end of 2025, gets the same success as that of Chandrayaan-3.