Why Vikram lander of Chandrayaan-3 has a higher chance of successful soft landing on Moon?

Lander module is like a big box where rover is placed

PTI07_11_2023_000178B The Launch Vehicle Mark-III (LVM3) M4 vehicle with Chandrayaan-3 at the launch pad at Satish Dhawan Space Centre | PTI

The Vikram lander, which was part of the Chandrayaan-2 mission by the Indian Space Research Organisation (ISRO), lost communication less than two minutes before its scheduled moon landing. The lander was merely 2.1 km away from achieving the milestone. The lander was trying to make a controlled landing near the south pole of the Moon, where scientists expect to find water ice. It started descending at 1.38 am, on September 7, 2019, and took 10 minutes to slow down from a speed of 1,640 meters per second to 140 meters per second. However, during the final moments, when it was getting closer to the Moon's surface, communication was lost.

As ISRO's Chandrayaan-3 mission from the Satish Dhawan Space Centre in Sriharikota gets ready for launch on July 14 at 2.35 pm, it is expected that the Vikram lander of the Chandrayaan-3 mission will have a higher chance of a successful landing. The lander will be called 'Vikram' in honour of Vikram Sarabhai, the father of the Indian space programme, and the rover will be named 'Pragyan'.

The anticipated landing of the Chandrayaan-3's lander, Vikram, and rover, Pragyaan, on the Moon is expected to occur around August 23 or 24. Roughly one month after its launch, Chandrayaan-3 will enter lunar orbit. The Chandrayaan-2 mission landed near the south pole of the Moon at a latitude of 70 degrees.

“The lander module is a really important part of Chandrayaan-3. Its job is to safely land on the Moon's surface. It will travel with the spacecraft module in a circular shape around 100 km above the Moon. Then, the propulsion module and the lander module will separate from each other. The lander module for Chandrayaan-3 is like a big box where the rover is placed. It has a large solar panel and a big cylinder on top. The lander is designed to land softly on a specific spot on the Moon and allow the rover to analyze the Moon's chemistry,” space and aerospace expert Girish Linganna told THE WEEK.

The lander weighs 1.75 tonnes and carries a robotic rover, Pragyan. The rover weighs 26 kilograms and has six wheels. It is designed to explore the Moon for around 14 Earth days. “The lander will have equipment to measure the density of ions and electrons close to the Moon's surface and observe how it changes. It will also measure the temperature of the Moon's surface, search for moonquakes, and study the movements and behavior of the Moon system,” said Linganna.

The lander of Chandrayaan-3 has improved capabilities. “Chandrayaan-3, taking into account what was learned from Chandrayaan-2, has improved capabilities in its lander. It includes 'lander hazard detection & avoidance cameras' that help the lander coordinate with the orbiter and mission control while descending to the Moon's surface. Unlike its predecessor, Chandrayaan-3 will have two of these cameras instead of just one,” explained Linganna.

He said for Chandrayaan-3 mission, ISRO has made several improvements, particularly for the lander thrusters, based on the issues faced during Chandrayaan-2. “ISRO has developed better sequences for a safe landing and the lander now has four thruster engines instead of five. The legs of the lander are stronger, and it has larger solar panels. Furthermore, in order to effectively deal with potential disruptions and ensure a higher level of safety for the mission, extra fuel will be included in the lander. This increased fuel capacity will enhance its ability to manage unforeseen circumstances and increase the likelihood of a successful recovery if required,” said Linganna.

According to the ISRO, the landing velocity of Vikram has also been increased to 3m/second from 2m/second. This ensures that even at 3m/sec, the lander will not crash or break its legs. ISRO has also made enhancements to the software of Chandrayaan-3 to increase its resilience to failures such as engine disruptions, thrust disruptions, and sensor failures. Additionally, they have removed the central or fifth engine, which was added hastily during the Chandrayaan-2 mission.

The selection of the landing site plays a pivotal role in ensuring a favourable touchdown. A carefully chosen area spanning 4 kilometers in length and 2 kilometers in width provides an optimal terrain, factoring in crucial aspects such as surface topography, illumination conditions, and potential hazards. This meticulous site selection process minimizes risks and maximizes the chances of a safe landing.

“The Vikram lander employs a sophisticated propulsion system, featuring four throttleable engines generating 800 Newtons of thrust. This propulsion setup enables precise adjustments to the lander's velocity and trajectory during the descent phase, ensuring a controlled and gentle landing on the lunar surface. Instrumentation and sensing capabilities are paramount for a successful touchdown. Equipped with advanced sensors like accelerometers, altimeters, Doppler velocimeters, star sensors, inclinometers, and hazard detection cameras, the lander continuously collects real-time data. These sensors enable precise navigation, altitude control, and hazard avoidance, contributing to a secure landing process. The lander's landing legs and thrusters further enhance stability and control during the descent. With four landing legs and four landing thrusters, each generating 800 Newtons of thrust, the lander expertly maintains its equilibrium, mitigating potential risks as it approaches the lunar surface,” remarked Srimathy Kesan, founder and CEO of Space Kidz India.

Kesan said Vikram lander also incorporates increased instrumentation redundancy and strengthened impact legs, bolstering reliability and resilience. “These enhancements ensure the lander's ability to withstand unexpected challenges and potential contingencies, fortifying its capability to execute a smooth and controlled descent.”