New Delhi: Chandrayaan-3, the soft-landing process, which is considered the most challenging part of the mission, will be entirely autonomous and will depend on the computers and sensors on board the lander
Chandrayaan-3, which is expected to touch down on the lunar surface on Wednesday, will face a crucial technical challenge when it enters the final 15 minutes before landing.
The final 15 minutes, also known as the ’15 minutes of terror’, will determine the fate of the mission. On September 7, 2019, Chandrayaan-2 lander Vikram failed to land safely on the moon during this phase, due to a problem in switching from horizontal to vertical orientation and losing control.
However, this time, things are different. While the mission control at ISRO Telemetry, Tracking and Command Network (ISTRAC) in Bengaluru and the mission scientists will monitor the landing attempt, they will not be able to intervene or send any commands to the lander. Here’s why.
The entire landing process of Chandrayaan-3 during the critical 15 minutes of descent will be controlled by computer logic that has already been programmed into the lander’s computers, guidance and navigation systems, a report in The Indian Express said.
The ISTRAC centre in Bengaluru will receive data on signals sent by the Chandrayaan 3 lander and it will be relayed to the Deep Space Network at Bengaluru, the Jet Propulsion Laboratory in the US and a European Space Agency station in Spain.
However, the mission control centre cannot send any commands to the lander when the descent manoeuvre begins at 17:47 on Wednesday, with the touchdown scheduled at 6:04 pm.
Sensors play a vital role in a remotely operated craft as they provide information about its location, speed and orientation. The sensors fitted in the lander will perform calculations as it descends from a height of 30 km above the surface of the moon to a height of 7.42 km in the first 10 minutes of the 15-minute landing process.
“The core of Chandrayaan 3 is its sensors. When you have something that is remotely operated then everything depends on its ability to sense its location, what it is its speed, what is the orientation. There are different sensors used for this purpose. There are the velocimeters and altimeters which give a reference for the speed and the height of the lander,” ISRO chairman S Somnath reportedly said.
There are also cameras in the craft including a hazard avoidance camera and inertia-based cameras. When the sensors are fused together using an algorithm, it provides an indication of where the lander is positioned.
Moreover, ISRO scientists are also using AI systems for navigation, guidance and control systems of the lander. The system helps to position the lander correctly for a safe and soft landing.
S Somnath also said that Chandrayan-3 has been designed to land safely even if all the sensors fail, provided the propulsion system works well.
This is how it has been designed. Even if two of the engines do not work also this time the lander will be able to land. It has been designed in such a way that it should be able to handle multiple failures. If the algorithms work well, we should be able to do a vertical landing,” the ISRO chairman said.
Chandrayaan-3 lander can touch down at a maximum speed of 10.8 km per hour without damage.