The Indian Space Research Organisation (ISRO) is all set for Chandrayaan-3, armed with lessons from the failed Chandrayan-2 mission.
If the Chandrayaan-3 mission — slated for launch on Friday, July 14 — goes as planned, it will place India in the elite club of four nations that have set their footprints on the lunar surface by landing a space vehicle.
Such a landing will also fuel the country's efforts to send a man to the moon. The countdown for Chandrayaan-3 began at 1.05 pm on Thursday, July 13.
The Chandrayaan-3 mission will blast off from the launch pad at Sriharikotta at noon on Friday and is expected to land on the moon on August 23 or 24. Dr S Unnikrishnan, the Director of the Vikram Sarabhai Space Centre (VSSC), who played a significant role in the mission, spoke to Manorama Online.
What are the peculiarities of the LVM-3 (Launch Vehicle Mark-III) rocket being used in the mission?
LVM-3 is India's most powerful rocket. The indigenously made rocket is capable of placing a satellite weighing four or five tonnes on an orbit 36,000 kilometres away from Earth. The same rocket will be modified to facilitate Gaganyaan, the mission to send a man to the moon. This will be LVM's third mission. Though some modifications have been made as part of the Gaganyaan mission, the rocket, fundamentally, is the same.
What are the modifications made to the rocket to suit the Gaganyaan mission?
We have added a crew module to accommodate the crew and a safety facility to be used in case of an accident. The electronic system, joints and seals were strengthened, besides making modifications to make the rocket more effective. The VSSC manufactures the Gaganyaan launch vehicle. The VSSC will be responsible for propelling the Gaganyaan module to an orbit 400 kilometres away. The VSSC has a centre specifically for this purpose in Bengaluru. About 66 percent of the project's work is being executed by the VSSC. Four people have been selected for the mission. They are being trained. The safety module to be used in case of an accident has been tested.
The Chandrayaan-2 mission in 2019 partially failed. It could not safely land on the lunar surface. What were the lessons learnt from the previous mission?
The Chandrayaan-2's landing failed. We received data on factors that led to the failure, and accordingly, we made changes to Chandrayaan-3. The propulsion system. software and algorithms have been changed, and we added new sensors. The solar panel's area has been extended. We utilised all lessons learnt from Chandrayaan-2.
The lander is next to the propulsion module. This lander is heavier, 300 kilograms more than that of Chandrayaan-2. We reduced the weight of the propulsion module proportionately to focus more on the lander. Also, the lander's propulsion system has been altered. Its legs have been made stronger so that even if it crashes on the lunar surface, it should land safely. Sensors have been fixed to monitor the lander's landing speed and direction. We are confident since we have fixed the mistakes.
You have artificially created the lunar environment to conduct experiments for the Chandrayaan-3 mission. What were they?
We suspended the lander from a helicopter without operating its thruster. We tested whether the sensors were working properly and sending data. The artificial atmosphere was created in Bengaluru. We operated the thrusters after suspending the lander from a crane in Sriharikota. This was to test the sensors and other functions. Additionally, we checked if we can totally control the lander and the software and hardware aspects as well.
What would be the challenges you may face while landing the lander on the lunar surface?
Landing on the moon is a complex operation. A pilot will have control over his aircraft's landing. There is no one to control the lander according to the situation. The lander lands with the help of sensors and other equipment. It has challenges. If something happens while on the earth, human intervention is possible.
In outer space, the lander faces the situation with the help of algorithms and software. Once the lander is detached from the propulsion module, four thruster burns provide an opposing force to allow the lander to land safely. The propulsion module will deliver the lander 100 kilometres from the lunar surface, and it will be brought down to 30 kilometres and gradually land it. The entire process comprises several phases.
What are your focus areas while landing the lander?
The lander is meant to be on the lunar surface for one lunar day, which is equivalent to 14 days. The sunlight is available on one part of the moon only for 14 days. The lander is mainly dependent on solar energy, and it would get solar power only for 14 days. So, after 14 days, it won't get enough power. We have made certain adjustments accordingly to the lander.
The lander weighs 1.4 tonnes. Dust and rock cover the lunar surface for five to 10 metres. The lander will kick up dust when its lands. The moon's gravitational force is 1/6th of the earth's force. So the dust will take more time to settle down. We will have to wait for the dust to settle. Once the dust settles, the lander's ramp will open and the rover will roll out. The rover, weighing 25 kilograms, has two payloads, which will collect samples from the lunar surface. The collected samples will be handed over to the lander. The rover is incapable of transmitting data back to the Earth.
Where do you plan to land on the moon?
We are planning to land on the moon's south pole. Scientists are interested in that area since it has water content. The sunlight and temperature there, too, are suitable.
What are the other payloads in the lander?
The propulsion module has a payload called SHAPE — Spectro- polarimetry of Habitable Planet Earth. After ejecting the lander, the propulsion module will orbit at 100 kilometres above the lunar surface. The SHAPE is meant to study the Earth from the moon's orbit. We can gather information on the living planet from a higher orbit. The SHAPE will also help in identifying planets outside the solar system. The rocket will take Chandrayaan to an elliptical orbit 170 x 36,000 kilometres high. The Chandrayaan will burn its four thrusters to break free from the Earth's gravitational pull. It will then get into the moon's gravitational force.
What are the future missions?
We will launch a mission, Aditya-L1, to observe the sun in August. To achieve this, we have to place a satellite in an orbit 15 lakh kilometres away between the Earth and the sun. It should be outside the earth's gravitational force. It then can study the sun.
