CHANDRAYAAN-3
Indian Space Research Organisation (ISRO) has been achieving success for the last few years. The latest success is the successful landing of Chandrayaan-3 on the Moon. India is one of the few countries competing for Moon exploration.
Chandrayaan-3
ISRO launched Chandrayaan-3 on board the Launch Vehicle Mark-3 (LVM-3) on 14 July, 2023 from Satish Dhawan Space Centre at Sriharikota in Andhra Pradesh. The space vehicle crossed Earth’s gravity on 5 August and entered the orbit of the Moon. On 23 August 2023 at 06.04 PM its lander along with the rover soft landed on Moon surface creating history.
As the name tells, it is India’s third mission to the Moon. The Chandrayaan-1 was launched in 2008. It had an orbiter and a probe. The data collected from its instruments identified water molecules on Moon. Chandrayaan-2 was launched on 22 July, 2019. It had an orbiter, a lander named Vikram and a rover named Pragyan. The space vehicle entered lunar orbit on 20 August and the lander along with the rover were released to the lunar surface on 6 September, 2019. But instead of soft landing the lander was crashed due to some software error and no communication was received from it. It was declared that part of the mission failed. But the orbiter is still functional and sending critical data. ISRO scientists say that the mission was about 90 percent success. Now, they have learnt the lesson and have rectified the mistakes in Chandrayaan-3. It is to be noted that the design and goal of the Chandrayaan-2 and Chandrayaan-3 are same.
Chandrayaan-3 at Launch Pad
Chandrayaan-3 consists of two modules- a propulsion module and a lander module. The lander module contains the lunar rover within it. The Propulsion module took the lander module to a 100 km lunar orbit. After deorbiting to a 30 km – orbit and deboosting, lander module was released to the lunar surface on 23 August 2023. As planned, after 20 minutes the lander along with the rover safely landed near the South Pole of the Moon.
Trajectory of Chandrayaan – 3
Objectives of the Mission
The mission has three objectives – to demonstrate safe and soft landing (which could not be achieved with Chandrayaan-2), to demonstrate rover abilities on the Moon surface and to conduct in-situ scientific experiments.
The propulsion module contains a single experimental pay load that will study the spectro-polarimetric signatures (the polarisation of light emitted by celestial objects) of Earth in the near infrared wavelength. Its life has been designed for 3 months.
Chandrayaan – 3 Lander
The 1724 kg lander contains four payloads – Lander Hazard Detection and Avoidance Camera (LHDAC) andbthree instruments. The camera was used to identify a safe location for landing, and prevent the craft from ending up unintentionally in craters or on slopes. The instruments are meant for measuring plasma density, thermal levels and seismic activity. The 26 kg – rover has rolled out of the lander on the lunar surface and is carrying out in-situ chemical analysis of the lunar surface. It has two payloads on it – the Alpha Particle X-Ray Spectrometer which will analyse minerals on the surface and the Laser Induced Breakdown Spectroscope which will analyse elements in the soil around the landing site. Both the lander and the rover have been designed to function for one lunar day (equivalent to 14 Earth days). They can’t survive the extreme drop in temperature during lunar nights and hence had to land right at dawn and will work till dusk (i.e. one lunar day).
Chandrayaan – 3 Rover
Landing Site
The landing site has been selected near the South Pole at 70 degree latitude. It is about 300 km from the lunar South Pole. Actually, it is a difficult task for the lander to function at the South Pole. Before this. all other lunar missions have landed in the equatorial region of the Moon – a few degrees north or south of equator. NASA’s Surveyor-7, which landed near 40 degree S latitude in 1968, is the farthest that any craft had landed from the equator. China’s Chang’e-4 mission, which in January 2019, became the first spacecraft to land on the far side of the Moon – the side that does not face the earth-descended on the lunar surface near the 45 degree latitude.
Why has no spacecraft ever landed near the South Pole?
The answer is that it is easier and safer to land near the lunar equator. The terrain and temperature are more hospitable and conducive for long and sustained working of the instruments on board. The surface in this region is even and smooth, very steep slopes are almost absent, and there are fewer hills or craters. There is abundant sunlight, at least on the side facing the Earth, offering a steady supply of energy for solar-powered instruments.
On the other hand, the polar regions of the Moon are a very different, difficult, terrain. Many areas close to the lunar poles lie in a completely dark region where sunlight never reaches, and temperature can fall to below minus 230 degree Celsius (For contrast, the minimum temperature on Earth goes to minus 92 degree Celsius at Antarctica). The absence of sunlight and extremely low temperature make it difficult for working of the instruments. In addition, the lunar surface here is littered with deep craters of sizes ranging from a few centimetres to several thousand kilometres.
Landing of Chandrayaan – 3 lander (Picture taken from direct telecast of ISRO)
Why does India choose to explore the South Pole?
Although no lander or rover has landed in South Pole region, it is known from orbiter missions including India’s Chandrayaan-1 that substantial amount of ice molecules and precious minerals are present there. Also due to extremely cold temperature in this region, the rocks and soil have not changed from the days of the formation of Moon and it could provide clues to the early solar system. India wants to explore this.
Picture of lunar surface taken by Chandrayaan – 3 after landing
Changes in Comparison with Chandrayaan-2
If India succeeds in landing there it will be the first nation to do that. The ISRO scientists have confidence of it, because they have rectified the errors of Chandrayaan-2. For example, Chandrayaan-2 crashed instead of soft landing because of higher velocity of the lander. The five engines that were used for the reduction of velocity developed a higher entry thrust than was intended. The lander was designed in such a way that by the time it was about 400 metre from the lunar surface, it would start the process of hovering above the targeted site of landing to ensure soft vertical landing. Due to extra speed it was crashed. Some changes in the current mission have been done.
- The landing spot for Chandrayaan-2 was limited to 500 m by 500 m, which did not provide enough flexibility for the craft to overcome possible errors. This time the marked landing area has been increased to 4 km by 2.5 km.
- The fuel capacity has been increased so that it can move to an alternative landing site in case of an unforeseen problem during landing.
- The lander will no longer depend only on the pictures it clicks during the descent for determining the landing site. High resolution images from the Chandrayaan-2 orbiter have been fed into the lander and it will click the images just to confirm that it has reached the correct location.
- The central thruster on the lander has been removed, reducing the number from five to four.
- The legs have been made sturdier to ensure it can land even at a higher velocity.
- More solar panels have been added to the body of the lander.
Conclusion
The 48-day-long Chandrayaan-3 mission covered 384,400 km, the average distance between the Earth and the Moon. India became the fourth country to achieve the soft landing on the lunar surface. Earlier, USA, Russia and China have achieved this. The first soft landing of USA and Russia was way back in 1966 and China did it in 2019. Further, India became the first country to land a spacecraft on the South Pole. This achievement has enhanced the prestige and reliability of ISRO. It has made India one of the leaders in space explosion. Now ISRO aims for solar mission (Aaditya L1) and sending astronauts to the space (Gaganyaan mission).
Er. Mayadhar Swain
Editor, Science Horizon
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