The lander module (LM) of ISRO’s ambitious third lunar mission, Chandrayaan-3, will touch down on the lunar surface on Wednesday night, with India hoping to become the first country to reach the unknown South Pole of Earth’s only natural satellite. The lunar module, consisting of a lander (Vikram) and a rover (Pragyan), is scheduled to make a soft landing near the Moon’s South Pole region at 6:04 p.m. Wednesday.
If ISRO successfully lands on the moon and lands a rover on its Chandrayaan-3 mission for the second time in four years, India will become the fourth country to master the technology of soft landing on the lunar surface after the United States, China and the former Soviet Union.
Chandrayaan-3 is the follow-up mission to Chandrayaan-2, and its goal is to demonstrate safe soft landings on the lunar surface, lunar rovers, and conduct on-site scientific experiments.
On September 7, 2019, when Chandrayaan-2 was trying to land, its lander “Vikram” crashed into the surface of the moon due to an abnormality in the braking system when it was trying to land, and the moon phase failed. Chandrayaan-2’s first mission was in 2008.
The Rs 6 billion Chandrayaan-3 mission was launched on July 14 on a Mark-III launch vehicle (LVM-3) on a 41-day voyage to the vicinity of the Moon’s South Pole.
Russia is attempting a soft landing just days after its Luna-25 spacecraft crashed out of control into the moon.
Following the second and final decompression maneuver on August 20, the lunar module was placed in a 25 km x 134 km orbit around the moon.
The module will undergo internal inspections and wait for sunrise at the designated landing site, ISRO said, adding that power descent is expected to begin around 5:45 for a soft landing on the lunar surface. Wednesday afternoon.
The key process of the soft landing, dubbed by many, including ISRO officials, “the horrific 17 minutes”, is entirely autonomous, with the lander having to start its engines at the correct time and altitude, use the correct amount of fuel, and eventually Scan the lunar surface for any obstacles, hills or craters before landing.
After checking all parameters and deciding to land, ISRO will upload all required commands from the Indian Deep Space Network (IDSN) in nearby Byalalu and to the lunar module a few hours before the scheduled landing time.
On touchdown, at an altitude of about 30 kilometers, the lander entered a dynamic braking phase and began using its four thruster engines to gradually reduce speed to the lunar surface by “reverse firing,” according to ISRO officials. This is to ensure that the lander does not crash, as the moon’s gravity also plays a role.
They noted that at an altitude of about 6.8 kilometers, only two engines will be used, with the other two turned off in order to provide reverse thrust to the lander as it descends further, and then, at an altitude of about 150 kilometers. At -100 meters, the lander uses sensors and cameras to scan the ground, checks for any obstacles, and then begins to descend for a soft landing.
ISRO Chairman S Somanath recently said that the most critical part of the landing will be the process of decelerating the lander from an altitude of 30 kilometers to the speed of its final touchdown, and the ability to reorient the spacecraft from a horizontal to a vertical orientation. “That’s the trick we have to play here,” he said.
“The speed at the beginning of the landing process was almost 1.68 kilometers per second, but at this speed (the lander) was level with the lunar surface. Chandrayaan-3 was tilted almost 90 degrees here, and it had to “become vertical.” So, the whole process of going from horizontal to vertical is a very interesting calculation mathematically. We do a lot of simulations. This is where we had problems last time (Chandrayaan-2),” Somanath explained.
After a soft touchdown, the rover will descend from the lander’s belly to the lunar surface, using one of its side panels, which will act as a ramp.
The mission life of the lander and rover is 1 lunar day (about 14 Earth days) to study the surrounding environment there. ISRO officials, however, did not rule out the possibility of their resurrection on another lunar day.
The lander will be able to soft-land at a designated lunar site and deploy a rover that will conduct in situ chemical analysis of the lunar surface as it travels. Landers and rovers have science payloads to conduct experiments on the lunar surface.
“After the power is lowered to the landing site, the ramp and the rover will be deployed. After that, all the experiments will be performed one after the other — all of which have to be done in one day on the moon, which is 14 days,” Somnath said.
He said that as long as there is sunlight, all systems will be powered. “The moment the sun goes down, everything is pitch black and the temperature will be as low as minus 180 degrees Celsius, so there is no way these systems can survive. If it can survive further, then We should be happy that it came back to life again, and we’ll be able to work on the system again, and we hope that happens.” The polar regions of the moon have very different topography due to circumstances and difficulties, and so remain unexplored. All previous spacecraft to the Moon have landed in equatorial regions, latitudes a few degrees north or south of the Moon’s equator.
The lunar south pole region is also being explored because of the possible presence of water in permanently shadowed regions around it.
Lunar module payloads include RAMBHA-LP for measuring near-surface plasma ion and electron densities and their variations, ChaSTE Chandra’s Surface Thermophysics Experiment for measuring the thermal properties of the near-polar regions of the lunar surface. – and ILSA (Lunar Seismicity Instrument), to measure seismicity around the landing site and map the structure of the Moon’s crust and mantle. After a soft landing, the rover will descend the lander module and study the lunar surface with its payload APXS (Alpha Particle X-ray Spectrometer) to obtain chemical composition and infer mineral composition to further enhance the understanding of the lunar surface.
The rover also has another payload, the Laser-Induced Breakdown Spectrometer (LIBS), which is used to determine the elemental composition of lunar soil and rocks around the lunar landing site.
Before the planned moon landing, Chandrayaan-3’s lunar module had established two-way communication with the Chandrayaan-2 orbiter, which continues to orbit the moon. The two-way link may provide ground controllers (MOX-Mission Operations Complex in Bangalore) with more channels to communicate with Chandrayaan-3.
The Chandrayaan-2 spacecraft, consisting of an orbiter, lander and rover, was launched in 2019. The lander with the rover crashed into the lunar surface and failed to achieve a soft landing. The mission life of the Ch-2 orbiter, which is separated from the lander and rover, was extended to seven years due to precise launch and orbital maneuvering, ISRO said.
Instead of a success-based design on Chandrayaan-2, the space agency opted for a failure-based design on Chandrayaan-3, Somanat said, focusing on what could fail and how to protect it and ensure success landing.
“We look at a lot of failures — sensor failures, engine failures, algorithm failures, calculation failures. So whatever failure is there, we want it to land at the desired speed and rate. So different failures are calculated and programmed internally Scene.” The lunar module of Chandrayaan-3 successfully separated from the propulsion module on August 17, 35 days after the July 14 satellite launch.
Meanwhile, the space agency says the propulsion module, whose main function is to inject the lander module from the launch vehicle into the lander separation orbit, will continue to operate in its current orbit for several months/years.
In addition to this, the propulsion module also has a scientific payload as an added value. The SHAPE (Spectral Polarimetric Measurement of Habitable Planet Earth) payload on board, and its future discovery of smaller planets in reflected light, will allow us to detect a wide variety of exoplanets that meet the conditions for habitability (or the presence of life).
After Chandrayaan-3 was launched on July 14, it entered lunar orbit on August 5, and the satellite underwent orbit reduction operations on August 6, 9, 14 and 16, followed by its two separate modules. 17, in preparation for the August 23 landing.
Previously, in the three weeks since its launch on July 14, ISRO had lifted the Chandrayaan-3 spacecraft into an orbit farther and farther away from Earth.
Then, on Aug. 1, through a crucial maneuver — a slingshot maneuver — the spacecraft successfully flew from Earth orbit to the Moon. Following this cross-moon injection, the Chandrayaan-3 spacecraft detached from Earth orbit and began following a path that would bring it near the Moon.
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