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On Wednesday evening, the Lander Module (LM) of ISRO’s ambitious Chandrayaan-3 third Moon mission will touch down on the lunar surface in an effort to make history as the first nation to travel to the unexplored south pole of Earth’s sole natural satellite. At 6:04 p.m. on Wednesday, the LM, which consists of the lander (Vikram) and the rover (Pragyan), is planned to gently land close to the south polar region of the Moon.
After the US, China, and the former Soviet Union, India will become the fourth nation to perfect the technology of soft-landing on the lunar surface if the Chandrayaan-3 mission’s goal of making a touchdown on the moon and successfully landing a robotic lunar rover in ISRO’s second attempt in four years is achieved.
A follow-up mission to Chandrayaan-2, Chandrayaan-3’s goals include wandering on the Moon, demonstrating safe and soft landings, and conducting in-situ scientific experiments.
On September 7, 2019, Chandrayaan-2’s lunar phase mission ended in failure when its lander, “Vikram,” collided with the Moon’s surface as it attempted to touch down due to problems with the lander’s braking mechanism. 2008 saw the first mission of Chandrayaan.
Launch Vehicle Mark-III (LVM-3) rocket carrying the Rs 600 crore Chandrayaan-3 mission lifted off on July 14 on a 41-day journey to a location close to the lunar south pole.
Days after Russia’s Luna-25 spacecraft crashed onto the Moon after spinning out of control, a soft landing is being tried.
The LM is put into a 25 km x 134 km orbit around the Moon on August 20 following the second and final deboosting procedure.
According to ISRO, the module would go through internal inspections and wait for sunrise at the planned landing spot before beginning the powered descent to make a soft landing on the Moon. This is anticipated to begin at around 5:45 pm on Wednesday.
Many people, including ISRO officials, have referred to the crucial soft-landing process as “17 minutes of terror” because the entire procedure is autonomous and the lander must fire its engines at the proper times and altitudes, use the appropriate amount of fuel, and scan the lunar surface for any obstacles, hills, or craters.
A few hours prior to the scheduled time of arrival, ISRO will upload all the necessary commands to the LM from its Indian Deep Space Network (IDSN) at Byalalu nearby after evaluating all the criteria and opting to land.
According to ISRO officials, the lander enters the powered braking phase for landing at about 30 km altitude and starts to use its four thruster engines by “retro firing” them to progressively reduce the speed to reach the moon’s surface. This will prevent the lander from crashing because the Moon’s gravity will also be at work.
The lander would use its sensors and cameras to scan the surface to see if there are any obstacles before starting to descend to make a soft landing. They noted that on reaching an altitude of about 6.8 km, only two engines would be used, shutting down the other two to give the lander the reverse thrust as it descended further.
S. Somanath on Chandrayaan-3
According to ISRO Chairman S. Somanath, the capacity to rotate the spacecraft from a horizontal to a vertical position and reduce the lander’s velocity from 30 km above the ground to the final landing will be the most crucial aspects of the landing. “This is the trick we have to play here,” he said.
“At the beginning of the landing phase, the lander is moving at a rate of almost 1.68 km per second, yet at this speed, it is horizontal to the Moon’s surface. The Chandrayaan-3 must become vertical because it is almost 90 degrees slanted in this location. So, mathematically speaking, the entire process of going from horizontal to vertical is quite interesting. We’ve run numerous simulations. The issue with Chandrayaan-2 occurred just here, according to Somanath.
After the soft landing, the rover will use one of the lander’s side panels as a ramp to drop from the belly onto the Moon’s surface.
One lunar day (or around 14 days on Earth) will be the lander and rover’s mission duration as they explore the area. ISRO representatives do not rule out the chance that they could reanimate for a subsequent lunar day, though.
The lander will be able to soft-land at a chosen location on the moon and release the rover, which will do in-situ chemical analysis of the lunar surface as it is moving. Both the lander and the rover are equipped with scientific packages that will conduct lunar surface research.
“The ramp will be deployed and the rover will emerge after powered descent into the landing spot. The experiments would next be conducted one after the other and must all be finished in a single lunar day, or 14 days, according to Somnath’s earlier statement.
Since all systems have power as long as the sun is shining, he claimed, “The moment the sun sets, everything will be in pitch darkness, and the temperature will drop as low as minus 180 degrees Celsius; so it is not possible for the systems to survive.
If it survives further, however, then we should be happy that it has come to life once again and we will be able to work on the system once again, and we hope that to happen.” Due to their environment and the challenges they bring, the polar areas of the moon have not been visited and feature significantly varied terrain. A few degrees latitude north or south of the lunar equator, all previous spacecraft that have visited the Moon have touched down in the equatorial zone.
It is also being investigated whether there is water in the permanently dark regions surrounding the south pole of the moon.
The lunar lander (LM) is equipped with a number of payloads, including RAMBHA-LP, which will measure the density of near-surface plasma ions and electrons and how it changes, ChaSTE Chandra’s Surface Thermo Physical Experiment, which will measure the thermal characteristics of the lunar surface near the polar region, and ILSA (Instrument for Lunar Seismic Activity), which will map the structure of the lunar crust and mantle. After soft-landing, the rover would ramp down the lander module and examine the moon’s surface using its payload, the Alpha Particle X-Ray Spectrometer (APXS), to determine the chemical composition and infer the composition of the moon’s minerals in order to improve understanding of the lunar surface.
The Laser Induced Breakdown Spectroscope (LIBS) is a second payload on the rover that measures the elemental composition of rocks and dirt around the lunar landing site.
Before Chandrayaan-3’s planned lunar landing, the LM established two-way communication with Chandrayaan-2’s orbiter, which is still in lunar orbit. The possibility of multiple channels of communication with Chandrayaan-3 for ground controllers (MOX-Mission Operations Complex in Bengaluru) is provided by the two-way contact.
A lander, orbiter, and rover were launched as part of the Chandrayaan-2 mission in 2019. In its attempt to make a soft landing, the lander with a rover inside slammed into the moon’s surface. According to the ISRO, the Ch-2 orbiter’s mission life, which had separated from the lander and rover, has been extended to seven years as a result of the accurate launch and orbital maneuvers.
According to Somanath, the space agency chose a failure-based design for Chandrayaan-3 instead of a success-based design for Chandrayaan-2, focusing on what could go wrong and how to protect it in order to ensure a successful landing.
“We examined a large number of failures, including sensor failure, engine failure, algorithm failure, and computation failure. We therefore want it to land at the necessary speed and rate, regardless of the failure. As a result, various failure scenarios have been estimated and coded. On August 17, Chandrayaan-3’s LM successfully disengaged from the Propulsion Module, 35 days following the satellite’s July 14 launch.
The Propulsion Module will continue its voyage in the current orbit for months or years, according to the space agency. Its primary job was to transport the Lander Module from the launch vehicle injection to the lander separation orbit.
In addition to this, the Propulsion Module carries one additional scientific payload for value. The SHAPE (Spectro-polarimetry of Habitable Planet Earth) payload on board would enable us to investigate a variety of Exo-planets that would meet the criteria for habitability (or for the presence of life) in the future by revealing smaller planets in reflected light.
Chandrayaan-3 was launched on July 14 and entered lunar orbit on August 5. Thereafter, orbit reduction maneuvers were performed on the spacecraft on August 6, 9, 14, and 16 in preparation for the separation of both of its modules on August 17 and the upcoming landing on August 23.
Earlier, ISRO had launched the Chandrayaan-3 spacecraft into orbits that were farther and farther away from Earth through a total of five maneuvers in the three weeks following the launch on July 14.
Then, on August 1, the spacecraft was successfully launched from Earth’s orbit toward the Moon in a crucial maneuver known as a slingshot. The Chandrayaan-3 spacecraft left its orbit around the Earth after its trans-lunar injection and started traveling in a direction that would bring it close to the moon.