ISRO’s Chandrayaan 2 mission successfully performed its second de-orbiting maneuver but signals were lost in the ’15 minutes of terror’. What is the danger of the dreaded window exactly?
Chandrayaan 2 is the second lunar exploration mission developed by ISRO which will be landing on the Moon. It is also the advanced version of the previous Chandrayaan-1 mission that launched in 2008. The first mission discovered the presence of water deposits in the South Pole in the form of water ice.
On 4th September, Chandrayaan-2 second de-orbiting maneuver was successfully performed. The orbit of Vikram Lander is 35km x 101km. and the craft Orbiter will continue to orbit the Moon at 96km x 125km. “Both the Orbiter and the Lander are healthy and safe,” said an ISRO Scientist.
Chandrayaan 2 Moon landing
ISRO mission with Chandrayaan-2 aims to investigate the unexplored lunar South Pole.
If India manages to accomplish this, then it will be the fourth country to do so after the US, Soviet Union (Russia) and China. The Vikram Lander is scheduled for powered descent between 0100 – 0200 hours IST on September 07, 2019. The touch down of Lander will take place between 0130 – 0230 hours IST.
We could have lost the craft: Dr. K Sivan on Chandrayaan 2 Moon Landing
On 20th August at 09:02 am, Chandrayaan-2 was successfully able to enter the lunar (Moon’s) orbit. The process of spacecraft’s insertion into the Moon’s orbit took place when Moon was at its farthest from the Earth which is called apogee. It is the point when Earth’s gravitational pull is at a minimum.
This made the insertion easy into the Moon’s gravitational influence for the spacecraft.
Dr. Kailasavadivoo Sivan, Chairperson of ISRO, said, “the process lasted for around 30 minutes. The manoeuvre that made this feat possible was crucial as we would have lost the craft otherwise.”
15 minutes of terror
ISRO’s faith in Vikram’s autonomous landing system that will be attempting to place its four-legged Lander gently on Moon’s surface is a 15 minutes heart racking terror for the Indian scientists and also for entire world who are closely watching the Chandrayaan-2 progress towards the Moon.
Dr. Kailasavadivoo Sivan, in an event, said, “landing on the lunar surface involves a lot of technical complexities.” He further added, “During its journey, Vikram will be on its own and not micromanaged by ground control. “This is a learning from the earlier attempts of soft landing on the Moon, only 37 percent of which have been successful.”
The Final Descent
On 7th September, at 1:40 am, Vikram Lander’s power will be activated for the final descent. Dr. K Sivan said the Lander would have to reach and adjust itself to a position which should be perpendicular to the lunar surface; it’s the most crucial bit for the Lander for landing on the poles.
In an attempt for the soft landing, the Lander will use its four thrusters along with a central engine. The thruster will fire to slow down the craft’s descent to make it almost zero from the speed of 6km a second.
Dr Sivan called it the last leg of Vikram’s journey, i.e. “15 minutes of terror.”
But ISRO has it under control
He further added that the 90-degree angle is not required in the equatorial regions where soft landing has been already attempted before. He called this relatively easy, referring to the landing of Chinese lunar crafts- Chang’e 4 in January 2019.
The landing area has to be an inclination less than 12 degrees; otherwise, the spacecraft can topple upon landing. When the Lander will reach the perpendicular position, then it will start capturing images of the lunar surface with its onboard camera.
How ISRO decided the landing spot
Although, the landing spot has already been decided by ISRO’s scientist, therefore, the Lander will only compare the taken images with the images that it has been carrying from Earth to ascertain the accurate landing spot.
According to ISRO scientist, the Lander is designed to select a landing site free of large boulders, the team’s engineers worry that if the site is slightly sloping, or pockmarked with small rocks, the craft could topple, ending its mission.
Dr. Sivan also said in a press conference that the automated landing will be the “most terrifying moments” for the organization.
Gravitational force is still a concern
Earth’s gravitational pull is so powerful that a small bulge has been created on the Moon’s surface. This bulge was observed for the first time by NASA’s scientist from there satellites.
Earth also has a bulge at the center or equator. The major reason behind the bulge is the centrifugal force from the rotation that is the reason for the difference gravity at a different latitude on the Earth.
Moreover, the significant difference found that the gravity at the equator, i.e. 9.780 m/s2 is less than the poles, which is 9.832 m/s2. So the object at poles will be 0.5% heavier than the equator. Although, Moon has a low gravitational force than Earth but still has the same gravity difference in its equator and poles. And the gravity at poles will be slightly higher than the equator.
Beresheet Spacecraft by Israel crashed on Moon
Before ISRO’s Chandrayaan 2 mission’s Moon landing, an Israel mission suffered failure in 2019. In April this year, the $100 million spacecraft Beresheet built by SpaceIL and Israel Aerospace Industries (IAI), during the landing time lost its communication with the space agency. The communication failure took place when the Beresheet was traveling at a speed of 2,110 mph and a height of 120 km from the intended landing spot.
The program managers tried to re-establish communication and also fixed the issue occurred in the spacecraft’s main engine. They re-establish the communication with the spacecraft when it was just about 150 meters above the lunar surface. Israel’s spacecraft could not make it and landed on Moon with a big crash.