CONTACT LOST WITH VIKRAM LANDER
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The ISRO’s ground station lost contact with lander Vikram as it was merely 2.1 km above the lunar surface
The Vikram lander and Pragyan rover were supposed to land on the moon and carry out observations and experiments for 14 days.
- GSLV Mark 3, ISRO’s heaviest launch vehicle fired on July 22 to put the Chandrayaan 2 composite spacecraft on its way to the Moon
- Then over the next 40 days ISRO scientists conducted intricate manoeuvres to first put Chandrayaan 2 into a lunar orbit.
- And in the first week of September they successfully separated the Moon lander Vikram, carrying the rover Pragyan in its belly, from the orbiter and prepared it for a touchdown on the lunar surface.
- It was to be a historic moment as ISRO had never done this before, and if it had succeeded, India would be the fourth nation to complete a soft-landing of a spacecraft on the Moon — after Russia, the US and China.
- The critical manoeuvre lasting 15 minutes termed as ‘autonomous powered descent’ to the lunar surface which involved intricate and rapid changes in the flight path and velocity of the spacecraft, was controlled by its onboard computer.
- The spacecraft’s velocity to be brought down to near zero, and also the descent was to be done in a controlled manner to enable landing at a pre-determined spot near the South Pole of the Moon – the first time a spacecraft by any nation was doing so.
- The soft landing sequence was divided into three distinct phases that would steadily decelerate the spacecraft and its altitude till it reaches near zero at touchdown.
- To do that, Vikram was equipped with a cluster of five engines that would perform specific pre-programmed functions.
- It seemed to go well as the first phase, called the Rough Braking Phase, saw four of its five rockets employed for decelerating the spacecraft and also ensuring a steady loss of altitude.
- The speed of Vikram was down to 22 kms per hour and its altitude was 7 kms.
- Trouble seems to have begun between the transition period between two critical phases – termed as Absolute Navigation Phase and the Fine Breaking Phase.
- During these phases the altitude was to be brought down from 7 km to around 400 metres and the orientation of Vikram would be with its four lander legs facing downwards.
- The spacecraft was at a height of 2.1 km above the lunar surface. At this point, all communication snapped and the trajectory on the large console tracking its path showed a steep dip.
- Vikram not only seemed to have lost communication but also suffered a control loss in the terminal phase of its descent.
Reasons for failure:
- Some scientists believe the problem occurred in the functioning of one or many of the four engines that were involved in the de-boost stage.
- These engines need to be operated with perfect synchronicity to achieve not only the required descent, but also the perfect inclination.
- The engines were throttled ones which allowed it to vary the thrust given to the spacecraft to facilitate the critical manoeuvres. This was the first time that ISRO was using such engines.
- The other cause could be a catastrophic failure of communication either due to overheating or a system malfunction that then resulted in the loss of control of the spacecraft.
40% lunar missions in last 60 years failed: NASA fact sheet:
- The success ratio of lunar missions undertaken in the last six decades is 60 per cent, according to US space agency NASA’s ‘Moon Fact Sheet’.
- Of the 109 lunar missions during the period, 61 were successful and 48 had failed.
- Israel, too, launched its lunar mission Beresheet in February 2018 but it crash landed in April.
- Chandrayaan 2 is a follow-on mission to the Chandrayaan 1 Mission.
- Chandrayaan-2 was India’s first attempt at landing a spacecraft on the moon.
- Only three countries — the United States, the erstwhile USSR and China — have managed to place a spacecraft on Moon so far.
- The Chandrayaan-2 mission comprises of three modules – the Orbitor, Vikram lander and Pragyaan rover.
- The lander which is named after Dr. Vikram A Sarabhai, who is considered as the father of the Indian Space Programme, carries the Pragyaan rover.
- Unlike Chandrayaan-1, Chandrayaan-2 attempted to soft land its Vikram module on the lunar surface and deploy a six-wheeled Rover, Pragyaan on the Moon to carry out several scientific experiments.
- The lift-off mass of Chandrayaan-1 was 1380 kg while Chandrayaan-2 weighs 3850 kg.
What is soft landing? How was it supposed to take place? Challenges therein?
- A soft-landing protects the object from impact while a hard landing doesn’t.
- Soft-landing ensures that the object is able to carry out further experimentation on the target planet or satellite, mostly with the help of a rover vehicle.
- Soft-landing on any planetary surface is complicated. Vikram was to use five thrusters — four at the corners and one at the centre to make its final descent.
- Maintaining the required velocity with such thrusters is difficult as a fine balance among them needs to be maintained.
- Then there is the issue of moon dust which could wreck the engines of the thrusters.
Why the south pole?
- The south polar region of the Moon has not received sunlight for billions of years and is among the coldest spots in the Solar System.
- This, makes lunar south pole region ripe to contain tonnes of water and “an undisturbed record” of the Solar System’s origins.
- The Orbiter component of Chandrayaan-2, however, was doing fine and continued to communicate with the control room.
- Though the expected soft-landing of the Vikram lander was not accomplished, the Chandrayaan-2 mission is far from over.
- Chandrayaan-2’s lander Vikram is unbroken but lying tilted on the surface of the moon after a hard landing very close to the scheduled touchdown site.
- Images sent by the orbiter’s on-board camera shows that though the lander hit the lunar surface hard while landing, it is still very close to the scheduled touchdown site.
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