Despite passing Moon landing shock test, Why did Chandrayaan 2's Vikram Lander go silent?

New Delhi, Sep 15: As the team of Indian Space Research Organisation (ISRO) scientists make efforts to communicate with the Chandrayaan-2 lander, Vikram, that went silent on September 7, which lies on the lunar surface not very far from its actual landing site, there had been a lot of talk ever since then as to 'what went wrong, when will ISRO try connecting to the lander'.

This one-week window of opportunity for ISRO, the Indian space agency, to restore link with Vikram Lander will close on September 21.

Even though hopes are fading with every passing moment, ISRO is pulling all possible ways to strike a communication with Vikram Lander. Not only ISRO, even NASA too has joined in to help ISRO have this breakthrough of communicating with Chandrayaan-2 Vikram Lander.

The European Space Agency had earlier said,"The surface (south pole) of the Moon is a complex environment where charged particles and radiation meet fine lunar dust. The results can be surprising, unpredictable and hazardous.''

Keeping all this in mind, Chandrayaan 2 mission was launched. But, soft-landing a rover on the moon to explore its surface involved new challenges and complex technology that ISRO had to master.

In order to do all this, they first had to simulate a lunar environment to test their hardware. Specifically, ISRO needed an environment to test the Vikram moon lander and the Pragyaan rover.

The plan, when the mission reaches the moon, is for Vikram to detach from the lunar orbiter and make a soft-landing on the Moon's surface. It will then open up and release the rover (housed inside it) which will explore and carry out surface experiments.

Importing lunar soil like substance from the US was a costly affair and ISRO looked for a local solution as its need was about 60/70 ton of soil. Many geologists had told ISRO that near Salem in Tamil Nadu there were "anorthosite" rocks that would be similar to features of moon soil or regolith.

The ISRO finalised to take the "anorthosite" rocks from Sithampoondi and Kunnamalai villages in Tamil Nadu for moon soil. Initially a sum of Rs 25 crore was budgeted for the purpose but it came down drastically. Artificial lighting was also set up to resemble the Sun-lit environment on the moon.

Helium balloons were used to reduce the weight of the rover to simulate the moon's gravity which is less than that of the Earth's.

The communication compatibility of rover and the lander were also checked at HAL's facility. In order to test the lander, a test bed was created at ISRO's facility at Challakere in Chitradurga district in Karnataka.

Artificial moon craters were created at Challakere, similar to the site where lander Vikram was about to land. Prior to its landing, Vikram's sensors would also check whether the terrain is safe to land. Even after landing if the terrain is not suitable then the lander will go up and settle down at a nearby spot.

The actuators of the lander were also tested at ISRO centre at Mahendragiri and the thrusters were also tested. The strength of the lander legs was also tested in two ways-falling when the engines were switched off and in a calibrated landing. The legs have to absorb the landing shock.

The landing process is divided into "rough braking" and "fine braking".

The descent trajectory of Vikram has to take into account the variation in local gravity. Further the landing site, landscape features should not result in a communication shadow area.

The next challenge is the moon dust. The moon's surface is covered with craters, rocks and dust. Firing the onboard motors close to the surface will result in backward flow of hot gases and miniscule, hard/barbed/jagged dust.

Its negative charge makes it stick to most surfaces, causing a disruption in deployment mechanisms, solar panel and sensor performance.

If the lander, which was named after the father of the country's space programme, Vikram Sarabhai, had succeeded, it would have been a fitting finale to the 50th anniversary celebrations of the Indian Space Research Organisation (ISRO).

Chandrayaan-2 (Moon vehicle 2) entered the Moon's orbit on 20 August and was due to land on the lunar surface a little after midnight India local time (1800 GMT) on 7 September - a month after it first shot into space.

But contact was lost moments before the lander (named Vikram, after Isro founder Vikram Sarabhai) was expected to touch down at the lunar south pole.

The orbiter has since spotted the lander on the surface of the Moon - unbroken, but tilted on its side. So far, scientists have not been able to establish contact with it.