Chandrayaan-2 Indian step

India’s first attempt to land a spacecraft on the Moon has not been successful.

1. Chandrayaan-2 mission comprises an orbiter, lander, and rover.

2. While the orbiter part is functioning normally, ISRO lost contact with the lander.

3. Most of the scientific investigations of the mission are supposed to be carried by instruments onboard the orbiter, including studies to find more evidence of water on the Moon.

4. The lander and rover had a mission life of only 14 days while the orbiter will function for at least one year.

5. About 80-90 per cent of the science output of the mission has to come from the orbiter, and that has not been affected at all.

What is the status of the lander?

1. The lander, Vikram, did not slow down at the expected rate towards the latter part of its descent, and most likely hit the lunar surface at a speed greater than required for safe landing.

2. The ground control station lost contact with the lander when it was about 2.1 km above the Moon.

3. Vikram had been located on the Moon, and a thermal image of it had been taken by instruments on board the Chandrayaan-2 orbiter that is going around the Moon in a near-circular orbit of 100 km.

4. But efforts to re-establish contact with the lander had not yet been successful.

Why Vikram couldn’t make a soft landing on the moon?

1. The contact was lost, when it was travelling at 50 to 60 metres per second (180 to 200 km per hour).

2. It was decelerating, but not fast enough to slow down to a speed of 2 metres/second (7.2 km/hr) that was required for a safe landing.

3. Vikram was designed to absorb the shock of an impact even at 5 metres/second (18 km/hr). At the rate it was decelerating, it could not attain  speed less than 5 metres/second.

4. It is likely to have hit the Moon at a far greater speed, possibly damaging itself and instruments on board.

When contact could be restored?

1. The lander has already been located. At the time it had begun to deviate from its pre-programmed flight path, the lander was barely a few kilometres from the Moon.

2. The difficult part is to restore contact with the lander. That would depend on how much damage it has suffered, and whether its communication unit is intact.

3. The individual instruments onboard the lander and several of its components are capable of sending signals that can be picked up either through other nearby space assets or by the ground station.

4. Every such signal will offer valuable clues to its current state and what it could have gone through.

5. Restoration of contact can be done only in the next two weeks. After that, the Moon will enter its night (14 Earth days) during which temperatures would be so cold that the instruments are unlikely to behave normally.

Which instrument has been used in the lander for communication?

1. NASA-built Laser Retroreflector Array, essentially only a group of mirrors. This was only meant to be deployed on the Moon.

2. These mirrors are used by control stations on the ground to reflect signals from the Moon. At least five such reflectors are already on the Moon, deployed by earlier missions.

3. They are used for a variety of purposes. It is by sending signals back and forth to these mirrors that the distance between the Earth and the Moon has been calculated to a very high degree of precision.

4. All these existing retroreflectors are in the equatorial region of the Moon. The one being carried by Vikram lander would have been deployed near the polar region for the first time.

5. If this instrument has not been totally destroyed, it can be used. It is supposed to be a “passive” instrument; it only has to act as a reflector of signals.

6. The rover could have come out of the lander only when it was standing vertically. Now it is unlikely that the rover and the two instruments on it could be put to any use now.

How big a setback this is to ISRO?

1. ISRO, and other space agencies as well, has gone through several such setbacks in space exploration.

2. It is most probably a good learning experience. Even Chandrayaan-1, launched in 2008, had suffered a partial failure due to problems in heat shielding.

3. It had a mission life of two years but remained functional for nine months.  However, the main science objectives of Chandrayaan-1 had already been achieved by that time. This included the most important finding of irrefutable evidence of the presence of water on the Moon.

4. Similarly, the major objective of Chandrayaan 2 is also expected to be achieved.