Sources said Vikram’s antennas have a beam width of 180°, which means they can stay connected with the orbiter only if the antennas’ angular manoeuvre is within 180°

CHENNAI: Vikram, the Chandrayaan-2 mission lander, tumbled and crashed on the lunar surface, which resulted in the snapping of communication links with the orbiter, confirmed ISRO sources to TNIE even as the space agency said through Saturday that it was analysing the data. 

Sources said Vikram’s antennas have a beam width of 180°, which means they can stay connected with the orbiter only if the antennas’ angular manoeuvre is within 180°. “If the lander starts to tumble and when antennas face the lunar surface, the communication link is lost. It’s like losing your DTH connection when the antenna on your terrace is pushed by a bird or the wind. Here the situation is far more grave as Vikram was tumbling. The rotation was so high that Vikram along with Pragyan rover crashed,” said an ISRO scientist, who was inside the Mission Control Room, on condition of anonymity.

To a query on why Vikram tumbled, sources said there could be multiple reasons, including design failure. They even said the lander was not put through elaborate tests. “The tests were conducted using a crane manually, instead of testing it in a free-fall condition with a balloon in autonomous mode. Only the last 60 metres descent was tested. A spare lander should have been used to drop it from an aircraft and see if all the parameters were met. This would have given a more realistic picture,” sources said.

Soft landing was always a challenge. However, the 1,471-kg Vikram completed its rough braking phase as envisaged bringing smiles, but little after the commencement of the fine braking phase and just before the hover phase was set to begin, Vikram was seen drifting away from the designated descent trajectory on the telemetry screen.