in the vertical velocity, which means the Vikram could be performing somersault while descending, so it oscillate between acceleration and deceleration. But doubtless it crashed onto the surface at high velocity, which makes me wonder, why did the Indian bother to try contacting the Vikram after the crash, do they really believe it can survive a 170-200 kmph impact, or do they really believe it did an autonomous soft landing?Amateurs used an old 25-meter radio telescope owned by the Netherlands Institute for Radio Astronomy to track Vikram’s descent. The frequency of the lander’s radio transmissions shifted based on its speed relative to Earth. That phenomenon, known as the Doppler effect, is similar to the changing pitch of train whistles and police sirens as they speed by.
Cees Bassa, an astronomer at the Dutch institute who participated in the effort, calculated the lander’s velocity, which matched predictions during the first phase of the firing of the engines.
But then the velocity of the spacecraft oscillated, which was not expected to occur.
“It confirms that something was wrong,” Dr. Bassa said.
He could not say what caused the oscillations, but he now believes that the end of the radio transmissions coincided with Vikram hitting the ground. It was supposed to touch down at less than five miles per hour.
The Doppler data indicate that Vikram was instead moving at more than 110 miles per hour.
Related link: NYT - Did India’s Chandrayaan-2 Moon Lander Survive? The Chances Are Slim
