Contact with the Chandrayaan-2 lander Vikram was likely lost when it was far closer to the lunar surface than what has been assumed. Ever since the Indian Space Research Organisation (ISRO) lost contact with the Vikram lander, the popular perception has been that the probe was 2.1 km above the lunar surface when it lost contact.
However, in reality, Vikram was likely as close as 400 m to the Moon surface.
The reason for the confusion could be put down to a possible misinterpretation of the statement released by the Indian Space Research Organisation on it losing contact with the Vikram lander. And, the clarity comes from an image of a graph that was following Vikram’s decent on to the Moon.
Of the three elliptic lines seen in the image, the centre line corresponds to Vikram’s descent. The red line shows the planned path that Vikram was to take to land on the Moon. The green line is Vikram’s actual path.
Now, for the most part of the landing, the green line perfectly coincides with the red line, indicating that Vikram’s descent was going exactly according to plan.
Between the altitudes of 5 and 3 km, there are variations in Vikram’s actual descent trajectory and the one that was planned. But these seem minor.
Now, at an altitude of 2.1 km, the green line deviates sharply from the red line, suggesting that Vikram had gone off course.
The green line ends in a blip at an altitude of around 400 m.
This suggests that Vikram was in touch with the Isro command centre in Bengaluru till it was 400 m above the lunar surface. That is when the Chandrayaan-2 lander seems to have stopped communicating with Isro.