Explained: How Chandrayaan-2’s Vikram lander was lost, and found

Vikram Lander impact point and associated debris field. Green dots indicate spacecraft debris; blue dots locate disturbed soil; S indicates debris identified by Shanmuga Subramanian. (Source: NASA/Goddard/Arizona State University)

On Monday, NASA announced that India’s Vikram lunar lander, which crashed on the Moon’s surface in September, has been found. This has been partly due to the efforts of an amateur space enthusiast.

How it was the Vikram lander lost

The Vikram lander is part of the Indian Space Research Organisation’s Chandrayaan-2 Moon mission, all other parts of which are going on as planned. The landing of Vikram was targeted for a plain about 600 km from the south pole of the Moon. However, ISRO lost contact with their lander shortly before the scheduled touchdown on September 7.

On September 26, NASA released a mosaic image of the site (taken by its Lunar Reconnaissance Orbiter, or LRO, on September 17). NASA invited the public to compare the released image with previous images of the same area so that they could find signs of the lander. Many people downloaded the mosaic to search for signs of Vikram.

How was the Vikram lander found

Shanmuga Subramanian, 33, an IT professional from Chennai, contacted the LRO project. “I had a side-by-side comparison of those two images on two of my laptops… on one side there was the old image, and another side there was the new image released by NASA,” the news agency AFP quoted him as saying.

@NASA has credited me for finding Vikram Lander on Moon’s surface#VikramLander #Chandrayaan2@timesofindia @TimesNow @NDTV pic.twitter.com/2LLWq5UFq9

— Shan (@Ramanean) December 2, 2019

After receiving Subramanian’s tip, the LROC team confirmed the identification by comparing before and after images. When the images for the first mosaic were acquired, the impact point was poorly illuminated and thus not easily identifiable.

Two subsequent image sequences were acquired on October 14 and 15, and November 11. The LROC team scoured the surrounding area in these new mosaics and found the impact site (70.8810°S, 22.7840°E, 834 m elevation) and associated debris field, NASA said.

The #Chandrayaan2 Vikram lander has been found by our @NASAMoon mission, the Lunar Reconnaissance Orbiter. See the first mosaic of the impact site https://t.co/GA3JspCNuh pic.twitter.com/jaW5a63sAf

— NASA (@NASA) December 2, 2019

The debris first located by Subramanian is about 750 metres northwest of the main crash site. The November mosaic shows best the impact crater, ray and extensive debris field. The three largest pieces of debris are each about 2×2 pixels and cast a one-pixel shadow.

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