Why NASA’s Lunar Orbiter Failed To Take A Clear Picture Of Chandrayaan-2’s Vikram Lander 

by Prakhar Gupta - Sep 25, 2019 01:07 PM +05:30 IST
Why NASA’s Lunar Orbiter Failed To Take A Clear Picture Of Chandrayaan-2’s Vikram Lander Illustration of the Lunar Reconnaissance Orbiter.(NASA’s Goddard Space Flight Center)
  • NASA’s lunar orbiter couldn’t take a clear picture of the Vikram-Lander during its flyby over the Chandrayaan-2 landing site on Monday.

    Here’s why it failed.

On Monday, NASA’s Lunar Reconnaissance Orbiter (LRO) photographed during its flyby over the Moon’s south pole the site where Chandrayaan-2’s Vikram-Lander had hard-landed in the early hours of 7 September.

However, it appears that the pictures of the landing site taken by LRO are not clear enough.

LRO’s flyover came just days after Chandrayaan-2’s Orbiter had spotted the Lander 500 meters away from its designated landing site. The Lander had hit the lunar surface at a much higher velocity than it should have and is not in the orientation that it was supposed to be, making communication difficult.

But ISRO has not released any images of the landing site taken by the Orbiter. There is no clarity on the state in which the Lander is — whether it has disintegrated due to the high-velocity impact with the lunar surface or not. There are many more questions, like those regarding its orientation on the lunar surface, that continue to remain unanswered.

This is what makes LRO’s flyby important.

“Per NASA policy, all LRO data are publicly available,” Noah Petro, LRO’s project scientist at NASA’s Goddard Space Flight Center, had said last week, adding, “NASA will share any before and after flyover imagery of the area around the targeted Chandrayaan 2 Vikram lander landing site.”

But, adding to the disappointment over the loss of communication, NASA’s LRO was unable to spot the Vikram-Lander at the landing site.

LRO’s job was tough. At Vikram’s landing site, the end of the lunar day, which is equivalent to 14 earth-days, is just three days away. This means that, at the landing site, the Sun is low on the horizon and it is near dusk in the region.

Moreover, near the lunar south pole, where Vikram has landed (around ~71° south of the lunar equator), the Sun does not rise higher than ~19° in the sky.

These conditions must have created long shadows on the surface, covering the Lander. As a result, LRO failed to capture the details it could have otherwise.

In a report late on Monday (17 September), New-York based Aviation Week Network confirmed that the “long shadows in the area may be obscuring the silent lunar explorer,” adding, “ Vikram may not be in the LRO’s field of view.”

On 24 September, NASA also confirmed that LRO flew over the site “when the local lunar time was near dusk; large shadows covered much of the area”.

LRO will have more opportunities to photograph the Vikram-Lander, but only after the end of the lunar night. The lunar night, equivalent to 14 earth days, will kick-in when the lunar day ends in the next 72 to 96 hours.

The Lander is unlikely to survive the lunar night as the temperature may drop up to -180º Celsius.

Since the Israeli Beresheet Lander crashed earlier this year, LRO has been trying to search for NASA’s Retroreflector that it was carrying. The Vikram-Lander also carried NASA’s Laser Retroreflector Array, a passive instrument for the precise measurement of the distance between the Earth and the Moon.

The Laser Retroreflector is expected to have survived the hard landing and NASA will continue to search for it after the end of the lunar night.

NASA has said that LRO is scheduled to fly over the Chandrayaan-2 landing site on 14 October. Lighting conditions will be more favorable around that time. The agency has also said that it will release the results of its flyover “as soon as possible after a necessary period of validation, analysis, and review.”

The LRO, launched by NASA in 2009, has been orbiting the Moon for a decade now. It carries a system of three high-resolution cameras, two of which are narrow-angle cameras providing images with 50 cm (19.7 inch) resolution.

For the record, Chandrayaan-2 carries a camera with a resolution of 32 cm (12.6 inches) — better than LRO and other lunar orbiter missions to date. It can, therefore, capture much more details of the landing site than LRO.

But again, ISRO has not released the images that the Orbiter has captured, nor have they described what those images show.

Over the years, LRO has captured high-resolution images of the Moon for various applications, including those of the Apollo landing sites. Most recently, it had captured images of China’s Chang’e 3 and Chang’e 4 Landers on the Moon’s surface, and located the Beresheet Lander earlier this year.

Prakhar Gupta is a senior editor at Swarajya. He tweets @prakharkgupta.

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