Chandrayaan 2 Lander wreckage found

NASA’s Lunar Reconnaisance Orbiter (LRO) payload, Lunar Reconnaisance Orbiter Camera (LRO-C) released news early morning on December 3, 2019 that they had located wreckage of Vikram, the lander on India’s Chandrayaan 2 mission. The post credited the find to a Chennai based techie, Shanmuga Subramanian.

Vikram impact point and associated debris field. Green dots indicate spacecraft debris (confirmed or likely). Blue dots are locating disturbed soil, likely where small bits of the spacecraft churned up the regolith. “S” indicates debris identified by Shanmuga Subramanian. Portion of NAC mosaic made from images M1328074531L/R and M1328081572L/R acquired 11 November [NASA/GSFC/Arizona State University].

Shanmuga located the wreckage by comparing images released by LRO-C on September 26 (but taken on September 17) with the ones released earlier. He alerted NASA and ISRO about his find via Twitter. NASA’s LROC team then imaged the area again in October and November to confirm the debris. He got no response from ISRO as per news reports.

On the next day, ISRO’s Chairman in a statement to the press said that they had already located the lander on the day after the crash. ISRO’s statements from the period said that while the lander was located, efforts were on to establish communication with it. NASA’s Deep Space Network (DSN) continued efforts to hail Vikram after the crash.

As a scientific organisation, ISRO should know that until they publish, they cannot claim a discovery. The Chairman’s reference to the statement published on the ISRO website only says that they have located the lander. LROC’s success here is locating the debris and publishing the same with image data.

Media reports then claimed that the lander was intact. This was based on a statement received from someone within ISRO. I don’t think news organisations would publish something like this without an inside source. This points to the fact that ISRO did not know the condition in which the Lander was in.

The text released with the LROC image states that the lander wreckage is found 750 meters from the landing site. In Parliament, ISRO submitted a report stating that Vikram hard landed within 500 meters from the designated landing site. This is an aberration. Sankaranarayanan Viswanathan analysed NASA’s own orbital data and released it on Reddit that the site maybe 520 meters from the designated landing site. This seems closer to ISRO’s report than the LROC team’s finding.

This is a nice finish for the articles I write on the Chandrayaan 2 lander, the last of which you can find here. This allows scientists to study the debris to understand Vikram’s last few minutes on the Moon that could help scientists better design Chandrayaan 3’s lander.

I do hope ISRO proactively releases information like this and encourage citizen scientists like Shanmuga. We need more not less of this.

Search for Vikram

It has been about 5 days since my last post here. When we last left Vikram, we had left it incommunicado close to the surface of the Moon.

Since then, there has been a lot of speculation with little or no information. There is no information from ISRO including what it seems to be doing now. Information is coming in at a tangent, from astronomers studying Doppler readings of the Lander and the Orbiter.

ISRO’s last official update (at the time of writing) states that it had located the lander and that it was trying to establish communication with it. There was a lot of speculation initially about the status of the lander. Many foreign observers (like Jonathan McDowell, Cees Bassa, Chris B etc.)said that the lander had very little chance of survival knowing the speed at which it was travelling at the time ISRO received the last telemetry from the lander. ISRO released information to some sections of the media (PTI report ) that the lander was intact but toppled. This was not found as an update on the ISRO website.

Science reporters then began to question ISRO’s claim that the mission was 90-95% success. Vasudevan Mukunth for The Wire considered the method by which they arrived at the success rate. Jacob Koshy writes in The Hindu with much more depth and history for the reasons why this quote now looks like a way to airbrush the failure. There has been no official response yet. S M Ahmed who had an instrument on board the Moon Impact Probe of Chandrayaan 1 discusses possibilities as to the fate of the lander on his blog.

The lack of information now has people studying the few statements that ISRO has already made. A story in India Today seems to re-interpret ISRO’s message to say that they were in touch with Vikram till about 400 m above the surface of the Moon and not 2.1 km like many media reports have since claimed.

Meanwhile, Ryan Watkins, a planetary scientist tweeted that NASA’s Lunar Reconnaissance Orbiter (LRO) will look for Vikram on September 17. LRO’s camera has a resolution of 0.5 m at an orbit of 100 km. It is believed that at this altitude, the images would not discern enough detail to let us know whether the lander is intact. There were reports that ISRO will lower the orbit of the Chandrayaan 2 orbiter to take a closer look. The orbiter has a camera with a better resolution than LRO. We got word from Edgar Kaiser, an amateur radio astronomer today that Chandrayaan 2 orbiter has now lowered its orbit above the South Pole.

Chandrayaan 2 orbiter orbit change detected on Doppler. Image: Edgar Kaiser

This seems contrary to rumours that K Sivan, ISRO Chairman has asked scientists to move on and focus on future missions. There were also some fairly stupid remarks from DRDO Chairman saying that PM Modi’s hug enabled ISRO to find Vikram.

While I’ve mostly given up on chances of locating Vikram intact we can await efforts from Deep Space Network (DSN) to hail the lander in hopes that it will be able to contact it.

Doppler seems to be bursting various balloons of hope that ISRO has created. It seems to be breaking news about the orbiter and lander. In space, you can’t lie. Covering up mistakes makes the situation much worse than needs to be.

Vikram Landing

Vikram is what ISRO calls the landing module of the Chandrayaan 2 spacecraft. The last we checked in on Chandrayaan 2, we witnessed the separation of the two modules of Chandrayaan 2. The orbiter module was in the correct orbit at the time of the separation.

Vikram then performed a couple of orbit lowering manoeuvre to reduce its orbit around 100 km by 30 km. As it approached the landing site, the spacecraft followed the desired trajectory through the rough braking phase where the speed of the vehicle was reduced drastically. All seemed to be going well up to this phase. The telemetry data sent back to ISRO Tracking Centre (ISTRAC) followed the mission plan.

The spacecraft then seemed to be deviating a bit from its track but seemed to be making an effort to return to the original path. The animation on the screen showed the spacecraft toppling over. It seems that Vikram was trying to stay in the correct orientation. At this point, ISRO said that they lost communication with Vikram at about 2.1 km above the lunar surface.

Doppler data from Vikram. Image: Cees Bassa, Dwingeloo Radio Telescope, Tweet.

We don’t have data as to what happened after this point. Doppler data received from Amsterdam’s Dwingeloo Radio Telescope was tweeted by Cees Bassa, an astronomer who was following Vikram at the telescope. This seems to show a “zoom” at the end which seemed to indicate a crash, according to him.

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ISRO’s own telemetry screen at the last available data point seems to indicate speeds which were considered too high for a proper landing to take place at the end. The above tweet is from Jason Davis of The Planetary Society who also has a good summary of events with some international context on their blog.

I was initially unhappy that the Prime Minister Narendra Modi walked away from ISTRAC letting ISRO Chairman K Sivan do the announcement. But, today morning he came back and with data announced that communication was lost. The data is still being analysed.

There are currently two orbiters in orbit around the Moon, Chandrayaan-2’s orbiter module and NASA’s Lunar Reconnaisance Orbiter. Each should be having an orbit around 2 hours and so might come over the landing site within this month and we should be able to have a look. This would give final confirmation on what happened early today morning.

Is Chandrayaan 2 landing on the Moon’s South Pole?

No.

Rachana, over on Twitter, asked why the CNN covered Chandrayaan 2’s Moon landing on September 7 as that of the second landing on the far side of the Moon rather than as the first polar landing by any country. Rachana is a space professional and her tweets earlier on space have been worth following. She has also written useful FAQs for students and young professionals interested in space science. At the end, I felt Rachana may have shared the tweet only with the intention of sharing the discussion on the Reddit post.

Based on this tweet, I asked Ram Ramgopal of CNN the reason for this coverage. I immediately felt lazy for not following up the question myself before asking Ram and hence went looking on Wikipedia. I recognized the error and informed Ram apologising for the complaint. I still had a few queries regarding the lunar poles that @zingaroo kindly answered. Also, if you follow the link to her tweet it goes to Reddit where Ohsin also responds to the question. I learnt that we are landing neither on the Moon’s pole nor on its far side. I am saving as reference what I learnt here.

The tilts of Earth and the Moon. Image: Peter Sobchak, Wikimedia Commons

On Earth, the polar region is defined by Earth’s tilt at 23.4 degrees. Hence, areas above the latitudes of 66.6 degrees are considered the polar region. I mapped the same onto the Moon. Here, is where @zingaroo corrected me. Moon’s tilt is only 6.68 degrees. Hence, the Moon’s polar region is only that North or South of 83.32 degrees. The Chandrayaan landing site is well outside the Moon’s poles.

As for the Moon’s far side, ISRO’s search for a landing site required the site to be on the near side of the Moon.

Chandrayaan 2 Lander Module seperation

I was away for a few days from the blog as my parents were visiting. I got news about the separation of the orbiter and lander module as I was having lunch today.

Let’s backtrack a bit, to my last update on the mission. That update was provided when the spacecraft was placed in lunar orbit. At the time, the spacecraft was one integrated unit. It is made of two components – a lunar orbiter module and a lunar lander module.

Lander (Vikram) Module and Orbiter Module of Chandrayaan 2. Image: ISRO Launch Kit

Once it reached lunar orbit, the spacecraft performed the opposite of what did in Earth orbit. In Earth orbit, it used to fire its engines at the point closest to Earth to increase its speed. Now, in lunar orbit, the spacecraft turns around and does the same to reduce its speed. As it does so, the orbit lowers and the spacecraft gets closer to orbit around the Moon.

When we met the spacecraft last, it was in lunar orbit of 114 km x 18072 km. Since then, it did four engine firings on August 21, August 28, August 30 and September 1. Yesterday’s engine firing put the spacecraft in a 119 km x 127 km orbit around the Moon.

ISRO’s tweet visualises the lander module going closer to the Moon while the orbiter module staying in lunar orbit. Image: ISRO Twitter

Today, the lander module and the orbiter module separated. Currently, both are in the same orbit. While the orbiter will continue to be in its current orbit, the lander module will eventually achieve an orbit of 110 km x 36 km. The lander module will then perform a rocket powered descent to the surface of the Moon.

You can follow the latest updates from the mission on the ISRO website. News coverage from The Wire, The Times of India (which has a 51 second video from Times Now which has animated the picture above), ThePrint (which also gives you an idea on what comes next).

Chandrayaan 2 in lunar orbit

The Chandrayaan 2 spacecraft entered into an orbit around the Moon on August 20, 2019 at 09:02 AM (IST).

This was a result of a lunar orbit insertion (LOI) manoeuvre the spacecraft performed that lasted about 1738 seconds. The spacecraft was in Earth orbit and used it’s gravity to be propelled towards the Moon. As the spacecraft reached close to the Moon it used its on-board motor to perform a breaking to decrease its speed (this was demonstrated in Mission Mangal) and allowed itself to be captured by the Moon’s gravitational force.

The spacecraft entered into a 114 km x 18,072 km orbit around the Moon. This means that the spacecraft’s closest distance from the Moon (caller perilune) is 114 km and it’s farthest distance (called the apolune) is 18,072 km. The next day it performed another similar manoeuvre to reduce its speed and moved into an 118 km x 4,412 km orbit. This is the opposite of what it did in Earth orbit and will continue till it achieves a circular orbit of 100 km.

Image from the ISRO Launch Kit for Chandrayaan 2 which shows the mission sequence.
The Chandrayaan 2 spacecraft is now in its Lunar Bound Phase. Image: ISRO Launch Kit
Moon as viewed by Chandrayaan-2 LI4 Camera on 21 August 2019 19:03 UT
Moon as viewed by Chandrayaan-2 LI4 Camera on 21 August 2019 19:03 UT

Today, ISRO released pictures taken by the LI4 camera on board the Vikram lander of the Chandrayaan 2 spacecraft. LI4 probably stands for Landing Imager 4. It should be one of the cameras on the lander that would be used to guide the lander to the surface of the Moon.

The next manoeuvre is slated for August 28, early in the morning. You can follow the updates of Chandrayaan 2 directly from the ISRO website page.

Chandrayaan 2 on the way to the Moon

Chandrayaan 2, India’s second mission to the Moon lifted off from Sriharikota on July 22, 2019. The spacecraft was launched on board India’s GSLV Mk-3 rocket on it’s maiden non-development flight.

Photograph of the launch of the GSLV Mk-3 with the Chandrayaan 2 spacecraft by ISRO.
GSLV Mk 3 lifts-off with Chandrayaan 2. Image Courtesy: ISRO

It came after a launch scrub surrounding which there was lack of information and a lot of speculation. I watched the launch with my grandmother in Mumbai.

Since the launch, the spacecraft which currently has an orbiter and lander attached to each other performed 5 orbit raising manoeuvres on the way to the Moon.

India adopted this gradual orbit raising manoeuvre in order to balance the limitation of the spacecraft and the launch vehicle. A lower mass of the spacecraft would enable the launch vehicle to place the spacecraft into lunar orbiter but it would then not be able to carry any meaningful payload. The launch vehicle had only enough power to place Chandrayaan 2 in a geosynchronous transfer orbit.

Image of the Earth taken by LI4 camera on board the lander on Chandrayaan 2.
Image of Earth taken by the LI 4 camera on board Chandrayaan 2. Image Courtesy: ISRO

After the 5th orbit raising manoeuvre, the spacecraft will push off towards the Moon called Trans Lunar Insertion on August 14. Afterwards, the spacecraft will perform one more burn called the Lunar Orbit Insertion on August 20 that will let the spacecraft be captured by Moon’s gravity.