Category: Space

  • 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.

  • Remote sensing in India

    I wrote an article for The Wire on India’s remote sensing programme, that got published today.

    While writing the article I discovered the orphaned Wikipedia page that was once updated with launches of Indian remote sensing satellites. The article had not been updated for a very long time. The focus now seems to be on the List of Indian satellites launched by the decade. Working on the article helped me get back into Wikipedia editing and helped me discover one of the points that I raised in the article.

  • Cansats

    Today, we see many engineering colleges that are keen to work on a cubesat or a micro satellite project. However, what happens practically is that components are obtained Commercial off the shelf (COTS). This means that when working on the project, you get exposure to the project at a systems level and understanding how things work with each other but not really working too much on testing the limits of the payload.

    Image: Internal mechanism of a cansat

    The payload is the heart of any project. Everything else is just effort taken to take the payload to a destination. If you want to develop your skills regarding developing payloads in very cramped environments, cansats may give you much more challenging problems. In this post, I am exploring the world of cansats.

    Cansats carry payloads inside a Coca-Cola can. It can be a can of any other soft drink too. Today, we get cans of varying types and I think it would be more interesting to test these before or while working on your project. A cansat lets you think outside the box, no can. It also lets you work within restrictions.

    Most of the payloads for cansats look at measuring temperature, altitude, attitude, pressure or a combination of these. You could also check for more complex things like chemical composition as well but the complexity of the payload goes up. These deliver scientific data from your payload. These payloads make sense if you belong to a science department.

    There are engineering experiments you can do with cansats as well. You could carry payloads that work on attitude control as well. These try to keep the can pointed straight up as they descend. You could design ways to store and deploy parachutes to slow down the cansat as it comes down. This increases the time for which the payload remains active and collects data. At the end, you could devise ways on how to find the cansat on the ground using things like light or radio beacons. These make sense if you belong to an engineering college or department.

    The question is – how do you launch cansats? It could be using a model rocket, trace a parabolic path and land somewhere. There could be other innovative launching methods as well, within the boundaries of safety. You could drop them from the top of a skyscraper or just a building. If you can get your hands on a drone, maybe launch it from the top of a drone. If you have access to a small airplane, maybe drop them from the window of a small airplane. You could drop one down from the top of a telephone tower. TIFR in Hyderabad has a balloon facility that you could use or piggyback on. In launches safety is an important consideration. Alert people about what you are going to do. Better safe than sorry.

  • 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.

    https://platform.twitter.com/widgets.js

    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.

  • Helium

    Wikipedia’s entry for Helium has these lines:

    The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a wavelength of 587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Jules Janssen during a total solar eclipse in Guntur, India.

    Wikipedia entry for Helium

    The source of the information is an article in the Journal of the British Astronomical Association by R K Kochhar in 1991 ( Kochhar, R. K. (1991). “French astronomers in India during the 17th – 19th centuries“. Journal of the British Astronomical Association. 101 (2): 95–100)

    Portrait of Pierre Jules Cesar Janssen circa 1895
    Pierre Jules Cesar Janssen, c. 1895, Wikipedia

    The article is also a study of the work done in India by the French at the dawn of the field of astrophysics in the middle of the 19th century. Pierre Jules Cesar Janssen (1824 – 1907) had come to India to observe the total solar eclipse on August 18, 1868. Gustav Kirchoff’s work on using the solar spectrum to understand the chemical composition of the Sun was applied using a spectroscope.

    The spectrometer separates elements of the electromagnetic spectrum and identifies elements by matching the spectrum to the wavelength of each element.

    During the eclipse, Janssen was observing the solar prominence. These are gases that are blown off the Sun but still connected to the Sun’s surface. While studying these gases with a spectroscope, Janssen observed hydrogen gas but also observed light in another spectrum which did not correspond to any known element at the time. The observed spectrum was so bright, in fact, that Janssen thought that he did not have to wait for an eclipse to observe them again.

    He was stationed at Guntoor from August 18 to September 4 when he observed the same spectral line each day. To continue studying the Sun on a daily basis, he built an instrument called a spectrohelioscope that he used to observe the Sun from Shimla.

    His spectrohelioscope was used by other observers till 1891 when it was superseded by a spectroheliograph. Edward Frankland named this new element Helium after Helios, the Greek word for the Sun. When Janssen returned to France, he became Director of a new astrophysical observatory that the French government had built in Meudon, on the outskirts of Paris. He was President of the French Astronomical Society from 1895 to 1897.

  • Review: Mission Mangal (2019)

    I went to PVR Cinemas at Pune’s Phoenix Marketcity Mall to watch Mission Mangal on Friday, August 15, 2019. Being a self-professed space geek, I expected the movie to be a cringe-show. It was.

    Poster of Mission Mangal
    Poster of Mission Mangal

    Mission Mangal (2019) is a Bollywood movie inspired by the Mars Orbiter Mission (MOM). The mission involved the Indian Space Research Organisation (ISRO) flying a mission to Mars. The mission, a technology demonstrator, succeeded on it’s first attempt. The movie carries a disclaimer at the start of the movie which says that it is a fictionalised account.

    The on-film depiction of ISRO is no where near it’s original. I don’t think a scientist in ISRO are insecure in their knowledge that they would feel threatened by a person who got his experience working in NASA and who returns to serve his country. This is the description of the villain of the movie. I think MOM borrowed and learnt a lot from NASA for the actual mission. MOM’s first signal acquisition was in fact from NASA’s Deep Space Network in Australia. I don’t think the movie really needed a villain.

    The other issue that bothered me a lot is the need for a hero. Akshay Kumar is no where near the scientist that ISRO has. His imitation of talking to former President Abdul Kalam in Tamil was the lowest point of the film, in my opinion.

    The Polar Satellite Launch Vehicle (PSLV) was made much more muscular and eye-candy than it actually is. There were a lot of holds on that American launch pad. Bollywood also made it into a two stage launch vehicle rather than the four stage rocket it is. I loved the sound and capture of the lift-off which reminded me so much of the Shuttle launches. India countsdown in minutes and seconds and not from 100 seconds.

    There are struggles of the women scientist in ISRO. Tackling pressure at home, managing family, managing expectations of mother-in-laws, difficulty in getting a flat because of belonging to a certain religion and live-in-relationships. I would have been happier if these stereotypes would not all be pushed throughout the film. Also, I didn’t miss the stereotype of a woman who could not drive on road handling navigation for an interplanetary mission.

    So, with all those things that I didn’t like in the movie, it still pulled through because it manages something that I think ISRO fails at communicating. How difficult it is to get funding for a mission. What parameters are considered and how difficult it is to plan a mission. It also attempted to explain orbital mechanics. The movie takes a dig at superstitious practices that ISRO itself follows. Akshay Kumar’s only positive show in the movie seems to be standing up as a rational person to some superstitious practices in the Mission Control Room.

    I still think that the movie is a good starting point for a movie based on a scientific mission. For that, it is worth seeing. As I said at the beginning, I cringed a lot while watching the movie.

    It took me a long time to write this review. Two other reviews are worth your time – Vasudevan Mukunth’s and Raja Sen for the Hindustan Times.

    The movie ends crediting ISRO on it’s 50th anniversary and the women on whom the film is loosely based.

  • 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.