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Chandrayaan-2 India's Daring Moon Mission

Chandrayaan-2 India's Daring Moon Mission

COVER STORY Chandrayaan-2 ’s Daring Mission Biman Basu

14 | Science Reporter | November 2019 Fifteen Minutes of Terror This was, however, not entirely unexpected. Chandrayaan-2 was an extremely complex mission the like of which ISRO had never tried before. The critical manoeuvre of soft landing lasting 15 minutes was what the ISRO Chairman K. Sivan had described as “Fifteen minutes of terror”. It was to be an ‘autonomous powered descent’ to the lunar surface and was the most difficult part of the whole mission. Since it involved intricate and rapid changes in the velocity and flight path of the , the entire manoeuvre was controlled by the ’s onboard computer, without any guidance from the ground. The time-lag to execute Artist’s impression of Chandrayaan-2 in commands from the to the Moon Moon ruled out ISRO’s mission control centre in Bengaluru controlling the lander’s descent. AST 1:00 a.m. on 7 September As minutes ticked by and powered 2019, millions in India and across descent of the lander was initiated, Before the descent began, Vikram P the world had their eyes glued everything seemed all right. The lander was travelling at a speed of about to their TV screens in expectation of followed the assigned path. But in 6,000 km per hour at a height of 35 a grand finale to India’s 48-day-old the end, the expected did not happen. km. But within minutes, not only was Chandrayaan-2 mission – a soft landing Seconds before the landing, contact was the spacecraft’s velocity to be brought by the lander Vikram that would set a lost with the lander without any clue as down, but also the direction of its motion new landmark in India’s 56-year-old to what happened to it. gradually changed from horizontal to space programme. vertical in a controlled manner to enable

VIKRAM DESCENT TRAJECTORY

Deviation

Altitude (km) Fine Braking Phase

Down Range (km)

The descent trajectory of Vikram lander showing the deviation (arrow) where contact with the lander was lost

November 2019 | Science Reporter | 15 Chandrayaan-2 lunar soft landing sequence After Chandrayaan-2 achieved a final orbit of about 100 km from the surface of the moon, the Vikram lander separated from the composite module on September 2 to begin its descent onto the moon. The orbiter will continue to revolve around the moon and conduct missions for about a year.

Separation 100 km above lunar surface Vikram lander separates from the orbiter near the North Pole

Deboost phase The lander travelling at about 1.6 km/s undergoes de-orbiting maneuvers using thruster burns Powered descent Rough braking phase Once the lander is hovering above the As the lander reaches a landing site, the four point closest to the Moon engines are shut off. A near the South Pole, further central thruster is used to de-boost burns are used for slowly reduce the vertical horizontal braking of the velocity for a soft landing. 6 km above lander using four thrusters engines. The central thruster lunar surface ensures that the lunar dust is blown away from the site without letting it cloud the lander after the touchdown. A few hours after landing and scanning the surrounding area, the Vikram lander’s ramp will open to deploy the Precision braking phase rover. Using the throttle control in the thruster engines, the lander is slowly prepared for vertical descent.

13 m above The lander scans the lunar lunar surface surface and compares the topography with onboard imagery. It then makes the required calibrations and decides the final safe site for soft landing. Lunar dust

Source: Indian Space Research Organization

Diagrammatic representation of the lunar soft-landing sequence

16 | Science Reporter | November 2019 landing at a pre-determined between three-dimensional map of the Moon hours after landing. It was designed two craters dubbed Manzinus C and and analysing its mineral composition. to study the lunar surface from close Simpelius N, about 600 km from the quarters after rolling out and had a While it did not complete its mission lunar south pole. total range of 500 metres. Both Vikram life of two years, the Chandrayaan-1 and Pragyan are solar-powered and The soft-landing sequence was mission had several achievements. It were designed to work for 14 days, divided into three distinct phases that was the first interplanetary mission for equivalent to one lunar day. were meant to steadily decelerate the ISRO and heralded the way for other lander and reduce its altitude till it missions to follow, including one to Chandrayaan-2 was ISRO’s first reached near-zero at touchdown. To , and the present Chandrayaan-2 inter-planetary mission designed to carry out the entire manoeuvre, Vikram mission. Its most significant scientific land a rover on any celestial body. was equipped with a cluster of five achievement was the discovery of water ISRO had planned to land the rover engines that were supposed to perform on the Moon. near the Moon’s south pole because specific pre-programmed functions. it is a “very tricky area” with rocks formed a million years ago. It has very Everything seemed to go well as the Chandrayaan-2 old rocks the study of which could first phase called the ‘Rough Braking Chandrayaan-2 consisted of three possibly help us understand the origin Phase’ got underway when four of the components: the orbiter, the lander and of the universe. Another reason behind five rockets employed for decelerating the rover. The lander was named Vikram landing the rover near the lunar south the spacecraft performed perfectly in honour of Dr , who pole was that the area has not been as planned, ensuring a steady loss of is considered the Father of India’s space explored by other missions. Most of altitude. At the end of 10 minutes and 20 programme. The six-wheeled rover was the lunar missions in the past have seconds, the large consoles at the ISRO named Pragyan, meaning ‘wisdom’ and explored the area around the equator control room indicated that all was going was designed to roll out of Vikram a few of the Moon. smoothly. The speed of Vikram was down to 22 km per hour and its altitude was 7 km. The descent trajectory of the lander, Why was Chandrayaan-2 Delayed? as displayed on the large screen at the Chandrayaan-2 was conceived in 2007, well before the ISRO control centre in Bengaluru and launch of Chandrayaan-1 in 2008 and was originally watched by TV viewers around the scheduled to be launched in 2011. Originally, Chandrayaan-2 world, perfectly matched the planned was supposed to be a joint collaborative mission between trajectory till the lander was about 2 India and Russia. ISRO was to provide the rocket, the orbiter kilometres above the lunar surface when and the lander and the rover were to come from Russia’s suddenly, deviating from the planned space agency. ISRO did not have the capability trajectory, the graph showed a deviation to build its own lander and rover at that time. and a steep drop when contact with the However, Russia had to eventually pull itself out in 2012 lander was lost. From the graph, it from the collaboration because the kind of lander that it appeared that Vikram had landed, but was preparing to send on Chandrayaan-2 developed a probably it didn’t make a soft landing. problem on its -Grunt mission to the Martian moon The unexpected end was a big Phobos. Although Roscosmos did make design corrections, disappointment for ISRO scientists the new proposed design was found to be incompatible and millions others who were eagerly with Chandrayaan-2. awaiting a perfect landing after a ISRO was left with no option but to develop its own flawless flight from Earth. lander and rover through R&D. This set the mission back by several years, although it allowed the Chandrayaan-2 that Chandrayaan-1 took off in July 2019 to be a totally home-grown product. The first Indian Moon mission The delay also provided ISRO additional time to improve Chandrayaan-1 was launched on 22 on the design of the main spacecraft. October 2008 and included an orbiter and The current Chandrayaan-2 composite module is a far a – a small module superior design and incorporates several additional safety that separated from the orbiter and features that would have not been possible in the original crashed on the Moon near design that was scheduled to be launched in 2011. crater. The orbiter included several scientific instruments for creating a

November 2019 | Science Reporter | 17 To prepare for Chandrayaan-2 Women to the Fore landing, ISRO had created artificial A unique feature of the Chandrayaan-2 mission is that it as part of hazard avoidance and landing tests. The simulation tests was led by two women. on Chandrayaan-2 components were , carried out at centres in Bengaluru, Project Director of Mahendragiri and Chitradurga in Chandrayaan-2, is Karnataka. an electronics system Chandrayaan-2 was ISRO’s first engineer who, apart attempt to soft-land a craft on lunar from being the first-ever soil and involved a very complex set female project director of manoeuvres, including separation of of ISRO, has worked as the lander Vikram carrying the rover deputy project director Pragyan on-board from the orbiter and for -1 and guiding it down to the lunar surface. It Oceansat-2 and Megha- was a lunar mission that was designed to go where no country had ever gone Tropiques satellites. Apart before – the Moon’s south polar region. from being the first Moreover, this was a unique mission female project director of that aimed at studying not just one area Muthayya Vanitha, Project Director, ISRO, Vanitha was earlier Chandrayaan-2 of the Moon but all the areas combining heading the telecom and the exosphere, the surface as well as digital systems group division in ISRO’s U.R. Rao Satellite the sub-surface of the Moon in a single Centre. She has been responsible for the Chandrayaan-2 mission. project from the very beginning, which involved getting Despite a failed landing, however, the entire system configured, reviewed, assembled and not all is lost. The Chandrayaan-2 implemented. In 2006 she received the best female orbiter, which continues to orbit the scientist award. Chandrayaan-2 is the first space mission Moon at a height of 100 kilometres, in the world to be headed by a woman. is in perfect health and ISRO says the precise launch and mission management Ritu Karidhal, Mission Director, Chandrayaan-2, has has ensured a long life of almost seven handled the Chandrayaan-2 mission over the last few years instead of the planned one year. months as it navigated through space and found a way to the difficult, uncharted terrains of the south polar region With eight payloads onboard, of the Moon. Known as one of the “rocket women” of India, including the Optical High-Resolution Camera (OHRC), the orbiter is expected she was also involved with ISRO’s , to provide high-resolution images of the popularly known as the lunar surface for many years to come. Mangalyaan, in 2013. She According to ISRO, the OHRC is the is an aerospace engineer highest resolution camera (resolution 30 who completed her cm) in any lunar mission so far and shall graduation and post- provide high-resolution images “which graduation in physics will be immensely useful to the global from Lucknow and later scientific community”. completed master’s in The data collected by the orbiter aerospace engineering will enrich our understanding of the from IISc, Bengaluru. Moon’s evolution and help mapping of She had received the the minerals and water molecules in the ISRO Team Award for polar regions. They will also help us Mangalyaan and also prepare 3D maps of the lunar surface. received the ISRO Young Scientist Award from A Deferred Launch former president APJ The launch of Chandrayaan-2 was Abdul Kalam in 2007. Ritu Karidhal, Mission Director, Chandrayaan-2 originally scheduled for 15 July 2019

18 | Science Reporter | November 2019 but had to be scrapped following Vikram lander followed the detection of a minor leak in the the planned descent cryogenic filling system of the rocket. trajectory from its orbit The launch was rescheduled after of 35 km to just about 2 rectification of the fault and the launch km above the surface and finally took place on 22 July 2019 with then suddenly contact ISRO’s most powerful rocket GSLV was lost. Mk-III from Space According to ISRO, Centre. all the systems and The launch was perfect. In fact, the sensors of the lander performance of the GSLV Mk-III was functioned excellently much better than expected, as it carried until this point and proved the spacecraft to an altitude 6,000 km many new technologies higher than planned, thus obviating one such as variable thrust orbit-raising manoeuvre. propulsion technology Despite the delayed launch, it was used in the lander. essential that the landing took place on “The success criteria 6-7 September as originally scheduled. were defined for each This was necessary to avail of the and every phase of the Thermal image of lander Vikram sent back by Chandrayaan-2 sunlight during one full lunar day, mission and till date, orbiter (circled) which is equivalent to 14 Earth days, 90 to 95% of the mission objectives other cause could be a catastrophic as both the lander and rover were solar- have been accomplished and will failure of communication either due to powered. ISRO was able to achieve it continue to contribute to lunar overheating or a system malfunction that by adjusting the number of orbit-raising science, notwithstanding the loss of then resulted in the loss of control of the manoeuvres in Earth orbit and was able communication with the lander”. So, spacecraft. ISRO would be examining to insert the lander into the lunar orbit it would be unfair to term the mission all these possibilities to find out what on 20 August for it to be able to meet as a failure. went wrong. the original landing date. It may be mentioned here that out ISRO Chief K. Sivan announced After launch, Chandrayaan-2 was of a total number of 38 soft landing on 9 September that the Chandrayaan-2 attempts made by the space agencies of placed in a highly elongated parking lander had been found on the surface the world to soft-land on the Moon so orbit around Earth that varied in of the Moon by the spacecraft’s orbiter far, only 20 have succeeded, making a altitude from 169.7 km to 45,475 km. from which a thermal image has been success rate of 52 per cent. Thereafter, it was all smooth sailing, received. He said, from the thermal including five orbit-raising manoeuvres image taken by the orbiter, it seems between 23 July and 6 August 2019 What Went Wrong? that the lander is still intact as a single during which the spacecraft was raised piece, but it is in a tilted position. He to a 276 km x 1,42,975 km orbit in Although ISRO scientists are still not said it may have been a ‘hard landing’ steps. The final orbit-raising manoeuvre sure about what caused the lander rather than a soft landing. ISRO sources of the spacecraft was successfully to fail, it could have been caused by carried out on 14 August 2019, placing the malfunctioning of any of the five confirmed that the lander was found 500 it in the Lunar Transfer Trajectory from engines on the lander. These engines m away from the scheduled landing spot. where it was inserted into a 114 km x needed to be operated with perfect It is not known if ISRO will ever 18,072 km lunar orbit on 20 August synchronicity to achieve not only the be able to re-establish contact with the 2019. The orbit was subsequently required rate of descent but also the Vikram lander, but even without the soft reduced to 127 km x 119 km after five perfect inclination. The engines could landing, the Chandrayaan-2 mission can lunar-bound orbital manoeuvres after be throttled to vary the thrust given to be considered a big success. which the Vikram lander carrying the the spacecraft to facilitate the critical Pragyan rover inside was detached from manoeuvres. This was the first time that the orbiter on 1 September 2019. ISRO was using such engines. Mr Biman Basu, Author, Science On 3 September 2019, the orbit Probably an anomaly developed Communicator and Consultant and former of Vikram was further modified to 101 in one of the engines beyond the error Editor of Science Reporter. Address: C-203, km x 35 km and in the early hours on margin the on-board computer could Hindon Apartments, 25 Vasundhara Enclave, 7 September the powered descent to handle, leading to the lander deviating Delhi-110096. the lunar surface was initiated. The from the assigned trajectory. The Email: [email protected]

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