Chandrayaan-2


Chandrayaan-2 is the second lunar exploration mission developed by the Indian Space Research Organisation, after Chandrayaan-1. As of September 2019, it consists of a lunar orbiter, and also included the Vikram lander, and the Pragyan lunar rover, all of which were developed in India. The main scientific objective is to map and study the variations in lunar surface composition, as well as the location and abundance of lunar water.
The spacecraft was launched on its mission to the Moon from the second launch pad at the Satish Dhawan Space Centre in Andhra Pradesh on 22 July 2019 at 2.43p.m. IST by a GSLV Mark III M1. The craft reached the Moon's orbit on 20 August 2019 and began orbital positioning manoeuvres for the landing of the Vikram lander. The lander and the rover were scheduled to land on the near side of the Moon, in the south polar region at a latitude of about 70° south on 6 September 2019 and conduct scientific experiments for one lunar day, which approximates to two Earth weeks. A successful soft landing would have made India the fourth country after the Soviet Union, United States and China to do so.
However, the lander deviated from its intended trajectory while attempting to land on 6 September 2019 which caused a 'hard landing'. According to a failure analysis report submitted to ISRO, the crash was caused by a software glitch. ISRO may re-attempt a landing by the second quarter of 2021 with Chandrayaan-3.

History

On 12 November 2007, representatives of the Roscosmos and ISRO signed an agreement for the two agencies to work together on the Chandrayaan-1's follow-up project, Chandrayaan-2. ISRO would have the prime responsibility for the orbiter and rover, while Roscosmos was to provide the lander. The Indian government approved the mission in a meeting of the Union Cabinet, held on 18 September 2008 and chaired by Prime Minister Manmohan Singh. The design of the spacecraft was completed in August 2009, with scientists of both countries conducting a joint review.
Although ISRO finalised the payload for Chandrayaan-2 on schedule, the mission was postponed in January 2013 and rescheduled to 2016 because Russia was unable to develop the lander on time. In 2012, there was a delay in the construction of the Russian lander for Chandrayaan-2 due of the failure of the Fobos-Grunt mission to Mars, since the technical issues connected with the Fobos-Grunt mission which were also used in the lunar projects including the lander for Chandrayaan-2 needed to be reviewed. When Russia cited its inability to provide the lander even by 2015, India decided to develop the lunar mission independently.
The spacecraft's launch had been scheduled for March 2018 initially after the India's decision, but was first delayed to April and then to October to conduct further tests on the vehicle. On 19 June 2018, after the program's fourth Comprehensive Technical Review meeting, a number of changes in configuration and landing sequence were planned for implementation, pushing the launch to the first half of 2019. Two of the lander's legs received minor damage during one of the tests in February 2019.
Chandrayaan-2 launch was scheduled for 14 July 2019, 21:21 UTC, with the landing expected on 6 September 2019. However, the launch was aborted due to a technical glitch and was rescheduled. The launch occurred on 22 July 2019 at 09:13 UTC on the first operational flight of a GSLV MK III M1.
On 6 September 2019, the lander during its landing phase, deviated from its intended trajectory starting at altitude, and had lost communication when touchdown confirmation was expected. Initial reports suggesting a crash were confirmed by ISRO chairman K. Sivan, stating that "it must have been a hard landing". The Failure Analysis Committee concluded that the crash was caused by a software glitch. Unlike ISRO's previous record, the report of the Failure Analysis Committee has not been made public.

Objectives

The primary objectives of the Chandrayaan-2 lander were to demonstrate the ability to soft-land and operate a robotic rover on the lunar surface.
The scientific goals of the orbiter are:
The name Chandrayaan means "mooncraft" in Sanskrit and Hindi. The mission was launched on a Geosynchronous Satellite Launch Vehicle Mark III M1 with an approximate lift-off mass of from Satish Dhawan Space Centre on Sriharikota Island of Andhra Pradesh., the mission has an allocated cost of 9.78 billion which includes 6 billion for the space segment and 3.75 billion as launch costs on GSLV Mk III M1. Chandrayaan-2 stack was initially put in an Earth parking orbit of perigee and apogee by the launch vehicle.

Orbiter

The Chandrayaan-2 orbiter is orbiting the Moon on a polar orbit at an altitude of. It carries eight scientific instruments; two of which are improved versions of those flown on Chandrayaan-1. The approximate launch mass was. The Orbiter High Resolution Camera conducted high-resolution observations of the landing site prior to separation of the lander from the orbiter. The orbiter's structure was manufactured by Hindustan Aeronautics Limited and delivered to the ISRO Satellite Centre on 22 June 2015.
The mission's lander is called Vikram named after Vikram Sarabhai, who is widely regarded as the founder of the Indian space programme. The Vikram lander detached from the orbiter and descended to a low lunar orbit of using its liquid main engines. After checking all of its on-board systems it attempted a soft landing that would have deployed the rover, and performed scientific activities for approximately 14 Earth days. Vikram crash-landed during this attempt. The combined mass of the lander and rover was approximately.
The preliminary configuration study of the lander was completed in 2013 by the Space Applications Centre in Ahmedabad. The lander's propulsion system consisted of eight thrusters for attitude control and five liquid main engines derived from ISRO's liquid apogee motor. Initially, the lander design employed four main throttle-able liquid engines, but a centrally mounted fixed-thrust engine was added to handle new requirements of having to orbit the Moon before landing. The additional engine was expected to mitigate upward draft of lunar dust during the soft landing. Vikram was designed to safely land on slopes up to 12°.
Some associated technologies include a high resolution camera, Laser Altimeter, Lander Hazard Detection Avoidance Camera, Lander Position Detection Camera, Lander Horizontal Velocity Camera, an 800 N throttleable liquid main engine, attitude thrusters, Ka band radio altimeters, Laser Inertial Reference & Accelerometer Package, and the software needed to run these components. Engineering models of the lander began undergoing ground and aerial tests in late October 2016, in Challakere in the Chitradurga district of Karnataka. ISRO created roughly 10 craters on the surface to help assess the ability of the lander's sensors to select a landing site.
The mission's rover was called Pragyan with a mass of, and would have operated on solar power. The rover was to move on six wheels, traversing on the lunar surface at the rate of per second, perform on-site analyses and send the data to the lander, which would have relayed it to the Mission Control on the Earth. For navigation, the rover would have used:
The expected operating time of Pragyan rover was one lunar day, or around 14 Earth days, as its electronics were not designed to endure the frigid lunar night. However, its power system has a solar-powered sleep/wake-up cycle implemented, which could have resulted in longer service time than planned. Two aft wheels of the rover had the ISRO logo and the State Emblem of India embossed on them to leave behind patterned tracks on the lunar surface.
ISRO selected eight scientific instruments for the orbiter, four for the lander, and two for the rover. While it was initially reported that NASA and ESA would participate in the mission by providing some scientific instruments for the orbiter, ISRO in 2010 had clarified that due to weight restrictions it will not be carrying foreign payloads on the mission. However, in an update a month before launch, an agreement between NASA and ISRO was signed to include a small laser retroreflector from NASA to the lander's payload to measure the distance between the satellites above and the microreflector on the lunar surface.

Orbiter

Payloads on the orbiter are:
The payloads on the Vikram lander were:
Pragyan rover carried two instruments to determine the abundance of elements near the landing site:

Launch

The launch of Chandrayaan-2 was initially scheduled for 14 July 2019, 21:21 UTC. However, the launch was aborted 56 minutes and 24 seconds before launch due to a technical glitch, so it was rescheduled to 22 July 2019. Unconfirmed reports later cited a leak in the nipple joint of a helium gas bottle as the cause of cancellation.
Finally Chandrayaan-2 was launched on board the GSLV MK III M1 launch vehicle on 22 July 2019 at 09:13 UTC with a better-than-expected apogee as a result of the cryogenic upper stage being burned to depletion, which later eliminated the need for one of the apogee-raising burns during the geocentric phase of mission. This also resulted in the saving of around 40 kg fuel on board the spacecraft.
Immediately after launch, multiple observations of a slow-moving bright object over Australia were made, which could be related to upper stage venting of residual LOX/LH2 propellant after the main burn.

Geocentric phase

After being placed into a 45,475 × 169 km parking orbit by the launch vehicle, the Chandrayaan-2 spacecraft stack gradually raised its orbit using on-board propulsion over 22 days. In this phase, one perigee-raising and five apogee-raising burns were performed to reach a highly eccentric orbit of 142,975 × 276 km followed by trans-lunar injection on 13 August 2019. Such a long Earth-bound phase with multiple orbit-raising manoeuvres exploiting the Oberth effect was required because of the limited lifting capacity of the launch vehicle and thrust of the spacecraft's on-board propulsion system. A similar strategy was used for Chandrayaan-1 and the Mars Orbiter Mission during their Earth-bound phase trajectory. On 3 August 2019, the first set of Earth images were captured by the LI4 camera on the Vikram lander, showing the North American landmass.

Selenocentric phase

After 29 days from its launch, the Chandrayaan-2 spacecraft stack entered lunar orbit on 20 August 2019 after performing a lunar orbit insertion burn for 28 minutes 57 seconds. The three-spacecraft stack was placed into an elliptical orbit that passed over the polar regions of the Moon, with aposelene and periselene. By 1 September 2019 this elliptical orbit was made nearly circular with aposelene and periselene after four orbit-lowering manoeuvres followed by separation of Vikram lander from the orbiter on 7:45 UTC, 2 September 2019.

Planned landing site

Landing siteCoordinates
Prime landing site
Alternate landing site

Two landing sites were selected, each with an ellipse of. The prime landing site was at 70.90267°S 22.78110°E, and the alternate landing site was at 67.87406°S 18.46947°W. The prime site was on a high plain between the craters Manzinus C and Simpelius N, on the near side of the Moon.

Loss of ''Vikram''

Vikram began its descent at 20:08:03 UTC, 6 September 2019 and was scheduled to land on the Moon at around 20:23 UTC. The descent and soft-landing were to be performed by the on-board computers on Vikram, with mission control unable to make corrections. The initial descent was considered within mission parameters, passing critical braking procedures as expected, but the lander's trajectory began to deviate at about above the surface. The final telemetry readings during ISRO's live-stream show that Vikram final vertical velocity was at above the surface, which a number of experts noted, would have been too fast for the lunar lander to make a successful landing. Initial reports suggesting a crash were confirmed by ISRO chairman K. Sivan, stating that "it must have been a hard landing".
Radio transmissions from the lander were tracked during descent by analysts using a radio telescope owned by the Netherlands Institute for Radio Astronomy. Analysis of the doppler data suggests that the loss of signal coincided with the lander impacting the lunar surface at a velocity of nearly . The powered descent was also observed by NASA's Lunar Reconnaissance Orbiter using its Lyman-Alpha Mapping Project instrument to study changes in the lunar exosphere due to exhaust gases from the lander's engines. K. Sivan, tasked senior scientist P. S. Goel to head the Failure Analysis Committee to look into the causes of the failure.
Both ISRO and NASA attempted to communicate with the lander for about two weeks before the lunar night set in, while NASA's LRO flew over on 17 September 2019 and acquired some images of the intended landing zone. However, the region was near dusk, causing poor lighting for optical imaging. NASA's LRO images, showing no sight of the lander, were released on 26 September. The LRO flew over again on 14 October under more favorable lighting conditions, but was unable to locate it. The LRO performed a third flyover on 10 November.
On 16 November 2019, the Failure Analysis Committee released its report to the Space Commission, concluding that the crash was caused by a software glitch. Phase One of descent from an altitude of 30 km to 7.4 km above the Moon's surface went as intended with velocity being reduced from 1,683 m/s to 146 m/s. But velocity reduction during the second phase of descent was more than expected. This deviation from nominal was beyond the designed parameters of on-board software, causing Vikram to land hard, though it managed to impact relatively near the intended landing site. The complete findings have not been made public.
Vikram impact site was located at by the LROC team after receiving helpful input from Shanmuga Subramanian, a volunteer from Chennai, Tamil Nadu, who located debris from the spacecraft in pictures released by NASA. While initially estimated to be within of the intended landing site, best-guess estimates from satellite imagery indicate initial impact about 600 m away. The spacecraft shattered upon impact, with debris scattered over almost two dozen locations in an area spanning kilometres.
The orbiter part of the mission, with eight scientific instruments, remains operational, and will continue its seven-year mission to study the Moon.

Aftermath

There was an outpouring of support for ISRO from various quarters in the aftermath of the crash landing of its lunar lander. However, prominent Indian news media also criticized ISRO's lack of transparency regarding the crash of the lander and its analysis of the crash. Indian media also noted that unlike ISRO's previous record, the report of the Failure Analysis Committee was not made public. ISRO's lack of consistency regarding the explanation around the rover's crashing was criticized, with the organization providing no proof of its own positions until the efforts of NASA and a Chennai based volunteer located the crash site on the lunar surface. In the wake of the events surrounding Chandrayaan-2, former ISRO employees criticized unverified statements from the ISRO chairman and what they claimed is the top-down leadership and working culture of the organization.

Scientists involved in the mission


Key scientists and engineers involved in the development of Chandrayaan-2 include:
In November 2019, ISRO officials stated that a new lunar lander mission is being studied for launch in Q2 2021; this new proposal is called Chandrayaan-3 and it would be a re-attempt to demonstrate the landing capabilities needed for the Lunar Polar Exploration Mission proposed in partnership with Japan for 2024. If funded, this re-attempt would not include launching an orbiter. The proposed configuration would have a detachable propulsion module, a lander and a rover. According to VSSC director, S. Somanath, there will be more follow-up missions in the Chandrayaan programme.
According to The Times of India, work on Chandrayaan-3 commenced on 14 November 2019. In December 2019, it was reported that ISRO requested the initial funding of the project, amounting to, of which is intended for machinery, equipment and other capital expenditure, while the remaining is sought under revenue expenditure head. Confirming the existence of the project, K. Sivan stated that its cost would be around.