Chandrayaan-2 (; from Sanskrit: , "Moon" and , "craft, vehicle") is the second lunar exploration mission developed by ISRO after Chandrayaan-1. It consists of a lunar orbiter, the Vikram lunar lander, and the Pragyan 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 from the second launch pad at the Satish Dhawan Space Centre in Andhra Pradesh on 22 July 2019 at 09:13:12 UTC by a LVM3-M1 rocket. The craft reached lunar orbit on 20 August 2019. The Vikram lander attempted a lunar landing on 6 September 2019; the lander crashed due to a software error.
The lunar orbiter continues to operate in orbit around the Moon. A follow-up landing mission, Chandrayaan-3, was launched in 2023 and successfully performed a lunar landing.
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, rover and the launch by GSLV, 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 to 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. The changes proposed by Roscosmos necessitated increase in lander mass and required ISRO to decrease mass of its rover and accept some reliability risk. When Russia cited its inability to provide the lander even by a revised time-frame of 2015 due to technical and financial reasons, India decided to develop the lunar mission independently. With new mission timeline for Chandrayaan-2 and an opportunity for a Mars mission arising with launch window in 2013, unused Chandrayaan-2 orbiter hardware was repurposed to be used for the Mars Orbiter Mission.
Chandrayaan-2 launch had been scheduled for March 2018 initially, but was first delayed to April and then to October 2018 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 which increased the gross lift-off mass of spacecraft from 3,250 kg to 3,850 kg. Initially an uprated GSLV Mk II was the chosen launch vehicle for Chandrayaan-2 but this increased spacecraft mass and issues with launch vehicle upratement forced the launch vehicle to be switched to more capable LVM3. Issues with engine throttling were found during testing pushing the launch to the early 2019 and later two of the lander's legs received minor damage during one of the tests in February 2019 delaying the launch even further.
Chandrayaan-2 launch was scheduled for 14 July 2019, 21:21 UTC (15 July 2019 at 02:51 IST local time), 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 09:13:12 UTC (14:43:12 IST) 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. However, just days before the Chandrayaan 3 launch, the then ISRO chief S Somanath noted during the sidelines of the India Space Congress that the primary issues were the higher thrust by the 5 engines used to reduce the velocity, the artificial limit which restricted the craft to a maximum of 10 degrees change per second, and the small landing area.
Objectives The primary objectives of the Chandrayaan-2 lander were to illustrate the ability to soft-land and operate a robotic rover on the lunar surface.
The scientific goals of the orbiter are
to study lunar topography, mineralogy, elemental abundance, the lunar exosphere, and signatures of hydroxyl and water ice; to study the water ice in the south polar region and thickness of the lunar regolith on the surface; and to map the lunar surface and help to prepare 3D maps of it.
Design The name Chandrayaan means "mooncraft" in Sanskrit and most other Indian languages.Monier Monier-Williams, A Sanskrit-English Dictionary (1899):
candra: "[...] m. the moon (also personified as a deity Mn. &c)"
yāna: "[...] n. a vehicle of any kind, carriage, wagon, vessel, ship, [...]" The mission was launched on a GSLV Mk 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 (approximately US$141 million 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 (OHRC) 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.
Dimensions: 3.2 × 5.8 × 2.2 m Gross lift-off mass: Propellant mass: Dry mass: Power generation capacity: 1000 watts Mission duration: ~ 7.5 years, extended from the planned 1 year owing to the precise launch and mission management, in lunar orbit
Vikram lander
The mission's lander is called Vikram () named after cosmic ray scientist Vikram Sarabhai (1919–1971), 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.India's Moon Mission Continues Despite Apparent Lander Crash. Mike Wall, space.com, 7 September 2019, Quote: "India's Moon Mission Continues Despite Apparent Lander Crash". 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 (SAC) 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. The four throttle-able engines of lander were capable of throttling between range of 40 to 100 percent incrementally in steps of 20%. Vikram was designed to safely land on slopes up to 12°.
Some associated technologies include: A high resolution camera, Laser Altimeter (LASA) Lander Hazard Detection Avoidance Camera (LHDAC) Lander Position Detection Camera (LPDC) Lander Horizontal Velocity Camera (LHVC) 800 N throttleable liquid main engine Attitude thrusters Ka-band radio altimeters Laser Inertial Reference and Accelerometer Package (LIRAP) 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.
Dimensions: Gross lift-off mass: Propellant mass: Dry mass: Power generation capability: 650 watts Mission duration: ≤14 days (one lunar day)
Pragyan rover
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 :
Stereoscopic Camera-based 3D Vision : Two 1 megapixel, monochromatic navcams in front of the rover to provide the ground control team a 3D view of the surrounding terrain, and help in path-planning by generating a digital elevation model of the terrain. IIT Kanpur contributed to the development of the subsystems for light-based map generation and motion planning for the rover. Control and Motor Dynamics : The rover has a rocker-bogie suspension system and six wheels, each driven by independent brushless DC electric motors. Steering is accomplished by differential speed of the wheels or skid steering.
The expected operating time of Pragyan rover was one lunar day, or ~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.
Dimensions: Power: 50 watts Travel speed: Mission duration: ~14 Earth days (one lunar day)
Telemetry, tracking, and command (TT&C) During various phases of launch and spacecraft operations of Chandrayaan-2 mission, the TT&C support was provided by ISRO Telemetry, Tracking and Command Network (ISTRAC), Indian Deep Space Network (IDSN), NASA Deep Space Network and National Institute for Space Research's (INPE) ground stations located in Alcântara and Cuiabá.
Science payload
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 European Space Agency (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
The orbiter has several scientific payloads.
The Chandrayaan-2 Large Area Soft X-ray Spectrometer (CLASS) from the ISRO Satellite Centre (ISAC), which makes use of X-ray fluorescence spectra to determine the elemental composition of the lunar surface.