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.[16][17] ISRO would have the prime responsibility for the orbiter, rover and the launch by GSLV, while Roscosmos was to provide the lander.[18] The Indian government approved the mission in a meeting of the Union Cabinet, held on 18 September 2008 and chaired by Prime MinisterManmohan Singh.[19] The design of the spacecraft was completed in August 2009, with scientists of both countries conducting a joint review.[20]
Although ISRO finalised the payload for Chandrayaan-2 on schedule,[21] the mission was postponed in January 2013 and rescheduled to 2016 because Russia was unable to develop the lander on time.[22][23][24] 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.[23] The changes proposed by Roscosmos necessitated increase in lander mass and required ISRO to decrease mass of its rover and accept some reliability risk.[25][18] 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.[22][26] 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.[27]
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.[28][29] On 19 June 2018, after the program's fourth Comprehensive Technical Review meeting, a number of changes in configuration[30] and landing sequence[31] were planned for implementation which increased the gross lift-off mass of spacecraft from 3,250 kg to 3,850 kg.[32] Initially an uprated GSLV Mk II[33][34] was the chosen launch vehicle for Chandrayaan-2 but this increased spacecraft mass and issues with launch vehicle upratement[35] forced the launch vehicle to be switched to more capable LVM3.[30] Issues with engine throttling were found during testing[36] pushing the launch to the early 2019[37] and later two of the lander's legs received minor damage during one of the tests in February 2019 delaying the launch even further.[38][39]
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.[40] However, the launch was aborted due to a technical glitch and was rescheduled.[9][41][42] 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.[43]
On 6 September 2019, the lander during its landing phase, deviated from its intended trajectory starting at 2.1 km (1.3 mi) altitude,[44] and had lost communication when touchdown confirmation was expected.[45][46] Initial reports suggesting a crash [47][48] were confirmed by ISRO chairman K. Sivan, stating that "it must have been a hard landing".[49] The Failure Analysis Committee concluded that the crash was caused by a software glitch.[50] Unlike ISRO's previous record, the report of the Failure Analysis Committee has not been made public.[51]
Chandrayaan-2 orbiter performed a collision avoidance manoeuvre at 14:52 UTC on 18 October 2021 to avert possible conjunction with Lunar Reconnaissance Orbiter. Both spacecraft were expected to come dangerously close to each other on 20 October 2021 at 05:45 UTC over the Lunar north pole.[52]
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.
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.[56][57] The mission was launched on a GSLV Mk III M1 with an approximate lift-off mass of 3,850 kg (8,490 lb) from Satish Dhawan Space Centre on Sriharikota Island of Andhra Pradesh.[3][11][14][31] As of June 2019[update], 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.[58][59] Chandrayaan-2 stack was initially put in an Earth parking orbit of 170 km (110 mi) perigee and 40,400 km (25,100 mi) apogee by the launch vehicle.[60]
Orbiter
Chandrayaan-2 orbiter at integration facility
The Chandrayaan-2 orbiter is orbiting the Moon on a polar orbit at an altitude of 100 km (62 mi).[61] It carries eight scientific instruments; two of which are improved versions of those flown on Chandrayaan-1. The approximate launch mass was 2,379 kg (5,245 lb).[4][5][21][62] The Orbiter High Resolution Camera (OHRC) conducted high-resolution observations of the landing site prior to separation of the lander from the orbiter.[2][61] The orbiter's structure was manufactured by Hindustan Aeronautics Limited and delivered to the ISRO Satellite Centre on 22 June 2015.[63][64]
Mission duration: ~ 7.5 years, extended from the planned 1 year owing to the precise launch and mission management, in lunar orbit [1][65]
Vikram lander
Rover Pragyan mounted on the ramp of Vikram landerImages of the Earth captured by Chandrayaan-2 Vikram lander camera LI4[66]
The mission's lander is called Vikram (Sanskrit: Vikrama, lit. 'Valour' [67]) Pronunciationⓘ named after cosmic ray scientist Vikram Sarabhai (1919–1971), who is widely regarded as the founder of the Indian space programme.[68] The Vikram lander detached from the orbiter and descended to a low lunar orbit of 30 km × 100 km (19 mi × 62 mi) using its 800 N (180 lbf) 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. Vikramcrash-landed during this attempt.[1][47] The combined mass of the lander and rover was approximately 1,471 kg (3,243 lb).[4][5]
The preliminary configuration study of the lander was completed in 2013 by the Space Applications Centre (SAC) in Ahmedabad.[22] The lander's propulsion system consisted of eight 58 N (13 lbf) thrusters for attitude control[69] and five 800 N (180 lbf) liquid main engines derived from ISRO's 440 N (99 lbf) liquid apogee motor.[70][71] Initially, the lander design employed four main throttle-able liquid engines, but a centrally mounted fixed-thrust engine [72] 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.[31] The four throttle-able engines of lander were capable of throttling between range of 40 to 100 percent incrementally in steps of 20%.[73]Vikram was designed to safely land on slopes up to 12°.[74][75]
Some associated technologies include:
A high resolution camera, Laser Altimeter (LASA)[76]
Laser Inertial Reference and Accelerometer Package (LIRAP)[80] and the software needed to run these components.[2][61]
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.[81][82]
Dimensions: 2.54 m × 2 m × 1.2 m (8 ft 4 in × 6 ft 7 in × 3 ft 11 in) [8]
The mission's rover was called Pragyan (Sanskrit: Prajñāna, lit. 'Wisdom' [83][84]) Pronunciationⓘ)[83][85] with a mass of 27 kg (60 lb), and would have operated on solar power.[4][5] The rover was to move on six wheels, traversing 500 m (1,600 ft) on the lunar surface at the rate of 1 cm (0.39 in) 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.[21][58][62][86][87]
For navigation, the rover would have used:
Stereoscopic camera-based 3D vision: two 1 megapixel, monochromaticnavcams 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.[88]IIT Kanpur contributed to the development of the subsystems for light-based map generation and motion planning for the rover.[89]
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.[90]
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.[91][92] 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.[93][94]
ISRO selected eight scientific instruments for the orbiter, four for the lander,[3][97][98] and two for the rover.[21] 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,[99] ISRO in 2010 had clarified that due to weight restrictions it will not be carrying foreign payloads on the mission.[100] However, in an update a month before launch,[101] an agreement between NASA and Indian Space Research Organisation (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.[102][103]
Orbiter
Chandrayaan-2 orbiter in clean-room being integrated with payloadsChandrayaan-2 composite
The orbiter has several scientific payloads.[1][3][98]
The Solar X-ray monitor (XSM) from Physical Research Laboratory (PRL), Ahmedabad, primarily supports CLASS instrument by providing solar X-ray spectra and intensity measurements as input to it. Additionally these measurements will help in studying various high-energy processes occurring in the solar corona.[21][105]
The Dual Frequency L-band and S-bandSynthetic Aperture Radar (DFSAR) from the Space Applications Centre (SAC) for probing the first few metres of the lunar surface for the presence of different constituents. DFSAR is expected to provide further evidence confirming the presence of water ice, and its distribution below the shadowed regions of the Moon.[21][106] It has lunar surface penetration depth of 5 m (16 ft) (L-band).[65][98]
The Imaging IR Spectrometer (IIRS) from the SAC for mapping of lunar surface over a wide wavelength range for the study of minerals, water molecules and hydroxyl present.[21][107] It features an extended spectral range (0.8 μm to 5 μm), an improvement over previous lunar missions whose payloads worked up to 3 μm.[65][108][109]
The Terrain Mapping Camera-2 (TMC-2) from SAC for preparing a three-dimensional map essential for studying the lunar mineralogy and geology [21][111]
The Radio Anatomy of Moon Bound Hypersensitive Ionosphere and Atmosphere – Dual Frequency Radio Science experiment (RAMBHA-DFRS) by SPL for the studying electron density in the lunar ionosphere[112]
The Orbiter High Resolution Camera (OHRC) by SAC for scouting a hazard-free spot prior to landing. Used to help prepare high-resolution topographic maps and digital elevation models of the lunar surface. OHRC has a spatial resolution of 0.32 m (1 ft 1 in) from 100 km (62 mi) polar orbit, which is the best resolution among any lunar orbiter mission to date.[98][113][114][115]
A laser retroreflector array (LRA) by the Goddard Space Flight Center for taking precise measurements of distance between the reflector on the lunar surface and satellites in lunar orbit.[101][102][119][120] The microreflector weighed about 22 g (0.78 oz) and cannot be used for taking observations from Earth-based lunar laser stations.[102]
Pragyan rover
Pragyan rover carried two instruments to determine the abundance of elements near the landing site:[3][98]
Hydroxyl and Water molecules: The Chandrayaan-1 probe detected water on the Moon for the first time. Chandrayaan-2 detected Water, as well as Hydroxyl ions on the Moon, August 2022. It distinguished between these two with the aid of IIRS (Imaging Infrared Spectrometer). Between 29 and 62 degrees north latitude, the probe detected the presence of these two molecules. Along with this, it also observed that the sunlit regions contain higher concentrations of these two.
Distribution of Gas in Lunar Atmosphere: Chandra Atmospheric Composition Explorer-2, detected Argon-40 in Lunar exosphere. The distribution of Ar-40 has significant spatial heterogeneity. The NASA probe, LADEE, detected Argon near the Equatorial region, but Argon far from that, was detected for the first time. There are localised enhancements (termed as Argon bulge) over several regions including the KREEP (potassium (K), rare-earth elements, and phosphorus (P)) and South Pole Aitken terrain.
Presence of Rare elements: Chandra's Large Area Soft X-ray Spectrometer (CLASS), detected magnesium, aluminium, silicon, calcium, titanium, iron etc. It also examined and detected minor elements – chromium and manganese, for the first time. The findings have paved the path for adding knowledge about the magmatic evolution of the Moon, its nebular conditions and much more.
Solar X-ray Monitor (XSM), has witnessed a huge amount of microflares outside the active regions of the Sun for the first time.
The DFSAR instrument studied the subsurface features of the Moon, detected signatures of the sub-surface water-ice, mapped lunar morphological features in the polar regions in high resolution.
The TMC 2, which is conducting imaging of the Moon at a global scale, found interesting geologic signatures of lunar crustal shortening, and identification of volcanic domes. The OHRC, mapped Moon With a resolution of 25 cm at 100 km altitude.
DFRS experiment, studied the ionosphere of the Moon, which is generated by the solar photo-ionisation of the neutral species of the lunar tenuous exosphere. The experiment showed that Moon's ionosphere has a plasma density of the order of 10^4 cm^3, in the wake region which is at least one order of magnitude more than that is present in the day side.
Chandrayaan-2 lifting off on 22 July 2019 at 02.43 PM IST
The launch of Chandrayaan-2 was initially scheduled for 14 July 2019, 21:21 UTC (15 July 2019 at 02:51 IST local time).[40] 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.[9][41] Unconfirmed reports later cited a leak in the nipple joint of a helium gas bottle as the cause of cancellation.[42][127][128]
Finally Chandrayaan-2 was launched on board the LVM3 M1launch vehicle on 22 July 2019 at 09:13:12 UTC (14:43:12 IST) 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.[43][129][130] This also resulted in the saving of around 40 kg fuel on board the spacecraft.[131]
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.[132][133]
Geocentric phase
Chandrayaan-2's trajectory
After being placed into a 45,475 × 169 km parking orbit by the launch vehicle,[43] 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[134] followed by trans-lunar injection on 13 August 2019.[135] 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.[136] 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.[66]
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.[137] The three-spacecraft stack was placed into an elliptical orbit that passed over the polar regions of the Moon, with 18,072 km (11,229 mi) aposelene and 114 km (71 mi) periselene.[138] By 1 September 2019, this elliptical orbit was made nearly circular with 127 km (79 mi) aposelene and 119 km (74 mi) periselene after four orbit-lowering manoeuvres [139][140][141][142] followed by separation of Vikram lander from the orbiter on 07:45 UTC, 2 September 2019.[143]
The flat highland between craters Manzinus C and Simpelius N was the planned landing zone for the Vikram lander.
Two landing sites were selected, each with an ellipse of 32 km × 11 km (19.9 mi × 6.8 mi).[144] The prime landing site (PLS54) was at 70.90267°S 22.78110°E (600 km (370 mi) from the south pole,[145]) and the alternate landing site (ALS01) was at 67.87406° South 18.46947° West. The prime site was on a high plain between the cratersManzinus C and Simpelius N,[146][147] on the near side of the Moon.
Failed landing attempt
Location of the Vikram lander impact site
Ejecta field around Vikram lander impact site
Before and after images of the impact site
Before and after images of the impact site
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.[148] The initial descent was considered within mission parameters, passing critical braking procedures as expected, but the lander's trajectory began to deviate at about 2.1 km (1.3 mi) above the surface.[149][150] The final telemetry readings during ISRO's live-stream show that Vikram's final vertical velocity was 58 m/s (210 km/h) at 330 m (1,080 ft) above the surface, which a number of experts noted, would have been too fast for the lunar lander to make a successful landing.[45][151][152] Initial reports suggesting a crash[47][48] were confirmed by ISRO chairman K. Sivan, stating that "it must have been a hard landing".[49][153][154] However, it contradicted initial claims from anonymous ISRO officials that the lander was intact and lying in a tilted position.[155][156]
Radio transmissions from the lander were tracked during descent by analysts using a 25 m (82 ft) 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 50 m/s (180 km/h) (as opposed to an ideal 2 m/s (7.2 km/h) touchdown velocity).[3][46] The powered descent was also observed by NASA's Lunar Reconnaissance Orbiter (LRO) using its Lyman-Alpha Mapping Project instrument to study changes in the lunar exosphere due to exhaust gases from the lander's engines.[157] K. Sivan, tasked senior scientist Prem Shanker Goel to head the Failure Analysis Committee to look into the causes of the failure.[158]
Both ISRO and NASA attempted to communicate with the lander for about two weeks before the lunar night set in,[115][159] while NASA's LRO flew over on 17 September 2019 and acquired some images of the intended landing zone.[114] However, the region was near dusk, causing poor lighting for optical imaging.[160][161] NASA's LRO images, showing no sight of the lander, were released on 26 September 2019.[145] The LRO flew over again on 14 October 2019 under more favourable lighting conditions,[162][163] but was unable to locate it.[164][165] The LRO performed a third flyover on 10 November 2019.[164]
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.[50] Phase One of descent the Rough Braking Phase from an altitude of 30 km to 7.4 km above the Moon's surface went as intended with velocity being reduced from 1683 m/s to 146 m/s. Anomalous deviation in performance began 693.8 seconds into powered descent after the end of first phase and with the beginning of Absolute Navigation Phase (also known as Camera Coasting Phase) where lander's orientation is deliberately kept fixed. It was found that lander's main engines had slightly higher thrust of 422 N (95 lbf) than nominal at 360 N (81 lbf),[166] so during this phase lander slowed down more than it should have. The thrust control algorithm was configured to apply corrections towards the end of the phase and not instantaneously allowing large navigation errors to be accumulated. After end of camera coasting phase, rate of applying corrections was limited due to builtin safety constraints such as maximum rate at which attitude can change. Other contributing issues were, coarse throttling of main engines,[73] polarity related software error,[166] wrong computation of remaining time of flight by onboard algorithm and very rigid requirement to land inside the planned 500×500 meter landing site regardless of non-nominal flight status. Subsequently, Vikram lander ended up increasing its horizontal velocity (48 m/s) to reach landing site while descending at high rate (50 m/s) causing Vikram to land hard,[167][168][169][170] though it managed to impact relatively near the intended landing site.[171] The complete official report has not been made public.[172][173][174]
Vikram's impact site was located at 70°52′52″S22°47′02″E / 70.8810°S 22.7840°E / -70.8810; 22.7840 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.[175][176] While initially estimated to be within 500 m (1,600 ft) of the intended landing site, best-guess estimates from satellite imagery indicate initial impact about 600 m away.[177] The spacecraft shattered upon impact,[178] with debris scattered over almost two dozen locations in an area spanning kilometres.[176] The crash site was later named Tiranga Point after the Chandrayaan-3 landing.[179]
Despite the failed landing, The orbiter part of the mission, with eight scientific instruments, remains operational, and will continue its seven-year mission to study the Moon.[150] The Orbiter would later serve as an relay for Chandrayaa-3 which landed close to the crash site. The orbiter also observed the Sun during a massive solar flare in May 2024 with the XSM and the CLASS intrument, in conjuction with XpoSAT & Aditya-L1.[191]
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.[192][156] Indian media also noted that unlike ISRO's previous record, the report of the Failure Analysis Committee was not made public[51] and RTI queries seeking it were denied by ISRO citing section 8(1) of the RTI Act.[193] 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.[194] In the wake of the events surrounding Chandrayaan-2, former ISRO employees criticized unverified statements from chairman K Sivan and what they claimed is the top-down leadership and working culture of the organization.[195][196][197] S Somanath who succeeded K Sivan as ISRO Chairman also expressed his dissatisfaction at the lack of transparency around landing failure, and misleading representation of it.[198][199][200]
Scientists involved in the mission
A view of Mission Operations Complex (MOX-1), ISTRAC[201] prior to the fourth Earth-bound burn[185]
Key scientists and engineers involved in the development of Chandrayaan-2 include:[202][203][204]
In November 2019, ISRO officials stated that a new lunar lander mission was being studied and prepared. It was launched on 14 July 2023;[209] with the designation Chandrayaan-3, which was a second attempt to demonstrate the landing capabilities needed for the Lunar Polar Exploration Mission proposed in partnership with Japan for 2025.[210][211] The new mission was designed with a detachable propulsion module, also behaving like a communications relay satellite,[212] a lander and a rover,[213][214][215] but with no orbiter. S. Somanath, the VSSC director, announced that there would be more follow-up missions in the Chandrayaan programme.[170][216]
In December 2019, it was reported that ISRO requested the initial funding of the project, amounting to ₹75 crore (US$9.0 million), of which ₹60 crore (US$7.2 million) is intended for machinery, equipment and other capital expenditure, while the remaining ₹15 crore (US$1.8 million) was sought under a revenue expenditure allowance.[217] K. Sivan stated that its cost would be around ₹615 crore (equivalent to ₹724 crore or US$87 million in 2023).[218] It performed a soft landing on the Moon on 23 August 2023.[219]
^ abcd"Chandrayaan-2 Latest Update". Indian Space Research Organisation. 7 September 2019. Archived from the original on 8 September 2019. Retrieved 7 September 2019.
^"Chandrayaan-2" (Press release). Department of Space. 14 August 2013. Archived from the original on 5 August 2019. Retrieved 26 August 2017. Chandrayaan-2 would be a lone mission by India without Russian tie-up.
^ ab"Chandrayaan-2: Three months on, ISRO yet to make public Vikram lander failure report details". The Indian Express. 19 December 2019. Archived from the original on 7 January 2020. Retrieved 17 January 2020. "This is unlike the ISRO's previous record. For instance, after the failure of an operational fourth flight of the heavy lift GSLV rocket — the GSLV-F02 mission — on 10 July 2006, a 15-member FAC was tasked with providing a report in a month. After the report was submitted to the government, ISRO made the details public on 6 September 2006, on its website. In 2010, when GSLV D3, a developmental flight and the fifth heavy lift GSLV rocket, failed after launch on 15 April 2010, an FAC report was submitted with the government on 24 May 2010. Details of the report were made public on 9 July 2010. The same year, when GSLV F06, an operational sixth flight for GSLV rocket, failed on 25 December 2011, ISRO went public on 31 December 2011, with findings of an analysis of failure done by a preliminary FAC comprising space experts".
^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, [...]"
^"Chandrayaan-2 FAQ". Archived from the original on 29 June 2019. Retrieved 24 August 2019. The name Chandrayaan means "Chandra- Moon, Yaan-vehicle", –in Indian languages (Sanskrit and Hindi), – the lunar spacecraft.
^ abc"Annual Report 2014–2015"(PDF). Indian Space Research Organisation. December 2014. p. 82. Archived(PDF) from the original on 4 March 2016. Retrieved 7 August 2016.
^"ISRO developing vehicle to launch small satellites". Frontline. Retrieved 29 August 2018. Making a throttleable engine of 3 kilonewtons or 4 kilonewtons is a totally new development for us. But we wanted to make use of available technologies. We have a LAM [liquid apogee motor] with a 400 newtons thruster, & we have been using it on our satellites. We enhanced it to 800 newtons. It was not a major, new design change.
^Mondal, Chinmoy; Chakrabarti, Subrata; Venkittaraman, D.; Manimaran, A. (2015). Development of a Proportional Flow Control Valve for the 800 N Engine Test. 9th National Symposium and Exhibition on Aerospace and Related Mechanisms, January 2015, Bengaluru, India. Archived from the original on 20 July 2021. Retrieved 29 August 2018.
^"Chandrayaan-2: First step towards Indians setting foot on moon in near future". The New Indian Express. 8 July 2019. Archived from the original on 8 July 2019. Retrieved 8 July 2019. As solar energy powers the system, a place with good visibility and area of communication was needed. Also, the place where the landing takes place should not have many boulders and craters. The slope for landing should be less than 12 degrees. The South pole has a near-flat surface, with good visibility and sunlight available from the convenience point of view.
^ ab"Chandrayaan-2 Spacecraft". Indian Space Research Organisation. Archived from the original on 18 July 2019. Retrieved 24 August 2019. Chandrayaan 2's Rover is a 6-wheeled robotic vehicle named Pragyan, which translates to "wisdom" in Sanskrit.
^Elumalai, V.; Kharge, Mallikarjun (7 February 2019). "Chandrayaan–II"(PDF). pib.nic.in. Archived from the original(PDF) on 7 February 2019. Retrieved 7 February 2019. Lander (Vikram) is undergoing final integration tests. Rover (Pragyan) has completed all tests and waiting for the Vikram readiness to undergo further tests.
^Subhalakshmi, K.; Basavaraj, B.; Selvaraj, P.; Laha, J. (22 December 2010). "Design of Miniature Space Grade Navigation Camera for Lunar Mission". 2010 International Symposium on Electronic System Design. pp. 169–174. doi:10.1109/ISED.2010.40. ISBN978-1-4244-8979-4. S2CID25978793.
^Annadurai, Mylswami; Nagesh, G.; Vanitha, Muthayaa (28 June 2017). ""Chandrayaan-2: Lunar Orbiter and Lander Mission", 10th IAA Symposium on The Future of Space Exploration: Towards the Moon Village and Beyond, Torin, Italy". International Academy of Astronautics. Archived from the original on 30 August 2017. Retrieved 14 June 2019. Mobility of the Rover in the unknown lunar terrain is accomplished by a Rocker bogie suspension system driven by six wheels. Brushless DC motors are used to drive the wheels to move along the desired path and steering is accomplished by differential speed of the wheels. The wheels are designed after extensive modelling of the wheel-soil interaction, considering the lunar soil properties, sinkage and slippage results from a single wheel test bed. The rover mobility has been tested in the lunar test facility wherein the soil simulant, terrain and the gravity of moon are simulated. The limitations w.r.t slope, obstacles, pits in view of slippage/sinkage have been experimentally verified with the analysis results.
^Curtain Raiser video (Hindi) (in Hindi). Indian Space Research Organisation. Event occurs at 1 minute 55 seconds. Archived from the original on 14 July 2019. Retrieved 4 September 2019.
^Mishra, Sanjeev (September 2019). "PRL News- The Spectrum"(PDF). Physical Research Laboratory. Archived(PDF) from the original on 26 September 2019. Retrieved 7 December 2021.
^India Heads to the Moon With Chandrayaan-2Archived 23 July 2019 at the Wayback Machine David Dickinson, Sky & Telescope, 22 July 2019, Quote: "Vikram carries a seismometer, thermal probe, and an instrument to measure variation and density of lunar surface plasma, along with a laser retro-reflector supplied by NASA's Goddard Spaceflight Center".
^Matta, M.; Smith, S.; Baumgardner, J.; Wilson, J.; Martinis, C.; Mendillo, M. (December 2009). "The sodium tail of the Moon". Icarus. 204 (2): 409–417. doi:10.1016/j.icarus.2009.06.017.
^ ab"ISRO finally admits to Chandrayaan-2's lander Vikram lying on Moon "in pieces"". The New Indian Express. 1 January 2020. Archived from the original on 28 July 2020. Retrieved 29 May 2020. On being persistently asked by the media on Wednesday why ISRO was not being transparent about the fate of the lander as the entire nation was waiting with bated breath for a successful landing, Sivan finally said, "Yes, yes...it is in pieces...!"
^ abIIST Foundation Day & Chandrayaan Utsav. 14 September 2023. Event occurs at 38 min. 36 sec. every engine instead of producing 360 N, it was producing 62 N more.
^"Unstarred Question number: 588". Parliament of India, Lok Sabha. Archived from the original on 20 November 2019. Retrieved 20 November 2019. The first phase of descent was performed nominally from an altitude of 30 km to 7.4 km above the moon surface. The velocity was reduced from 1683 m/s to 146 m/s. During the second phase of descent, the reduction in velocity was more than the designed value. Due to this deviation, the initial conditions at the start of the fine braking phase were beyond the designed parameters. As a result, Vikram hard-landed within 500 m of the designated landing site.
^"Vikram Lander Found". Lunar Reconnaissance Orbiter Camera. Archived from the original on 2 December 2019. Retrieved 2 December 2019. This article incorporates text from this source, which is in the public domain.
^"ISRO silent on NASA pictures of Vikram". The Hindu. 3 December 2019. Archived from the original on 27 July 2020. Retrieved 28 May 2020. "However, except for sketchy information, ISRO has shied away from sharing its own analysis of the crash".
^"ISRO: Time for Change of leadership". Newsroom 24x7. 18 December 2019. Archived from the original on 27 July 2020. Retrieved 28 May 2020. Question that remains to be answered by ISRO is where "the proof for what they have been claiming. Why no photographs or a video of the Lander's undocking from the Lunar Orbiter have been made public till now. Only an objective probe will find answers to the questions regarding Chandrayaan-2 and what led to the Lander's failure. There are also many lapses that should make the citizens of India, who fund ISRO's working, sit up straight
^"Chandrayaan-2: Was India's Moon mission actually a success?". BBC News. 30 September 2019. Archived from the original on 17 December 2020. Retrieved 28 May 2020. "Mr Sivan's remarks have been met with criticism from scientists who said it was too early for ISRO to term the mission a success, especially since its most important goal – to land a rover on the Moon's surface that can gather crucial data – remains unrealised".
^"Senior ISRO Scientist Criticises Sivan's Approach After Moon Mission Setback". The Wire. 22 September 2019. Archived from the original on 7 December 2019. Retrieved 28 May 2020. "Misra called attention to ISRO's top-down working culture and inadequate leadership, particularly in the face of Chandrayaan-2 having failed to execute its surface mission because the lander crashed on the Moon's surface instead of touching down".
^"No ISRO update on Chandrayaan-2 lander but social media goes wild with speculation". The Print. 10 September 2019. Archived from the original on 20 July 2021. Retrieved 29 May 2020. "The chairman also released a statement Friday, saying 90 to 95% of mission objectives have already been met. The statement was met with much criticism due to a lack of transparency on the calculation of these percentages".
^"K Sivan tried to prevent my elevation to ISRO chairman's post: Somanath". Onmanorama. Retrieved 13 January 2024. He further alleges that the chairman, instead of stating the truth that it was an error in the software that had caused the failure in the landing of Chandrayaan 2, declared that contact could not be established with the lander. Sivan made several changes to the Chandrayaan 2 mission, which started when Kiran Kumar was the chairman. Excessive publicity also affected the Chandrayaan 2 mission adversely.
^"Haven't Targeted Anyone In Autobiography, Says ISRO Chief S Somanath". NDTV.com. Retrieved 13 January 2024. He admitted that he mentioned in his book the lack of clarity in connection with the announcement of the failure of the Chandrayaan-2 mission. During the time of landing, it was not clearly said that there was communication failure and it would crash land, he said. "I believe that a good practice is to tell what has actually happened. It will increase transparency in the organisation. So I referred to that particular incident in the book," Mr Somanath added.
^Koshy, Jacob (4 November 2023). "ISRO Chairman Somanath withdraws memoir after controversy". The Hindu. ISSN0971-751X. Retrieved 13 January 2024. "That a software glitch was at fault was known only subsequently. However, the crashing of the lander was known on that day itself (September 6, 2019). There was no point in calling it a communication failure... [as Chairman Sivan had described it]. However, every Chairman can choose what they communicate. I believe that whatever success or failure happens should be transparently communicated. I'm not criticising Dr. Sivan though," said Mr. Somanath.
^Subramanian, T. S. (28 September 2016). "Cryogenic gains for GSLV". Frontline. Archived from the original on 27 July 2020. Retrieved 11 September 2019.
^"CHANDRAYAAN-III" (Press release). Delhi. Press Information Bureau. 27 November 2019. Archived from the original on 28 July 2020. Retrieved 1 December 2019.
Launches are separated by dots ( • ), payloads by commas ( , ), multiple names for the same satellite by slashes ( / ). Crewed flights are underlined. Launch failures are marked with the † sign. Payloads deployed from other spacecraft are (enclosed in parentheses).
_at_ISTRAC,_Peenya_before_commencement_of_fourth_orbit_raising_burn_for_Chandrayaan-2.jpg)
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