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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Chandrayaan programme | 4/7 | https://en.wikipedia.org/wiki/Chandrayaan_programme | reference | science, encyclopedia | 2026-05-05T12:59:47.013443+00:00 | kb-cron |
Chandrayaan-2 was the second mission under the programme and it included an orbiter, lander, and rover. After the failure of the Chandrayaan-1 orbiter, the Chandrayaan-2 orbiter enabled ISRO to conduct science with modern cameras and instruments. The primary objectives of this mission were to soft land on the surface and operate a rover, to study the lunar surface, its exosphere, minerals and water ice. While the Chandrayaan-2 composite (orbiter, lander and rover) weighed 3,850 kg (8,490 lb) in total, the orbiter alone weighed 2,379 kg (5,245 lb). It carried eight scientific instruments with two of the instruments; the Terrain Mapping Camera 2 (TMC-2) and Chandrayaan-2 Atmospheric Compositional Explorer 2 (ChACE-2) being upgraded versions of Terrain Mapping camera (TMC) and Chandra's Atmospheric Compositional Explorer (CHACE) onboard Chandrayaan-1 orbiter and Moon Impact Probe respectively. The Chandrayaan-2 was launched on 14 July 2019 and attained the lunar orbit on 20 August 2019. After five orbital reduction manoeuvres, the composite attained a near circular orbit of 127 km × 119 km (79 mi × 74 mi), which was followed by the separation of Vikram on 2 September 2019. The crash landing of Vikram left the orbiter as a sole successful component of the mission with its new mission duration being extended from one year to seven and a half years. The Orbiter High-Resolution Camera (OHRC) during the time remained the most advanced camera in the lunar orbit with a spatial resolution of 25 cm (9.8 in), four times higher than Chandrayaan-1 orbiter's 1 m (3 ft 3 in) resolution. The orbiter is currently studying the lava tubes and caves which were previously spotted by the Chandrayaan-1 orbiter.
==== Chandrayaan-3 ====
With the Chandrayaan-2 orbiter already operational and the need of demonstrating landing capabilities, Chandraayn-3's orbiter carried only a single payload and for its main purpose served as a propulsion module for carrying Vikram to the Moon. The Spectro-polarimetry of Habitable Planet Earth (SHAPE) payload was developed to study Earth's atmosphere from distance and it would aid in the study of Exoplanets' atmospheres, which employs a similar technique. Chandrayaan-3 was launched on 14 July 2023 aboard LVM3 and on 16 August 2023, the composite attained a final lunar orbit of 113 km × 157 km (70 mi × 98 mi). A day later, the orbiter separated from the lander and began its independent operations with SHAPE. The orbiter also known as Propulsion Module (PM) of Chandrayaan-3, was moved from its orbit around Moon to an orbit around Earth. While the initial plan was to operate SHAPE for about three months during the mission life of orbiter, the precise lower earth orbit injection by LVM3 and optimal earth / lunar burn maneuvers, resulted in the availability of over 100 kg (220 lb) of fuel in the orbiter after over one month of operations in the lunar orbit. It was decided to use the available fuel in it to derive additional information for future lunar missions and demonstrate the mission operation strategies for a sample return mission. In order to continue SHAPE payload for Earth observation, it was decided to re-orbit the orbiter to a suitable Earth orbit. This mission plan was worked out considering the collision avoidance such as preventing the orbiter from crashing on to the Moon's surface or entering into the Earth's GEO belt at 36000 km and orbits below that. Considering the estimated fuel availability and the safety to GEO spacecraft, the optimal Earth return trajectory was designed for October 2023. It operated until 22 August 2024.
=== Landers ===
==== Vikram (Chandrayaan-2) ==== The lander was named Vikram and it weighed 1,471 kg (3,243 lb) including the 27 kg (60 lb) rover named Pragyan that it housed inside. Vikram had eight 58 N (13 lbf) thrusters for attitude control and five 800 N (180 lbf) liquid main engines that were derived from ISRO's 400 N (90 lbf) liquid apogee motors and it was designed to safely land on slopes up to 12°. It carried four payloads to study lunar seismic activity, measure the lunar sub-surface temperatures and to measure density and variation of lunar surface plasma (using a langmuir probe). After two de-orbiting manoeuvers, Vikram attained a final orbit of 95 km × 119 km (59 mi × 74 mi) after which the powered descent phase began on 7 September 2019. During the descent and landing, the onboard computers had complete control over the lander. The initial descent and critical braking procedures went as intended but upon reaching 2.1 km (1.3 mi) altitude, the lander began deviating and lost its contact with the mission control after subsequent crash landing. Upon analysis, it was found that the main engines had higher thrust than normal which led to errors being accumulated over time and this meant the lander could not change its attitude at such a fast pace due to safety constraints in the onboard computer that had a limit on the maximum rate with which it can change its attitude. Coarse throttling of main engines, error in computing the remaining time in the mission and a small landing site of 500 x 500 m were the other reasons attributed to the failure.
==== Vikram (Chandrayaan-3) ====