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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Chandrayaan-2 | 4/6 | https://en.wikipedia.org/wiki/Chandrayaan-2 | reference | science, encyclopedia | 2026-05-05T12:59:52.302451+00:00 | kb-cron |
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 2.1 km (1.3 mi) above the surface. 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. Initial reports suggesting a crash were confirmed by ISRO chairman K. Sivan, stating that "it must have been a hard landing". However, it contradicted initial claims from anonymous ISRO officials that the lander was intact and lying in a tilted position. 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 2019. The LRO flew over again on 14 October 2019 under more favourable lighting conditions, but was unable to locate it. The LRO performed a third flyover on 10 November 2019. 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 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 (6058 to 525 km/h). 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), 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, polarity related software error, 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, though it managed to impact relatively near the intended landing site. The complete official report has not been made public. Vikram's impact site was located at 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. 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. The spacecraft shattered upon impact, with debris scattered over almost two dozen locations in an area spanning kilometres. The crash site was later named Tiranga Point after the Chandrayaan-3 landing.
=== Aftermath of failed landing attempt === 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 and RTI queries seeking it were denied by ISRO citing section 8(1) of the RTI Act. 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 chairman K Sivan and what they claimed is the top-down leadership and working culture of the organisation. 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.