The 3rd of November 1970 was scheduled to be a routine monthly maintenance shutdown. The East Auxiliary #2 mirror was being lowered down the telescope when its hoist cable slipped off of the drum. The carriage raced down the tunnel incline about 30-meters before impacting the main #2 mirror carriage! The East Auxiliary’s 0.9-m aluminum mirror broke free of its mounting and fell another 5-meters onto the main #2 carriage. The 1.6-m main imaging mirror was seen to “jump about 2 inches”. When the mirror settled back into its support, the clips at the mirror edge broke a roughly 15-cm round chip from the front edge (Figure 11).
Saturn's moon Daphnis up close
Impact on the comet's surface occurred 14.5 hours after its descent manoeuvre; the final data packet from Rosetta was transmitted at 10:39:28.895 UTC (SCET) by the OSIRIS instrument and was received at the European Space Operations Centre in Darmstadt, Germany, at 11:19:36.541 UTC. The spacecraft's estimated speed at the time of impact was 3.2 km/h (2.0 mph; 89 cm/s), and its touchdown location, named Sais by the operations team after the Rosetta Stone's original temple home, is believed to be only 40 m (130 ft) off-target. The final image transmitted by the spacecraft of the comet was taken by its OSIRIS instrument at an altitude of 20 m (66 ft) about 10 seconds before impact, showing an area 0.96 m (3.1 ft) across. Rosetta's computer included commands to send it into safe mode upon detecting that it had hit the comet's surface, turning off its radio transmitter and rendering it inert in accordance with International Telecommunication Union rules.