In a media briefing held at ESOC today, ESA confirmed "Philae" lander is alive and operational after three touchdowns on Comet 67/P, located some 511 million kilometers away from Earth. First analysis of the touchdown data suggests that the lander bounced twice before settling on the surface of the comet. The lander remains unanchored to the surface, but the instruments are running and are delivering images and data.
After first touchdown which happened at 15:34 UTC on November 12 (confirmed at 16:02 UTC), a clear strong signal was received, with some breaks. Lander telemetry stabilized at about 17:32 UTC and communication with the surface was maintained until the link to the orbiter was lost at 17:59 UTC due to Rosetta's orbit; this was about an hour earlier than predicted for the target landing site (most likely due to local horizon interference).
The following image was taken 40 seconds before the first touchdown.
Later on November 12, after analysing lander telemetry, the Lander Control Centre (in Cologne) and Philae Science, Operations and Navigation Centre (SONC, Toulouse) reported:
- There were three touchdowns at 15:34, 17:25 and 17:32 UTC; in other words, the lander bounced
- The firing of the harpoons did not occur
- The primary battery is working properly
- The mass memory is working fine (all data acquired until lander loss of signal at 17:59 UTC were transmitted to the orbiter)
- Systems on board the lander recorded a rotation of the lander after the first touchdown. This is confirmed by ROMAP instrument data, which recorded a rotation around the Z-axis (vertical).
The lander did receive some power from the solar panels on Wall No. 2, but it appears that parts of the lander were in shadow during the time that last night's surface telemetry were being transmitted, ESA explained on the mission blog.
During the second lander-orbiter communication slot, which ran from 06:01 UTC until 09:58 UTC this morning, "We had a perfect pass; the radio link was extremely stable and we could download everything according to the nominal plan," Rosetta Flight Director Andrea Accomazzo added.
Teams are still working to confirm the location and the overall power and thermal situation on board. Nonetheless, the lander appears to be performing well at this time.
Philae is most likely on the edge of the chosen landing site, as shown on the image below.
A re-bounce suggests there was a higher strength material where the first touchdown was made. "This was really a surprise," OSIRIS manager said. "We also see stuff shining through the dust."
The following is Philae's first image from the comet surface after it stabilized.
Philae is now positioned almost vertically to the comet which, unfortunately, means it has low source of sunlight needed for batteries to recharge. The lander receives about 1 – 2 hours of solar energy, instead of expected 6 – 7.
As it is, with limited sunlight and questionable battery recharging, the team will try to optimize battery consumption and recharging. The drill operations are on hold for now.
Philae was designed to enter hibernation mode when the battery drains, and if this happens it is possible it might "wake up" once there is sufficient amount of light from the Sun. The team does dare to expect this to happen, though.
The next operational period of the lander is expected later today and the next media briefing with updates is scheduled for 13:00 UTC tomorrow (November 14).
Today's full media briefing is embedded below (skip first 18 minutes):
Kudos to flight dynamics team for extreme precision and amazing job!
Tomorrow is another day for Philae, 2015 is a year for Rosetta as it follows the comet around the Sun.
Featured image credit: ESA/Rosetta/Philae/CIVA
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