Monday, June 15, 2015

Nocturnal Contact with Philae Lander

The surface of Comet 67P/Churyumov-Gerasimenko seen by Philae after the landing. Credit: ESA/Rosetta/Philae/CIVA

The Philae lander reported back on 14 June 2015. From 23:22 to 23:26 CEST, the lander sent some data packets that are now being evaluated at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR). "But this time, the connection to the lander was relatively unstable," says DLR Philae Lander Project Leader Stephan Ulamec. On 13 June 2015, the lander woke up for 85 seconds for the first time after a nearly seven-month hibernation and sent the first regarding its condition. The data acquired during the second contact confirms that Philae, which is on the surface of Comet 67P/Churyumov-Gerasimenko, is in good condition and ready for operations. Now, the trajectories of the Rosetta orbiter will need to be adapted to allow longer contact times with Philae.

There is now sufficient energy and a temperature that is not so low, so Philae is currently receiving at least three hours of sunlight per comet day, which supplies it with energy. Until now, the engineers had been expecting only 1.3 hours of illumination. Before the team at the DLR Lander Control Center can command Philae, which is about 304 million kilometres away from Earth, stable and long duration connections to the lander must be established. Only then, can the prepared procedures for the scientific work with its 10 instruments be uploaded and the next experiments begin.

The order in which the instruments will be activated will be determined once Philae's health has been fully analysed. "First, the non-mechanical instruments will be used – that is, instruments that do not drill or hammer," explains Ulamec. In the forefront will be those instruments that consume little energy and also send only small amounts of data to Earth. With the awakening of Philae, it could be possible to do research on a comet on site while it becomes active on the way to the Sun for the first time.

Philae’s memory has stored over 8000 packets of additional status data, but it is unclear from when in recent days they were recorded.

Engineers at the Lander Control Centre have determined that Philae is already being exposed to sufficient sunlight to heat it to an acceptable operating temperature and to generate electricity.

“Power levels increase during the local ‘comet day’ – the part of the about-12 hour comet rotation when Philae is in sunlight – from 13 W at comet sunrise to above 24 W,” notes ESA’s Patrick Martin, Rosetta Mission Manager. “It needs at least 19 W to switch on the transmitter.”

The telemetry downloaded covered the lander’s status for a full night–day cycle of the comet, which is helping ground teams to understand how the Sun is shining on the lander. The solar panels appear to be receiving power for over 135 minutes in each illumination period.

“While the information we have is very preliminary, it appears that the lander is in as good a condition as we could have hoped,” Ulamec says.

The main task now for all the mission partners – ESA for Rosetta operations and DLR and France’s CNES space agency for lander operations and science, respectively – is to determine how to optimise Rosetta's orbit so as to facilitate contact and enable new science investigations.

Credit: DLRESA

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