Comets eject gas and dust into space. Primarily, this takes place on the areas of the comet's surface exposed to direct sunlight. In mid-March, from a distance of 75 kilometres, the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) on board the Rosetta orbiter acquired images of an extraordinary phenomenon occurring on Comet 67P/Churyumov-Gerasimenko.
Although from 28 March 2015, following difficulties with its star trackers and navigation system, the Rosetta orbiter is now following a new and more distant trajectory around Comet 67P/Churyumov-Gerasimenko, the team at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Lander Control Center (LCC) will begin listening again for signals from the Philae lander at 02:00 CET on 12 April 2015.
Perhaps it is still too cold for the Philae lander to wake up on Comet 67P/Churyumov-Gerasimenko. Maybe its power resources are not yet sufficient to send a signal to the team at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) Lander Control Center.
It would be very lucky if a signal were to be received from Rosetta's Philae lander at 05:00 CET on 12 March 2015. The lander finally came to rest in a rather shaded location on Comet 67P/Churyumov-Gerasimenko and it needs to receive sufficient energy before it can wake up and begin communicating.
On 14 February 2015, the Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) on the Rosetta spacecraft observed the surface of comet 67P Churyumov-Gerasimenko with the Sun directly behind it, so the only shadow seen in the image is that of the photographer, the orbiter itself.
Comet 67P/Churyumov-Gerasimenko could lose up to 20 metres of surface material from its previously unilluminated south side when it heats up, starting in May 2015. The increasing heat as the comet approaches the Sun will trigger this 'diet', during which gases and solid materials will be ejected into space.
The Lander Control Center (LCC) at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is quiet. While the Philae lander is hibernating on the surface of Comet 67P/Churyumov-Gerasimenko, the control room team are able to take a break. Philae' s battery finally ran out at 01:36 CET on 15 November 2014, following a triple landing and more than 56 hours of scientific work.
It is still early days for the scientists involved in evaluating data that the 21 instruments on board the Rosetta spacecraft and its Philae lander have transmitted back to Earth. But preliminary results from seven of the 11 instruments on the Rosetta orbiter have been published in a special edition of the journal Science.
Just three kilometres from Comet 67P/Churyumov-Gerasimenko, the ROsetta Lander Imaging System (ROLIS) acquired images of the 'head' and underlying 'body' of Comet 67P. Immediately below is the planned landing site, Agilkia; in the top right of the field of view, one of the landing gear feet can be seen as the camera on the underside of the lander approaches the comet's surface at walking pace.
A short but significant 'thud' was heard by the Cometary Acoustic Surface Sounding Experiment (CASSE) as Philae made its first touchdown on Comet 67P/Churyumov-Gerasimenko. The two-second recording from space is the very first of the contact between a man-made object with a comet upon landing.
The MUPUS instrument, one of 10 experiments on the Philae lander that touched down on comet 67P/Churyumov-Gerasimenko encountered very hard material with a temperature of about minus 170 degrees Celsius – probably rich in ice.
Before going into hibernation at 01:36 CET on 15 November 2014, the Philae lander was able to conduct some work using power supplied by its primary battery. With its 10 instruments, the mini laboratory sniffed the atmosphere, drilled, hammered and studied Comet 67P/ Churyumov-Gerasimenko while over 500 million kilometres from Earth.
Update – the Philae lander entered sleep mode at 01:36 CET on 15 November 2014.
The Philae lander performed about 56 hours of continuous scientific measurements on the surface of Comet 67P, but by 01:15 CET on 15 November the energy state of the lander became so low that the engineers assumed that Philae would go into sleep mode during the night.
Not only was it the first ever landing on a comet – it was also the second and third. Since 18:32 CET on 12 November 2014, the Philae lander has been on the surface of Comet 67P/Churyumov-Gerasimenko, performing experiments and returning data.
Rosetta's lander Philae is safely on the surface of Comet 67P/Churyumov-Gerasimenko, as these first two CIVA images confirm.
The image shows comet 67P/CG acquired by the ROLIS instrument on the Philae lander during descent on Nov 12, 2014 14:38:41 UT from a distance of approximately 3 km from the surface.
On 12 November 2014, the Philae lander touched down on the surface of Comet 67P/Churyumov-Gerasimenko. This is the first time a man-made device has landed on a comet and collected data directly from the surface.
In 1969, Svetlana Gerasimenko and Klim Churyumov discovered the comet that the Philae lander will descend to on 12 November 2014.
The Philae lander on board the Rosetta spacecraft has been en route to its destination, Comet 67P/Churyumov-Gerasimenko, since 2 March 2004. On 12 November 2014, it will be released from its mother craft at an altitude of 22.5 kilometres above the comet and – if everything goes according to plan – will touch down on the surface of the comet about seven hours later.
Egyptian history has been explored, new words invented and appropriate comparisons sought for; a total of about 8300 suggestions for Philae’s landing site on Comet 67P/Churyumov-Gerasimenko were received at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), the French Space Agency (Centre National d'Etudes Spatiales; CNES) the Italian Space Agency (Agenzia Spaziale Italiana; ASI) and the European Space Agency (ESA).