The Philae lander

The Rosetta mission includes a landing module called Philae. It is a very complex device that communicates with Earth through the orbiter. It has a volume of just under 1 cubic meter and a mass of 100 kilograms (220 pounds), but its weight is only 1 gram in the low gravity field of the comet nucleus. It contains a variety of instruments, including a set of six panoramic cameras,  CIVA-P. The instrument CIVA-M has two microscopes, one for the visible light and the other for the infrared, for analysis of the dust collected by the SD2 instrument. The camera ROLIS recorded images of the nucleus during the descent of the lander. APX-S is a high-energy spectrometer for X-rays, a particles and protons that were supposed to analyze the atomic composition of the particles irradiated by its source, but it does not provide information because its window did not open.
The sample collection is provided by the instrument SD2 (Sample and Distribution Device), a driller that only managed to recover a few cubic millimeters of soil but which also collected the floating dust. COSAC includes a mass spectrometer and a gas chromatograph to measure the atomic mass of elements after the samples collected by SD2 have been evaporated or have been sucked directly. Ptolemy, which was to perform the same analysis of light elements and measure their isotopic ratios, ultimately was not activated because it would have consumed too much energy.

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L’atterrisseur Philae et ses instruments

Crédit : ESA/ATG medialab

The CONSERT instrument communicates with the almost identical instrument placed on the orbiter. The physical, thermal and mechanical properties of the soil are evaluated by the MUPUS instrument while SESAME studies the propagation of waves through the surface between the legs of the lander, and the properties of the dust raised during the impact. Finally ROMAP is a magnetometer for measuring the possible magnetic field of the comet.

L’atterrisseur Philae - 2

Le départ de Philae vu de l’orbiteur


Philae broke off from the orbiter without a problem on November 12, 2014, an important day. It arrived after a seven-hour travel on the ground of the nucleus close to the intended place, another great performance of celestial mechanics. But the device that was supposed to tackle it on the ground did not work, as well as the harpoons that were to hook it. So it rebounded, and traveled almost a kilometer, bouncing twice on the ground before it got stuck in a very unfavorable location. It nevertheless provided extremely interesting data during the lifetime of its batteries, about 60 hours. Then no more news until June 13, 2015, when a short contact could be established with the orbiter, the batteries being partially recharged by the solar panels despite a very sparse sunshine. Since then it has been mute.

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Le site final de Philae, avec une image prise par sa propre caméra montrant un de ses trois pieds

Crédit : ESA/Rosetta/Philae/CIVA