3. March 2015

Lots of light and lit­tle shad­ow on 67P Churyu­mov-Gerasi­menko

Overflight view
Over­flight view

Overflight view

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 in the Imhotep re­gion with the Sun di­rect­ly be­hind it from an al­ti­tude of six kilo­me­tres. The im­age res­o­lu­tion is 11 cen­time­tres per pix­el. The or­biter’s shad­ow is vis­i­ble as a dark rect­an­gu­lar patch in the low­er part of the im­age.
Above the Imhotep re­gion

Above the Imhotep region

The Roset­ta obiter passed over the Imhotep re­gion dur­ing its close fly­by over comet 67P Churyu­mov-Gerasi­menko.
Keep­ing its dis­tance af­ter the fly­by
Image 3/4, Credit: ESA/Rosetta/NAVCAM - CC BY-SA IGO 3.0.

Keeping its distance after the flyby

On 15 Febru­ary 2015, the nav­i­ga­tion cam­era on board the Roset­ta or­biter cap­tured im­ages of comet 67P Churyu­mov-Gerasi­menko from a dis­tance of 125 kilo­me­tres. Among oth­er things, the Imhotep re­gion is shown over which the or­biter had passed just one day pre­vi­ous­ly – on 14 Febru­ary 2015 – at an al­ti­tude of just six kilo­me­tres.
RO­LIS cap­tures Comet 67P Churyu­mov-Gerasi­menko
Image 4/4, Credit: SA/Rosetta/Philae/ROLIS/DLR .

ROLIS captures Comet 67P Churyumov-Gerasimenko

This im­age was ac­quired by the Roset­ta Lan­der Imag­ing Sys­tem (RO­LIS) on board the Phi­lae Lan­der from a height of ap­prox­i­mate­ly 40 me­tres, be­fore the first touch­down. The res­o­lu­tion is four cen­time­tres per pix­el.

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. "An image with this arrangement of the light source and camera really reveals the differences in brightness on the comet's surface. As there are no shadows, this difference must be due to the scattering of the light by the dust particles across the comet's surface," explains Ekkehard Kührt, a cometary researcher at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) and a scientist on the OSIRIS team. "This means, for instance, that it is possible to calculate the sizes of the dust particles spread across the surface, even though these are far below the camera's resolution threshold." The image was acquired as the orbiter passed over the comet at an altitude of just six kilometres.

Smooth plains and rugged areas

Measuring 228 by 228 metres, the terrain shows abruptly terraced steps separating flat ground from fissured areas. "The camera system is looking straight down from above, which makes estimating the actual height of the terraces quite difficult." Scientists have given this region, which is situated not far from the equator of the larger part of the comet nucleus, the name Imhotep. Unfortunately, it is on the opposite side to Philae's landing site, which means the scientists were denied the possibility of discovering the landing craft's location during this overflight. Rosetta's shadow is visible as a dark patch in the lower half of the image. The adjacent surface of the comet is brighter than the rest, as here the comet, the orbiter and the Sun are aligned precisely along the same axis.

The low-altitude overflight of 67P Churyumov-Gerasimenko did not last long; by 17 February 2015, the Rosetta orbiter had already reached a distance of 253 kilometres from the comet, before returning to within 76 kilometres on 25 February. It re-examined the surface from an altitude of 110 kilometres on 28 February.

Up close to the comet

The OSIRIS image of 14 February – the day the orbiter came closest to the comet – has a resolution of 11 centimetres per pixel. So far, only the Rosetta Lander Imaging System (ROLIS), installed on the bottom of the Philae lander, has been able to acquire higher resolution photographs of the comet's surface, taking images at a resolution of four centimetres per pixel as it descended towards 67P Churyumov-Gerasimenko. Scientists are currently analysing photographs of the comet's surface, which were taken immediately after landing using artificial light. It is hoped that these images, which have a resolution of less than one millimetre per pixel, will provide definitive information on the celestial body’s fine structure. Preliminary results are expected in April 2015.

The mission

Rosetta is an ESA mission with contributions from its member states and NASA. Rosetta's Philae lander is funded by a consortium headed by DLR, the Max Planck Institute for Solar System Research (MPS), CNES and the Italian Space Agency (ASI).

The OSIRIS camera was built by a consortium led by the Max Planck Institute for Solar System Research (Germany), in collaboration with the Center of Studies and Activities for Space (CISAS) at the University of Padua (Italy), the Laboratoire d'Astrophysique de Marseille (France), the Institute of Astrophysics of Andalusia (IAA-CSIC) (Spain), ESA's Scientific Support Office, the National Institute for Aerospace Technology (Instituto Nacional de Técnica Aeroespacial) (Spain), the Technical University of Madrid (Universidad Politécnica de Madrid) (Spain), the Department of Physics and Astronomy at Uppsala University (Sweden), and the Institute of Computer and Network Engineering at the Braunschweig University of Technology (Germany). OSIRIS was funded by national agencies in Germany (DLR), France (CNES), Italy (ASI), Spain (MEC) and Sweden (SNSB), as well as ESA's Technical Directorate.

ROLIS was developed by the DLR Institute of Planetary Research in Berlin.

  • Manuela Braun
    Ed­i­tor HR
    Ger­man Aerospace Cen­ter (DLR)
    Cen­tral HR Mar­ket­ing
    Telephone: +49 2203 601-3882
    Münchener Straße 20
    82234 Weßling
  • Dr.rer.nat. Ekkehard Kührt
    Ger­man Aerospace Cen­ter (DLR)

    In­sti­tute of Plan­e­tary Re­search, As­ter­oids and Comets
    Telephone: +49 30 67055-514
    Fax: +49 30 67055-340
    Linder Höhe
    51147 Köln
Images on this topic

Main menu