The first collection of cometary dust is initiated for the COSIMA mass spectrometer on-board Rosetta

The COSIMA instrument on board the Rosetta spacecraft will provide the first high resolution mass spectra of grains collected close to a comet. The imaging system of COSIMA, COSISCOPE, built by Institut d’Astrophysique Spatiale, will locate and characterize the collected cometary grains.

 The COSIMA instrument is managed by the Max-Planck Institute for Solar System Research (Göttingen, Germany). The dust densities expected at more than 3 AU (450 million km, the present distance from the sun of comet 67P/ Churyumov-Gerasimenko) are low, and the first three targets (10 mm x 10 mm each) have been exposed for one month starting August 10. Identifying collected cometary grains is a critical task. For this purpose, COSIMA images the targets before and after exposure with an imaging system, COSISCOPE, built by Institut d’Astrophysique Spatiale. Two LED provide grazing incidence illumination from opposite directions so as to identify small grains sticking out of the smooth and porous “metal black” layer (a few 10 µm in thickness) which covers the first exposed targets (see Figure). The COSIMA science team will select the regions to be placed under the ion gun of COSIMA so as to obtain mass spectra of cometary grains on the basis of images obtained by COSISCOPE after exposure in the direction of the comet. 

Image of the first target obtained before cometary dust exposure in late July 2014 by the COSISCOPE camera. The grazing illumination comes from the right and the resolution of the image is 14 µm / pixel. The collecting area (10 x 10 mm, center left) is constituted of a gold plate covered with a thin layer (30 mm) of gold nanoparticles (“gold black”). As demonstrated by this image, the target is nearly featureless before exposure, so that collected cometary grains should be relatively easy to identify.

Crédits: ESA/Rosetta/MPS pour l’équipe COSIMA/ MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

Contacts at IAS: Yves Langevin @ ias.u-psud.fr , Pascal Eng @ ias.u-psud.fr

Link to the corresponding post on the ESA Rosetta blog: Cosima reaches for dust