Note: In this – hopefully – daily series of postings I’ll highlight one of the many instruments on board of the Rosetta spacecraft and the Philae lander.
Hello Space Geeks, this is the second posting of this series and I’d like to talk about the OSIRIS system for now. OSIRIS was already switched on a few days ago (along with ALICE, more in the first posting of this series) so I’m a bit in a hurry to catch up with all the already working instruments before time runs out :-)
From ESA’s OSIRIS website:
OSIRIS (Optical, Spectroscopic, and InfraRed Remote Imaging System):
is a telephoto and wide-angle camera, which will take high-resolution images in different spectral bands for the characterisation of the nucleus and its surrounding environment.
Principal Investigator (PI): Holger Sierks, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany.
Co-Investigators: Stubbe Hviid, Jörg Knollenberg, Ekkehard Kührt, Institute of Planetary Research, German Aerospace Center, Berlin, Germany.
And that’s how the beauty looks like:
OSIRIS has wide- and narrow-angle optics and will be used to take high-resolution pictures of the comet in the visible and infrared-spectrum. This camera will become very important as soon as it comes to finding a proper landing site for Philae.
Keller et al. 2007, “OSIRIS – The Scientific Camera System Onboard Rosetta“, has all the juicy details about this shiny piece of technology, but don’t be disappointed: The resolution is “only” 2048 x 2048 pixels (4 Megapixels) but take this into account: Rosetta is now in space for 10 years and back, when OSIRIS was built, this was a huge deal! Also note that the CCD-sensors in space have to cope with a lot of nasty radiation, stuff which your average consumer camera will never encounter on earth. This puts constraints and limits on how you build the sensors; a broken pixel can’t be repaired and so you better go with a sturdy, boring, conservative system which is known to be working than with something shiny new which was probably never deployed to space before. I know, I wouldn’t take the risk :-)
Anyway, Rosetta will get really close to 67P in the final phase, so 4 MP with a 2.20 x 2.22° Field of View from the narrow-angle camera will give a pretty decent picture – one pixel on the picture will present 2 x 2 cm!
But it’s not only the size, what matters, but also what’s else in this camera. It comes with lot’s of different filters of various colors to improve contrast and with several IR- and UV-filters to lock at specific features only visible in these spectra. It’s often so that if you only want to see the infrared-portion of an image that you need to block out all other colors because they’re so much brigther (in intensity) than what you really want to look at (photographers call this “oversaturation“).
So. Lots of features to look at – lots of filters. I won’t go too much into detail, the people from the Planetary Society already did a really great job at explaining all these.
OSIRIS already caught first light in the commissioning phase before hibernation, but we still have to wait for the first pixels from 67P. In the meantime just look at this picture of M42, taken with the narrow angle camera (NAC).