Friday, June 7, 2013
Quick SOFIA update: The telescope power problems are now fixed, but not in time for last night's flight. Rob Lewis got to see his software development work in action as we analyzed data from the previous flight, and he got to poke around SOFIA, but unfortunately he did not get to fly. The next flight is scheduled for Tuesday, June 11, but Rob is on his way to a new life and job in Seattle so he'll have to fly another time. Meanwhile IC physics major, Martin Garay MacLean, is preparing for the journey to Palmdale to participate on the June 11 flight. We're all working hard to get FORCAST tests finish since we are scheduled to begin the first cycle of general observer observations as soon as our tests are complete. That means flight activity will transition from mostly testing new equipment to mostly using that equipment for astronomy! It's what we've been working towards for over ten years!
Now back to grisms!
A grism is a combination of a diffraction grating (an optical filter with microscopic parallel lines on it that disperse light into it's constituent spectrum of colors) and a prism, which does the same thing with a wedge of optical material. Hence the name, GRating + prISM = GRISM. Grisms are very useful to us because they allow us to transform the FORCAST infrared camera into a spectrometer by simply replacing a filter with the grism. No other optical alterations are necessary. Since FORCAST has many options for filters, allowing us to record images in many different infrared "colors", we can put grisms in place of a few filters and significantly increase the utility of the instrument for many different astronomical observations. Images tell us what an object looks like, how its brightness changes with position on the sky, and where it is relative to other objects int he same region of sky. Combinations of images taken through different filters can allow astronomers to infer physical characteristics of objects, but splitting the light into a spectrum adds even more detail. The combination of images and spectral measurements allow us to learn about the temperature, density, and chemical composition of the objects we observe.
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