Luke Keller

Luke Keller

Associate Professor and Chair, Department of Physics and Astronomy

Specialty:Astrophysics, airborne astronomy, spectroscopy, optical instrumentation, natural science general education
Phone:(607) 274-3966
Office:264 Ctr for Natural Sciences
Ithaca, NY 14850


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Preparing for astronomy with NASA's newest airborne observatory

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Posted by Luke Keller at 8:18PM   |  Add a comment
Raytrace diagram showig a grism in the FORCAST filter position dispersing light into an infrared spectrum.

Prior to shipping FORCAST to SOFIA's home at NASA's Dryden Aircraft Operations Facility in Palmdale, California, we are making final adjustments to the instrument, data analysis software, the instrument cart, and the calibration box.

On 19 February, 2009, I travelled to NASA Ames Research Center in Mountain View, CA:

I met with scientists from the SOFIA project today to discuss funding a upgrade to FORCAST that will enable the camera to have a spectroscopy mode. Spectroscopy is the study of the brightness distribution of light throughout a portion of the electromagnetic spectrum. If we replace the FORCAST imaging filters with devices that split light into a spectrum (like a prism splits white light into the rainbow spectrum of visible light colors), we can record the infrared spectrum using the existing camera optics and detectors. Because this spectral mode uses devices installed in the camera filter wheels, switching between imaging and spectral mode is a simple and relatively quick process allowing us to record both images and spectra of an object during a single SOFIA flight.

A little background: Over the past three years I have collaborated with a group of scientists to develop and install a set of devices called grisms that will allow FORCAST to become a spectrograph. Grisms are prisms with a pattern of narrow parallel grooves etched on one facet. The pattern of parallel lines iis called a 'grating' and the combination of that name with 'prism' gives the device its name, 'grism'. The group was led by Kim Ennico at the NASA Ames Research Center near Mountain View, California, and included Tom Green (also at NASA Ames), Dan Jaffe (University of Texas at Austin and my dissertation advisor), Terry Herter and Joe Adams (of the FORCAST team at Cornell University), Casey Deen (Dan's grad student at UT), and me. After designing the optical system, I was primarily responsible for developing software that will allow astronomers to look at the spectra as they gather FORCAST spectral data in flight. Our software will also provide a data reduction pipeline (automatically processing the data after each flight). Ithaca College physics student, Nirbhik Chitrakar, helped with the software design and did most of the coding in IDL (a computer language commonly used in astronomy research).

The initial project was very successful and resulted in a suite of 6 grims, all installed and tested in FORCAST, as well as our data processing and analysis software. The spectroscopy mode needs a lot of work in order to provide a facility class observing mode for SOFIA astronomer. That means a mode that any astronomer using FORCAST can easily use and that is well tested and calibrated to provide the highest quality data in an efficient and easy to use mode. In other words, the instrument works for us and now we need to make it work for everyone else!

In this meeting I presented my proposal and goal to develop FORCAST grism spectroscopy to the level of a facility class observing mode. The Universities Space Research Association has awarded me funding to continue developing FORCAST grism spectroscopy towards this goal.


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