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
E-mail:lkeller@ithaca.edu
Office:264 Ctr for Natural Sciences
Ithaca, NY 14850

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Preparing for astronomy with NASA's newest airborne observatory

Posted by Luke Keller at 9:05PM   |  Add a comment
One of the electronics patch panels for interfacing instruments on SOFIA.

We repeated last night's tests of the FORCAST - TA interface, controlling the chopping secondary mirror. No noise! When we use the on-board power source, the return signal from the telescope responding to our chopping signal looks very clean. Thanks to the telescope team for solving this problem!

We learned some important protocol today regarding use of the aircraft for instrument testing. To insure that the continuing modifications of the aircraft are not compromised or interrupted, and to maintain safety standards, any people or equipment entering the aircraft must do so with a specific plan that is submitted in writing to the DAOF team prior to the activities. A DAOF-certified person must do all of the interface work (e.g. even plugging power cords into the sockets on the aircraft) and all tests and results must be documented. This is to insure that the aircraft is left in exactly the same state as when we entered. Any tools or equipment we bring onto the aircraft must be logged in and out to insure that nothing is left behind that might interfere with the aircraft modifications, maintenance, or safe operation. We're not used to this kind of controlled environment back in Ithaca, but it makes good sense and we're learning the routine.


Posted by Luke Keller at 9:04PM   |  Add a comment
Working on getting FORCAST electronics connected to SOFIA telescope electronics.

During the evening we installed the FORCAST electronics and computer on the aircraft and spent about 3 hours testing the interface that allows FORCAST to control the SOFIA telescope and chopping secondary mirror. This mirror system allows us to repeatedly "chop" (switch) between blank sky and our object of interest during astronomical observations so that we can subtract the considerable infrared background from the sky, telescope, and instrument. We need FORCAST to initiate chopping patterns so that it can synchronize the image exposures with the movements of the telescope mirror. The test was successful; we sent a signal to the telescope control system and verified that the mirror was responding properly. But we also measured a lot of noise on the return signal, which we suspected might degrade our data. We determined that the noise was coming from the aircraft and not our electronics, but the telescope operators could not find the noise source in their system. Hmmm...strange. We called it a night, but still had no explanation for that electronic noise.


Posted by Luke Keller at 8:57PM   |  Add a comment
Page from a 747 pamphlet describing emerguency procedures.

In order to get a NASA security badge allowing us to move and work unescorted at Site 9 and in the SOFIA hangar, we have to take several safety training classes to learn about chemicals and lab equipment that we will use or that others use at the facility. For SOFIA these include acetone (the main ingredient in nail polish remover, though we use it to clean metal parts and tools), isopropanol (rubbing alcohol), and hydrazine (jet fuel on steroids). The first two are mainly lab fire hazards, though ingesting them or breathing their fumes is a bad idea too, but hydrazine is nasty stuff. It is very volatile (low ignition temperature and reactive with many common materials) and also very poisonous. Its volatility and reactivity make it an excellent rocket fuel (no oxygen necessary!) and it is the fuel used in one of the other aircraft housed with SOFIA at Site 9. We just need to know what to do if there is a hydrazine leak. Get ready...this IS rocket science, but it's easy...if you smell it, evacuate the building immediately to a position upwind. Oh, and by the way, if you can smell it (smells like amonia, apparently) you've already had an unsafe dose. Yucky. There is a hydrazine alarm system separate from the fire alarm system. We were all glad to hear that they have never had a hydrazine leak at Site 9. Other day-to-day hazards include heavy equipment lifting with various kinds of cranes, cryogenic liquids (nitrogen and helium to cool the infrared instruments including FORCAST), and compressed gasses like nitrogen and helium. Except for hydrazine, we work with these routinely in the labs at Ithaca College and Cornell, but it's good to have a refresher course and see how they do things at NASA. That's going to be a recurring theme, I think: learning how they do things at NASA!

And then there are the hazards associated with air travel. We spent the rest of the day learning how to use oxygen masks in the event of a cabin decompression (SOFIA will fly to altitudes between 41,000 and 45,000 feet), how to fight fires on an aircraft, and how to evacuate a 747 after an emergency landing. The oxygen masks we'll use are not the so-called "dixie cups" that pop out of the ceilings of commercial flights, these masks actually allow you to move around and do something useful like fight a fire or prepare for an emergency landing. There are no flight attendants on SOFIA (or rather WE'RE the flight attendants) so we rehearsed opening the aircraft doors and learned the locations of fire extinguishers and survival kits. We also learned how to deploy the evacuation slides/liferafts, though I was disappointed that we didn't actually use one. Seems it costs many thousands of dollars to stuff one of those slides back into the door! It was a long day of seminars and demonstrations, but I'm glad to have the training and to have met so many people that I will be working with over the next few years.

 

 


Posted by Luke Keller at 8:32PM   |  Add a comment
Image of the starship Enterprise from the Star Trek series.

...or at least where few from Ithaca have gone before. I traveled from Ithaca to LAX with Terry Herter and Joe Adams. We drove from Los Angels north to Palmdale--about an hour and a half--and checked into a hotel near DAOF. There we met with George Gull, Justin Schoenwald, and Chuck Henderson, all Cornell engineers working on FORCAST. Reasoning that we will be spending a lot of time here in Palmdale over the next few years, we began explorations of restaurants and entertainment with a quick dinner and a visit to the local movie theater to watch the new Star Trek movie. Yes, we're Trek fans. I'm probably an astronomer partly thanks to watching the original series reruns as a kid in the 1970;s. Great movie and a fun start to the week's work on SOFIA.


Posted by Luke Keller at 8:25PM   |  Add a comment
The SOFIA aircraft parked in its hangar at the NASA Dryden Aircraft Operations Facilty in Palmdale, CA.

NASA Dryden Aircraft Operations Facility (DAOF Site 9), Palmdale, CA

We're headed to DAOF to attend safety training classes and to have a Technical Interchange Meeting (TIM) with NASA and USRA people that we will be working with. If you haven't noticed already (or heard rocket science jokes) working on a NASA project involves learning lots of abbreviations and acronyms (I'm compiling a dictionary on the 'About' Page of this blog).


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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