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.
Wednesday, June 5, 2013
Sometimes the scientific process takes an unexpected turn and tonight was one of those times. Takeoff for our third commissioning flight on SOFIA was at 7:35 PM Pacific time. The flight manifest included NASA scientists and engineers, the Ithaca College and Cornell University FORCAST team members, journalists from an LA-area newspaper, and four public school science educators on board as part of the SOFIA Airborne Ambassador outreach program. Our flight plan took us on a tour of the american west and mid-west at an altitude of 39,000 feet and we were making good progress with tests of our camera when the telescope power system bagan to show low voltage levels. After only half of our flight, and just before our scheduled spectroscopic tests, the mission director made the decision to return to the SOFIA base in Palmdale since flying with the telescope underpowered could damage the system. Fortunately Casey Byrne got a little time at the controls of the data analysis computer to see the culmination of his work at IC over the past two years. He also spent some time with the Airborne Ambassadors, answering questions and explaining the work we were doing on the flight.
IC student, Rob Lewis (Physics '13) arrived in time to watch SOFIA takeoff and will pick up where Casey left off on this Thursday's flight. We're optimistic that the power system will be back to 100% and Rob will complete the tests we had scheduled for tonight.
Next post: What's a GRISM?
Tuesday, June 4, 2013
Friday, January 14, 2011
Seems it is time to change the subtitle of this blog from "Preparing for astronomy..." to "Doing astronomy with SOFIA." I am happy to report the transition of SOFIA from a flying telescope (amazing as that may be) to an observatory that can support a wide variety of astronomy and planetary science research projects. That was the goal of the Short Science series of flights that began in late November. It's called Short Science because the science team selected astronomical investigations and observations that required relatively short exposure times and would yield new research results that we could share with the public within weeks or months of the flights. It may sound like a long time to wait, but astronomical observations routinely require months of data processing and analysis.
After taking a break for the Thanksgiving holiday, we were back on the line with SOFIA on the night of Monday, November 30, rehearsing observing plans for SOFIA's initial science flight. This flight, the first of a three-flight series that ended in early December was the first were the primary goal was to conduct new astronomical observations that take advantage of the unique capabilities of SOFIA and contribute to new knowledge in the fields of astronomy and planetary science. The initial science flight (ISF) went very well and NASA held a press release just hours after we landed to announce the good news. Another goal of the ISF, and the subsequent two science flights, was to make infrared images that would demonstrate to the general public and the astronomical community that SOFIA is working well and producing interesting and useful data. The picture we chose for the first "science" image is a FORCAST view of the central massive star forming region in the Orion Nebula (M42). The two-color composite (false color image) uses red to indicate data taken through a 37 micron filter and green to indicate data taken through a 19 micron filter. Though ground-based telescopes are capable of imaging at 19 microns, such observations are highly dependent on excellent atmospheric conditions. Images like this will be routine on SOFIA. The 37 micron image is only possible from SOFIA since no existing or planned telescope anywhere (even in space) has instruments that operate in the 28 - 40 micron range of the infrared spectrum.
It was exciting to fly on the three Short Science flights for many reasons, but one in particular for me was the fact that we gathered data for so many different astronomical studies. We now have images of a comet that was in the neighborhood late last year, the planet Jupiter (which we revisited in much more detail than we did for the First Light images), a "starburst galaxy", and several regions of star formation in our own Milky Way galaxy. The exciting thing about the images we got is that they have yielded very high quality data. The science team now has unique information for each of those objects and we are working very hard on data analysis over the next weeks and months to publish and share the results with the astronomical research community and the general public.
After we'd had a chance to work on data analysis for a few weeks, NASA and USRA released our new, larger and (I think) even more spectacular image of the Orion star forming region. I also made a short movie comparing visible light and infrared images of this region of space, which Terry Herter (FORCAST principle investigator) presented with the first scientific results from SOFIA this week at the meeting of the American Astronomical Society in Seattle, Washington. We're looking forward to sharing more images and results soon.
Stay tuned: The next SOFIA flight series begins later this spring with observations using the German Receiver for Astronomy at Terahertz Frequencies (GREAT, which is one of my favorite SOFIA acronyms). GREAT is an extremely high frequency radio receiver. After the Short Science flights with GREAT, we will bring FORCAST back into service for a second series of science flights proposed by many scientists from the general astronomical community.
Sunday, November 21, 2010
On Thursday, November 18, we took off for the last of the observatory characterization flights. We tested several techniques that we will use to get the first science results in early December. The next time we fly we'll be conducting observations for new astronomical research.
The tests went very well. Follow this link to a short movie of an infrared image of a star taken with FORCAST while in flight. You will notice that the image of the star is two or three pixels across and moves around very quickly. The movie is actually five copies of a two-second clip for a total of ten seconds. The movie was recorded with FORCAST at a frame rate of 400 Hz (Hertz, or frames per second, see my previous post for a few more details). The purpose of this test was to understand telescope vibrations (and how they affect image motion) so that they can eventually be removed or at least minimized. Minimizing vibrations will improve the image quality since most objects we observe with SOFIA will be very faint so we will use long exposure times, which combined with the motion of the telescope will produce fuzzier images.
This and other tests went very well. Our final test included observations of the Orion Nebula (M42 for you astronomers), a region where stars are forming about 1500 light years from Earth. The data look so good that we expect to be able to use them for new astrophysics studies. In other words, SOFIA is ready for astronomy! [Images to come in a future post.]