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.

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.]

Today we took off on SOFIA for its second flight devoted 100% to measuring and characterizing the performance of the telescope and camera systems. It was very exciting for me to finally fly after working so long on the project. I was in charge of data quality control during the flight. We spent last week conducting line operations (we call them "line-ops"), using the observatory as if we were in flight but actually sitting on the ground. During the line-ops we practiced controlling the movement of the telescope with computer commands issued from the FORCAST camera. Juergen Wolf and his team from DSI and NASA/Ames also tested their new fine diagnostic camera (FDC), which can take visible light images at several hundred frames per second. For comparison, a movie or video camera usually records images 60 times per second. Why so fast? We wan't to "freeze" the star images, which move around in the telescope and camera viewers due to vibrations of the telescope and aircraft. Taking very fast movies in both visible (FDC) and infrared light (FORCAST) will allow the telescope team to understand in detail how the optical and telescope control systems are working. All of our testing so far indicates that the telescope and cameras are ready to go after a few small adjustments. Our first flight devoted to new astronomy (no more testing!) are scheduled for the week after Thanksgiving. 

Take-off time was 5:00 PM (Pacific Time) on Wednesday, November 10. The flight was scheduled to be 10 hours long, enough time for us to fly from LA to London, but instead we flew a back-and-forth flight plan as they did for the first light flight in May. Here's the flight plan from from last night's flight:

The flight began and ended at DAOF in Palmdale, CA (the white dot at the top of the map). The faint dotted outline in the upper right corner is the coast of southern California and Baja, Mexico. The light blue/green lines are the flight "legs" that add up to the full 10-hour flight plan. Each flight leg is plotted so that SOFIA can observe a particular object in the sky. For this flight the targets were bright stars that we used to test the cameras.

The flight crew including FORCAST team worked hard during the flight. This photo shows the FORCAST team working at the "PI Rack" that contains our camera control computer and the communication system that we use to communicate with one-another during the flight. Everyone wears headphones to reduce noise and enable efficient communication.

It's been a few months since we took the first infrared images with SOFIA and FORCAST. I promised some more detail on how we produced the "first light" images so here it is. Since people can't see infrared light we need a way to display the images from the camera using colors we can see. FORCAST records raw images through filters that pass infrared light of different wavelengths. These filters work just like red, green, or blue filters do in visibile light. When a computer displays a digital image it can be with any color map. A color map is a list of the colors the computer uses when it displays pixels of different brightness in an image. One of the simplest looking color maps is "gray scale"; shades of gray indicate brightness usually with white being brightest and black indicating faintest. But a color map can display brightness variations in an image in any color you like. Here's and image of Jupiter in visible light (color image at right) and in infrared light displayed with a blue color map:

For the first light image of Jupiter we used a red color map to represent infrared light recorded through a 37 micron filter, green to represent infrared light recorded through a 24 micron filter, and blue to represent 5.4 micron light. Here's the result:

Now we add the three images together to get a "false color" image of what Jupiter might look like if humans could see infrared (see www.ithaca.edu/frequent_flyer/first_light/ for more details on interpreting false color images). Note that false color images can represent any measurable quantity. Perhaps the most common false color image you have likely seen is a radar weather map of precipitation, which uses visible colors to represent reflectivity of radar waves (also a form of light that humans can't see) off of rain droplets. Our false color image displays infrared brightness at three different wavelengths. Here's the final result that USRA/FORCAST team member Jim De Buizer created:

The smaller dots in this image are three of Jupiter's moons. Note that we usually measure wavelength in microns (thousandths of a millimeter). We use the symbol 'µm' for microns so 5.4 µm is 0.0054 millimeters. For comparison, the average human hair diameter is about 50 µm.

We're back in Palmdale preparing for more SOFIA flights. We'll do two flights of telescope tests followed by three flights doing new astronomical observations! More updates coming soon.

SOFIA has flown with FORCAST running and returned its very first astronomical images!

I just returned to Ithaca after nearly two weeks helping prepare FORCAST and SOFIA for these first light images. I literally had goose bumps as I watched the airplane land early Thursday morning and then downloaded the data from our infrared camera on-board. I worked at DAOF with SOFIA scientists Jim De Buizer, Bill Vacca, and FORCAST lead Terry Herter all day Thursday to process the data and produce the first light images. After 11 years of work on theSOFIA project (and I'm one of the more "recent" additions to the team!) it was a true thrill to see these images take shape on our computers. My next post will include details of how we processed the data to make the color images. SOFIA's next flights will be devoted 100% to new astronomy research and I'll be flying!

NASA press release

Note on viewing infrared images: Infrared light has colors just as there are colors in visible light, but since infrared light is invisible to humans, astronomers use “false color” images to display infrared views of the universe. In false color images, like those presented here, visible light colors (blue, green, and red) are used as proxies for the brightness in three infrared colors captured by the SOFIA/FORCAST camera system. So the color image you see is a representation of how the object might look if you could see in infrared light. Different physical processes cause emission of infrared light in different infrared colors so the three colors presented in these images indicate differences in physical characteristics like temperature, density, and chemical composition. Finally, it is important to note that in astronomy visible light images often only show us the details on the surfaces of objects while viewing infrared light allows us to look deep into the objects. Using infrared images like those enabled by SOFIA and the FORCAST camera are the only way to remotely look deep into the atmosphere of Jupiter or into the very center of the M82 galaxy. Visible light shows us the tip of the iceberg while infrared light images show us what lies beneath.

Jupiter: Composite (false color) infrared image of Jupiter from SOFIA’s first light. Observations were at infrared wavelengths of 5.4 (blue), 24 (green) and 37 microns (red), made by Cornell University’s FORCAST camera. A recent visible-wavelength picture of approximately the same side of Jupiter is shown for comparison.  The white stripe in the infrared image is a region of relatively transparent clouds through which the warm interior of Jupiter can be seen. (Visible light image credit:  Anthony Wesley)

MORE DETAILS: Composite (false color) infrared image of Jupiter from SOFIA’s first light flight taken at infrared wavelengths of 5.4 (blue), 24 (green) and 37 microns (red), with Cornell University’s FORCAST camera. A recent visual-wavelength picture of approximately the same side of Jupiter is shown for comparison.  The white stripe in the infrared image is a region of relatively transparent clouds through which the warm interior of Jupiter can be seen. Visible light shows us the detailed structure of the surfaces (tops) of the clouds on Jupiter while the infrared image shows us the distribution of different atmospheric components and physical characteristics of material deep under the cloud surfaces. (Visible light image credit: Anthony Wesley)

Galaxy, M82: Composite (false color) infrared image of the central portion of galaxy M82, from SOFIA’s first light flight, taken at wavelengths of 19 (blue), 31 (green) and 37 microns (red). The middle inset image shows the same portion of the galaxy at visual wavelengths.  The infrared image views past the stars and dust clouds apparent in the visible-wavelength image into the star-forming heart of the galaxy. The long dimension of the inset boxes is about 5400 light years. (Visible light image credit:  N. A. Sharp/ NOAO/AURA/NSF)

MORE DETAILS: Composite (false color) infrared image of the central portion of galaxy M82, from SOFIA’s first light flight, taken at [infrared] wavelengths of 19 (blue), 31 (green) and 37 microns (red). The middle inset image shows the same portion of the galaxy at visible wavelengths.  The infrared image views through the stars and dust clouds apparent in the visible-wavelength image deep into the star-forming heart of the galaxy, which is totally invisible when viewed only in visible light.  Where the visible light images show features like stars and dust in the outer regions of the M82 galaxy, the infrared image reveals  the central regions of the galaxy where stars are forming much faster than they do in our own Milky Way galaxy. The long dimension of the inset boxes is equivalent to about 5400 light years at the distance of M82. (Visible light image credit:  N. A. Sharp/ NOAO/AURA/NSF)