Luke Keller

Luke Keller

Dana Professor, 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

Posted by Luke Keller at 12:13PM   |  Add a comment
SOFIA first light image of Jupiter

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.

SOFIA/FORCAST image of the planet Jupiter

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)

SOFIA/FORCAST image of the galaxy M82

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)


Posted by Luke Keller at 1:39PM   |  1 comment
FORCAST team leader, Terry Herter, operating FORCAST just after its first installation on the SOFIA telescope. (Photo: George Gull)

I spent last Friday teaching sixth grade classes in McLean, VA, at Spring Hill Elementary School where my nephew is a student. We discussed infrared astronomy and SOFIA. Kids ask some of the best questions, many that adults are curious about but bashful to ask. These kids had great questions about what it's like to work on the aircraft so I decided to post those here with answers in case anyone else is wondering:

How long are the flights and where do you go?
Flights will be about 8 hours long, of which about 6 hours will be spent conducting astronomical observations. It takes about 1 hour from takeoff to reach the cruising altitude and start observations, and another hour at the end of the flight to descend and land. SOFIA currently takes off and lands at NASA's Dryden Aircraft Operations Facility (DAOF), located in Palmdale, CA. So after an 8 hour flight we end up exactly where we started! The actual route of our flights depends on what objects in the sky we are observing. Since the SOFIA telescope only points our of the port (left) side of the aircraft, we fly from east to west when looking into the southern part of the sky, west to east when looking north, etc. Flight plans for SOFIA look very chaotic since the aircraft must change direction every time we point the telescope towards a new object for observations, typically every hour or so.
How many people fly on a SOFIA flight?
There are three pilots in the flight crew, 10 seats in the First Class section in the nose of the aircraft, and 17 seats in the science operations section farther back. Not all seats will be occupied on a given flight, though. The average crew for science operations, not including the pilots, includes the mission director, one person operating the science instrument (camera or spectrograph), at least one telescope operator, and at least one astronomer from the team conducting the astronomical observations. So a total of three in the cockpit and at least four in the science operations section of the aircraft. 
Why does SOFIA have First Class seats?
These seats will often be unoccupied, but when SOFIA missions become more routine over the next few years these seats will be available for science teachers who work with astronomers to gain experience participating in astronomical observations first hand. These teachers will be part of the Airborne Astronomy Ambassador program. Other guests of the SOFIA project may occasionally use these seats. Finally, SOFIA will eventually spend part of the year flying from a base in the southern hemisphere. This will allow observations of objects in the southern sky, which are not possible from locations in the northern hemisphere. During the southern deployments of SOFIA it may be necessary to fly maintenance and other personnel from DAOF and Ames to the southern site and back. Currently the site planned for southern deployments is Christchurch, New Zealand.
What do you eat and drink while flying on SOFIA?
That depends on the person. There is no "galley" (or kitchen) on SOFIA like on commercial aircraft so we have to bring our own snacks and drinks and they can't require cooking. Most astronomers I know, including me, will just bring snacks. We have to be very careful not to spill food or drinks on the electronics and computers, though, we don't want sticky fingers to ruin our observations. Work on airborne astronomy flights is often so busy that there is very little time for even thinking about eating.
What happens if there is an emergency while the plane is flying?
On a commercial jetliner the flight crew, including flight attendants, assist passengers in the event of an emergency. SOFIA has a crew of three or four pilots, but no flight attendants, so anyone who flies on SOFIA must take safety training classes at NASA prior to flying. In those classes, which last a few hours each, we learn how to open and close the aircraft door and how to deploy the emergency slides if we have to evacuate the aircraft quickly. We also learn where all of the on-board fire extinguishers are, where the oxygen masks are, where the first aid kits are, and how to use them. The modifications left SOFIA with not as many places for the emergency oxygen masks that pop out of the ceilings of commercial jets if the cabin looses pressure. If SOFIA losses cabin pressure, we'll put on oxygen masks located near our work spaces and then wait for the pilots to fly to a lower altitude where the air is thick enough for us to breath.
Why do you wear headphones?
SOFIA only has a few seats and the floors are not carpeted all over like in a commercial jet. Seats and carpeting, not to mention all of the other passengers, absorb a lot of sound. That means that SOFIA is very loud even inside the pressurized cabin. Since we need to be able to talk with people sitting all over the aircraft during flights and observations, we all wear headphones with microphones on them. These help us talk to and hear everyone with out having to yell or get up and walk around the aircraft. We can also get updates and instructions from the flight crew if necessary.
How high does SOFIA fly?
SOFIA can fly to a maximum altitude of 13.7 km (about 45,000 feet), but most astronomical observations with be conducted at altitudes of about 12.5 km (41,000 feet). Under normal operating conditions, the telescope cavity will never be opened below 10.7 km (35,000 feet). This is to keep the telescope optics clean since most of the dust, moisture, and pollution in our atmosphere are located below 10.7 km. For comparison, most commercial aircraft cruise at 10.7 to 11.9 km.
Is it scary on SOFIA?
No, it's very exciting. The people who made the aircraft modifications and the people in charge of aircraft testing safety at NASA have worked very hard to insure the safety of people flying on SOFIA. It is just as safe as a regular commercial flight on a 747. However, when you first walk onto SOFIA it can be startling to see all of guts of the cabin exposed. Most of the white plastic molding and fixtures (like walls, overhead bins for carryon luggage, and even the low ceiling) have been removed on SOFIA to access the wiring and instruments that are normally hidden in a commercial jet aircraft. Here's a picture of what it looks like inside SOFIA. There are more at my Frequent Flyer photo gallery.
Do you have parachutes? 
Nope. Neither do the pilots. But I'm not worried.
Is there a bathroom?
Yes, the aircraft lavatory in the front of the airplane is available for all on board. The rest of the lavatories were removed to make room for the telescope. With only 10 or so people on board, though, I don't expect lines for the potty.
Got a question of your own? Leave a comment and I'll do my best to answer.

Posted by Luke Keller at 2:10PM   |  1 comment
FORCAST (red with gold colored electronics boxes attached) is now installed on the SOFIA telescope. (Photo by George Gull)

FORCAST is now bolted to the telescope assembly on SOFIA! George Gull and Chuck Henderson, assisted by the engineering team at DAOF, have successfully installed the camera system. The process of lifting the instrument from the ground, rolling it onto the aircraft on its cart, and attaching it to the telescope went very smoothly. On Monday they restored all of the electrical cables and Terry Herter joined them as they powered all systems up. Everything is working well. I think it looks smaller on the telescope than it did in the lab, but that's not surprising since it is now attached to a 20-ton telescope!

The next step towards the first-light flight is to align the FORCAST camera optics with the telescope optical system and measure image quality while observing bright stars with the aircraft parked on the ground. Once we complete these so called line-operations (or "line-ops"), we will conduct rehearsals of our in-flight tests and observations. Flight time on SOFIA is very expensive so any work that we can do on the ground, or that we can make more efficient by practicing on the ground, will save us time (and therefore $$) during the flights. I will travel to DAOF next week to help with line-ops and set up the data processing and analysis software that my students and I have developed. I will also prepare for processing the data taken during the first light flight. Looks like FORCAST will be flying soon...

Posted by Luke Keller at 12:53PM   |  Add a comment
FORCAST pointed at the sky, measure the infrared sky brightness. Chuck Henderson at the controls.

SOFIA test flights have been successful and plans are in the final stages now for the "first light flight," the first flight on which we will conduct astronomical observations with a science instrument on the telescope. First light is a major milestone for any observatory; it's usually the first time that the entire telescope-instrument combination are used to gather data that could be used for astronomy (as opposed to data used to test the telescope). 

The SOFIA telescope assembly had it's first light in late 2008 while the aircraft was parked on the ground. For that initial test of the telescope system astronomers used the Lowell Observatory's High-Speed Imaging Photometer for Occultations (HIPO). That test verified that the telescope optics and aircraft observatory systems work together to allow astronomical observations. The FORCAST camera had it's own first light on a ground-based telescope. These tests showed that the FORCAST optical and electronic systems are ready. Last week SOFIA flew with the telescope cavity opens and the telescope tracking system on. Results of those tests showed that SOFIA can track astronomical objects well in flight.

Now it's time to put the SOFIA telescope and FORCAST together and test the performance of the telescope by making infrared images of bright stars. One measurement that we have made in preparation for these observations is to measure the infrared brightness of the sky using FORCAST from the ground with no telescope attached. George Gull and Chuck Henderson made those observations on May 5 and they are now installing FORCAST on the SOFIA telescope for the first time. The next step will be observations with FORCAST and SOFIA from the ground and, finally, the telescope characterization flight tests. Once those tests are completed successfully the plan is to image something that looks a bit more interesting.

FORCAST will be the instrument used for the first light in flight (I like to call it First [F]Light!). Stay tuned for the first astronomical data taken from SOFIA in flight!

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