In order to be on vampire time for tonight’s flight, we were encouraged to stay up as late as possible last night and sleep in this morning. I got up to eat breakfast about 7:00, then went back to sleep until 11:15. This is the only NASA workshop I’ve been to that has time in the schedule for mandatory naps.
We ate lunch at Panera Bread and also purchased sandwiches for tonight, then drove out to the Dryden Aircraft Operations Facility (DAOF) where we got permanent photo badges before entering the hangar building. Upstairs, we dropped off our baggage and were given an extensive tour of the SOFIA instrument and mirror coating facilities by Eric Sandberg.
Eric originally grew up in Cedar City, Utah and graduated from Cedar High School. He is an electronics engineer, and worked on the HAWC instrument at the University of Chicago before coming with it to Dryden, where he’s been for the last eight months. The HAWC, or High-resolution Airborne Wideband Camera, is currently at the Jet Propulsion Laboratory where its sensor is being upgraded to handle more pixels.
Eric showed us the instrument mounting simulator, or Pre-Flight Integration Facility: a black tube with an instrument flange identical to the one on SOFIA. The instruments, such as FORCAST, are initially mounted to this tube, which then sends a signal or simulated light beam to the instrument’s detector. This tube has exactly the same focal length as SOFIA, so it can be used to measure the precise location of the instrument’s focus. Knowing that, it can be more easily duplicated when the instrument is actually mounted in SOFIA.
He also showed us the side rooms where the various instruments are stored. GREAT (the German REceiver for Astronomy at Terahertz frequencies) is a spectrometer that uses niobium bolometers, a type of superconductor that is very sensitive to infrared photons when cooled to near absolute zero. It has twin dewer flask canisters, with an outer layer of liquid nitrogen to keep an inner layer of liquid helium cool, which in turns cools the bolometer sensors.
Other instruments were not there; HAWC, EXES (the Echelon-Cross-Echelle Spectrograph), and FIFI-LS (the Field Imaging Far-Infrared Line Spectrometer) are still being completed. FLITECAM (the First Light Infrared Test Experiment CAMera) and HIPO (the High-speed Imaging Photometer for Occultations) are both being updated. We also saw the pumps used for transferring the cryogenic liquids.
Eric then walked us around the side of the hangar past the DC-8 that is used for atmospheric research. It has nozzles and intake ports, instruments and radar aperatures sticking out of it on all sides and underneath. We counted about 20 instruments. It collects samples and data as it flies regarding atmospheric conditions and constituent gases. We have met a video team from Raytheon that is here to ride on the DC-8 as it records data of the IRIS mission this week.
We also saw the two ER-2 aircraft, which are U-2 spy planes converted for high-altitude atmospheric research (hence the ER name).
Eric then showed us the facility for recoating the SOFIA mirror every few years. The mirror is carefully removed and transported into this bay, where the aluminum finish and any oils or contaminants on the mirror are removed so that it is basically just glass (although a special type that resists cracking). It is then moved by ceiling crane into the next room and lowered into a large pressure vessel where all the air is pumped out and the mirror surface is electrically charged. Heating elements vaporize aluminum coils and the gas is attracted to the charged mirror. Within a few seconds, a new coating of aluminum about 1000 angstroms thick has been deposited.
We returned to a conference room on the second floor to await the pre-flight briefing. I took some photos of photographs in the hallway showing SOFIA, many of which I haven’t seen before. I will have to run them through my un-distortion process in Photoshop, but they will turn out as good as new once done.