Space | 17. April 2015 | posted by Friederike Wütscher

SOFIA flight 200

Credit: DLR (CC-By 3.0)
Scientific observations using the FIFI-LS instrument were performed during SOFIA flight 200

I was given the opportunity to fly as a passenger on SOFIA'S 200th flight during the night of 12 to 13 March 2015. It was also the second flight of the new observation campaign featuring the German-developed Field-Imaging Far-Infrared Line Spectrometer (FIFI-LS), an astronomical instrument developed by the University of Stuttgart. I have to say, though, that my interest was not so much the science; rather, I wanted to experience what SOFIA 'felt' like after undergoing a lengthy refurbishment at Lufthansa Technik in Hamburg. The overhaul had included an almost complete replacement of the air conditioning and cabin panelling. During the mission briefing, the meteorologists mentioned a possibility of turbulence in the northern section of the flight route. That's what I had been hoping for. After all, I wanted to see the telescope in action. Until then, I had only heard that the telescope remains firmly focused on its target – regardless of how 'shaky' a flight might be. The flight schedule looked interesting, with turning points over Seattle and San Francisco in the north, and Albuquerque, the Texas Panhandle and Las Vegas in the south.##markend##

Credit: DLR (CC-By 3.0)
Author Heinz Hammes at the Education and Public Outreach (EPO) console during the flight

I observed the Education and Public Outreach (EPO) console during the flight. This panel shows any teachers or journalists on board the same mission data that is displayed on the Mission Director’s console. On that night, I was accompanied only by Cathy who was looking after the mission systems – the observatory's data and communication systems. The new seats at the front of the aircraft and on the upper level were not occupied; overall, the flight was pretty empty – certainly if you count the number of observers. Alfred Krabbe, director of the German SOFIA Institute at the University of Stuttgart, laid out the scientific goals during the mission briefing. The researchers would use the flight to, among other things, observe the phenomena taking place in dense star-forming regions and to measure the composition of gas and dust clouds in nearby galaxies. The researchers had also scheduled the measurement of certain spectral lines in the cold gas of elliptical galaxies with supermassive black holes at their centres.

Credit: DLR (CC-By 3.0)
The flight plan – the blue lines indicate the observation flight segments. Red and yellow lines show the restricted zones.

The aircraft took off as scheduled at 19:28. The scientists completed final preparations during the time until the telescope door was opened. The programs for data pre-evaluation were loaded and the automatic scripts given a last check while the operators were busy setting up the telescope. It took three flight 'legs' to reach our position for the first observations. As is the case for aviation as a whole, the term 'leg' in relation to SOFIA describes each section of the route until the next turning point.  Take-off and landing are also described as  and counted as 'legs'. The schedule for this flight listed 16 legs, nine of which would be used for scientific observations.

The observations commenced just over one hour later. As usual, I would not have known that the telescope door had been opened had the Mission Director not made an announcement – it is imperceptible in the cabin. The noise does not increase and the aircraft does not move unexpectedly. However, it is very noisy in the cabin, making it almost impossible to have a conversation. This is why all those on board wear headsets, which allow one to follow the conversations between the scientists, the mission crew and the pilots on a number of different channels. I had activated the channels for the Mission Director, the telescope operators and the pilots, so I could be informed of our position (radio contact with the air traffic controllers) as well as what was happening with the telescope.

Credit: DLR (CC-By 3.0)
The SOFIA telescope's massive mechanical components at the rear of the aircraft are shown here. The FIFI-LS instrument is shown at the centre of the image (dark, rectangular box). It was used during the flight to observe star-forming regions.

As promised, I was 'rewarded' with turbulence in the area around the first northern turning point. I found it fascinating to observe how the telescope compensated for the impact and vibrations resulting from the turbulence – without ever losing sight of its target. The motors guiding the telescope responded with short, sharp movements or long, slow traverses to correct for the slightly inclement conditions. Installed in the rear of the aircraft, the mechanical components of the telescope appeared to turn. In reality, however, the telescope remains firmly focused on its target throughout while the aircraft moves around the telescope.

During the night, I had the chance to talk with the pilots and the flight engineer. They all agreed that the aircraft 'feels' altogether better. During my chat with the flight engineer, I discovered that he is now able to control the ventilation and air conditioning. Prior to the refurbishment in Hamburg, the cabin temperature required constant adjustment. The overhaul involved replacing almost all of the ventilation ducts – even the installation of new lines and sensors in the rear section of the cabin (around the telescope). Now, the flight engineer is able to regulate cabin temperature in such a way that it does not require adjusting every few minutes.

Credit: DLR (CC-By 3.0)
The logos of the SOFIA project partners were printed onto the panel during the aircraft overhaul

But it is still noticeably colder down in the cabin than on a normal long-haul flight, and you certainly would not want to have forgotten your jacket and pullover. In general, however, I found temperature in the cabin much milder than on my first flight a few years ago. The (almost) all-round panelling in the cabin keeps things reasonably bearable, and helps reduce the noise a little. Lufthansa Technik used the overhaul in Hamburg to equip the cabin with a special panel and fabric covering that is otherwise only used in VIP cabins. It is emblazoned with the logos of the SOFIA project partners – and naturally, slightly lower down, Lufthansa Technik, as well.

SOFIA's 200th flight was a resounding success – there were no major system or instrument failures and all observations were completed as planned. The scientists will spend the next few weeks evaluating the data and assessing their suitability for scientific publication. Krabbe showed me preliminary data from the previous day’s observations as a special treat during the flight. A brief glance at a certain frequency range indicated that the quality of this data is greater than similar information acquired with the Herschel spacecraft. However, detailed data evaluation will be needed to confirm this appraisal.

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About the author

Heinz Hammes studied safety engineering and has worked at the DLR Space Administration for more than 25 years. Hammes is currently seconded to Lufthansa Technik in Hamburg and is supervising the maintenance of SOFIA. to authorpage