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Lotte Bierdel, 09/22/2016 02:20 PM


IOP-1: Go with the flow

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The planning of the transfer flights for HALO and FALCON from Munich to Keflavik –scheduled for Thursday and Saturday- started beginning of the week. On Tuesday it already became apparent that there might be a NAWDEX ‘Golden Case’ showing up on Saturday: An upper-level trough was located South of Greenland with a ridge (with warm conveyor belt [WCB] outflow) building up to Iceland and a second trough was over Western Europe - perfect conditions for our airplanes travelling from Southern Germany to Iceland to catch the diabatic butterflies that travel up the WCB and disturb the downstream flow. During the course of the week this synoptic situation became more and more certain and the flight planning team saw the opportunity of turning the transfer flight into the first intensive observation period (IOP). This gave a lucky subset of the 85(!) NAWDEX participants the early opportunity to practice their flexibility (that meant some crew members and onboard scientists spontaneously trying to find accommodation in Munich on the first day of Oktoberfest) and they already got a glimpse of how quickly things can change during the planning-process (and later how rewarding it can be to go with the flow!).
On Saturday the Operation Center was turned fully operative and the first planning meeting took place – which, after the surprising encounter of a Golden Case right at the beginning of the campaign, revealed a very promising and exciting flow development for the coming days. In the early afternoon everyone on site rushed to the airport and bravely resisted the freezing Icelandic winds to welcome the airplanes – which arrived on schedule in the afternoon with satisfied mission scientists that reported on a successful zeroth campaign day.

(Lotte Bierdel)

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Working at the hangar

After successfully arriving in Keflavik and spending our first day off discovering Iceland the real work started. This means: let’s got to the hangar. HALO and Falcon are already waiting for us.
Before starting the work at the aircraft the first hurdle has to be overcome, the security check. There, the airport visitor badges have to be distributed and everyone has to be checked for illegal things and weapons of all kind. Passing the inspection and being airside the friendly drivers of SouthAir guides us the hangar. There, the DLR FX stuff sorted all the shipped boxes and containers with the equipment. Luckily the second container arrived on Tuesday evening. Now all necessary tools are available at the hangar.
Already on Monday the WALES crew set-up their cooler to run WALES on the ground and keeping the lasers at the right operation temperature. During flight a cooling device at the top of the aircraft is used for this purpose. Shortly before flight they cleaned the window which covers the inlet of telescope.
For SMART the usual calibration has to be performed. For this, small Ulbricht spheres are used - which produce homogeneous distributed (the technical term is: lambertian) radiation. This ensures constant data quality between every flight and during the whole campaign. Taking them as a reference the calibration of the laboratory is transferred into the hangar. All this effort is needed because even small disturbances in along the optical path can influence the proper measurement of the instrument.
Not only are the instruments important but also the persons who are dealing with them. To ensure proper training of the instrument PI's they were teaching each other how to operate the instruments and how to launch the important dropsondes.
On Wednesday shortly before flight specMACS flushed their spectrometer-system with gaseous nitrogen to reduce the humidity inside the instrument chamber. This lowers the propability of condensation at the outer window where the cameras look through HALO fuselage. Water and ice on the window reduces the transmissivity in the visible wavelength range and falsifies the infrared measurements. Therefore, decreasing the humidity is crucial to allow measurements in cold regions.
Further on the radiometers need a calibration. This is a 2-point-calibration using targets with an ambient temperature and a very low temperature - achieved with liquid nitrogen reaching a temperature of -196°C (77K). Using these two temperatures the calibration function is determined and used for data processing. The white devices on the photo show these targets which are made of special foam - opaque in the wavelength range of the human eye but transparent in the microwave range. Therefore the radiometers are looking directly on the liquid nitrogen measuring the low temperature.
At the same time the Falcon aircraft is maintained which carries two lidar systems for measureing the wind speed and direction. They tried to optimize the system performance and adjusted the lasers for proper wavelength-stability.
With all this work done, clean windows and fueled-up completely HALO and Falcon are well prepared for their first flight starting from Iceland. As everyone is curios for the results - let's see what this flight will bring...

(Kevin Wolf)

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