High Altitude and Longe Range Research Aircraft
The German research aircraft HALO is based on a modified G550 business jet (Gulfstream Aerospace Cooperation) and allows to perform flights over a large (intercontinental) range with a maximum ceiling height of 15 km.
The aircraft is operated by DLR in Oberpfaffenhofen and is available since 2009 for scientific mission in the field of atmosphere, climate and earth system research. For the investigation of atmospheric photochemistry, IEK-8 developed measurement instruments for atmospheric radicals (OH, HO2) and photoactinic solar radiation. The radiation measurements are performed by means of absolutely calibrated spectroradiometers and allow to calculate photolysis rates of atmospheric trace gases (e.g., ozone). The radiometers have been employed on several HALO missions so far (TECHNO, NARVAL, OMO, EMeRGe). The radical measurement instrument applies laser induced fluorescence for radical detection and was used 2015 in the first photochemistry mission (OMO, Oxidation Mechanism Observations) of HALO. For undisturbed airborne measurements of the highly reactive radicals, a special air inlet was developed at Forschungszentrum Jülich.