"Does anyone have a crisp idea?" With this question, Prof. Dr Engel, head of the "Statistical Physics" working group at the University of Oldenburg, aroused the students' interest in the "REXUS/BEXUS" programme. REXUS/BEXUS is a programme run by the German Aerospace Center (DLR) and the Swedish Space Corporation (SSC), which together offer students interested in science the opportunity to carry out their own experiments in a supersonic rocket (Rexus) or a stratospheric balloon (Bexus). Thomas Albin, Florian Grimsmann and Henning Elbers from the University of Oldenburg and Dirk Winzier and Markus Tomazic from TFH Bochum - supported by the working groups "Marine Physics" (headed by DP Dr Reuter) and "Ultrafast Nano-Optics" (headed by Prof. Dr Lienau) - developed an experimental setup that should make it possible to measure the changes in the solar spectrum as a function of altitude. Due to different layers of gas in the atmosphere (e.g. the ozone layer), different spectral ranges of light are attenuated to different degrees. If one passes through these layers with increasing altitude, changes in the spectrum should also become noticeable. This effect is to be measured using a measuring apparatus on Bexus. Ideally, this balloon will reach a maximum altitude of 35,000 metres. Solar spectra at different altitudes, on the one hand at sea level (light grey) and outside the Earth's atmosphere (medium grey). The irradiance is plotted as a function of wavelength. Characteristic absorption lines can be seen at sea level, while in space the solar spectrum can be described by a black body (dark grey). In the wavelength range of 300nm - 950nm, the experiment will measure the changes as a function of altitude. [Source: www.csr.utexas.edu/projects/rs/hrs/pics/irradiance.gif] The students' project proposal was favourably received by DLR and an invitation to the DLR site in Bonn followed at the beginning of December last year. A presentation and a subsequent discussion with representatives of DLR and SSC about the scientific and technical objectives convinced the jury to include the experiment in the programme. In the weeks that followed, the "Preliminary Design Review" (PDR) was prepared with the aim of creating initial sketches of the experiment, selecting components and estimating the dimensions and mass of the experimental setup. This PDR was presented and discussed during the "Training Week" from 26 February 2012 to 3 March 2012 in Esrange (European Space and Sounding Rocket Range) in Sweden. Esrange, a civilian facility for launching research rockets and balloons, is about 50 kilometres from the city of Kiruna and is located at 68 degrees latitude and thus within the Arctic Circle. It serves as a venue for numerous seminars and lectures on various aerospace topics, e.g. the development of cold-resistant electronics or compliance with relevant safety aspects. Esrange will also serve as a launch site for the experiment mounted on a Bexus balloon in mid-October.

The main building at Esrange, nestled in a picturesque, remote winter landscape. This is where the seminars and lectures take place.

The project is currently in its third phase, the "Critical Design Review" (CDR), in which all specifications are finalised. This design, which is to be completed by mid-May, will then be presented at the European Space Research and Technology Centre (ESTEC) in Noordwijk, Netherlands. [07.03.2012]