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Student projects on the Bexus stratospheric balloons: measurement by Medipix-2 and Timepix ionizing radiation detectors

Success of students from FMP-CU

Project duration: 2008 to 2010

Project manager: Jaroslav Urbář

Czech student teams performed first two experiments using the semiconductor pixel detectors of the Medipix family for energetic particle imaging in stratospheric environment. The original detecting device was based on the hybrid pixel detectors of Medipix-2 and Timepix developed at CERN with USB interface developed at Institute of Experimental and Applied Physics of Czech Technical University in Prague. The detectors were used in tracking mode allowing them to operate as an “active nuclear emulsion”. The actual flight time of BEXUS-7 with Medipix-2 on 8th October 2008 was over 4 hours, with 2 hours at stable floating altitude of 26 km. BEXUS-9 measurements of 3.5 hour duration by Timepix, Medipix-2 and ST-6 Geiger telescope instruments took place in arctic atmosphere till ceiling altitude of 24 km on 11th October 2009. Stratospheric balloon platform is the optimal realization for such in-situ measurements of atmospheric ionization. Suitable not only because of the high altitudes reached, but also due to its slow ascent velocity for statistically relevant sampling of the ambient environment for improving cosmic ray induced ionisation rate (CRII) model inputs. The scientific goal was to check energetic particle type altitudinal dependencies, simultaneously testing proper detector calibration by detecting fluxes of ionizing radiation while evaluating instrumentation endurance and performance. In-flight comparison (based on previous on-ground intercalibration) between Timepix and Medipix2 (equipped with neutron converter) and with STANDARD RAS STS-6 Geiger tube telescope was also undertaken.

The ionizing Terrestrial Cosmic Ray (CR) Flux is considered by the scientific community as a possible important agent influencing various atmospheric phenomena that range from Global Atmospheric Electric Circuit, dust concentrations, to cloud properties. Therefore, better experimental data on specific atmospheric fluxes along with particle types and energies present are an important input into various models. According to scientists it is important to develop automatic, small, and light CR stations for regular ship and aircraft lines for continuous planetary surveys. Such an extended network of both stationary and moving CR stations will be more effective for solving problems related to space situational awareness and space weather.

The REXUS/BEXUS flight opportunity for European student projects (Rocket/Ballon EXperiments for University Students)

The flight opportunity is provided every year by the Eurolaunch - Collaboration of Swedish National Space Board (SNSB) and German Space Agency (DLR) and supported by the Education department of the European Space Agency (ESA). Czech experiments for BEXUS were designed, developed and financed by students of Space Science group of the Department of Surface and Plasma Science, Faculty of Mathematics and Physics of the Charles University in Prague and Faculty of Electronics of the Czech Technical University in Prague. The team was supported technically by the Medipix team of the Institute of Experimental and Applied Physics of the Czech Technical University in Prague (IEAP CTU).

What would you name as main benefits of the project to you and your team?

“Thanks to these student efforts based in the Czech Republic was established strong link between IEAP CTU and ESA. Resulting projects were focused mostly on making the Medipix technology available to real space applications. Along with this line, it continues with other associated measurements during flights on the additional stratospheric balloons and Cubesat projects. By the end of 2011, Timepix is scheduled to be placed onboard of the International Space Station (ISS) as an active radiation dosimeter. Many students were able to get precious hands-on activity with the space instrumentation and space project basics.”