EUSO-SPB1 project and laser test beams for space-based optical cosmic ray detectors, The

Abstract

The most energetic particles in the universe are ultra high energy cosmic rays with energies up to \SI{3e20}{eV}. However their flux is highly suppressed at the highest energies ($\sim$ 1 particle/km$^2$/century for E=\SI{e19.75}{eV}), leaving the sources and the acceleration mechanisms unknown. The detection of ultra-high energy cosmic rays from space via the fluorescence method is very compelling because of the large observable area to overcome this issue. The Extreme Universe Space Observatory (EUSO) collaboration is developing such an instrument. \par To develop and test the technologies and method for a space based cosmic ray detector, the collaboration built prototypes (ground-based and balloon-born). In this thesis we discuss the use and development of a laser test beam setups, including an airborne version used in an helicopter underflight for testing of the first balloon prototype. A ground laser system was used extensively to characterize the ground based prototype. An algorithm to reconstruct the geometry was implemented in this thesis.\\ An other major milestone was reached in April 2017 by launching the Extreme Universe Space Observatory on board a Super Pressure Balloon (EUSO-SPB1) was designed to measure cosmic rays for the first time from above via fluorescence light. The instrument was flown as a NASA Mission of Opportunity from Wanaka, NZ. Due to issues with the balloon, the mission was terminated prematurely after only 12 days and the instrument splashed in the Pacific Ocean 300 km SE of the Easter Island. The preflight calibration in the laboratory and during field tests are discussed here. The launch preparation and the flight itself are discussed in details. An expected event rate for the shorten flight of 1.3 events is calculated based on simulations. Even though no cosmic ray track was found in the data, EUSO-SPB1 was a successful mission providing crucial developments for the next balloon mission.