Investigating UV nightglow within the framework of the JEM-EUSO Experiments

Abstract: The main mission of the JEM-EUSO (Extreme Universe Space Observatory) Collaborationis to observe Cosmic Rays. These high energy particles come from a variety of sources and bombard the Earth all the time. However, the higher the energy, the lower the flux, and particles with an energy above 1018eV (called Ultra High Energy Cosmic Rays or UHECRs) are so sparse that just a few might hit the atmosphere in a year. When CRs, and UHECRs, hit the atmosphere they cause what is called Extensive Air Showers, EAS, a cascade of secondary particles. This limits the effectiveness of ground based observatories, and that is where theJEM-EUSO Collaboration comes in. The goal is to measure UHECRs, by observing the fluorescence of the EAS from space. This way huge areas of the atmosphere can be covered and both galactic hemispheres can be studied. Since the JEM-EUSO instruments are telescopes measuring in the near UV range, a lot of other phenomena can be observed. One of these applications is UV nightglow. Airglow in general are lights in the sky which are emitted from the atmosphere itself, while nightglow is simply the nighttime airglow. There are many uses of airglow, and one of these is as a medium to observe atmospheric gravity waves. The aim of this thesis is to investigate how a space-based photon counting telescope, such as those of the JEM-EUSO Collaboration, can be used to measure disturbances in the terrestrial nightglow, to identify atmospheric gravity waves. To accomplish this, a theoretical basis for these interactions was explored and a simple scenario was built to explore the plausibility of measuring UV nightglow modulations. The aim was to see what variables would affect a measurement, and how important they were. Along side this, a calibration was conducted on one of the JEM-EUSO Collaborations instruments, the EUSO-TA (EUSO-Telescope Array). The goal in the end was to try and measurethe night sky, to complement the calculations. The investigation showed that the conditions during the measurement are very important to the measurement. This includes things like background intensity, nightglow activity, and magnitude/shape of the modulations. Of more importance though are the parameters which can be actively changed to improve the measurement, the most important of which is measurement time. It was concluded that a measurement of the nightglow modulation should be, under the right conditions, possible to do with a currently operating instrument, the Mini-EUSO, or similar instrument. The calibration of the EUSO-TA involved a series of repairs and tests, which highlighted some strengths and weaknesses of the instrument. However, the calibration itself produced few workable results that in the best case scenario reduced the focal surface to an unevenly biased 2-by-2 Elementary Cell square. Unfortunately this would not be sufficient to do proper measurements with, but the process did point out shortcomings with the then involved sensors, as well as some problematic aspects of the software operating the instrument.