The TWINS-LAD mission: Observations of terrestrial Lyman-α fluxes

Abstract

The TWINS project (Two Wide-angle Imaging Neutral-atom Spectrometers) is mainly devoted to measure high energy neutral atoms (ENAs) originating via charge exchange of protons with geocoronal hydrogen atoms in the plasmasphere and magnetosphere. In order to unfold the local ion density along the line-of-sight (LOS) from the integrated ENA flux measurements, a good knowledge of the geocoronal hydrogen density distribution is needed. Therefore, two Lyman-α detectors (LADs) - designed and calibrated by the authors - were added to the TWINS package. These detectors register line-integrated Lyman-α resonance emission intensities which then can be used to get the actual local hydrogen densities with the help of a numerical inversion routine.