3575 20180920143353.0 CTALK-2018-0063 Katsiyannis, Athanassios The detection of ultra-relativistic electrons in low Earth orbit by the LYRA instrument on board the PROBA2 satellite 2018 2018-08-28 We present the analysis of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESA's Project for On-board Autonomy 2 (PROBA2) satellite in the form of microbursts of <10 ms, with a phenomenon duration of 100 s. Combining Energetic Particle Telescope (EPT/PROBA-V) observations with LYRA data for an overlapping period of time, we identified these particles as electrons with an energy range of 2 to 8 MeV. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. Additionally, they are well confined geographically within the L=4-6 McIlwain zones, and they show prominent dawn-dusk and day-night asymmetries. Those detections clearly illustrate that although LYRA is built as an EUV irradiometer, it can also reliably detect in-situ relativistic electrons. The scientific value of this discovery and its implication to solar irradiometer designs will also be discussed. 2BRAIN_SOL3CAM, 3PRODSIDCEXPLOIT/ 2BRAIN_SOL3CAM, 3PRODSIDCEXPLOIT/ 2BRAIN_SOL3CAM, 3PRODSIDCEXPLOIT STCE Dominique, Marie 2018 INSPIRE and Small Sat Workshop, Paris, France thanassis.katsiyannis@observatoire.be https://events.oma.be/indico/event/51/overview 2208056 http://publi2-as.oma.be/record/3575/files/perturbations_talk_inspire.pptx Powerpoint presentation Contributed CTALKCONT