Aims. To better understand the radiation environment in low Earth orbit (LEO), the analysis of in-situ observations of a variety of particles, at different atmospheric heights, and in a wide range of energies, is needed. Methods. We present an analys
is of energetic particles, indirectly detected by the Large Yield RAdiometer (LYRA) instrument on board ESAs Project for On-board Autonomy 2 (PROBA2) satellite as background signal. Combining Energetic Particle Telescope (EPT) 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. Results. The observed events are strongly correlated to geo-magnetic activity and appear even during modest disturbances. They are also well confined geographically within the L=4-6 McIlwain zone, which makes it possible to identify their source. Conclusions. Although highly energetic particles are commonly perturbing data acquisition of space instruments, we show in this work that ultra-relativistic electrons with energies in the range of 2-8 MeV are detected only at high latitudes, while not present in the South Atlantic Anomaly region.
The UK Schmidt camera was used to observe the Virgo cluster of galaxies, where a total of 13 R-band Kodak Tech-Pan films were obtained. The latter, were scanned by the APM machine (Cambridge, UK),digitally aligned, co-added, corrected for vignetting
effects andfinally cleaned of stellar features. The resulting image covers an area of ~6.2x6.2 degree^2 with a resolution of ~2 arcsec/pixel, where extended objects with a surface brightness up to 28 mag/arcsec^2 can been detected. Some of those results have already be published in previous papers. Here we wish topresent a choice of faint detections and discuss some interesting implications of this project.
