The GRBAlpha nanosatellite, a 1U sized CubeSat, was launched in March 2021 into low Earth Sun-synchronous orbit, and it carries on board a gamma-ray detector capable of detecting gamma-ray transient events. The detector consists of 75 mm x 75 mm x 5 mm CsI(Tl) scintillator, read out by a dual-channel multi-pixel photon counter (MPPC) setup. One of the goal of GRBAlpha is to measure the levels of the background at low Earth orbit. The nanosatellite has proven its functionality and it has recorded plenty of valuable measurements which should be analysed in detail. One of the advantage of the innovative detector on board of GRBAlpha is that it can operate also inside the Van Allen radiation belts (polar regions and the South Atlantic Anomaly) where the particle flux is several orders of magnitude higher than in the quiescent low latitude regions. Beyond all expectations the satellite has also detected several gamma-ray bursts.

The goal of this project is to compare the in situ measurements of the background levels with the existing models of the trapped charged particle fluxes, such as NASA's legacy AE-8/AP-8 or newer AE-9/AP-9 models. These models are available either through the AFRL's software or via the ESA's WWW interface SPENVIS. Study of the distribution of the background levels, the temporal variability and possibly also anisotropy of the trapped charged particle flux will be highly beneficial for the planned low Earth satellite missions.

The accurate understanding of the recorded background is important for the efficient search of gamma-ray transients with the astrophysical origin such as gamma-ray bursts, soft gamma repeaters and solar flares. The next goal of this project is thus to search for these transient events in the observed light curves.

Another nanosatellite called VZLUSAT-2 is scheduled to be launched in Dec 2021 and it is anticipated that it will also bring plenty of valuable measurements which can be also analysed within this project.