A STRATOSPHERIC BALLOON FLIGHT PLATFORM AND ITS EMPLOYMENT IN GRAVITATIONAL WAVE COUNTERPART OBSERVATION EXPERIMENTS

The Cubesats Applied for MEasuring and LOcalising Transients (CAMELOT) initiative proposes to deploy a fleet of 3U nanosatellites in order to localise GRBs with all-sky coverage. The operation is based on measuring the time delay of the event trigger between satellites that are otherwise uniformly distributed around the Earth in low-Earth orbit (between 500 - 600 km of altitude). In this design, caesium-iodide crystals interact with soft gamma radiation by emitting optical photons. Utilization of this effect, each member of the fleet is equipped with four of such scintillators and the emitted photons are detected by multi-pixel photon counters (MPPCs). Precise timing is crucial for this concept, the timestamping of the events and the synchronisation is provided by GPS. In order to demonstrate the feasibility of the CAMELOT concept, a single-unit CubeSat, named "GRBAlpha" is currently being developed. GRBAlpha is equipped with a single block of scintillator but the other subsystems are all the same as it will be on the CAMELOT units. We describe this single-unit platform system, focusing on the model versions suitable for high-altitude stratospheric balloon flights. This model has a standardized layout (including pin-out configuration, signalling and bus communication) and compatible with significant proportion of CubeSat system vendors. This system of ours is also capable of hosting multiple payloads at the same time, optimizing the utilization of balloon experiments.