Simulation of Scientific VHF Telemetry Data for the French Payload of the SVOM Satellite

Abstract: The Space Variable Objects Monitor (SVOM) is a future French-Chinese satellite mission which is dedicated to the observation and characterisation of Gamma Ray Bursts (GRBs). When a GRB is detected by the satellite, the position and initial characterisation data are transmitted to ground via a VHF telemetry link, in order to trigger immediate follow-up observations of the transient GRB afterglow by ground-based telescopes. To optimise the prioritisation of this telemetry flow in various scenarios, detailed simulations of the VHF telemetry are required. In this thesis, a new telemetry simulator was thus developed: the MXT VHF Data Simulator. This simulator generates all VHF messages of the Micro X-ray Channel Telescope (MXT) instrument that would be expected during a typical operational scenario.  Each message is constructed byte by byte, with the required data formats, encodings and packet structures as specified by the SVOM telemetry standards and the MXT VHF TM specification database. To generate the scientific packet contents several approaches were combined. An existing camera frame simulator, developed at the LAL institute, was modified to simulate raw photon data for the given scenario, generating a set of binary camera frame files which is then parsed and integrated by the MXT VHF Data Simulator. MXT instrument scientists provided an example GRB profile with the temporal evolution of certain GRB parameters. In addition, several parameters were simulated manually, with an effort to achieve as realistic contents as reasonably possible, and in coordination and discussion with the MXT instrument scientists and software engineers. The output of the simulation consists of a set of MXT VHF telemetry files in binary and CSV formats. To verify the correct formatting and contents of the data, the files were validated using the internal CNES telemetry analysis framework PrestoTools. This analysis confirmed correct formatting and encodings in accordance with the telemetry specifications, as well as the expected data in the packet contents. Finally, the resulting data was integrated into the CNES VHF Simulator, and an analysis of a full VHF telemetry scenario with all four instruments was performed for the Data Challenge 1 (DC1) systems test scenario.