A Scientific Trigger Unit for space-based Real-Time Gamma Ray Burst detection II - Data Processing Model and benchmarks

The Scientific Trigger Unit (UTS) is a satellite equipment designed to detect Gamma Ray Bursts (GRBs) observed by the onboard 6400 pixels camera ECLAIRs. It is foreseen to equip the low-Earth orbit French-Chinese satellite SVOM and acts as the GRB trigger unit for the mission. The UTS analyses in real-time and in great details the onboard camera data in order to select the GRBs, to trigger a spacecraft slew re-centering each GRB for the narrow field-of-view instruments, and to alert the ground telescope network for GRB follow-up observations. A few GRBs per week are expected to be observed by the camera; the UTS targets a close to 100% trigger efficiency, while being selective enough to avoid fake alerts. This is achieved by running the complex scientific algorithms on a radiation tolerant hardware, based on a FPGA data pre-processor and a CPU with a Real-Time Operating System. The UTS is a scientific software, firmware and hardware co-development. A Data Processing Model (DPM) has been developed to fully validate all the technical choices deeply impacted by the ITAR restriction applied to the development. The DPM permits to evaluate the processing power and the memory bandwidth, and to adjust the balance load between software and firmware. This paper presents the UTS DPM functionalities and architecture. It highlights the results obtained with the full GRB trigger algorithms implemented on a rad-tolerant ITAR-free processor.