The Radiative Transfer Equation inversion on FPGA. The case of the Photospheric Magnetic field Imager

We present the radiative transfer equation (RTE) inverter core, a high performance SIMD architecture, to interpret the data obtained by the Polarimetric and Magnetic field Imager (PMI) instrument aboard the ESA’s Vigil mission. After some pre-processing, the spectropolarimetric data will be translated on board into physical quantities of the solar atmosphere to be directly downloaded to Earth, hence strongly reducing the telemetry needs of such a deep space mission. The RTE inverter is direct heritage from that in the Polarimetric and Helioseismic Imager (PHI) aboard the ESA/NASA’s Solar Orbiter mission. The more stringent requirements of Vigil as compared to Solar Orbiter, as well as the production discontinuation of the FPGA used in the PHI instrument, have driven the migration of the inverter architecture to a brand-new, more powerful FPGA device (Xilinx Kintex UltraScale XQRKU060).