Reverse-fly computer simulations of the new ion-electron spectrometer (NIES)

We present the transmission characteristics of the New Ion Electron Sensor (NIES) based on a computer simulation technique that influenced the design and testing of two instruments: the Space Weather Follow-on at L1 Solar Wind Plasma Sensor (SWFO-L1 SWiPS) and the Lunar Vertex Magnetic Anomaly Plasma Spectrometer. The instrument described here builds on the ion-electron spectrometer flown on the Rosetta mission. NIES uses electrostatic deflection to increase its angular look direction on a three-axis stabilized spacecraft. Electrostatic elements used to deflect charged particles into the instrument radically change their transmission envelope and phase space coverage. This work presents the modeled transmission response and compares it to the laboratory calibration results of the SWiPS instrument. The "reverse-fly" technique models instrument response starting at the detector, including post-analyzer acceleration potentials. Simulations conducted in this manner yield improved evaluation of instrument transmission with significantly better performance compared to forward-fly methods, with the reverse-fly almost seven times more efficient in time and transmission. In addition, transmitted particle characteristics collected at one energy can be rapidly scaled to investigate transmission at different energies or due to variations in instrument operation, including deflection and ion species-specific radio frequency attenuation.