The calibration of the Cassini-Huygens CAPS Electron Spectrometer
Schippers, P.; André, N.; Lewis, G. R.; Coates, A. J.; Linder, D. R.; Kataria, D. O.; Jones, G. H.; Lagg, A.; Mitchell, D. G.; Young, D. T.; Arridge, C. S.; Morooka, M.; Persoon, A.; Rymer, A. M.; Gilbert, L. K.; Collinson, G. A.; Wahlund, J.; Livi, S. A.
United Kingdom, United States, Netherlands, France, Sweden, Germany
Abstract
We present the two-stage method used to calibrate the electron spectrometer (ELS), part of the plasma spectrometer (CAPS) on board the Cassini spacecraft currently in orbit around Saturn. The CAPS-ELS is a top-hat electrostatic analyser designed to measure electron fluxes between 0.5 eV and 26 keV. The on-ground calibration method described here includes the production of photoelectrons, which are energised and passed into the CAPS-ELS in a purpose designed calibration facility. Knowledge of the intensity of these incident electrons and the subsequent instrument output provides an on-ground calibrated geometric factor. Comparative studies of physical quantities such as plasma density and electron differential flux calculated using on-ground calibration factor with the quantities deduced from the wave experiment and high energy electron detector provide in-flight calibration. The results of this are presented together with a comparison of the experimentally calibrated values with simulated calibration values.