On-orbit calibration of geostationary electron and proton flux observations for augmentation of an existing empirical radiation model

Abstract

Challenges faced in the quantitative use of long-term radiation belt data sets include establishing their relative accuracy and correcting for on-orbit degradation. An existing empirical model of energetic plasmas (0.001-40 keV) in geosynchronous orbit has been extended in energy to several hundred keV by incorporating observations from the Geostationary Operational Environmental Satellite (GOES) 13 and 15 magnetospheric electron detector (MAGED) and magnetospheric proton detector (MAGPD). In order to ensure the accuracy of this energy range extension, the following steps were taken: (1) removing noise bursts; (2) intra-calibrating the nine solid state telescopes comprising each MAGED or MAGPD; (3) cross-calibrating GOES 13 and 15; and (4) cross-calibrating magnetospheric plasma analyzer (MPA) and GOES fluxes, the necessary final step in augmenting an MPA-based model with GOES data. The MAGED and MPA electron fluxes were demonstrated to agree well at the energy (40 keV) where they overlap, while the MAGPD proton fluxes exhibited a severe long-term degradation compared to MPA. This problem is related to the well-known long-term degradation of the proton fluxes from the similar medium energy proton and electron detector (MEPED) proton telescopes on the POES and Metop satellites in low-Earth orbit. Results of this on-orbit calibration work are used to reconsider long-standing hypotheses about the cause of degradation in similar proton telescopes.