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.
Highlights
Empirical models of plasma and radiation populations in Earth’s magnetosphere are valuable for a wide range of scientific and engineering purposes
In the late 1960’s, several satellites in geosynchronous orbit suffered a rapid decrease in power output (20% within weeks of launch) that was determined to be due to exposure of incompletely-covered solar cells to low-energy proton fluxes (Hughes Aircraft Company, 1968; Statler & Curtin, 1971; Tada et al, 1982)
This paper describes the methods and results of the extensive on-orbit corrections and cross-calibrations applied to the Geostationary Operational Environmental Satellite (GOES) magnetospheric electron detector (MAGED) and magnetospheric proton detector (MAGPD) fluxes in order to make them suitable for augmenting the magnetospheric plasma analyzer (MPA)-based empirical geosynchronous plasma sheet-radiation belt model of Denton et al (2015, 2016). (By “on-orbit,” we mean corrections and calibrations performed on the ground using data taken by multiple satellite instruments after launch, where the aim is to compute factors by which these data are made consistent)
Summary
Empirical models of plasma and radiation populations in Earth’s magnetosphere are valuable for a wide range of scientific and engineering purposes. This paper describes the methods and results of the extensive on-orbit corrections and cross-calibrations applied to the GOES MAGED and MAGPD fluxes in order to make them suitable for augmenting the MPA-based empirical geosynchronous plasma sheet-radiation belt model of Denton et al (2015, 2016). The agreement among the electron measurements from the three satellites is excellent (apart from during injections and dropouts, probably due to local time differences), while the proton fluxes from GOES-13 are noticeably lower than those from the other two satellites The two pairs of dashed lines on the 40-keV electron plot correspond to the flux levels of 2 Â 103 and This comparison shows that some effect other than linear calibration offsets caused large discrepancies between the GOES-15 and -13 MAGPD fluxes during this period in 2010 soon after the launch of GOES-15. Three of the five steps provide a partial correction for the long-term degradation of MAGPD
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