The Space Environment In-Situ Sensor Suite (SEISS) has been built for the NOAA GOES-R program to provide space weather data in geostatioary orbit. The suite consists of four instruments which detect different types of particles over a wide dynamic range in energy of 7 orders of magnitude (30 eV to 500 MeV for protons and 30 eV to 4 MeV for electrons) and 17 orders of magnitude in flux. The lowest energy instrument is the Magnetospheric Particle Sensor-Low (MPS-LO) which covers the range of 30 eV to 30 keV with 15 logarithmically spaced differential energy bands and a field-of-view of 180o by 5o, centered on the anti-Earth direction, for both ions and electrons. The field-of-view is divided into twelve unique 15o by 5o angular zones. Magnetospheric Particle Sensor-High (MPS-HI) makes measurements of electrons (ETel) with energies between 50 keV and 4 MeV in 10 differential energy bands and one integral band for energy above 2 MeV. MSP-HI also measures protons (PTel) with energies from 80 keV to 12 MeV in 11 differential bands. Each species is measured by five telescopes arranged in a fan, each with a 15o half-angle field-of-view separated by 35o and together spanning 170o in the same orientation as the MPS-LO. The fluxes of protons with energies from 1 to 500 MeV are measured by the Solar and Galactic Proton Sensor (SGPS) in 13 differential energy bands and one integral band above 500 MeV. There are two SGPS sensors on the satellite, one facing east and one west. The fourth instrument is Energetic Heavy Ion Sensor (EHIS) which is used for detection of heavy ions up to copper with energies between 10 and 200 MeV/nucleon. In this paper, we report in detail on the calibration programs for the MPS-HI and SGPS sensors and their application to the GOES-R space environment data. Similarity of response of the three sets of instruments is also discussed.
Each set of the instruments (three full sets of flight model units to date) was beam tested at five different accelerator facilities to cover the full operating energy range of the sensors and to allow on-orbit cross calibration among the GOES-R instruments. In addition, this work will enable GOES-R calibration validation by comparison with well-established data from the GOES-NOP satellites. The calibration measurements included the instrument response to a normally incident particle beam as well as to beams directed at oblique angles so that the energy dependent geometric factors could be calculated directly. In all cases, the experimental results were compared to modeled instrument responses derived from GEANT4 code calculations which covered the energy range from 40 keV to 10 MeV for electrons and 40 keV to 1,200 MeV for protons.
The MPS-HI PTel consists of three silicon solid-state, coaxially mounted detectors. The pattern of energy loss in the detectors is used to distinguished incident protons from electrons and to measure their energy. The same principle is used for ETel, except that is a more complicated structure with eleven coaxially mounted silicon detectors. The lowest energy range MPS-HI calibrations were carried out at the NASA Goddard Space Flight Center Radiation Effects Facility (REF) and ranged from 40 keV to 1.2 MeV for both protons and electrons. While the lowest part of the MPS-HI energy range does not overlap with MPS-LO, during conditions where the particle flux is isotropic, the measured slope of the energy dependent particle flux of both instruments should be nearly continuous across the energy gap. REF has two accelerators, a Cockcroft-Walton (40 to 120 keV) and a Van de Graaff (100 -1,200 keV for electrons and 50‑1,200 keV for protons). The data from the crossover point for electrons, 100-120 keV, is found to be in good agreement. The calibration of electrons is continued to higher energies, 800‑3,200 MeV, at the Van de Graaff accelerator at the Massachusetts Institute of Technology. Once the GEANT model, modified as needed, is validated by the calibration data, it is used to complete the determination of the instrument response to regions where measurements are impractical or impossible.
The SGPS instrument consists of three telescopes for the measurement of protons and alpha particles. Tel1 has two silicon detectors and covers 1 to 25 MeV (six differential energy channels) while Tel2, 25-80 MeV (two differential channels), and Tel3, 80 – 500 MeV (five differential energy channels and one integral channel) have three silicon detectors each. Tel2 and Tel3 differ from each other in the amount of degrader and detector thickness in each.
Most of the SGPS calibration work was carried out at cyclotron at Francis H Burr Radiation Treatment Facility at the Massachusetts General Hospital. This accelerator produces proton beams with energies from 25 to 219 MeV. This energy range is sufficient to test the aliveness of Tel1, the full range of Tel2 and the lower range of Tel3. It should be noted that cosmic ray muons produce a signal in the detector similar to that of protons in the SGPS integral energy channel (E > 500 MeV). Thus, it is possible to test the aliveness and roughly measure the response of that channel without an accelerator. The lower energy range of the instrument response was measured for one of the units at the cyclotron accelerator at Crocker Nuclear Laboratory at the University of California at Davis. This measurement covered the energy range from 1.2 to 30 MeV. One of the units was calibrated at the NASA NSRC facility at the Brookhaven National Laboratory with protons with energies from 200 to 2,000 MeV. This covered the entire upper range of the instrument response.
This paper will summarize the calibration program of the GOES-R SEISS MPS-HI and SGPS instruments and describe the similarity of response among multiple units. We will also review the usage of the new capabilities to maintain the current data products and derive new ones.