AE9, AP9 and SPM: New Models for Specifying the Trapped Energetic Particle and Space Plasma Environment

Abstract

The radiation belts and plasma in the Earth's magnetosphere pose hazards to satellite systems which restrict design and orbit options with a resultant impact on mission performance and cost. For decades the standard space environment specification used for spacecraft design has been provided by the NASA AE8 and AP8 trapped radiation belt models. There are well-known limitations on their performance, however, and the need for a new trapped radiation and plasma model has been recognized by the engineering community for some time. To address this challenge a new set of models, denoted AE9/AP9/SPM, for energetic electrons, energetic protons and space plasma has been developed. The new models offer significant improvements including more detailed spatial resolution and the quantification of uncertainty due to both space weather and instrument errors. Fundamental to the model design, construction and operation are a number of new data sets and a novel statistical approach which captures first order temporal and spatial correlations allowing for the Monte-Carlo estimation of flux thresholds for user-specified percentile levels (e.g., 50th and 95th) over the course of the mission. An overview of the model architecture, data reduction methods, statistics algorithms, user application and initial validation is presented in this paper.

The Energetic Particle Telescope: First Results

“…Because the mirror points are located in the high atmosphere in the Southern hemisphere, the particles are lost and this leads to very low fluxes in the Northern hemisphere above Europe. These low fluxes are not displayed by the AE8 model (Vette 1991) or more recent AE9 model (Ginet et al 2013) available on SPENVIS (www.spenvis.oma.be). Figure 5 illustrates the electron flux in Channel 5 (1-2.4 MeV) observed during one month.…”

Quantifying the effect of magnetopause shadowing on electron radiation belt dropouts

“…Energetic electrons are measured by two subsystems: the low-energy particle (LEP) subsystem resolves 0.14 to > 1.25 MeV electrons into five energy channels; the highenergy X-ray and particle (HXP) subsystem resolves 1.3 to > 5.8 MeV electrons into six energy channels (see also Denton and Cayton, 2011). The CXD electron count rates are inverted to obtain the omni-directional differential number flux, j , by solving the spectral inversion function (Ginet et al, 2013) …”

“…The inversion of Eq. (1) is carried out using InvLib, a C inversion library developed by Paul O'Brien at Aerospace Corporation and used in the data preparation for the AE9/AP9/SPM radiation belt climatology model (see Ginet et al, 2013, and references therein). For each time we assess the goodness of fit of the relativistic Maxwellian and discard those data that cannot adequately be described by the chosen energy spectrum.…”

Space as a Tool for Astrobiology: Review and Recommendations for Experimentations in Earth Orbit and Beyond

“…Direct measurements are from the EXPOSE-E & EXPOSE-R radiometerdosimeter on the exterior of the ISS (Dachev et al 2015(Dachev et al , 2012, the Radiation Assessment Detector on the Mars Science Lander (Zeitlin et al 2013), the Lunar Reconnaissance Orbiter (Mazur et al 2011), and the Advanced Composition Explorer probe located at lunar Lagrange point L1 (Stone et al 1998). Model results are from CREME 96 for GCRs (Tylka et al 1997), ESP-PSYCHIC for SEPs (Xapsos et al 2007(Xapsos et al , 1998, AE9/AP9 for trapped radiation in Earth orbit (Ginet et al 2013), and SHIELDOSE-2Q for dose vs. shielding thickness (Seltzer 1994;Truscott 2010). Note that AE9/AP9 is an accumulation of 32 empirical data sets spanning a 35-year period for altitudes and inclinations covering the supermajority of possible Earth orbits (Ginet et al 2013), and is currently the most accurate general tool for predicting threshold dose attributable to Earth's trapped particle radiation.…”

“…Model results are from CREME 96 for GCRs (Tylka et al 1997), ESP-PSYCHIC for SEPs (Xapsos et al 2007(Xapsos et al , 1998, AE9/AP9 for trapped radiation in Earth orbit (Ginet et al 2013), and SHIELDOSE-2Q for dose vs. shielding thickness (Seltzer 1994;Truscott 2010). Note that AE9/AP9 is an accumulation of 32 empirical data sets spanning a 35-year period for altitudes and inclinations covering the supermajority of possible Earth orbits (Ginet et al 2013), and is currently the most accurate general tool for predicting threshold dose attributable to Earth's trapped particle radiation. For the purpose of this comparison, this entry also generally includes transit to a variety of locations around the Solar System of current interest in space-faring nations, including Mars, its moons, the moons of Jupiter, and various near-Earth objects.…”