Colorado Student Space Weather Experiment: Differential Flux Measurements of Energetic Particles in a Highly Inclined Low Earth Orbit

Abstract

The Colorado Student Space Weather Experiment (CSSWE) is a three-unit (10 cm  10 cm  30 cm) CubeSat mission funded by the National Science Foundation; it was launched into a low Earth, polar orbit on 13 September 2012 as a secondary payload under NASA's Educational Launch of Nanosatellites program. The science objectives of CSSWE are to investigate the relationship of the location, magnitude, and frequency of solar flares to the timing, duration, and energy spectrum of solar energetic particles reaching Earth and to determine the precipitation loss and the evolution of the energy spectrum of radiation belt electrons. CSSWE contains a single science payload, the Relativistic Electron and Proton Telescope integrated little experiment (REPTile), which is a miniaturization of the Relativistic Electron and Proton Telescope (REPT) built at the Laboratory for Atmospheric and Space Physics. The REPT instrument will fly onboard the NASA Radiation Belt Storm Probes mission, which consists of two identical spacecraft launched on 30 August 2012 that will go through the heart of the radiation belts in a low-inclination orbit. CSSWE's REPTile is designed to measure the directional differential flux of protons ranging from 10 to 40 MeV and electrons from 0.5 to >3 MeV. Such differential flux measurements have significant science value, and a number of engineering challenges were overcome to enable these clean measurements to be made under the mass and power limits of a CubeSat. The CSSWE is an ideal class project, providing training for the next generation of engineers and scientists over the full life cycle of a satellite project.

First results from CSSWE CubeSat: Characteristics of relativistic electrons in the near‐Earth environment during the October 2012 magnetic storms

“…The Colorado Student Space Weather Experiment (CSSWE: http://lasp.colorado.edu/home/csswe/) is a three‐unit (10 cm × 10 cm × 30 cm) CubeSat mission funded by the National Science Foundation, launched into a low‐altitude, highly inclined orbit on 13 September 2012 as a secondary payload under NASA's Educational Launch of Nanosatellites program [ Li et al ., , , ]. CSSWE contains a single science payload, the Relativistic Electron and Proton Telescope integrated little experiment (REPTile).…”

“…REPTile uses the depth of penetration of the particle into the detector stack to infer the energy of incoming particles. Particles must also have adequate energy to penetrate through a thin beryllium foil to reach the first detector [ Li et al ., ], and then the particle species is determined based on the energy deposited in each detector. Particles depositing 0.25 < E < 1.5 MeV are classified as electrons, and those depositing E > 4.5 MeV as protons.…”

“…Figure shows yearly window‐averaged sunspot numbers and weekly window‐averaged solar wind speed (km/s) in the top panel and monthly window‐averaged fluxes of ~2 MeV electrons (#/cm 2 ‐s‐sr) from Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) [ Cook et al ., ] and Colorado Student Space Weather Experiment (CSSWE) [ Li et al ., , , ]. The period covers from SAMPEX's launch (3 July 1992, into a 550 × 650 km altitude and 82° inclination orbit) to almost its reentry (13 November 2012) and extends to include CSSWE measurements (5 October 2012 to 7 March 2013) from a similar orbit.…”

Modeling the Quasi‐Trapped Electron Fluxes From Cosmic Ray Albedo Neutron Decay (CRAND)

“…This process is called cosmic ray albedo neutron decay, or CRAND. Recently, relativistic electrons near the inner edge of the inner radiation belt were measured by the Colorado Student Space Weather Experiment CubeSat (Li et al, 2012 and identified as CRANDproduced . CRAND was identified as an important source for the inner proton radiation belt six decades ago (Kellogg, 1959;Selesnick et al, 2014;Singer, 1958), but not as a significant source of trapped electrons (Lenchek et al, 1961;Walt & Farley, 1976).…”

Design and scientific return of a miniaturized particle telescope onboard the Colorado Student Space Weather Experiment (CSSWE) CubeSat

“…Funding for CSSWE was received in January 2010 for $840k from the NSF. CSSWE's primary science objective is to study space weather in Earth's magnetosphere [1]. The science payload, the Relativistic Electron and Proton Telescope integrated little experiment (REPTile) [2], is a miniaturized version of the Relativistic Electron and Proton Telescope (REPT) [3] on board NASA's Van Allen Probes mission [4].…”