Year: 2026
Type: preprint
Abstract: We present the design methodology, implementation, and data products of the Energetic Particle Detector (EPD) instrument on-board the Electron Losses and Fields Investigation (ELFIN) dual SmallSat mission. ELFIN was designed to study the time-evolution of energetic particle distributions in Earth's magnetosphere, having operated in polar Low Earth Orbit (LEO) from 2018 to 2022. Each satellite's instrument payload contained a pair of detector heads to sense differential-directional fluxes of 50 keV to $\sim$5 MeV electrons (EPDE), and 50 keV to $\sim$2 MeV atomic ions (EPDI), with an energy resolution better than 50% ($ΔE/E<0.5$). The satellites were spinning with a nominal period of 2.8 s in a plane containing Earth's background magnetic field, with particle counting intervals subdivided into 16 consecutive spin sectors. Each EPD was paired with a three-axis Fluxgate Magnetometer (FGM) sampled at 80 Hz for local pitch-angle determination. Each detector head operated on the principle of pulse-height analysis (PHA) in solid state media, collimated by a rectangular 22.5$^\circ$ field of view and entrance aperture. The EPDE contained a stack of 6 silicon detectors (0.7 cm total thickness) with 0.15 cm$^2$ str geometric factor, with ion contamination mitigated by an aperture foil and digital coincidence logic. The EPDI contained a stack of 2 silicon detectors (0.1 cm total thickness) with 0.03 cm$^2$ str geometric factor, with electron contamination mitigated by a magnetic broom stage and digital anti-coincidence logic. The total assembled mass, volume, and power required for the EPD detector heads and circuit boards were 939 g, 10$\times$9.8$\times$8.4 cm$^3$, and 2.3 W, respectively. We describe each EPD design element alongside instrument data products and processing.
Source: arXiv (Cornell University)
Authors: Wilkins, Colin, Caron, Ryan, Tsai, Ethan, Shaffer, Chris, Cruce, Patrick, Chung, Maxwell, Runov, Andrei, Liu, Jiang, Turner, Drew, Shprits, Yuri, Li, Wen, Lawson, Michael, Masongsong, Emmanuel, Russell, Cindy, Grimes, Eric, Wu, Jiashu, Allen, Matthew, Artinger, Jessica, Flemming, Alex, Hesford, Brayden, Iglesias, Laura, King, James, Norris, Austin, Pedersen, Carter, Thomlinson, Daniel, Turner, Wynne, Angelopoulos, Vassilis
Institutions: University of California, Los Angeles, The Aerospace Corporation, University of Alberta, Northrop Grumman (United States), Johns Hopkins University Applied Physics Laboratory, GFZ Helmholtz Centre for Geosciences, Boston University, Goddard Space Flight Center, PsiQuantum (United States), University of California, Riverside, Apple (United States), Orange Coast College
Language: English
Subfield: Space and Planetary Science
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
Awards: G3450036804, Collaborative Research: Causes and Consequences of Relativistic Electron Precipitation as Revealed by the CubeSat Mission ELFIN’s Pitch-Angle Resolved Loss Cone Measurements, CubeSat: Electron Losses and Fields INvestigation (ELFIN), THE ELFIN-STAR (ELFIN*) CUBESAT WILL RESOLVE THE ROLE OF ELECTROMAGNETIC ION CYCLOTRON (EMIC) WAVES FOR (AND DETERMINE THE RATE OF) RELATIVISTIC ELECTRON PRECIPITATION DURING STORMS. FROM A NEAR-POLAR (I>65O) LOW-EARTH (400KM ALTITUDE) ORBIT ELFIN* WILL PROVIDE UNIQUE PITCH-ANGLE- AND ENERGY-RESOLVED SPECTRA OF RELATIVISTIC ELECTRON FLUXES WITHIN THE LOSS CONE TO DETERMINE WHETHER THEY BEAR THE CHARACTERISTIC SIGNATURES OF EQUATORIAL SCATTERING BY EMIC WAVES. COMPARING ITS OBSERVATIONS WITH DIFFUSION MODELS FOR EMIC CHORUS MAGNETOPAUSE SHADOWING AND OTHER LOSS MECHANISMS ELFIN* WILL ESTABLISH WHETHER LOSSES ARE DOMINATED BY EMIC WAVES OR ARE DUE TO OTHER PROCESSES. ENERGETIC PARTICLE DETECTOR (EPD) ELECTRON MEASUREMENTS (0.1-5MEV) AT RESOLUTION 11.25O (0.4O 0.8O AT THE EQUATOR AT L=5-7) RESOLVING THE LOSS-CONE INCLUDING TRAPPED PARTICLES ACHIEVE CLOSURE. IF EMIC WAVES PROPAGATE TO THE IONOSPHERE ELFIN* S MAGNETOMETER (MAG) WILL ALSO DETECT THEM (DESIRED BUT NEITHER NECESSARY NOR SUFFICIENT FOR CLOSURE). ELFIN* S INTEGRATED DATA ANALYSIS APPROACH AND RAPID DISSEMINATION STRATEGIES VIA THE SPACE ENVIRONMENT DATA ANALYSIS SYSTEM (SPEDAS AN OFF-SPRING OF THEMIS) OPTIMIZE SCIENCE YIELD AND ENSURE WIDEST COMMUNITY BENEFITS. ELFIN* S POTENTIAL IS COMPOUNDED BY CONJUNCTIONS WITH CONCURRENT EQUATORIAL MISSIONS IN 2016 (THEMIS RBSP ERG MMS) THAT WILL COMPLEMENT ITS UNIQUE LOSS-CONERESOLVING SPECTRA.OUR SIMILAR PROPOSAL TO NSF IN 2012 (ELFIN) IS ONE OF TWO FRONT-RUNNERS BUT HAS NOT BEEN SELECTED (YET) DUE TO PROGRAMMATIC CONSIDERATIONS IN A TOUGH FISCAL ENVIRONMENT. IF ELFIN IS SELECTED BY NSF WE HEREBY PROPOSE UNDER H-TIDES TO EXECUTE ELFIN* S STAR OPTION. ELFIN* WILL BUILD AN IDENTICAL SATELLITE TO NSF S ELFIN AND RELEASE IT ON THE SAME LAUNCH VEHICLE INTO A FORMATION ORBIT WITH ITS TWIN. SPRING-SEPARATION PROVIDES A NATURAL VARIATION OF THE INTER-CUBESAT DISTANCE WITH A FULL-ORBIT LAP ONCE PER 30DAYS.ELFIN* S SMALL-SEPARATION RADIATION BELT CROSSINGS (0-15MIN 33% OF THE TIME) WILL RESOLVE THE TEMPORAL VARIABILITY (LOSS-CONE FILL RATE) AND SPATIAL EXTENT OF THE RELATIVISTIC ELECTRON PRECIPITATION AND DETERMINE ITS AGREEMENT WITH EQUATORIAL EMIC WAVE DIFFUSION RATES OVER TIME SCALES COMPARABLE TO SUCH DIFFUSION (MINUTES). THUS FOR AT LEAST 2 STORM-TIME PRECIPITATION EVENTS OVER ITS BASELINE (6- MONTH) MISSION ELFIN* WILL DETERMINE THE GLOBAL ROLE OF EMIC WAVES ON RADIATION BELT PRECIPITATION. A RADIATION MARGIN OF>2 AND EMPHASIS ON PARTS SELECTION FOR A>1YR DESIGN-LIFE IS EXPECTED TO DOUBLE THIS SCIENCE YIELD TO>4 STORMS.ELFIN* RESOLVES A FUNDAMENTAL SPACE- AND PLASMA-PHYSICS QUESTION RELATED TO RELATIVISTIC ELECTRON SCATTERING AND LOSS IN THE OUTER RADIATION BELT. ITS STAR OPTION IF EXERCISED WILL DETERMINE THE GLOBAL EFFECTS OF SUCH SCATTERING. FOR PURPOSES OF UNDERSTANDING SPACE WEATHER AND FUNDAMENTAL PLASMA PROCESSES DETERMINING STORM-TIME OUTER BELT ELECTRON LOSS RATES AND MECHANISMS IS JUST AS IMPORTANTAS DETERMINING ACCELERATION OR TRANSPORT. ELFIN* IS THEREFORE KEY IN THE HELIOPHYSICS DISCIPLINE S ASPIRATION BOTH FOR A COMPREHENSIVE NATIONAL SPACE WEATHER PROGRAM AND TO UNDERSTAND FUNDAMENTAL MICROSCOPIC PHYSICS AS WELL AS THE GLOBAL SYSTEM BEHAVIOR AS RECOMMENDED BY THE 2012 HELIOPHYSICS DECADAL SURVEY. ELFIN* DIRECTLY ADDRESSES ALL THREE STATED HELIOPHYSICS OBJECTIVES (IN THE 2010 SMD SCIENCE PLAN) TO UNDERSTAND: THE FUNDAMENTAL PHYSICAL PROCESSES OF THE SPACE ENVIRONMENT HOW TECHNOLOGICAL SYSTEMS ARE AFFECTED BY SOLAR VARIABILITY AND DEVELOPING THE CAPABILITY TO PREDICT EXTREME AND DYNAMIC CONDITIONS IN SPACE . THESE ALSO TIEDIRECTLY TO HELIOPHYSICS SCIENCE GOALS #2 AND #4 LISTED IN THE DECADAL SURVEY (P-S2). ELFIN* S APPROACH TO ADDRESS LOSSES SYSTEM-WIDE BY INTEGRATING ITS UNIQUE DATASET WITH THOSE OF OTHER NASA MISSIONS ADDRESSES THE PRIMARY RECOMMENDATION OF THE DECADAL SURVEY(FIG. 1.2) FOR SYSTEM-SCIENCE WITH THE INTEGRATED HELIOPHYSICS SYSTEM OBSERVATORY.
OpenAlex ID: W7221824721