Ulysses HISCALE Data Analysis Handbook
Appendix 9 Geometric Factor Study for the Deflected and Unscattered Electrons of HISCALE (Buckley MS Thesis)
A9.2 Chapter 2 - The Geometric Factor and Fluxes
Space scientists are interested in particle fluxes for a given particle type at a given energy and location in time and space. This integral flux J is therefore a function of energy E, particle type a, position x, and time t.
Raw data comes in the form of R counts/second. Space scientists need to convert these count rates into particle fluxes. Part of this conversion involves the geometric factor G. The raw count rate R is related to the intensity I of the particle stream by G, the gathering power of the telescope involved:
R =GI
For a telescope which is able to distinguish a single particle species over a given energy passband DE, we have for I isotropic that G = G, hence
R = GI0, I0 Isotropic intensity.
To calculate this G for a simple geometry, imagine that you have a telescope with a detector near the bottom, as in Figure A9-3. The detector has surface area S, and is broken up into surface elements ds. An excellent formulation in calculating G for simple geometries is given by J. D. Sullivan2
where Ω is the domain of solid angle ω, which is determined from the telescope geometry, dω=dϕdcosθ, and dσ•r is the effective element of area looking into ω.
So, roughly speaking we can think of G as being an area times an effective solid angle Ω:
G=ΔAΔΩ
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Updated 8/8/19, Cameron Crane
QUICK FACTS
Mission End Date: June 30, 2009
Destination: The inner heliosphere of the sun away from the ecliptic plane
Orbit: Elliptical orbit transversing the polar regions of the sun outside of the ecliptic plane