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Appendix 9  Geometric Factor Study for the Deflected and Unscattered Electrons of HISCALE (Buckley MS Thesis)

Note:  John Buckley's thesis is included here in its entirety.  Sections, tables, and figures have been renumbered in accordance with the numbering systems being used in this handbook.  The original thesis is available at Fundamental Technologies, LLC, and at the Anschutz Science Library at the University of Kansas.

Abstract.  HISCALE is the Heliosphere Instrument for Spectral, Composition and Anisotropy at Low Energies aboard the Ulysses spacecraft.  One requirement needed to obtain space plasma fluxes from spacecraft is knowledge of the geometrical factors of the instrument.  For the complex geometry of the deflected electron system aboard HISCALE, a numerical method is required to find these factors.

The numerical method presented in this thesis is based on Shodhan's method3, and the necessary refinements have been made to obtain results for this particular instrument.

Included in this thesis is a comparison of the results with experimental data.  It has been found that the results of the simulation only partially agree with the data; reasons for the discrepancies are discussed, and an overall evaluation of this method given.

Table of Contents

A9.1 Chapter 1 -- Introduction

The goal of this study is to calculate the energy-dependent geometric factors for deflected electrons for the HISCALE instrument aboard the Ulysses spacecraft.  Included in this thesis is a brief overview of the HISCALE mission, the definition of a geometrical factor, a formal discussion of how the geometric factor is calculated using a computer simulation, and the results of the calculation.

A9.1.1  Ulysses Spacecraft

The Ulysses spacecraft has been designed to study various solar phenomena out of the ecliptic plane.  Launched in October of 1990, the spacecraft was first sent to fly by Jupiter where it received a gravitational boost that sent it into its polar orbit about the sun.  Aboard the craft are nine scientific instruments, each designed to study specific aspects of the interplanetary media.  One of these instruments is HISCALE--Heliosphere Instrument for Spectral, Composition, and Anisotropy at Low Energies, a part of which is the focus of this investigation.  HISCALE will collect count rates for interplanetary ions and electrons over specific energy ranges.  This information will allow scientists to study solar wind and coronal phenomena in a region never explored before.

HISCALE itself consists of five telescope apertures, two low energy magnetic spectrometers (LEMS), two low energy foil spectrometers (LEFS), and the other a composition aperture (CA).  A picture of these five apertures is shown in Figure A9-1.  The LEMS detectors contain magnets designed to deflect electrons away from the detector, hence leaving just the ions to hit the detector surface.  The LEFS detectors on the other hand contain a thin foil sheet over the detector which stops low energy ions from hitting the detector surface.  The composition aperture utilizes a DE vs. E detector, and is able to differentiate counts for the heavier ions such as a's, C's, N's, O's, etc.  See Reference 1 for further details on instrument specifications and design.

T. Hunt-Ward, 5/14/09