Date of Award

Spring 1-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Kevin France

Second Advisor

James Green

Third Advisor

Nils Halverson

Fourth Advisor

Scott Palo

Fifth Advisor

Jeremy Darling

Abstract

We describe the scientific motivation, technical development, and flight performance of the Colorado High-resolution Echelle Stellar Spectrograph (CHESS). CHESS is a far ultraviolet rocket-borne instrument designed to study the atomic-to-molecular transitions within translucent cloud regions in the interstellar medium. CHESS is an objective echelle spectrograph, which uses a mechanically-ruled echelle, a powered (f/12.4) cross-dispersing grating, and a cross-strip anode microchannel plate detector, and is designed to achieve a resolving power R > 100,000 over the bandpass λ λ 1000--1600 A. The final two flights of the instrument (CHESS-3 and CHESS-4) observed Β Scorpii (Β Sco) and γ Arae (γ Ara). For CHESS-4, we describe our novel method for increasing the resolution of the instrument by physically stressing the echelle grating, introducing a curvature to the surface of the optic. We present flight results of interstellar molecular hydrogen absorption, including measurements of the column densities and temperatures, on the sightlines. For Β Sco, we find that the derived column density of the J'' = 1 rotational level differs by a factor of 2--3 when compared to the previous observations of Savage et al. 1977. We discuss the discrepancies between the two measurements and show that the source of the difference is likely due to the opacity of higher rotational levels contributing to the J'' = 1 absorption wing, increasing the inferred column density in the previous work. We extend this analysis to 9 \copr and 13 \fuse spectra to explore the interdependence of the column densities of different J'' levels and how the H2 kinetic temperature is influenced by these relationships. Based off of our results, we find a revised average gas kinetic temperature of the diffuse ISM of T10 = 68 plus/minus 13 K, 12% lower than the value found in the previous work.

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