Imaging Science Ph.D. Defense: Kate Oram
Ph.D. Dissertation Defense
Exploration of the use of digital micromirror devices for highly multiplexed spectroscopy applications in astronomy
Kathleen Oram
Imaging Science Ph.D. Candidate
Chester F. Carlson Center for Imaging Science, RIT
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Abstract:
Highly multiplexed spectroscopic capabilities are critical to future astronomy space missions. Such capabilities enable large samples of spectral data to be collected in an efficient manner. The individual mirrors of a Digital Micromirror Device (DMD) can serve as slits in a multi-object spectrograph (MOS). This work explores several areas vital to the inclusion of DMDs in future astronomy missions: space qualification, optical performance, and the implementation of Hadamard Transform Spectral Imaging (HTSI). While DMDs were not designed for space, this work reports on testing that demonstrates that the devices can withstand the environmental conditions of a space mission. The optical properties of a DMD ultimately drive the wavelength range and quality of spectral data obtained from a DMD-based MOS. We have characterized the reflectance and contrast ratio of various DMDs from near ultra-violet through visible wavelengths and discuss the results. This work also discusses efforts in expanding the spectral sensitivity of DMDs. Maximizing spectral information over a spatial field of view (FoV) on the sky is highly desirable. In the multi-object spectroscopy mode, individual DMD micromirrors are selected to generate a sparse sample of spectra at individual locations. Additionally, a DMD can be used for integral field spectroscopy (IFS) by forming a long slit from a line of micromirrors, which is then altered to effectively scan across the FoV. In this work we evaluate an alternative technique, HTSI. HTSI has the advantage of a gain in signal-to-noise ratio (SNR) as compared to direct measurements with a long slit, when the observed signals are not photon-noise dominated. We have simulated the performance of HTSI with a DMD-based MOS to identify the limitations of the technique and scenarios where it is most advantageous. With both MOS and IFS capabilities, a DMD-based instrument is a versatile asset fit for a variety of astronomy missions.
Intended Audience:
Undergraduates, graduates, and experts. Those with interest in the topic.
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