A double-Fourier interferometer testbed for spectral imaging in the far-infrared
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Date
2024
Authors
Scott, Jeremy P.
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy
Abstract
The far-infrared band of the electromagnetic spectrum is one of the least explored areas of astronomy despite its critical importance for understanding the formation and evolution of planets, stars, and galaxies. Part of this disparity is explained by the challenges associated with conducting observations with the sub-arcsecond spatial resolution required to resolve the structures of interest. Much of the utility of far-infrared astronomy is due to the wealth of spectral features residing within this band, which probe the full range of physical conditions within the interstellar medium. As such, the ideal instrument is one that provides broad spectral imaging capabilities with enhanced spatial resolution. A promising candidate is the double-Fourier interferometer that combines a spatial interferometer with a Fourier transform spectrometer. The two techniques have separately been studied extensively and used productively, however, their combination into a single instrument is relatively new and has yet to be fully validated.
The primary objective of this thesis, and the work presented within, is to validate the double-Fourier technique by demonstrating the key observing capabilities of the instrument. First, it must be shown that the data collected with the instrument can be used with traditional aperture synthesis techniques to produce images with enhanced spatial resolution. Second, it must be shown that the instrument is sensitive to spectral variation within the source, and thus, allow for the production of spectral images with enhanced spatial resolution. This is the main advantage a double-Fourier system has over transitional narrow band spatial interferometers. Third, it must be demonstrated that these techniques can be extended to wide field applications where multiple detectors, sensitive to different regions of the source plane, are used within a detector array.
The observing capabilities listed above were demonstrated independently using simple test cases. This thesis also includes a detailed report on the design, operation, and characterization of the particular double-Fourier interferometer used in this work. Analytical models and empirical measurements were leveraged to predict and better understand the results and limitations of the instrument observations. This analysis extends to the unconventional bolometer technology that was employed for the detector system of the interferometer. The full observation process is presented including data acquisition, calibration, and each step of image reconstruction. Both real data and simulated models are provided when discussing data reduction, and when presenting final results, which provide confidence in the accuracy and quality of the analysis. With the inclusion of a review of the underlying theoretical framework for spatial interferometry and Fourier transform spectroscopy, this thesis serves as an appreciably comprehensive end-to-end reference for double-Fourier interferometry.
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Keywords
interferometry , imaging , optics , instrumentation