Terahertz Astronomy Cryogenic IF Design Calibration and Measurement

Studying the interstellar medium (ISM) is the key to answering questions about how material that exists between the stars drives the evolution of galaxies. Current models for the ISM life-cycle exist, but several steps lack observational evidence. Inthis dissertation I present the work I completed in support of up-coming mission to further study the ISM. This work includes ancillary data analysis of the Carina Nebula for the upcoming balloon mission: astrophysics stratospheric telescope for high spectral resolution observations at submillimeter wavelengths (ASTHROS). I present a derived molecular gas map of Carina from Herschel dust continuum emission maps at wavelengths between 70-500 microns. I compare it to the distribution of atomic gas, using HI 21 cm data, and of multiple CO isotopologues for the J = 1 → 0 rotational transition. I use these data sets to separate the CO–dark and CO–bright molecular components to study their relative contribution to the total molecular gas mass budget in Carina. I studied the transition between atomic and molecular gas in this region, by deriving the molecular fraction as a function of position, and comparing it to theoretical models of this transition. I also present the flight hardware design, testing, and space qualification of the intermediate frequency (IF) harness for the galactic/extragalactic ultra long duration balloon spectroscopic terahertz observatory (GUSTO). The harness transmits signal via novel cryogenic flexible stripline based transmission lines operating from 0.3 - 6.0 GHz. I designed three sets of 8-channel ribbons with characteristic insertion loss of 3.07 dB/ft at 5 GHz while the line was at a temperature gradient between 20 K - 300 K. Missions like GUSTO make use of non-linear mixing elements to achieve down-conversion of higher frequencies into IF bands. The mixers have a temperature dependent impedance that is difficult to measure. The last chapters of this work detail my attempt to carry out in-situ vacuum cryogenic calibrations using industry standard commercial off-the-shelf calibration kits and cryogenic RF electro-mechanical latching switches. I present the complex impedance of a non-linear superconducting transmission line as measured with a cryogenic calibration.