Ganley, ShannonHoward, ThomasCavity ringdown spectroscopy (CRDS) is a highly sensitive technique that allows for the detection and analysis of extremely dilute chemical species. This tool is particularly useful for the collection of high-resolution spectra of molecules of astrochemical interest, which can be used to assist molecular detection efforts and improve our understanding of the chemistry that can occur in space. We present two iterations of a near-IR (1.5 µm) continuous-wave CRDS system which has been under development at the University of Maryland. HCN is chosen as a test molecule for each of these systems due to its importance in astrochemistry and its well-studied—experimentally and theoretically—spectra in the infrared. The rovibrational spectrum of the first overtone of the C-H stretch is analyzed on each system at room temperature, and in our newest system at cryogenic temperatures. The rotational temperature of HCN is calculated from this spectral data, and will be used in future work to quantify the rotational energy of neutral gaseous species for kinetics studies.en-USChemistryCMNSAstrochemistryHigh Resolution SpectroscopyInstrument DesignOther