|Abstract:||Of the roughly 210 species detected outside our Solar System, about a quarter of them are radicals. Radicals are sensitive probes of their chemical and physical environments and have been implicated in the formation of complex organic molecules (COMs). Astronomical observations of these species with mm-wave telescopes such as the Atacama Large Millimeter Array depend upon accurate rest frequencies of rotational transitions derived from laboratory spectroscopic measurements. Owing to uncertainties in theoretical rotational constants, centrifugal distortion, and angular momentum coupling, identification of a new radical from direct mm-wave spectroscopy is challenging in the absence of cm-band measurements at low J, requiring extensive frequency searches. We aim to determine mm-wave transition frequencies indirectly through rovibrational spectroscopy, which substantially alleviates the frequency search challenges of pure rotational spectroscopy in the mm-wave region. However, the much greater Doppler broadening at higher optical frequencies has traditionally prevented rovibrational spectroscopy from achieving the ~1 MHz accuracy required for astronomical applications. To overcome this, we are combining cavity enhanced frequency modulation spectroscopy with an AC magnetic field generated by a solenoid to achieve a sensitive, radical-selective, and Doppler-free technique that we call NICE-OHZMS (Noise Immune Cavity Enhanced Optical Heterodyne Zeeman Modulation Spectroscopy). In conjunction with absolute frequency calibration afforded by an optical frequency comb, we expect to measure rovibrational transitions of radicals with an accuracy and precision of better than 1 MHz. Here, the status of the instrument and proof-of-concept measurements of the first overtone band of nitric oxide will be discussed.