Spectra from 0.5 to 0.6THz play critical roles in planetary science, astrophysics and radio-astronomy as various chemical species including water, nitrates (NO2, N2O, NH3) and organics (CH4 and HCN) can either absorb or reflect radiation in this frequency regime. Accordingly, NASA and ESA have developed a wide range of spectroscopic sounding instruments to investigate our solar system. Current LO chains for spectroscopic receivers are implemented with discrete III-V devices and heavy waveguide assemblies. For instance, the 600GHz NASA PISSARRO spectrometer for Europa begins with a 33GHz PLL, tripled to 100GHz, doubled to 200GHz, and then tripled again to 600GHz via multiple waveguides. This LO chain occupies over 3000cm3, weighs 2.5kg, and consumes 11.5W of DC power.