The G-band (183 GHz, 1.5 mm wavelength) Water Vapor Radiometer (GVR) measures brightness temperature at 183.31 GHz +-1, +-3, +-7 and +-14 GHz to estimate low concentrations of precipitable water vapor and liquid water path. The airborne version of the instrument is packaged and wired to operate from a standard PMS probe canister.