^^Abstract^^
The CubeSat Hydrometric Atmospheric Radiometer Mission (CHARM) at JPL is developing a compact radiometer instrument (<4 x 4 x 6 inches) operating at the 183 GHz water-vapor line in order to validate new low-noise amplifier technology and demonstrate the first Cubesat-based radiometer. The instrument will be delivered for integration with a 3U (4 x 4 x 12 inches) Cubesat flight system developed at UT Austin. I will speak about the instrument development, focusing on the design choices and challenges related to the extreme size, weight and power constraints of the Cubesat standard.