MASC is a recently developed cross-track scanning (30 RPM) microwave sounder with channels near the 118 GHz oxygen line and the 183 GHz water-vapor line. It has previously participated in the PECAN campaign and the OLYMPEX GPM ground validation campaign. During both of these campaigns, it was deployed on the DC-8. MASC leverages recently developed technology and is a low-cost, compact instrument that weighs only 10 lbs. It is designed to be packaged as a 6U CubeSat and serves as an engineering prototype for the TEMPEST-D EVI-2 technology demonstrator. MASC uses MMIC-based millimeter-wave radiometers developed for GeoSTAR and HAMSR.