We offer an ultra-compact klystron amplifier for remote sensing on CubeSats. It will operate at 35.7 GHz, have 400 MHz bandwidth, and output greater than 32 watts with 35 dB gain. It employs a two-stage depressed collector, allowing prime efficiency of 50%. Comparable solid state power amplifiers have 15% efficiency and output only 7 W. klystrons are the only amplifier technology that can be miniaturized to this degree. Volume with power conditioner and driver is less than 0.500 cm3, half the allowed space. It uses a breakthrough ultra-miniature scandate cathode capable of 100A/cm2 at 1000 degrees C and 5A/cm2 at less than 800 degrees C. At this temperature, life is more than 100,000 hours. The klystron uses cathode ray tube construction, which lowers weight, size and cost (two to five times less than standard brazed ceramic-metal construction). Parts are fastened via glass rods or mechanical capture or by spot welding. Most parts are standard off-the-shelf, which further lowers cost. It uses a glass vacuum envelope, glass feedthroughs, combination RF window-coupler and barium getters to maintain vacuum. In Phase I we successfully built two beam testers. In Phase II we construct an entire amplifier package in CubeSat volume. E beam, inc. is a leader in innovative miniature cathodes, electron guns and vacuum electron devices generally. It has long promoted cathode ray tube construction as a way to mass produce medium power microwave tubes.