The paper discusses advances of testing GaN on Si switches for MHz-power-converter technologies for satellite applications. Radiation testing is discussed for technologies operated up to 600 V for power conversion suitable for compact power converter designs. Promising results have been obtained with respect of radiation stability for GaN switches on Si substrates. Further GaN mm-wave PA technologies suitable for up to Eband communication links and space-born tube drivers are demonstrated with the space-specific technology requirements incorporated for packaging while maintaining the performances. Further, representative Mm-wave RF-MMIC designs operating at E-band are being discussed for operation between 70 and 84 GHz based on this technology. With the advances in reliability demonstrated in parallel these circuits become relevant for space operation.