This article reviews vacuum electronic device (VED) and high power solid state phased array radar transmitter technology for space-domain awareness (SDA) applications to detect and track satellites and millions of potentially hazardous space objects. Advanced VEDs including gyrotron amplifiers in the W-band are capable of as much as 160 kW peak power. Solid state technology currently enable amplifiers capable of 1 kW in the X-band and 30 kW in the C band, and advances in power combiner technology promise a potential 5-fold increase in output power in the X-band. MMICs are finding use in SDA applications at 92 to 100 GHz. Advances in solid state phased array radar for SDA applications is advancing rapidly.