Power & Thermal Subsystem

Electronic Power Converters

The EPCs provide regulated power to the Travelling Wave Tube Amplifiers (TWTAs) in the Telemetry, Tracking and Command (TTC) subsystem, which amplifies Ulysses' X-band downlink signal. There are two EPCs operating in cold redundancy, however because of the importance of their role an automatic changeover logic is provided. If the current in the active EPC falls below 0.7A for more than 100ms, the redundant EPC will be switched on automatically, and the waveguide switch connecting the active TWTA to the High Gain Antenna (HGA) will be switched to the correct position. The TWTA, HGA and waveguide connectivity with the TTC is shown in a schematic of the TWTA interface unit


An operating EPC/TWTA is the most power hungry unit on the spacecraft, continually consuming about 64W.