Ulysses’ power profile

Over more than 17.5 years of operation, the power provided to the Ulysses spacecraft by the Radioisotope Thermoelectric Generator (RTG) has been declining naturally. The RTG eventually became unable to provide enough heat to the craft and its payload. In mid-January 2008, the situation worsened when the main radio transmitter also failed – its warmth otherwise kept the fuel from freezing.