Doesn't look to have solar panels.
And even hypergolic fuels needs some sort of power to pump the fuels together. And the unit needs to be properly aligned for the burn, which involves computers and thrusters with valves, sensors, radio receivers, transmitters
None of those may be high power items, but they do add up.
Would batteries have survived all the radiation over the years? I don't know.
Or was it a plutonium generator at the end of one of those rods sticking out of the side? Might have been, would it be operational. Beats the hell out of me. Maybe Wikipedia would be revealing.