The majority of the time, turn off with this meaning is a transitive verb. I'd say, I turned off the stove, but I'd be less likely to say the stove turned off; I'd only say the latter if it was clear from context that something happened to the stove to make it turn itself off.
Power down and switch off are similar. Shut down is similar as well, but we're probably more familiar with seeing this used intransitively because we often think of computers or software as doing things for themselves. In your example, the telescopes turn themselves off, because they are at the end of their lives. We can infer that they will run out of power, or they will receive a signal to turn off, much as we say a computer shuts down.
Some examples of intransitive use from COCA:
" My father says that the lights will turn off like that every night. " " That can't be right, " said Mircea. " Last night it was just some technical problem. "
Most evenings after dinner I hear his radio switch off, then his door open and shut...
The armor would power down, of course, once I removed it.