Could it be a typo for "and one by one they will be turned off"? CNN:
Many of the existing space telescopes, Hubble included, are nearing the end of their lifetimes, and one by one they will turn off. Without the James Webb Space Telescope, our eyes on the universe would be closed for the foreseeable future.
Best Answer
There is no mistake here.
Turn off is active. When transitively used ("subject turns object off"), the subject is turning off the object. When intransitively used ("subject turns off"), the subject turns itself off.
Be turned off is passive, indicating that the subject is not doing anything to turn itself off, and implying that some other force is acting on it to turn it off.
In this case, the active form was presumably used because the telescopes will (actively) use up their power (causing themselves to turn off) rather than someone flipping a switch somewhere to turn them off. So since it will be the telescopes' power drainage or mechanical failure that turns them off, the telescopes are described as turning themselves off.