What were they thinking?
"The Side B back-up has not been fired up since Hubble went aloft 18 years ago"
Long ago I learnt the truism that a backup is only as good as your confidence it will work. Which all good SysAdmins know which is why they test their backups regularly.
Seems the scientists are of the view that because it worked 18 years ago it must work now. Which is pretty sad and probably qualifies for an epic fail.