It isn't often that I see a porcupine descend (or even ascend) a tree but every time is as exciting & nail biting as the first.
Any noise (and that can include the click from the camera shutter) or slight movement can send a porcupine back up the tree. They don't see very well but their hearing and sense of smell are both acute. And that can mean a very long silent wait for another potential descent.
Then if you add in early evening light (and not dusk) and a clear view of the tree & the climber, it doesn't get more perfect to document the event.