"This photo is obviously a fake."

No, it is a composite image made from several Hasselblad images.

" First and foremost is who took the picture?"

Composite from Hasselblad images, not one picture.

" My question is what are the origins of the photo? My guess is that Alan Shepard had it made for his book."

And you are of course correct. As I noted above, there was no pictures of the event, so he had a composite made to show what it probably would have looked like. Not much unlike a artist's drawing.