 Why did the man take Craig's picture when he arrived on Terra?
Flight Officer Robert Craig surrendered the tube containing his service record tapes and stood waiting while the bored process clerk examined the seal. "Mr. Craig," the psychologist said slowly, "you have my authorization for you to return to Terra as a private citizen of that planet. On the eighth day, two attendants, who showed the effects of massive doses of PON to protect themselves from the centrifugal force, had to carry a man out of the tank. Two white-clad figures, ridiculously out of proportion, hovered wraithlike over him. They were now ready to become inhabitants of planets again, instead of free-falling ships. Then they again began taking paraoxylnebutal in preparation for the free-fall flight to Terra.
 The man is a customs official.
 Terran society identifies and monitors everyone.  The man is a customs official.  The photo is for Craig's job ID.  Craig is the first spaceman he had ever seen.