 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. "Grav 1—Terra," fumbled Craig. "No specific destination," supplied the man as he punched a key on a small instrument, "Air-lock ahead and to your right. "Place your clothing in the receptacle provided and assume a stationary position on the raised podium in the center of the lock." Craig obeyed the robot voice and began reluctantly to remove his flight jacket. When he withdrew his arm, the scratch was neatly coated with a layer of flesh-colored plastic material. "No, but my father—" "Your parents left Terra during the Second Colonization of Cassiopeia II, didn't they?" He was uncomfortable; Wyandotte seemed to know all about him. Short of Gravitational conditioning, there is nothing to stop you from going to Terra." Through the ports of the headquarters base satellite, he scanned the constellations for the scores of worlds he had visited during his eleven years in space. He had been on Einstein IV, the planet of eight moons, and had felt the pulse of all eight of the satellites at once that no PON could completely nullify. "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. "How ... how do they know when you ought ... to come out?" Two white-clad figures, ridiculously out of proportion, hovered wraithlike over him. By the fourteenth day, Craig knew he could stand Grav 1. Either that or they had begun to produce ultra-sonic waves. The huge headquarters base centrifuge aboard the man-made satellite had gradually caused their bodies to respond once more to a single source of pull. They were now ready to become inhabitants of planets again, instead of free-falling ships. On the eighteenth day, automatic machinery freed them from their imprisoning cots. Then they again began taking paraoxylnebutal in preparation for the free-fall flight to Terra. Only one of the score of men in the centrifuge tank remained voluntarily in his cot. "Not to Chociante, if that's what you mean. They just jerked his space card and gave him a one-way ticket 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.