Who is Joe Calvert from Rendezvous with Rama and what is their importance?

Joe Calvert is the lieutenant of the vessel Endeavour. He maneuvers the ship the initial landing of Endeavour on the northern hemisphere of Rama. He later takes part in the initial scouting team that evaluates the possible problems of descending Rama through one of the long stairways along the northern entrance point. He later joins Commander Bill Norton in the first mission that attempts to reach the "bottom" of Rama. During in the last missions on Rama, he operates the laser torch to cut through the sealed building in London.