“zenith” and “nadir,” which were space lingo for basically “up away from Earth” and “down toward Earth.” If you arranged yourself so that your back was to the tori and your face toward Amalthea, with the “port” stuff on your left hand and the “starboard” stuff on your right, then your head would be aimed toward the zenith and your feet toward the nadir and the surface of Earth four hundred kilometers below.
