1. the elapsed time it takes for a signal to travel from Earth to a spacecraft (or other body) and back to the starting point; [syn: round-trip light time, RTLT]
WordNet (r) 3.0 (2006):
round-trip light time
n 1: the elapsed time it takes for a signal to travel from Earth
to a spacecraft (or other body) and back to the starting
point [syn: round-trip light time, RTLT]