 The propulsion subsystem consisted of a main fuel tank and a Re-repressurization system which were activated shortly after lunar orbit insertion.All times are in EDT (UTC-4).Unlike the Apollo program missions, which took three days to reach the Moon, GRAIL made use of a three- to four-month low-energy trans-lunar cruise well outside the Moon's orbit and passing near the Sun-Earth Lagrange point L1 before looping back to rendezvous with the Moon.