There are two instantaneous (1 sec.) launch windows at 8:37:06 a.m. and 9:16:12 a.m. EDT. The launch period, the last for Delta IIs at the Cape, extends through Oct. 19. The launch times occur approximately four minutes earlier each day.
GRAIL’s primary science objectives are to determine the structure of the lunar interior, from crust to core, and to advance understanding of the thermal evolution of the moon.