The GRAIL mission was managed by NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, for NASA's Science Mission Directorate in Washington. The mission was part of the Discovery Program managed at NASA's Marshall Space Flight Center in Huntsville, Alabama.
However, the astronomers will require more HST observations in order to obtain accurate measurements in order to determine if the moon's orbit is circular or elliptical. Preliminary estimates suggest that if the moon is in a circular orbit, it finishes a circle around Makemake in 12 days or longer.
Ganymede, and four other moons dwelling in our Sun's family, possess liquid water beneath their frigid crusts of ice. The others are Saturn's moons, Titan and Enceladus, and two other Galilean moons of Jupiter--Europa and Callisto. Planetary scientists think the oceans of Europa and Enceladus are in contact with rock--thus making these two moons high-priority targets for future astrobiology missions.