yee@trident.arc.nasa.gov (Peter E. Yee) (07/20/89)
Voyager Status Report July 18, 1989 Neptune's new moon, 1989 N1, is becoming a new guidepost for the Voyager navigation team and is a candidate to help better determine the location of Neptune itself. Neptune was discovered in 1846, and the planet takes 165 years to orbit the Sun; thus, Neptune won't return to the position where astronomers first saw it until 2011. This leaves great uncertainty in the precise knowledge of Neptune's orbit that Voyager navigators need to get the spacecraft to the targeted area of the planet at the right time. But the new Neptunian moon, 1989 N1, will provide the navigation team with a better idea of Neptune's exact location. The discovery of the moon fulfilled expectations of Voyager navigators who were hoping to find at least one new object in the Neptune system whose orbit could potentially be used to gauge the relative positions of Triton, Neptune and various background stars, said Don Gray, Voyager Navigation Team Chief. Many of the images coming back from the spacecraft are optical navigation frames. Ideally, the frames show a moon against a field of stars. Using stars as dim as 10th magnitude as reference points, the Voyager navigators progressively update and refine the location of Neptune and its moons. This new information is then integrated into commands that adjust Voyager's flight path and retarget the spacecraft's observations, if necessary. The next trajectory correction maneuver is being designed and will be uplinked to the spacecraft late next week. The maneuver is one of the final three that will be conducted between now and closest approach to bring the spacecraft within about 100 miles (150 kilometers) of the point at which it's aimed -- about 3,000 miles (4,850 kilometers) from Neptune's cloud tops. DISTANCE TO EARTH: 2,686,949,000 miles DISTANCE TO NEPTUNE: 33,805,000 miles HELIOCENTRIC VELOCITY: 42,192 mph