Goals: Lunar Orbiter 1 was designed to photograph the Surveyor 1 landing site and scout potential landing sites for the Apollo program in the Moon's southern equatorial region. It's cameras were to provide the first clear images of the far side of the Moon.
Accomplishments: Lunar Orbiter 1 was the first U.S. spacecraft to orbit the Moon. It took 207 pictures of the lunar surface, covering an area of more than 5 million square kilometers. The high-resolution photos were smeared, but the medium-resolution images were the best lunar-surface images returned to date. Included was the first picture of Earth as seen from the Moon. Tracking of the spacecraft's orbit around the Moon confirmed the Luna 10 finding of strong gravitational variations. The tracking data from Lunar Orbiter 1, combined with the data for the four subsequent Lunar Orbiters, led scientists to conclude that the gravity anomalies were caused by large, dense masses of material ("mascons," for mass concentrations) underlying the Moon's near-side basins.