The Voyager program is a space exploration program of the United States' NASA agency. It consists of a pair of unmanned scientific probes, "Voyager 1" and "Voyager 2". They were launched in 1977 to take advantage of a favorable planetary alignment of the late 1970s. Although they were officially used to study just Jupiter and Saturn, the two probes were able to continue their mission into the outer solar system. They have since continued out and exited the solar system. These probes were built at JPL and were funded by NASA.