Originally named Mariner Jupiter-Saturn, the last two spacecraft of NASA’s Mariner series, Voyager 1 and 2 were the first in that series to be sent to explore the outer solar system. Preceded by the Pioneer 10 and 11 missions, Voyager 1 and 2 were to make studies of Jupiter and Saturn, their satellites, their potential to harbor life, and their magnetospheres as well as studies of the interplanetary medium. An option designed into the Voyager 2 trajectory, and ultimately exercised, would direct it toward Uranus and Neptune to perform similar studies.
Although launched sixteen days after Voyager 2, Voyager 1’s trajectory was a faster path, arriving at Jupiter in March of 1979. Voyager 2 arrived about four months later in July 1979. Jupiter, with it’s very high radiation field and probable ring particles, represented a risk to the health of the spacecraft and science instruments, so trajectories for Voyager 1 and 2 were chosen that would take Voyager 1 within 350,000 km of Jupiter, whereas a safer distance for Voyager 2, at 720,000 km from Jupiter, would guarantee survival for important observations at Jupiter and Saturn if Voyager 1 did not survive. Voyager 1 was successful and the two spacecraft went on to make complementary measurements for both Jupiter and Saturn and their moons. After the successful Voyager 2 Jupiter encounter, the mission trajectory was redesigned to go on to Uranus and Neptune and Voyager 1’s encounter at Saturn was designed to take it out of the plane of our Solar System ecliptic.
Data collected by Voyager 1 and 2 were not confined to the periods surrounding encounters with the outer gas giants, with the various fields and particles experiments and the ultraviolet spectrometer collecting data nearly continuously during the interplanetary cruise phases of the mission. Data collection continues as the renamed Voyager Interstellar Mission searches for the edge of the solar wind’s influence (the heliopause) and exits the solar system.
- Photopolarimeter System (PPS)
- PPS Science team: C.W. Hord, C.F. Lillie, A.L. Lane, D.L. Coffeen, J.E. Hansen, J.T. Bergstralh, R.A. West, W.R. Pryor, & L.W. Esposito
The Photopolarimeter experiment consisted of an 8-in. (20-cm) f/1.1 telescope that sent radiation through a polarizer and a filter for one of eight bands in the 2200- to 7300-A spectral region, then on to a photomultipler tube. By study of these emission intensity data, information on surface texture and composition of Jupiter, Saturn, Uranus, and Neptune was obtained, along with information of size distribution and composition of Saturn’s and Uranus’ rings and information on atmospheric scattering properties and density for all planets. The PPS made the highest resolution Saturn ring observation to date.
The primary scientific objectives of the photopolarimeter investigation on the Voyager mission were divided into three categories—studies of atmospheres, satellite surfaces, and rings.
Launch date: August 20, 1977 (Voyager 2); September 5, 1977 (Voyager 1)
Launch location: Kennedy Space Center, Cape Canaveral, Florida
Launch vehicle: Titan III E-Centaur
Mission target: Outer Solar System
Mission duration: Ongoing
Other organizations involved:
- NASA’s Jet Propulsion Laboratory (JPL)
- University of Iowa
- Massachusetts Institute of Technology
- University of Delaware
- Johns Hopkins University Applied Physics Laboratory (JHU/APL)