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The Voyager-1 spacecraft was launched on September 5, 1977 and subsequently encountered Jupiter on March 5, 1979, Saturn on November 12, 1980 and the heliospheric termination shock on December 16, 2004. Voyager-1 crossed into Interstellar Space on August 25, 2012.

The Voyager-2 spacecraft was launched on August 20, 1977 and subsequently encountered Jupiter on July 9, 1979, Saturn on August 25, 1981, Uranus on January 24, 1986, Neptune on August 25, 1989 and the heliospheric termination shock on August 30, 2007. Voyager-2 crossed into Interstellar Space on November 5, 2018.

Both space craft are now traveling out of the Solar System with the mission objective of extending NASA's exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun's sphere of influence and beyond.

Graphic of Position of Voyager 1 and Voyager 2 outside of the heliosphere

A detailed description of Voyager's past and current mission can be found at the Jet Propulsion Laboratory's Voyager Project Home Page.


The Voyager Cosmic Ray Subsystem (CRS) is designed to exploit to the fullest practical degree the proposed trajectories of Voyager-1 and -2. The significance of these measurements will be greatly enhanced by concurrent measurements with similar particle telescopes on satellites such as the Pioneers, IMPs, and similar series in near-earth orbits. The principal scientific objectives of this experiment are:
  • To measure the flow patterns of energetic solar and galactic particles separately in the inter-planetary field. To interpret this measurement, simultaneous determination of the energy spectrum, radial gradient, distribution, and streaming parameters is required for each nuclear species and over as wide an energy range as is practicable.

  • To measure the energy spectra, and isotopic composition of galactic and solar cosmic rays from the lowest practical energies up to ~800 MeV/nucleon and (by use of objective 1) to unfold the primary flare and interstellar spectrum.

  • To measure the time variations of the differential energy spectra of electrons, hydrogen and helium nuclei over the corresponding energy intervals. During flare events, to obtain time histories; during quiet times, to relate gross time variations to those near earth thus deducing a spatial gradient for galactic cosmic rays.

  • To study the energy spectra, time variations and spatial gradients associated with recurrent and non-flare associated interplanetary proton and helium streams and to define the related solar or inter-planetary acceleration processes.

  • To provide information on the energetic particle distribution surrounding Jupiter and Saturn.

  • To try to determine the extent of the solar cavity, the energetic particle phenomena occurring at this interface and the cosmic ray density in nearby interstellar space.

To accomplish these objectives CRS makes the following measurements:

  • Galactic cosmic ray protons and Solar proton intensities in the energy range 1.8 - 200 MeV

  • Galactic cosmic ray helium and Solar helium intensities in the energy range 1.8 - 500 MeV/nucleon

  • Galactic and Solar electron intensities in the energy range 0.2- 13.0 MeV

  • Li,Be,B,C,N,O,F,Ne intensities and their isotopic composition in the energy range 6 MeV/nuc - 200 MeV/nuc

  • Integral flux of IONS > 70 MeV
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Last Updated: 11/22/2017