Voyager RSS MISSION.CAT

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PDS_VERSION_ID                    = PDS3
LABEL_REVISION_NOTE               = "2001-01-01, S. JOY (PPI),
                                     ADDED SOLAR SYSTEM AS TARGET"
RECORD_TYPE                       = STREAM

OBJECT                            = MISSION
 MISSION_NAME                     = "VOYAGER"

 OBJECT                           = MISSION_INFORMATION
  MISSION_START_DATE              = 1972-07-01
  MISSION_STOP_DATE               = UNK
  MISSION_ALIAS_NAME              = "MJS77"
  MISSION_DESC                    = "

  Mission Overview
  ================
    The twin Voyager spacecraft, over the course of a dozen years,
    drew back the curtain on nearly half of the solar system.  From
    launch in 1977 through the spectacular parting shots of Neptune
    at the outer reaches of the solar system in 1989, this pair of
    spacecraft explored four planets -- Jupiter, Saturn, Uranus and
    Neptune -- as well as dozens of moons, and the rings and
    magnetic environments of those planetary systems.

    The Voyagers were designed to take advantage of a rare geometric
    arrangement of the outer planets that occurs only once every 176
    years.  This configuration allows a single spacecraft to swing
    by all four gas giants without the need for large onboard
    propulsion systems; the flyby of each planet both accelerates
    the spacecraft and bends its flight path.  Without these gravity
    assists, the flight time to Neptune would have been 30 years.

    The second of the two Voyager spacecraft, Voyager 2, was
    launched first, on 20 August 1977.  It was followed on 5
    September 1977 by Voyager 1, which was put on a faster, shorter
    trajectory to Jupiter.  Both launches took place from the Cape
    Canaveral Air Force Station in Florida.

    Eighteen months after launch, Voyager 1 reached Jupiter, 650
    million kilometers away.  The spacecraft made its closest
    approach on 5 March 1979, while Voyager 2 followed on 9 July
    of the same year.  Images streamed back from the pair of
    spacecraft showing the complex, swirling turbulence of
    Jupiter's atmosphere in exquisite detail.  A giant storm, three
    times the size of Earth, raged in Jupiter's upper atmosphere,
    surrounded by rippling currents that rotated about it.
    Voyager 1 found nine active volcanoes erupting on Io, the
    innermost of Jupiter's four major moons.  Four months later,
    Voyager 2 found that eight of the nine volcanoes were still
    active.  A thin, dusty ring was also discovered around Jupiter,
    forcing revision of theories about origins and mechanics of
    planetary ring systems.

    At Saturn, both Voyagers took high-resolution images to help
    determine ring composition and dynamics.  The Voyager 1
    encounter took place in November 1980 and the Voyager 2
    encounter was in August 1981.  Voyager 1 was targeted to fly
    close to Saturn's largest moon Titan.  This resulted in a
    south polar passage of Saturn, which redirected the spacecraft
    northward of the ecliptic.

    Voyager 2 continued on to Uranus where ten new moons were
    discovered in the Uranus system.  The planet's magnetic
    field was found to be significantly offset from the planet's
    axis of rotation.

    In August 1989, Voyager 2 flew past Neptune.  Because Neptune
    receives so little sunlight, many scientists had expected to
    see a placid, featureless planet.  Instead, Voyager showed a
    dynamic atmosphere with winds blowing westward, opposite the
    direction of rotation, at speeds faster than the winds of any
    other planet.  Neptune revealed its Great Dark Spot, a storm
    system that resembled Jupiter's Great Red Spot, and a smaller,
    eastwardly moving cloud, called 'scooter', which went around
    the planet about every 16 hours.  The blue planet was circled
    by diffuse, dusty rings; six new moons were discovered.

    Voyager 2 passed over the north polar region on Neptune,
    using the planet's gravity to redirect the trajectory for a
    final encounter -- with Neptune's largest moon Triton.  It then
    departed the solar system southward of the ecliptic.

    At about the same time as Voyager 2 was encountering Neptune,
    Voyager 1, continuing its journey to the edge of the solar
    system on the north side of the ecliptic, turned its cameras
    back to look at the planets and take one last parting shot.
    Voyager 1's 'family portrait' illustrates the vastness of the
    solar system and the huge expanses of emptiness within which
    the outer planets lie.

    Both Voyagers are now headed for the outer boundary of the
    solar system, where the Sun becomes just one of many
    contributors to the interstellar environment.  That edge is
    thought to be somewhere between 8 billion and 23 billion
    kilometers from the Sun.  Engineers are optimistic that the
    Voyagers will still be transmitting data when that boundary is
    encountered sometime in the first quarter of the twenty-first
    century.

    The spacecraft were assembled at and the mission was managed by
    the Jet Propulsion Laboratory, Pasadena, CA.  Early parts of
    the mission have been described in more detail by
    [MORRISON1982].


  Mission Phases
  ==============

    VOYAGER 1 LAUNCH
    ----------------
      The launch vehicle for Voyager 1 was a Titan/Centaur.  The
      first stage Titan was powered by both solid and liquid fuel
      engines.  The Centaur stage, 20 meters long and 3 meters in
      diameter burned a fuel combination of liquid hydrogen and
      liquid oxygen.  The Titan boosted the Voyager Centaur
      combination into low Earth orbit, and the Centaur plus a
      small solid fuel rocket provided the energy for Voyager 1 to
      escape Earth orbit.

      Spacecraft Id                  : VG1
      Mission Phase Start Time       : 1977-09-05
      Mission Phase Stop Time        : 1977-09-05
      Spacecraft Operations Type     : LAUNCH


    VOYAGER 1 EARTH-JUPITER CRUISE
    ------------------------------
      During the period between Launch and Jupiter Encounter,
      Voyager 1 probed the interplanetary medium and conducted
      tests and calibrations of its systems.

      Spacecraft Id                  : VG1
      Mission Phase Start Time       : 1977-09-05
      Mission Phase Stop Time        : 1979-01-06
      Spacecraft Operations Type     : CRUISE


    VOYAGER 1 JUPITER ENCOUNTER
    ---------------------------
      The Voyager 1 flyby of Jupiter took place on 5 March 1979 at
      12:04:36 UTC with the spacecraft closest approach only 348890
      kilometers from the center of Jupiter.  Among the highlights
      of the encounter were the discovery of a faint ring and one
      new satellite.  Satellite encounter information is given
      below; 'UNK' denotes 'unknown' at time of this writing.  The
      Voyager 1 Jupiter encounter is described in more detail by
      [STONE&LANE1979A].

        Satellite    Satellite     Radial    Closest  Approach
           Name      Dimensions   Distance    Date    Distance
                        (km)        (km)     (1979)     (km)
        ---------   -----------  ----------  ------  ---------
        Metis            40         128,000    UNK       UNK
        Adrastea      24x20x14      129,000    UNK       UNK
        Amalthea    270x166x150     181,300   5 Mar    420,200
        Thebe         110x90        222,000    UNK       UNK
        Io              3630        422,000   5 Mar     20,570
        Europa          3138        661,000   5 Mar    733,760
        Ganymede        5262      1,070,000   5 Mar    114,710
        Callisto        4800      1,883,000   6 Mar    126,400
        Leda             16      11,094,000    UNK       UNK
        Himalia          186     11,480,000    UNK       UNK
        Lysithia         36      11,720,000    UNK       UNK
        Elara            76      11,737,000    UNK       UNK
        Ananke           30      21,200,000    UNK       UNK
        Carme            40      22,600,000    UNK       UNK
        Pasiphae         50      23,500,000    UNK       UNK
        Sinope           36      23,700,000    UNK       UNK

      Spacecraft Id                  : VG1
      Target Name                    : JUPITER
      Mission Phase Start Time       : 1979-01-06
      Mission Phase Stop Time        : 1979-04-13
      Spacecraft Operations Type     : FLYBY


    VOYAGER 1 JUPITER-SATURN CRUISE
    -------------------------------
      During the period between Jupiter Encounter and Saturn
      Encounter, Voyager 1 probed the interplanetary medium,
      observed selected celestial targets, and conducted tests and
      calibrations of its systems.  Mission planners used the 16
      months to develop and test activity sequences which would be
      used during the Saturn Encounter.

      Spacecraft Id                  : VG1
      Mission Phase Start Time       : 1979-04-13
      Mission Phase Stop Time        : 1980-08-22
      Spacecraft Operations Type     : CRUISE


    VOYAGER 1 SATURN ENCOUNTER
    --------------------------
      The Voyager 1 flyby of Saturn took place on 12 November 1980
      at 23:46 UTC with the spacecraft closest approach only 184300
      kilometers from the center of Saturn.  Among the highlights
      of the encounter were the separate encounter with Titan,
      discovery of intricate patterns within the ring system, and
      observation of variations among the many moons of Saturn.
      Closest approaches to some of the satellites were on the
      dates and at the distances shown below.  'UNK' denotes
      'unknown' at the time of this writing.  The encounter is
      described in more detail by [STONE&MINER1981].

        Satellite    Satellite     Radial     Closest Approach
           Name      Dimensions   Distance    Date     Distance
                        (km)        (km)     (1980)      (km)
        ---------   -----------  ----------  ------  ----------
        Pan              10         133,583   12 Nov      UNK
        Atlas          40x20        137,670    UNK      219,000
        Prometheus  140x100x80      139,353    UNK      300,000
        Pandora      110x90x80      141,700   12 Nov    270,000
        Epimetheus  140x120x100     151,472   13 Nov    121,000
        Janus       220x200x160     151,422   12 Nov    297,000
        Mimas           392         185,520   12 Nov     88,440
        Enceladus       520         238,020   12 Nov    202,040
        Tethys         1060         294,660   12 Nov    415,670
        Telesto      34x28x26       294,660   12 Nov    233,000
        Calypso      34x22x22       294,660   13 Nov    432,000
        Dione          1120         377,400   12 Nov    161,520
        Helene       36x32x30       377,400   13 Nov    237,000
        Rhea           1530         527,040   12 Nov     73,980
        Titan          5150       1,221,860   12 Nov      6,490
        Hyperion    410x260x220   1,481,000   13 Nov    880,440
        Iapetus        1460       3,560,830   14 Nov  2,470,000
        Phoebe          220      12,952,000    UNK   13,500,000

      Spacecraft Id                  : VG1
      Target Name                    : SATURN
      Mission Phase Start Time       : 1980-08-22
      Mission Phase Stop Time        : 1980-12-14
      Spacecraft Operations Type     : FLYBY


    VOYAGER 1 INTERSTELLAR MISSION
    ------------------------------
      After conclusion of the Saturn Encounter, Voyager 1 left the
      ecliptic at an angle of about 30 degrees.  Its scan platform
      instruments were turned off, but some of the remaining
      instruments (primarily fields and particles) continued to
      monitor the environment in the outer solar system as the
      spacecraft traveled outward toward the heliopause.

      Spacecraft Id                  : VG1
      Mission Phase Start Time       : 1980-12-14
      Mission Phase Stop Time        : UNK
      Spacecraft Operations Type     : CRUISE


    VOYAGER 2 LAUNCH
    ----------------
      The launch vehicle for Voyager 2 was a Titan/Centaur.  The
      first stage Titan was powered by both solid and liquid fuel
      engines.  The Centaur stage, 20 meters long and 3 meters in
      diameter burned a fuel combination of liquid hydrogen and
      liquid oxygen.  The Titan boosted the Voyager Centaur
      combination into low Earth orbit, and the Centaur plus a
      small solid fuel rocket provided the energy for Voyager 2 to
      escape Earth orbit.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1977-08-20
      Mission Phase Stop Time        : 1977-08-20
      Spacecraft Operations Type     : LAUNCH


    VOYAGER 2 EARTH-JUPITER CRUISE
    ------------------------------
      During the period between Launch and Jupiter Encounter,
      Voyager 2 probed the interplanetary medium and conducted
      tests and calibrations of its systems.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1977-08-20
      Mission Phase Stop Time        : 1979-04-25
      Spacecraft Operations Type     : CRUISE


    VOYAGER 2 JUPITER ENCOUNTER
    ---------------------------
      The Voyager 2 flyby of Jupiter took place on 9 July 1979 at
      22:29 UTC.  This was 18 weeks after the Voyager 1 Jupiter
      Encounter and was at a closest approach distance of 721670
      kilometers from the center of Jupiter.  The Voyager 2
      trajectory was chosen to complement that of Voyager 1,
      including a much closer approach to Europa, probing southern
      latitudes in Jupiter's atmosphere, and an extensive
      investigation of Jupiter's magnetotail.  Satellite encounter
      information is given below; 'UNK' denotes 'unknown' at time
      of this writing.  The Voyager 2 Jupiter encounter is
      described in more detail by [STONE&LANE1979B].

        Satellite    Satellite     Radial     Closest Approach
           Name      Dimensions   Distance    Date    Distance
                        (km)        (km)     (1979)     (km)
        ---------   -----------  ----------  ------  ---------
        Metis            40         128,000    UNK       UNK
        Adrastea      24x20x14      129,000    UNK       UNK
        Amalthea    270x166x150     181,300   9 Jul    558,370
        Thebe         110x90        222,000    UNK       UNK
        Io              3630        422,000   9 Jul  1,129,900
        Europa          3138        661,000   9 Jul    205,720
        Ganymede        5262      1,070,000   9 Jul     62,130
        Callisto        4800      1,883,000   8 Jul    214,930
        Leda             16      11,094,000    UNK       UNK
        Himalia          186     11,480,000    UNK       UNK
        Lysithia         36      11,720,000    UNK       UNK
        Elara            76      11,737,000    UNK       UNK
        Ananke           30      21,200,000    UNK       UNK
        Carme            40      22,600,000    UNK       UNK
        Pasiphae         50      23,500,000    UNK       UNK
        Sinope           36      23,700,000    UNK       UNK

      Spacecraft Id                  : VG2
      Target Name                    : JUPITER
      Mission Phase Start Time       : 1979-04-25
      Mission Phase Stop Time        : 1979-08-05
      Spacecraft Operations Type     : FLYBY


    VOYAGER 2 JUPITER-SATURN CRUISE
    -------------------------------
      During the period between Jupiter Encounter and Saturn
      Encounter, Voyager 2 probed the interplanetary medium,
      observed selected celestial targets, and conducted tests and
      calibrations of its systems.  Mission planners used the 22
      months to develop and test activity sequences which would be
      used during the Saturn Encounter.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1979-08-05
      Mission Phase Stop Time        : 1981-06-05
      Spacecraft Operations Type     : CRUISE


    VOYAGER 2 SATURN ENCOUNTER
    --------------------------
      The Voyager 2 closest approach to Saturn was on 26 August
      1981 at 03:24 UTC and at a distance of 161000 km from the
      center of Saturn.  The trajectory was chosen so that the
      spacecraft could obtain a gravitational assist from Saturn
      and continue on to Uranus; the timing was selected to provide
      better views of several satellites than had been obtained
      from Voyager 1.  Design of science sequences was influenced
      by Voyager 1 results.  Satellite encounters were on the dates
      and at the closest approach distances shown below; 'UNK'
      denotes 'unknown' at the time of this writing.  The
      scan platform seized temporarily 110 minutes after Saturn
      closest approach, causing the central computer to disable
      further commands and resulting in loss of some data.  When
      commanded again three days later (at low rate), it moved as
      instructed.  A gyroscope calibration error between closest
      approach and five hours later also caused loss of data.
      Scan platform activities ended on 5 September 1981.  This
      encounter is described in more detail by [STONE&MINER1982].

        Satellite    Satellite     Radial      Closest Approach
           Name      Dimensions   Distance     Date     Distance
                        (km)        (km)      (1981)      (km)
        ---------   -----------  ----------   ------  ----------
        Pan              10         133,583   26 Aug       UNK
        Atlas          40x20        137,670   26 Aug     287,000
        Prometheus  140x100x80      139,353   26 Aug     247,000
        Pandora      110x90x80      141,700   26 Aug     107,000
        Epimetheus  140x120x100     151,472   26 Aug     147,000
        Janus       220x200x160     151,422   26 Aug     223,000
        Mimas           392         185,520   26 Aug     309,930
        Enceladus       520         238,020   26 Aug      87,010
        Tethys         1060         294,660   25 Aug      93,010
        Telesto      34x28x26       294,660   26 Aug     270,000
        Calypso      34x22x22       294,660   26 Aug     151,590
        Dione          1120         377,400   26 Aug     502,310
        Helene       36x32x30       377,400   25 Aug     314,090
        Rhea           1530         527,040   26 Aug     645,260
        Titan          5150       1,221,860   24 Aug     666,190
        Hyperion    410x260x220   1,481,000   24 Aug     431,370
        Iapetus        1460       3,560,830   22 Aug     908,680
        Phoebe          220      12,952,000    4 Sep   2,075,640

      Spacecraft Id                  : VG2
      Target Name                    : SATURN
      Mission Phase Start Time       : 1981-06-05
      Mission Phase Stop Time        : 1981-09-25
      Spacecraft Operations Type     : FLYBY


    VOYAGER 2 SATURN-URANUS CRUISE
    ------------------------------
      During the period between Saturn Encounter and Uranus
      Encounter, Voyager 2 probed the interplanetary medium,
      observed selected celestial targets, and conducted tests and
      calibrations of its systems.  Mission planners used the 49
      months to develop and test activity sequences which would be
      used during the Uranus Encounter.  Considerable attention was
      paid to the scan platform capabilities, following its seizure
      during the Saturn Encounter.  Full scan platform operation
      was restored before the end of 1981.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1981-09-25
      Mission Phase Stop Time        : 1985-11-04
      Spacecraft Operations Type     : CRUISE


    VOYAGER 2 URANUS ENCOUNTER
    --------------------------
      The Voyager 2 closest approach to Uranus was on 24 January
      1986 at 17:59 UTC at a distance of 107000 km from the
      center of Uranus.  The trajectory was chosen so that the
      spacecraft could obtain a gravitational assist from Uranus
      and continue on to Neptune; NASA permission for the Neptune
      Encounter was granted during the approach to Uranus.  The
      timing of the Uranus closest approach was selected to
      provide a close approach to Miranda and to allow capture of
      radio occultation data at the DSN tracking station in
      Australia (southern declination of Uranus meant that
      Australia was preferred for DSN tracking).  Radio
      occultation data were also collected using the 64-m
      antenna at Parkes in Australia.  Satellite encounters were
      on the dates and at the closest approach distances shown
      below.  'UNK' denotes 'unknown' at the time of this writing.
      Satellite images were improved by implementation of image
      motion compensation on the spacecraft.  Reed-Solomon encoding
      was used for the first time; real-time imaging data rates
      were reduced by almost 70 percent.  Ground antennas were
      arrayed to increase receiving aperture.  This encounter is
      described in more detail by [STONE&MINER1986].

        Satellite    Satellite     Radial      Closest Approach
           Name      Dimensions   Distance     Date     Distance
                        (km)        (km)      (1986)      (km)
        ---------   -----------  ----------   ------  ----------
        Cordelia         26         49,800      UNK       UNK
        Ophelia          30         53,800      UNK       UNK
        Bianca           42         59,200      UNK       UNK
        Juliet           62         61,800      UNK       UNK
        Desdemona        54         62,700      UNK       UNK
        Rosalind         84         64,400      UNK       UNK
        Portia          108         66,100      UNK       UNK
        Cressida         54         69,900      UNK       UNK
        Belinda          66         75,300      UNK       UNK
        Puck            154         86,000      UNK       UNK
        Miranda         472        129,900    24 Jan     29,000
        Ariel         1,158        190,900    24 Jan    127,000
        Umbriel       1,172        265,969    24 Jan    325,000
        Titania       1,580        436,300    24 Jan    365,200
        Oberon        1,524        583,400    24 Jan    470,600

      Spacecraft Id                  : VG2
      Target Name                    : URANUS
      Mission Phase Start Time       : 1985-11-04
      Mission Phase Stop Time        : 1986-02-25
      Spacecraft Operations Type     : FLYBY


    VOYAGER 2 URANUS-NEPTUNE CRUISE
    -------------------------------
      During the period between Uranus Encounter and Neptune
      Encounter, Voyager 2 probed the interplanetary medium,
      observed selected celestial targets, and conducted tests and
      calibrations of its systems.  Mission planners used the 39
      months to develop and test activity sequences which would be
      used during the Neptune Encounter.

      The DSN used this time to add a 34-m tracking antenna at the
      Madrid complex, to increase the diameter of their 64-m
      antennas to 70 meters, and to make the 70-m systems more
      efficient.  A special microwave link was installed to permit
      the Parkes radio telescope to be arrayed with the Canberra
      DSN antenna in Australia.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1986-02-25
      Mission Phase Stop Time        : 1989-06-05
      Spacecraft Operations Type     : CRUISE


    VOYAGER 2 NEPTUNE ENCOUNTER
    ---------------------------
      The Voyager 2 closest approach to Neptune was on 25 August
      1989 at 03:56 UTC at a distance of 29240 km from the
      center of Neptune.  The trajectory and timing were chosen so
      that the spacecraft could obtain a gravitational assist from
      Neptune and continue on for an encounter with Neptune's large
      satellite Triton about five hours later (closest approach at
      09:10 UTC).  The timing was also selected so that radio
      occultation data would be collected at the DSN tracking
      station in Australia (southern declination of Neptune meant
      that Australia was preferred for DSN tracking).  Radio
      occultation data were again collected with the Parkes antenna
      and with a new 64-m antenna at Usuda in Japan.  Satellite
      encounters were on the dates and at the closest approach
      distances shown below.  'UNK' denotes 'unknown' at the
      time of this writing.  Data rates were increased over those
      at Uranus by including the Very Large Array (VLA) in New
      Mexico for receiving and by taking advantage of DSN upgrades
      made over the previous three years.  This encounter is
      described in more detail by [STONE&MINER1989].

        Satellite    Satellite     Radial      Closest Approach
           Name      Dimensions   Distance     Date     Distance
                        (km)        (km)      (1989)      (km)
        ---------   -----------  ----------   ------  ----------
        Naiad            54          48,000   25 Aug       UNK
        Thalassa         80          50,000   25 Aug       UNK
        Despina         180          52,500   25 Aug       UNK
        Galatea         150          62,000   25 Aug       UNK
        Larissa         190          73,600   25 Aug      60,180
        Proteus         400         117,600   25 Aug      97,860
        Triton        2,700         354,760   25 Aug      39,790
        Nereid          340       5,509 090   25 Aug   4,652,880

      Spacecraft Id                  : VG2
      Target Name                    : NEPTUNE
      Mission Phase Start Time       : 1989-06-05
      Mission Phase Stop Time        : 1989-10-02
      Spacecraft Operations Type     : FLYBY


    VOYAGER 2 INTERSTELLAR MISSION
    ------------------------------
      After conclusion of the Neptune Encounter, Voyager 2 left the
      ecliptic at an angle of about -30 degrees.  Its scan platform
      instruments were turned off, but some of the remaining
      instruments (primarily fields and particles) continued to
      monitor the environment in the outer solar system as the
      spacecraft traveled outward toward the heliopause.  During
      the Shoemaker-Levy 9 impact with Jupiter in July 1994, the
      ultraviolet spectrometer was trained on Jupiter and radio
      signals were recorded; but no emissions from the impact were
      detected.

      Spacecraft Id                  : VG2
      Mission Phase Start Time       : 1989-10-02
      Mission Phase Stop Time        : UNK
      Spacecraft Operations Type     : CRUISE"


  MISSION_OBJECTIVES_SUMMARY      = "

  Mission Objectives Summary
  ==========================
    Voyager's primary objective was exploration of the two giant
    planets, Jupiter and Saturn, their magnetospheres, and their
    satellites.  Major emphasis was placed on studying the
    satellites, many of which are planet-sized worlds, in as much
    detail as possible.  The study of Titan, the only satellite in
    the solar system known to have an extensive atmosphere, was
    nearly as high a priority as studies of Saturn itself
    [MORRISON1982].  After the successful Voyager 1 encounter with
    Titan, it was decided to expand the Voyager objectives to
    include at least Uranus; Uranus and Neptune could both be
    reached by proper reprogramming of the Voyager 2 trajectory.
    Comparative studies then could include the four largest planets
    in the solar system.

    Eleven investigations were approved for the Voyager mission.
    Investigation names and Principal Investigators, or Team
    Leaders in the cases of ISS and RSS, are shown in the table
    below; the trailing 'S' stands for 'subsystem' in most
    acronyms.

      Investigation, P/I or T/L                            Acronym
      ------------------------------------------------     -------
      Imaging Science Investigation                          ISS
                     B.A. Smith
      Infrared Interferometer and Radiometer Investigation   IRIS
                     R.A. Hanel (Jupiter - Uranus)
                     B.J. Conrath (Neptune)
      Photopolarimeter Investigation                         PPS
                     C.F. Lillie (Voyager 1 Jupiter)
                     C.W. Hord (Voyager 2 Jupiter)
                     A.L. Lane (Saturn - Neptune)
      Radio Science Investigation                            RSS
                     V.R. Eshleman (Jupiter)
                     G.L. Tyler (Saturn - Neptune)
      Ultraviolet Spectrometer Investigation                 UVS
                     A.L. Broadfoot
      Magnetometer Investigation                             MAG
                     N.F. Ness
      Plasma Science Investigation                           PLS
                     H.S. Bridge (Jupiter - Uranus)
                     J.W. Belcher (Neptune)
      Plasma Wave Investigation                              PWS
                     F.L. Scarf (Jupiter - Uranus)
                     D.A. Gurnett (Neptune)
      Planetary Radio Astronomy Investigation                PRA
                     J.W. Warwick
      Low-Energy Charged Particle Investigation              LECP
                     S.M. Krimigis
      Cosmic Ray Investigation                               CRS
                     R.E. Vogt (Jupiter - Saturn)
                     E.C. Stone (Uranus - Neptune)


    Broadly stated, the science goals of the mission were: high
    resolution imaging of the gas planets and inference of
    atmospheric dynamics; high resolution imaging of satellites and
    inference of geologic processes; spectral measurements of
    atmospheres and satellite surfaces, inference of compositions,
    and inference of thermal properties and structure;
    identification and study of aerosols and surface physical
    structure using polarized light; occultation measurement of
    atmospheric thermal, ionospheric charged particle, and ring
    structure; and measurement of magnetic fields and particle
    environments and inference of Sun-planet-satellite
    interactions, magnetospheric structure, and mechanisms within
    each planetary system for generating the observed fields.


    Jupiter
    -------
      The largest planet in the solar system, Jupiter is composed
      mainly of hydrogen and helium, with small amounts of methane,
      ammonia, water vapor, traces of other compounds and a core of
      melted rock and ice.  One of the objectives of Voyager was to
      quantify the composition of the atmospheres of Jupiter and
      the other giant planets.

      Colorful latitudinal bands, atmospheric clouds, and storms
      characterize Jupiter's dynamic atmosphere.  By taking a
      series of images, Voyager could show the time variability of
      the atmosphere.  The Great Red Spot was revealed as a complex
      storm moving in a counterclockwise direction.  An array of
      other smaller storms and eddies were found throughout the
      banded clouds.

      Jupiter is now known to possess 16 moons.  An objective of
      the Voyager mission was to search for new moons and to obtain
      high resolution quantitative measurements on those that had
      been discovered earlier.  Active volcanism on the satellite
      Io was easily the most surprising discovery at Jupiter.  It
      was the first time active volcanoes had been seen on another
      body in the solar system.  Together, the Voyagers observed
      the eruption of nine volcanoes on Io, and there is evidence
      that other eruptions occurred between the Voyager encounters.

      Although interpretations vary, the cratered surfaces of the
      terrestrial planets (and the Moon) are believed to contain
      the record of small body populations in the inner solar
      system from as far back as 4 billion years ago.  One of the
      objectives of the Voyager mission was to obtain similar
      cratering data from satellites in the outer solar system.
      Impact craters on Io have been obliterated by that satellite's
      volcanism.  Rather than craters, Europa was distinguished by
      a large number of intersecting linear features with almost no
      topographic relief.  There is a possibility that Europa is
      internally active due to tidal heating at a level one-tenth
      or less than that of Io and that the crust is very thin (less
      than 30 kilometers).  Ganymede has two distinct types of
      terrain -- cratered and grooved -- suggesting that its entire
      icy crust has been under tension from global tectonic
      processes.  Callisto has a very old, heavily cratered crust
      showing remnant rings of enormous impact craters.  The
      largest craters have apparently been erased by the flow of
      the icy crust over geologic time.  Almost no topographic
      relief is apparent in the ghost remnants of the immense
      impact basins, identifiable only by their light color and the
      surrounding subdued rings of concentric ridges.

      Indirect evidence from Pioneer 10/11 suggested the presence
      of a thin ring around Jupiter.  One of the objectives of the
      Voyager mission was to search more systematically for such a
      ring, and to quantify both the number-density and the size
      distribution of particles within rings in the outer solar
      system.  A faint, dusty ring of material was found around
      Jupiter.  Its outer edge is 129,000 kilometers from the
      center of the planet, and it extends inward about 30,000
      kilometers.

      Two new, small satellites, Adrastea and Metis, were found
      orbiting just outside the ring.  A third new satellite,
      Thebe, was discovered between the orbits of Amalthea and Io.

      Jupiter's rings and moons exist within an intense radiation
      belt of electrons and ions trapped in the planet's magnetic
      field.  These particles and fields comprise the jovian
      magnetosphere, or magnetic environment, which extends three
      to seven million kilometers toward the Sun, and stretches in
      a windsock shape at least as far as Saturn's orbit -- a
      distance of 750 million kilometers (460 million miles).

      As the magnetosphere rotates with Jupiter, it sweeps past Io
      and strips away about 1,000 kilograms (one ton) of material
      per second.  The material forms a torus, a doughnut-shaped
      cloud of ions that glow in the ultraviolet.  The heavy ions
      in the torus migrate outward, and their pressure inflates the
      jovian magnetosphere to more than twice its expected size.
      Some of the more energetic sulfur and oxygen ions fall along
      the magnetic field into the planet's atmosphere, resulting in
      auroras.


    Saturn
    ------
      A major objective of the Voyager mission was to determine in
      which ways the gas giants are the same and in which ways they
      are different.  Saturn, like Jupiter, is mostly hydrogen and
      helium.  Its hazy yellow hue has broad atmospheric banding
      similar to (but much fainter than) that found on Jupiter.  It
      also has a complex ring system, the details of which were
      sketchy before Voyager, but which represented an important
      objective in themselves.

      It is thought that the rings formed from one or more moons
      that were shattered by impacts of comets and meteoroids.  The
      resulting material, ranging in size from dust to house-sized
      particles, has accumulated in a broad plane in which both the
      shape and density vary in ways which depend intricately on
      gravitational interactions with satellites.  This is most
      obviously demonstrated by the relationship between the F-ring
      and two small moons that 'shepherd' the ring material.  The
      variation in the separation of the moons from the ring may
      explain the ring's kinked appearance.  Shepherding moons were
      also found by Voyager 2 at Uranus.  Very diffuse rings and
      'spokes' (neither detected from Earth) were also found by
      Voyager.

      Winds blow at extremely high speeds on Saturn -- up to 1,800
      kilometers per hour.  Their primarily easterly direction
      indicates that the winds are not confined to the top cloud
      layer but must extend at least 2,000 kilometers downward into
      the atmosphere.

      Saturn has 18 known satellites ranging from Phoebe, a small
      moon that travels in a retrograde orbit and is probably a
      captured asteroid, to Titan, the planet-sized moon with
      an atmosphere that had been detected from Earth before
      Voyager.  A major objective of Voyager was to
      investigate these satellites and, in particular, to learn a
      great deal more about Titan.  Titan's surface temperature and
      pressure were found to be 94 K and 1.6 atmospheres.
      Photochemistry converts some atmospheric methane to other
      organic molecules, such as ethane, that may accumulate in
      lakes or oceans.  Other more complex hydrocarbons form the
      haze particles that eventually fall to the surface, coating
      it with a thick layer of organic matter.  The chemistry in
      Titan's atmosphere may resemble that which occurred on Earth
      before life evolved.

      The most active surface of any moon seen in the Saturn system
      was that of Enceladus.  The bright surface of this moon,
      marked by faults and valleys, showed evidence of tectonically
      induced change.  Voyager 1 found that the surface of Mimas is
      dominated by a crater so large that the impact nearly broke
      the satellite apart.

      Saturn's magnetic field is weaker than Jupiter's, extending
      only one or two million kilometers.  The axis of the field is
      almost perfectly aligned with Saturn's rotation axis.


    Uranus
    ------
      Uranus is distinguished by the fact that it is tipped on its
      side.  This unusual orientation is thought to be the result
      of a collision with a planet-sized body early in the solar
      system's history.  Clues to this event, as well as more basic
      data about this planet (which has polar regions exposed to
      sunlight or hidden in darkness for long periods) were
      important Voyager objectives.  At about the time of Voyager's
      launch, observations from Earth showed that Uranus was
      circled by rings -- not bright and wide, as was the case
      for Saturn, but extremely narrow and very dark.

      Voyager 2 found that one of the most striking influences of
      the orientation of the rotation axis is its effect on the
      tail of the magnetic field, which is itself tilted 60 degrees
      from the planet's axis of rotation.  The magnetotail was
      shown to be twisted by the planet's rotation into a long
      corkscrew shape behind Uranus.

      The existence of a magnetic field at Uranus was not known
      until Voyager's arrival.  The intensity of the field is
      roughly comparable to that of Earth's, though it varies much
      more from point to point because of its large offset from the
      center of the planet.  The peculiar orientation of the
      magnetic field suggests that the field is generated at an
      intermediate depth in the interior where the pressure is high
      enough for water to become electrically conducting.

      Radiation belts at Uranus were found to be similar in
      intensity to those at Saturn.  The intensity of radiation
      within the belts is such that irradiation would quickly
      darken (within 100,000 years) any methane trapped in the icy
      surfaces of the inner moons and ring particles.  This may
      have contributed to the darkened surfaces of the moons and
      ring particles, which have lower albedos than coal and are
      almost uniform in color.

      A high layer of haze was detected around the sunlit pole,
      which also was found to radiate large amounts of ultraviolet
      light, a phenomenon dubbed 'dayglow'.  Surprisingly, the
      illuminated and dark poles, and most of the planet, show
      nearly the same temperature at the cloud tops.

      Voyager found 10 new moons, bringing the total number at
      Uranus to 15.  Most of the new moons are small, with the
      largest measuring about 150 kilometers in diameter.

      The five large moons appear to be ice-rock conglomerates like
      the satellites of Saturn.  Titania is marked by huge fault
      systems and canyons indicating some degree of geologic
      (probably tectonic) activity in its history.  Ariel has the
      brightest and possibly youngest surface of all the Uranian
      moons and also appears to have undergone geologic activity
      that led to many fault valleys and what seem to be extensive
      flows of icy material.  Little geologic activity has occurred
      on Umbriel or Oberon, judging by their old and dark surfaces.

      The moon Miranda, innermost of the five large moons, was
      revealed to be one of the strangest bodies yet seen in the
      solar system.  Detailed images from Voyager's flyby of the
      moon showed huge fault canyons as deep as 20 kilometers,
      terraced layers, and a mixture of old and young surfaces.
      One theory holds that Miranda may be a reaggregation of
      material from an earlier time when the moon was fractured by
      a violent impact.

      All nine rings discovered from Earth in the 1970's were
      studied by the spacecraft and showed the Uranian rings to be
      distinctly different from those at Jupiter and Saturn.  The
      ring system may be relatively young and did not form at the
      same time as Uranus.  Particles that make up the rings may be
      remnants of a moon that was fractured by a high-velocity
      impact or torn up by gravitational effects.


    Neptune
    -------
      Less was known about Neptune than about Uranus at the
      beginning of the Voyager mission.  Approximately the same
      size as Uranus, Neptune was expected to be a twin except for
      having a rotation axis more likely to be normal to the
      ecliptic.  About five years before the Voyager 2 Neptune
      encounter, evidence began accumulating that Neptune had
      atmospheric structure and (possibly) rings.  The ring data
      were very ambiguous; only exotic ring models (transient
      rings, partial rings, polar rings, etc.) were consistent
      with the observations from Earth.

      Even though Neptune receives only three percent as much
      sunlight as Jupiter, it is a dynamic planet and showed
      several large, dark spots reminiscent of Jupiter's
      hurricane-like storms.  The largest spot, dubbed the Great
      Dark Spot, is about the size of Earth and is similar to the
      Great Red Spot on Jupiter.  A small, irregularly shaped,
      eastward-moving cloud was observed 'scooting' around Neptune
      approximately once every 16 hours.

      Long bright clouds, similar to cirrus clouds on Earth, were
      seen high in Neptune's atmosphere.  At low northern
      latitudes, Voyager captured images of cloud streaks casting
      their shadows on cloud decks below.

      The strongest winds on any planet were measured on Neptune.
      Most of the winds blow westward, or opposite to the rotation
      of the planet.  Near the Great Dark Spot, winds blow up to
      2,000 kilometers an hour.

      The magnetic field of Neptune, like that of Uranus, turned
      out to be highly tilted -- 47 degrees from the rotation axis
      and offset at least 0.55 radii (about 13,500 kilometers or
      8,500 miles) from the physical center.  The extreme
      orientation may be characteristic of flows in the interiors
      of both Uranus and Neptune -- and not related, in the Uranus
      case, to the planet's rotation axis tilt or to any possible
      field reversals at either planet.  Voyager studies of radio
      emissions caused by the magnetic field revealed the length
      of a Neptunian day (16.11 hours).  The spacecraft also
      detected auroras, though they are much weaker than those on
      Earth and other planets.

      Triton, the largest Neptunian moon, was shown to be not only
      the most intriguing satellite of the system, but also one
      of the most interesting in all the solar system.  Intricate
      surface patterns suggest a remarkable geologic history,
      while Voyager 2 images captured active geyser-like eruptions
      spewing invisible nitrogen gas and dark dust particles
      several kilometers into the tenuous atmosphere.  Triton's
      relatively high density and retrograde orbit offer strong
      evidence that it is not an original member of Neptune's
      family but, rather, is a captured object.  If so, tidal
      heating could have melted Triton in its originally eccentric
      orbit, and the moon may have been liquid for as long as one
      billion years after its capture by Neptune.

      An extremely thin atmosphere extends about 800 kilometers
      above Triton's surface.  Nitrogen ice particles may form thin
      clouds a few kilometers above the surface.  The atmospheric
      pressure at the surface is about 14 microbars, 1/70,000th the
      surface pressure on Earth.  The surface temperature is about
      38 K -- the coldest known temperature of any body in the
      solar system.

      The new moons found at Neptune by Voyager are all small and
      remain close to Neptune's equatorial plane.

      Searches for 'ring arcs,' or partial rings, showed that
      Neptune's rings actually are complete, but are so diffuse and
      the material in them so fine that they could not be fully
      resolved from Earth.  The arcs are confined by the actions of
      nearby satellites.  Particle sizes are smaller than at Uranus.


    Interstellar Mission
    --------------------
      The Voyager spacecraft are continuing to return data about
      interplanetary space and some of our stellar neighbors near
      the edges of the Solar System.  Their fields, particles, and
      waves instruments are studying the environment around them.
      In May 1993, the plasma wave experiment began picking up radio
      emissions that originate at the heliopause, the outer edge of
      our solar system, where the interstellar medium restricts the
      outward flow of the solar wind and confines it within a
      magnetic bubble called the heliosphere.  By studying the
      radio emissions, scientists now theorize the heliopause
      exists some 90 to 120 astronomical units from the Sun.

      The Voyagers have also become space-based ultraviolet
      observatories and their unique location in the universe gives
      astronomers the best vantage point they have ever had for
      looking at celestial objects that emit ultraviolet radiation.

      The cameras on the spacecraft have been turned off and the
      ultraviolet instrument is the only experiment on the scan
      platform that is still functioning.  Voyager scientists
      expect to continue to receive data from the ultraviolet
      spectrometers at least until the year 2000.  At that time,
      there will not be enough electrical power for the heaters to
      keep the ultraviolet instrument warm enough to operate.

      Yet there are several other fields and particle instruments
      that can continue to send back data as long as the spacecraft
      can stay alive.  They include the cosmic ray subsystem, the
      low-energy charge particle instrument, the magnetometer, the
      plasma subsystem, the plasma wave subsystem and the planetary
      radio astronomy instrument."

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