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Missions to the Outer System, in order :
(Main asteroid Belt and beyond)
plus nation, launch date, result (bold = success, red = failure, gray = inactive or destroyed, SMALL CAPS = target or destination)
vehicle type in parentheses if launch failure
Note that the Outer Moons catalog has been moved.
Overall Outer System mission success: 7/7 = 100%

  1. Pioneer 10 - USA 03 March 1972.
    First artifact to cross asteroid belt
    First flyby of Jupiter
    First artifact to exit solar system on 13Jun1983
    Flew by JUPITER @ 130,000 km on 04Dec1973.
    Data feed turned off 31Mar1997, solar escape orbit (RA = 11.82 billion km (11 light-hours, or 77.3 AU), R-dot = 12.24 km/sec, theta = ? ° , Ø = ? ° ), will pass heliopause when?.
    Instruments: charged particle detector, IR radiometer, flux gate magnetometer, cosmic ray telescope, trapped radiation detector, helium vector magnetometer, plasma analyzer, high gain antenna, meteoroid detector panel, Geiger tube telescope, imaging photopolarimeter, UV photometer, asteroid-meteoroid detection sensor.

  2. Pioneer 11 - USA 06 April 1973.
    First flyby of Saturn
    Second artifact to escape solar system
    Flew by JUPITER @ 42,000 km on ??Dec1974
    Flew by SATURN @ ? km on 01Sep1979; discovered F Ring.
    In trans-solar trajectory, exited solar system 23Feb1990, (RA = 11.4 billion km, R-dot = 12? km/sec, theta = ? ° , Ø = ? ° ), retired ?1995. Click here to learn more about Pioneers 10 & 11. Same instrument payload as sister ship. Last tx in 1995.

  3. Voyager 2 - USA 20 August 1977.
    Earlier start than Voyager 1, slower flight, designed to take Grand Tour of outer solar system via once-in-179-year launch window.
    Jovian system flybys:
    Flew by JUPITER @ 643,290 km on 09Jul1979; and:
    • CALLISTO @ 240,000 km,
    • GANYMEDE @ 50,000 km,
    • EUROPA @ 190,000 km,
    • AMALTHEA @ 550,000 km.

    Saturnian system flybys:
    Flew by SATURN @ 101,000 km on 26Aug1981; and:

    • TITAN @ 350,000 km,
    • RHEA @ 250,000 km,
    • TETHYS @ 160,000 km,
    • ENCELADUS @ 90,000 km,
    • MIMAS @ 30,000 km,
    • DIONE @ 200,000 km.

    Uranian system flybys:
    Flew by URANUS @ ? km on 24Jan1986; discovered 2 additional Uranian rings and the moons Cordelia, Ophelia, Bianca, Juliet, Desdemona, Rosalind, Portia, Cressida, Belinda, Puck

    • Flew by MIRANDA @ ? km,
    any other flybys at Uranus? For more on the Voyager 2 mission to Uranus, see here

    Neptunian system flybys:
    Flew by NEPTUNE @ 4901 km on 25Aug1989; discovered Great Dark Spot, Neptunian 4-ring system and 6 moons: Naiad, Thalassa, Despina, Galatea, Larissa, and Proteus;
    Also flew by TRITON @ 40,000 km on 25Aug1989; discovered methane atmosphere and nitrogen geysers.

    In hyperbolic (solar escape) orbit (RA = 9.5 billion km, R-dot = 14.9? km/sec, theta = ? ° , Ø = -48 ° ), exited solar system southbound in the direction of Capricornus (declin = -14.9 °, R.A. = 315.3 °) on when?
    Will pass heliopause about 2004, extended mission to ~2021. Will eventually pass M4-class red dwarf AC +79 3888 @ 1.1 light years in 40,000-60,000 years. (In fact, Carl Sagan wrote that a flythru of its putative planetary system is possible with engine firings now). Later, Beta Centauri, Beta CMA, Pleiades, Scorpius, Alpha Centauri, Alpha Leo, Alpha Lyrae, Alpha Pavonis, Cal Lamps?, Sigma SGR? SCAT LIGHT?
    Instruments: wide- and narrow-angle television cameras, IR spectrometer and radiometer, low energy charged particle detector, planetary radioastronomy and plasma wave antenna, high- and low-field magnetometers, cosmic ray telescope, plasma analyzer, high gain antenna, photopolarimeter, UV spectrometer.

  4. Voyager 1 - USA 05 September 1977.
    Most distant human artifact
    Later departure, but faster flight resulted in first major discoveries at Jupiter and Saturn, with followup visits by Voyager 2.
    Jovian system flybys:
    Flew by JUPITER @ 286,130 km on 05Mar1979; discovered Jovian ring system, sulfur ion flux tube, and four inner moons - Metis, Adrastea, & Thebe, and later, Leda; discovered volcanoes on Io. Also flew by:
    • AMALTHEA @ 440,000 km,
    • IO @ 25,000 km,
    • EUROPA @ 750,000 km,
    • GANYMEDE @ 130,000 km,
    • CALLISTO @ 130,000 km.

    Saturnian system flybys:
    Flew by SATURN @ 124,000 km on 12Nov1980; discovered the moons Atlas, Prometheus, Pandora, Epimetheus, Janus, Telesto, Calypso, Helene; as well as the braided, spoked, and S rings. Also flew by:

    • TITAN @ 7000 km on 12Nov1980,
    • TETHYS @ 410,000 km,
    • MIMAS @ 100,000 km,
    • ENCELADUS @ 230,000 km,
    • DIONE @ 140,000 km,
    • RHEA @ 60,000 km.

    On north solar escape trajectory (RA = 12.6 billion km, R-dot = 17.4 km/sec, theta = ? ° , Ø = +35 ° ), exited system northbound in the direction of Ophiuchus (declin = +10.1 °, R.A. = 260 °) when? Surpassed distance of Pioneer 10 on 17Feb1998.
    Will pass heliopause in 2002-2004. Will also eventually pass M4-class red dwarf AC +79 3888 @ 1.7 light years in ~40,000-60,000 years. Click here to learn more about Voyager 1 and 2.
    Instrument payload: same as sister ship.

  5. Galileo - USA 18 October 1989.
    First encounter with an asteroid
    First probe into atmosphere of a gas giant
    Robotic interplanetary probe with 11? expts on circuitous six-year trajectory with multiple gravity assists. Launch delayed by Challenger disaster, launched from Shuttle Atlantis in LEO (STS-34) on IUS. High gain antenna failed (probably during storage before liftoff), data tx on low gain. Mission planned to terminate with plunge into Jovian atmosphere in Aug2003 to avoid risk of contaminating possible Europan biosphere with Terran biota.
    Flew by VENUS: flyby @ 60X Cassini flyby on 09Feb1990; returned radio science.
    Flew by EARTH twice - 08Dec1990 and 08Dec1992.
    Flew by asteroid 951 GASPRA @ 1600 km on 29Oct1991.
    Flew by asteroid 243 IDA @ ? km on 18Aug1993; discovered first natural satellite (nnnn DACTYL) of another asteroid.

    Jovian system exploration:
    Released Galileo Probe 07Jul1995, bus arrived in Jovian orbit & dropsonde entered Jovian atmosphere @ 6 ° N on 07Dec1995, tx'd data for 75 min., imploded @ 25 bar, z = -150 km. Bus has completed 28 orbits of Jupiter as of Dec2000. In 0.53 million km x 15.47 million km x 0 ° circumjovian orbit. Next flyby: Ganymede. Next perijove: 23May2001.

    • Flew by IO four? times: discovered biggest, hottest volcanoes in solar system, Io's iron core & magnetic field
      flew by @ 198 km on 23Feb2000,
      flew by @ 200 km on 06Aug2001,
      flew by @ 181 km on 0223 18Oct2001 over Io's south pole
      and 17Jan2002 over equator.
    • Flew by EUROPA eight? times: closest @ 586 km on ?, discovered probable subsurface ocean
    • Flew by GANYMEDE three? times: discovered Ganymedan magnetosphere, possible subsurface ocean,
      flew by @ 800 km on ??May2000; flew by @ 2326 km on 28Dec2000.
      flew by @ 102 km on 17Jan2002.
    • Flew by CALLISTO, discovered possible subsurface ocean. 5 flybys:
      flew by @ 125 km on 1124 25May2001.
    • Flew by AMALTHEA @ 160 km on 05Nov2002, discovered loose packing, rho ~ 0.9.
    In 0.32×25 million km Jovian orbit. See Oct99 article "The Hidden Ocean of Europa" in Scientific American, and the Feb00 article summarizing the entire Galileo mission.

  6. Ulysses - USA/ESA 06 October 1990.
    Solar observatory, launched from Shuttle Discovery in LEO (STS-41) on IUS plus gravity assist,
    Flyby of JUPITER@ ? km on 08Feb1992, returned data?
    Arrived in 1.3 × 5.4 AU elliptic orbit over SOLAR POLES on xxJun1994. See Inner System missions.

  7. Cassini - USA/ESA 15 October 1997.
    Likely last of NASA's Big Science missions. Robotic interplanetary probe with 12 experiments on circuitous seven-year gravity assisted trajectory, launched on Titan IVB
    Two flybys of VENUS for gravity assist - first @ 284 km on 26Apr1998, second @ ? km on 24Jun1999; searched for lighting with RPWS expt, found none.
    Flew by EARTH @ 725? km on 18Aug1999; control tested lightning detection.
    Flew by main belt asteroid 2685 MAZURSKY @ 1.6 million km on 23Jan2000
    Flew by JUPITER @ 9.7 million km on 30Dec2000,
    Saturnian system exploration:
    Will arrive in saturnian orbit 01Jul2004.
  8. Target TITAN:
    flyby @ xx km on 26Oct2004;
    flyby @ xx km on 13Dec2004;
    release Huygens dropsonde towards Titan on 25Dec2004;
    flyby @ 65,000 km on 16Jan2005 when probe enters Titanian atmosphere.
    Will map other satellites in circumsaturnian orbit for 4 years.
    Instruments (12):
    Radio and Pasma Wave Science expt;

Note: cometary probes such as Project Vega 1 & 2, Sakigake, Giotto, Planet A, and Deep Space 1 (in spite of its name) have not been included on this list because such intercepts took place in the Inner System. In the case of DS1, it is an engineering mission, albeit a highly successful one. However, if you don't agree, by all means email me robot@ultimax.com and I might change my policy. Space physics experiments of broad applicability (e.g. radiation measurement, magnetic mapping) are not included either.
Multiple visits to the same body by the same spacecraft (e.g. GEM) do not count as multiple missions (even if they do require multiple visits to Capitol Hill for funding). Multiple visits to different primaries do. A mere gravity assist maneuver without science return doesn't really count as a mission, either - a "flyby" requires at least one instrument to be pointed in the general direction of the celestial body. This was not an accounting issue until a few Big Science missions (e.g. Galileo, Project Vega) flew some very complex trajectories with multiple gravity assists.

Future Missions to the Outer Solar System

  • planned but never designed or built Jupiter/Sun probe - USSR circa 1995-96 on Proton
    According to Anatoliy Zak's RussianSpaceWeb, a 2000 kg-class mission was planned in 1986-87 for launch on a Proton in 1995-96. It would slingshot 'round Jupiter, followed by close approach to the Sun (5-7 radii). During flyby, 500 kg dropsonde would be released into Jovian atmosphere. Another version would continue on to Saturn and the outer system after Jovian slingshot maneuver.

  • New Horizons - USA 2006.
    The PKE (Pluto-Kuiper Express, formerly Pluto Fast Flyby, or PFF) mission has been canceled. A new mission has been funded: New Horizons: Shedding Light on Frontier Worlds, led by Southwest Research Institute, with Johns Hopkins University APL; Ball Aerospace, Stanford, Goddard SFC, and JPL.
    There may be Russian participation (possibly provide a launcher).
    Comprises launch vehicle, spacecraft and science instrument payload; and includes a remote sensing package that includes imaging instruments, a radio science investigation, and other experiments to characterize the global geology and morphology of Pluto and Charon, map their surface composition, and characterize Pluto's neutral atmosphere and its escape rate, before their atmospheres freeze out in 2016. As time goes on, one hemisphere increasingly falls into permanent shadow. No solar illumination - no science. Original mission was to continue on to investigate objects in the Kuiper Belt. New propulsion technology (solar-electric and/or solar sail) may actually permit an arrival in 2020, without a Jovian slingshot, even if liftoff is delayed to 2010-12.
    Pluto is a different kind of planet. It is not a rocky planet like Earth, Mars, Mercury or Venus, or a gas giant like Jupiter, Saturn, Uranus or Neptune. It is a Kuiper Belt Object, a class of objects composed of material left over after the formation of the other planets, which has never been exposed to the higher temperatures and solar radiation levels of the inner solar system. It is known that Pluto has large quantities of ices of nitrogen, and simple molecules containing combinations of carbon, hydrogen and oxygen that are the necessary precursors of life. These ices would be largely lost to space if Pluto had come close to the Sun. Instead they remain on Pluto as a representative sample of the primordial material that set the stage for the evolution of the Solar System as it exists today, including life.

  • Europa Orbiter - USA Proposed launch in 2007+ to arrive in Europan orbit in 2009? and look for subsurface ocean and thinnest spot in ice shell to depth of 1 km with active radar. $700M?

  • INSIDE Jupiter - USA. circa 2007. Proposed Interior Structure and Internal Dynamical Evolution of Jupiter mission is a Jupiter orbiter designed to observe and measure processes occurring within the Jovian magnetosphere and atmosphere. INSIDE Jupiter would determine the internal structure of the planet by obtaining high resolution maps of the magnetic and gravity fields. JPL $296 million.

  • Europa Lander - USA when? Proposed mission to land on surface of Jovian moon.

  • Icepick (Europan Ocean Explorer) - USA when? europan submersible
    Proposed submersible "hydrobot" to bore thru ice crust and navigate subsurface ocean.

  • Jovian System Cruiser? powered by tether/ion engine?

  • Interstellar Probe - USA circa 2017 proposed solar-sail-propelled mission to 200 AU towards heliospheric nose to explore Kuiper Belt, heliopause, interstellar medium.

A Tour of Satellites in the Outer Solar System

All the gas giants in this solar system have ring systems. Saturn's is merely the most visible, and may be less than 100 million years old. A number of the outer planets' moons actually lie within their ring systems, either shepherding the rings or regenerating ring material via impacts. Satellites around each of the outer planets are not at all randomly distributed, as you might think, but tend to grouped in classes, with a high degree of similarity within each group (diameter/mass, orbital radius, inclination to primary, and probably composition), arguing for a common genesis with each group. Exceptions to this rule are probably captured asteroids, planetismals, or Kuiper Belt Objects. The orbital planes within a given group are not necessarily congruent, however, it helps to visualize the separate classes as if they were. Click here for more detailed info.

Credit goes out to TRW Space Log 1957-1996, The Planetary Report published by The Planetary Society, JPL Flight Projects Office literature from Planetfest '89, Proton Mission Planner's Manual, and Jonathan's Space Report, and Chris Jones: clj@world.std.com. A tip o' the meteoroid shield-leaded visor to David Portree DSFPortree@aol.com for his sharp eyes.

What's Coming to this Page:

Pictures of flyby probes. Closeups of Jovian moons coming to the new page, Outer Moons of the Solar System. Your comments are welcome: robot-at-ultimax-dot-com
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