Pioneer 11

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  Pioneer 11 ·   Earth  ·   Jupiter  ·   Saturn
  • Animation of Pioneer 11 trajectory around Jupiter.gif
    Animation of Pioneer 11's trajectory around Jupiter from November 30, 1974 to December 5, 1974
      Pioneer 11 ·   Jupiter  ·   Io  ·   Europa  ·   Ganymede  ·   Callisto
  • Animation of Pioneer 11 around Saturn.gif
    Animation of Pioneer 11 around Saturn
       Pioneer 11 ·  Saturn ·  Epimetheus ·  Janus ·  Mimas ·  Enceladus

    • Encounter with Jupiter

    Pioneer 11 flew past Jupiter in November and December 1974. During its closest approach, on December 2, it passed 42,828 km (26,612 mi) above the cloud tops. The probe obtained detailed images of the Great Red Spot, transmitted the first images of the immense polar regions, and determined the mass of Jupiter's moon Callisto. Using the gravitational pull of Jupiter, a gravity assist was used to alter the trajectory of the probe towards Saturn and gain velocity. On April 16, 1975, following the Jupiter encounter, the micrometeoroid detector was turned off. [1]

    Commons-logo.svg Media related to Pioneer 11 Jupiter encounter at Wikimedia Commons

    Encounter with Saturn

    Pioneer 11
    An artist's impression of a Pioneer spacecraft on its way to interstellar space.jpg
    An artist's impression of Pioneer 11 on its way to interstellar space.
    Mission typePlanetary / Heliosphere exploration
    Operator NASA / Ames
    COSPAR ID 1973-019A OOjs UI icon edit-ltr-progressive.svg
    SATCAT no. 6421
    Website science.nasa.gov
    Mission duration22 years, 7 months and 19 days
    Spacecraft properties
    Manufacturer TRW
    Launch mass258.5 kg (570 lb) [1]
    Power155 watts (at launch)
    Start of mission
    Launch dateApril 6, 1973, 02:11:00 (1973-04-06UTC02:11Z) UTC [1]
    Rocket Atlas SLV-3D Centaur-D1A Star-37E
    Launch site Cape Canaveral LC-36B
    End of mission
    DisposalDecommissioned
    Last contactNovember 24, 1995 (1995-11-25)
    Flyby of Jupiter
    Closest approachDecember 3, 1974
    Distance43,000 km (27,000 mi)

    Pioneer 11 passed by Saturn on September 1, 1979, at a distance of 21,000 km (13,000 mi) from Saturn's cloud tops. [27]

    By this time, Voyager 1 and Voyager 2 had already passed Jupiter and were en route to Saturn, so it was decided Pioneer 11 would pass through the Saturn ring plane at the same position Voyager 2 would later have to fly through in order to reach Uranus and Neptune. If there were faint ring particles capable of damaging a probe in that area, mission planners felt it was better to learn about it via Pioneer. [27] Thus, Pioneer 11 was acting as a "pioneer" in a true sense of the word; if danger were detected, then Voyager 2 could be redirected further away from the rings but miss the opportunity to visit the ice giants in the process.

    Pioneer 11 imaged—and nearly collided with—one of Saturn's small moons, passing at a distance of no more than 4,000 km (2,500 mi). The object was tentatively identified as Epimetheus, a moon discovered the previous day from Pioneer's imaging, and suspected from earlier observations by Earth-based telescopes. After the Voyager flybys, it became known that there are two similarly sized moons (Epimetheus and Janus) in the same orbit, so there is some uncertainty about which one was the object of Pioneer's near-miss. Pioneer 11 encountered Janus on September 1, 1979, at 14:52  UTC, at a distance of 2,500 km (1,600 mi). At 16:20 UTC the same day, Pioneer 11 encountered Mimas at a distance of 103,000 km (64,000 mi).

    Besides Epimetheus, instruments located another previously undiscovered small moon and an additional ring, charted Saturn's magnetosphere and magnetic field, and found its planet-sized moon, Titan, to be too cold for life. Hurtling underneath the ring plane, the probe sent back pictures of Saturn's rings. The rings, which normally seem bright when observed from Earth, appeared dark in the Pioneer pictures, and the dark gaps in the rings seen from Earth appeared as bright rings.

    Commons-logo.svg Media related to Pioneer 11 Saturn encounter at Wikimedia Commons

    Interstellar mission

    On February 25, 1990, Pioneer 11 became the fourth human-made object to pass beyond the orbit of the planets. [29]

    By 1995, Pioneer 11 could no longer power any of its detectors, so the decision was made to shut it down. [30] On September 29, 1995, NASA's Ames Research Center, responsible for managing the project, issued a press release that began, "After nearly 22 years of exploration out to the farthest reaches of the Solar System, one of the most durable and productive space missions in history will come to a close." It indicated NASA would use its Deep Space Network antennas to listen "once or twice a month" for the spacecraft's signal, until "some time in late 1996" when "its transmitter will fall silent altogether." NASA Administrator Daniel Goldin characterized Pioneer 11 as "the little spacecraft that could, a venerable explorer that has taught us a great deal about the Solar System and, in the end, about our own innate drive to learn. Pioneer 11 is what NASA is all about – exploration beyond the frontier." [31] Besides announcing the end of operations, the dispatch provided a historical list of Pioneer 11 mission achievements.

    NASA terminated routine contact with the spacecraft on September 30, 1995, but continued to make contact for about two hours every two to four weeks. [30] Scientists received a few minutes of good engineering data on November 24, 1995, but then lost final contact once Earth moved out of view of the spacecraft's antenna. [1] [32]

    Timeline

    Pioneer 10 and 11 speed and distance from the Sun Pioneer speed and distance from Sun.svg
    Pioneer 10 and 11 speed and distance from the Sun
    Heliocentric positions of the five interstellar probes (squares) and other bodies (circles) until 2020, with launch and flyby dates. Markers denote positions on 1 January of each year, with every fifth year labelled. Plot 1 is viewed from the north ecliptic pole, to scale. Plots 2 to 4 are third-angle projections at 20% scale. In the SVG file, hover over a trajectory or orbit to highlight it and its associated launches and flybys. Interstellar probes trajectory.svg
    Heliocentric positions of the five interstellar probes (squares) and other bodies (circles) until 2020, with launch and flyby dates. Markers denote positions on 1 January of each year, with every fifth year labelled.
    Plot 1 is viewed from the north ecliptic pole, to scale.
    Plots 2 to 4 are third-angle projections at 20% scale.
    In the SVG file, hover over a trajectory or orbit to highlight it and its associated launches and flybys.
    Timeline of travel
    DateEvent
    1973-04-06
    		Spacecraft launched at 02:11:00.
    1974-04-19
    		Passage through the asteroid belt.
    1974-11-03
    		Start Jupiter observation phase.
    TimeEvent
    1974-12-02
    		Encounter with Jovian system.
    08:21:00
    		 Callisto flyby at 786,500 km.
    22:09:00
    		 Ganymede flyby at 692,300 km.
    1974-12-03
    03:11:00
    		 Io flyby at 314,000 km.
    04:15:00
    		 Europa flyby at 586,700 km.
    05:00:21
    		Jupiter shadow entry.
    05:01:01
    		Jupiter occultation entry.
    05:21:19
    		 Jupiter closest approach at 42,828 km.
    05:33:52
    		Jupiter shadow exit.
    05:43:03
    		Jupiter occultation exit.
    22:29:00
    		 Amalthea flyby at 127,500 km.
    1975-01-01
    		Phase stop.
    1979-07-31
    		Start Saturn observation phase.
    TimeEvent
    1979-08-29
    		Encounter with Saturnian system.
    06:06:10
    		 Iapetus flyby at 1,032,535 km.
    11:53:33
    		 Phoebe flyby at 13,713,574 km.
    1979-08-31
    12:32:33
    		 Hyperion flyby at 666,153 km.
    1979-09-01
    14:26:56
    		Descending ring plane crossing.
    14:50:55
    		 Epimetheus flyby at 6,676 km.
    15:06:32
    		 Atlas flyby at 45,960 km.
    15:59:30
    		 Dione flyby at 291,556 km.
    16:26:28
    		 Mimas flyby at 104,263 km.
    16:29:34
    		 Saturn closest approach at 20,591 km.
    16:35:00
    		Saturn occultation entry.
    16:35:57
    		Saturn shadow entry.
    16:51:11
    		 Janus flyby at 228,988 km.
    17:53:32
    		Saturn occultation exit.
    17:54:47
    		Saturn shadow exit.
    18:21:59
    		Ascending ring plane crossing.
    18:25:34
    		 Tethys flyby at 329,197 km.
    18:30:14
    		 Enceladus flyby at 222,027 km.
    20:04:13
    		 Calypso flyby at 109,916 km.
    22:15:27
    		 Rhea flyby at 345,303 km.
    1979-09-02
    18:00:33
    		 Titan flyby at 362,962 km.
    1979-10-05
    		Phase stop.
    1979-10-05
    		Begin Pioneer Interstellar Mission.
    1990-
    		Passed the orbit of Pluto.
    1995-09-30
    		Routine daily mission operations stopped. Pioneer 11 is 6.5 billion km from Earth.
    1995-11-24
    		Last signal received.
    [33] [1] [34]

    Current status

    Due to power constraints and the vast distance to the probe, the last routine contact with the spacecraft was on September 30, 1995, and the last good engineering data was received on November 24, 1995. [3] [1]

    As of June 24, 2024, Pioneer 11 is estimated to be 113.121 AU (16.9227×10^9 km; 10.5153×10^9 mi) from the Earth and 114.089 AU (17.0675 billion km; 10.6052 billion mi) from the Sun. It was traveling at 11.155 km/s (40,160 km/h; 24,950 mph) relative to the Sun and traveling outward at about 2.35 AU per year. [35] [36] The spacecraft is heading in the direction of the constellation Scutum near the current position (June 2024) RA 18h 54m dec -8° 46' (J2000.0), close to Messier 26. In 928,000 years, it will pass within 0.25 parsecs (0.82 light-years ) of the K dwarf TYC 992-192-1 [37] and will pass near the star Lambda Aquilae in about four million years. [38]

    Pioneer 11 has been overtaken by the two Voyager probes launched in 1977. Voyager 1 has become the most distant object built by humans and will remain so for the foreseeable future, as no probe launched since Voyager has the speed to overtake it. [39]

    Pioneer anomaly

    Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20 and 70 AU from the Sun had consistently indicated the presence of a small but anomalous Doppler frequency drift. The drift can be interpreted as due to a constant acceleration of (8.74 ± 1.33) × 10−10 m/s2 directed towards the Sun. Although it was suspected that there was a systematic origin to the effect, none was found. As a result, there has been sustained interest in the nature of this so-called "Pioneer anomaly". [40] Extended analysis of mission data by Slava Turyshev and colleagues determined the source of the anomaly to be asymmetric thermal radiation and the resulting thermal recoil force acting on the face of the Pioneers away from the Sun. [41] [42]

    Pioneer plaque

    Pioneer plaque Pioneer10-plaque.jpg
    Pioneer plaque

    Pioneer 10 and 11 both carry a gold-anodized aluminum plaque in the event that either spacecraft is ever found by intelligent lifeforms from other planetary systems. The plaques feature the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft. [43]

    Commemoration

    In 1991, Pioneer 11 was honored on one of 10 United States Postage Service stamps commemorating uncrewed spacecraft exploring each of the then nine planets and the Moon. Pioneer 11 was the spacecraft featured with Jupiter. Pluto was listed as "Not yet explored". [44]

    See also

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    References

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    Bibliography

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