Information AboutPioneer 11 |
| CATEGORIES ABOUT PIONEER 11 | |
| jupiter spacecraft | |
| pioneer program | |
| saturn spacecraft | |
| 1973 in space exploration | |
| spacecraft escaping the solar system | |
| inactive extraterrestrial probes | |
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Pioneer 11 was the second mission to investigate Jupiter and the Outer Solar System and the first to explore the planet Saturn and its main rings. Pioneer 11 (also called Pioneer G), unlike Pioneer 10 which only visited Jupiter, used Jupiter's Mass in a Gravitational Slingshot to alter its Trajectory toward Saturn. It passed close to Saturn and then it followed an escape trajectory from the Solar System . The ) sensor, and two Sun sensors. Attitude position could be calculated from the reference direction to Earth and Sun, with the known direction to Canopus as backup. Pioneer 11's star sensor gain and threshold settings were modified, based on experience gained from the settings used on Pioneer 10. Three pairs of rocket Thruster s provided spin-axis control (maintained at 4.8 rpm) and change the spacecraft's Velocity . The thrusters could be either fired steadily or pulsed, by command. Instruments studied the interplanetary and planetary Magnetic Field s; Solar Wind properties; Cosmic Ray s; the transition region of the Heliosphere ; Neutral Hydrogen abundance; distribution, size, mass, Flux , and velocity of Dust particles; Jovian Aurorae ; Jovian Radio Waves ; the Atmosphere s of planets and Satellite s; and the surfaces of Jupiter, Saturn, and some of their satellites. The instruments carried for these experiments were a Magnetometer , a Plasma Analyzer (for Solar Wind ), a Charged-particle Detector , an Ion Detector , non-imaging Telescope s with overlapping fields of view to detect Sunlight reflected from passing Meteoroid s, sealed pressurized cells of Argon and Nitrogen gas for measuring penetration of meteoroids, an Ultraviolet Photometer , an Infrared Radiometer , and an Imaging Photopolarimeter , which produced Photograph s and measured their Polarization . Further scientific information was obtained from Celestial Mechanics and Occultation Phenomena . was taken by Pioneer 11 on September 1 , 1979 , three days before its closest encounter. The Moon Titan is visible to the upper left. The rings appear dim because they were at a shallow angle to the sun at the time of Pioneer's visit.]] During its closest approach, December 4 , 1974 , Pioneer 11 passed to within 34,000 Km of Jupiter's cloud tops. It passed by Saturn on September 1 , 1979 , at a distance of 21,000 km from Saturn's cloud tops. (By this time Voyager 1 and Voyager 2 had already passed Jupiter and were also en route to Saturn.) It was decided to target Pioneer 11 to pass through the Saturn ring plane at the same position that the soon-to-come Voyager probe would use in order to test the route before Voyager arrived. If there were faint ring particles that could damage a probe in that area, mission planners felt it was better to learn about it via Pioneer. Thus, Pioneer 11 was acting as a "pioneer" in a true sense of the word. (If danger was detected, then the Voyager probes could be rerouted further away from the rings, but missing the opportunity to visit Uranus and Neptune in the process.) The spacecraft has operated on a backup transmitter since launch. Instrument power sharing began in February 1985 due to declining generator power output. Science operations and daily Telemetry ceased on September 30 , 1995 when the RTG power level was insufficient to operate any experiments. As of the end of 1995, when its mission ended, the spacecraft was located at 44.7 AU from the Sun at a nearly Asymptotic Latitude of 17.4 degrees above the Solar Equatorial Plane and was heading outward at 2.5 AU /year (12 km/s). on board the Pioneer spacecraft]] Like its sister ship, Pioneer 10, Pioneer 11 carried a Plaque with a message from Humankind . If the Space probe is ever found by extraterrestrial intelligences, this message is meant to provide information about the origin of the spacecraft. It includes a drawing depicting a man, a woman, the transition of a hydrogen atom, and the location of the Sun and Earth in the Galaxy . PIONEER ANOMALY ''Main article: Pioneer Anomaly '' Analysis of the radio tracking data from the Pioneer 10 and 11 spacecraft at distances between 20–70 AU from the Sun has consistently indicated the presence of an anomalous, small Doppler frequency drift. The drift can be interpreted as being due to a constant acceleration of (8.74 ± 1.33) × 10−10 m/s2 directed towards the Sun. Although it is suspected that there is a systematic origin to the effect, none has been found. As a result, the nature of this Anomaly has become of growing interest. SEE ALSO EXTERNAL LINKS
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