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- Pioneer_anomaly abstract "The Pioneer anomaly or Pioneer effect is the observed deviation from predicted accelerations of the Pioneer 10 and Pioneer 11 spacecraft after they passed about 20 astronomical units (3×109 km; 2×109 mi) on their trajectories out of the Solar System. The apparent anomaly was a matter of tremendous interest for many years.Both Pioneer spacecraft are escaping the Solar System, but are slowing under the influence of the Sun's gravity. Upon very close examination of navigational data, the spacecraft were found to be slowing slightly more than expected. The effect is an extremely small acceleration towards the Sun, of (8.74±1.33)×10−10 m/s2, which is equivalent to slowly accelerating to a velocity of one kilometer per hour (0.6 mph) over a period of ten years. The two spacecraft were launched in 1972 and 1973 and the anomalous acceleration was first noticed as early as 1980, but not seriously investigated until 1994. The last communication with either spacecraft was in 2003, but analysis of recorded data continues.Various explanations, both of spacecraft behavior and of gravitation itself, were proposed to explain the anomaly. Over the period 1998–2012, one particular explanation became accepted. The spacecraft, which are surrounded by an ultra-high vacuum and are each powered by a radioisotope thermoelectric generator (RTG), can shed heat only via thermal radiation. If, due to the design of the spacecraft, more heat is emitted in a particular direction—what is known as a radiative anisotropy—then the spacecraft would exhibit a small acceleration in the direction opposite that of the excess emitted radiation due to radiation pressure. Since this force is due to the recoil of thermal photons, it is also called the thermal recoil force. If the excess radiation and attendant radiation pressure were pointed in a general direction opposite the Sun, the spacecrafts’ velocity away from the Sun would be decelerating at very slightly greater rate than could be explained by previously recognized forces such as gravity and trace friction due to the interplanetary medium (imperfect vacuum).By 2012 several papers by different groups, all reanalyzing the thermal radiation pressure forces inherent in the spacecraft, showed that a careful accounting of this could explain the entire anomaly, and thus the cause was mundane and did not point to any new phenomena or need for a different physical paradigm. The most detailed analysis to date, by some of the original investigators, explicitly looks at two methods of estimating thermal forces, then states "We find no statistically significant difference between the two estimates and conclude that once the thermal recoil force is properly accounted for, no anomalous acceleration remains."".
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- Pioneer_anomaly wikiPageID "980666".
- Pioneer_anomaly wikiPageRevisionID "602083339".
- Pioneer_anomaly hasPhotoCollection Pioneer_anomaly.
- Pioneer_anomaly subject Category:Gravitation.
- Pioneer_anomaly subject Category:Pioneer_program.
- Pioneer_anomaly subject Category:Unsolved_problems_in_physics.
- Pioneer_anomaly type Abstraction100002137.
- Pioneer_anomaly type Attribute100024264.
- Pioneer_anomaly type Condition113920835.
- Pioneer_anomaly type Difficulty114408086.
- Pioneer_anomaly type Problem114410605.
- Pioneer_anomaly type State100024720.
- Pioneer_anomaly type UnsolvedProblemsInPhysics.
- Pioneer_anomaly comment "The Pioneer anomaly or Pioneer effect is the observed deviation from predicted accelerations of the Pioneer 10 and Pioneer 11 spacecraft after they passed about 20 astronomical units (3×109 km; 2×109 mi) on their trajectories out of the Solar System. The apparent anomaly was a matter of tremendous interest for many years.Both Pioneer spacecraft are escaping the Solar System, but are slowing under the influence of the Sun's gravity.".
- Pioneer_anomaly label "Anomalia Pioneer".
- Pioneer_anomaly label "Anomalia das Pioneers".
- Pioneer_anomaly label "Anomalia sond Pioneer".
- Pioneer_anomaly label "Anomalie Pioneer".
- Pioneer_anomaly label "Anomalía de las Pioneer".
- Pioneer_anomaly label "Pioneer anomaly".
- Pioneer_anomaly label "Pioneer-Anomalie".
- Pioneer_anomaly label "Pioneeranomalie".
- Pioneer_anomaly label "Эффект «Пионера»".
- Pioneer_anomaly label "パイオニア・アノマリー".
- Pioneer_anomaly sameAs Anomálie_sond_Pioneer.
- Pioneer_anomaly sameAs Pioneer-Anomalie.
- Pioneer_anomaly sameAs Anomalía_de_las_Pioneer.
- Pioneer_anomaly sameAs Pioneerren_akatsa.
- Pioneer_anomaly sameAs Anomalie_Pioneer.
- Pioneer_anomaly sameAs Anomalia_Pioneer.
- Pioneer_anomaly sameAs パイオニア・アノマリー.
- Pioneer_anomaly sameAs 파이어니어_어노멀리.
- Pioneer_anomaly sameAs Pioneeranomalie.
- Pioneer_anomaly sameAs Anomalia_sond_Pioneer.
- Pioneer_anomaly sameAs Anomalia_das_Pioneers.
- Pioneer_anomaly sameAs m.03wbpq.
- Pioneer_anomaly sameAs Q569091.
- Pioneer_anomaly sameAs Q569091.
- Pioneer_anomaly sameAs Pioneer_anomaly.
- Pioneer_anomaly wasDerivedFrom Pioneer_anomaly?oldid=602083339.
- Pioneer_anomaly isPrimaryTopicOf Pioneer_anomaly.