http://news.discovery.com/space/oh-pioneer-mysterious-anomaly-may-finally-be-solved-110414.html Mysterious Pioneer Anomaly May Finally Be Solved
Analysis by Jennifer Ouellette
Thu Apr 14, 2011 03:55 PM ET
A flurry of recent papers could lay to rest once and for all a longstanding mystery in astrophysics: the so-called "Pioneer anomaly," an as-yet-unexplained deceleration of NASA's Pioneer 10 and Pioneer 11 spacecraft in their wanderings beyond our solar system.
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In particular, Phong shading has allowed the Portuguese team to include for the first time the effect of heat emitted from a part of the spacecraft called the main equipment compartment. It turns out that heat from the back wall of this compartment is reflected from the back of the spacecraft's antenna. Since the antenna points Sunward, towards Earth, reflections off its back would tend to decelerate the spacecraft. "The radiation from this wall will, in a first iteration, reflect off the antenna and add a contribution to the force in the direction of the sun."
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Darn it!