The anomaly Pioneer or the effect Pioneer indicates the difference between the trajectory observed and the awaited trajectory in a certain number of not controlled space probes travelling in-outside Solar system or on its margins, in particular the probes Pioneer 10 and 11. There is no yet universally accepted explanation of this phenomenon; it can have a completely banal cause (still should it be explained why it is the same one on the two probes), but the possibility that it is about an entirely new physical phenomenon is also considered.

Observations

The anomaly is measured by using the Doppler effect. It makes it possible to measure a tiny but constant deceleration, about 8,74  x  10^-10  m/s ², for the two probes.

The data coming from Galileo and Ulysses indicate a similar anomaly, but for various reasons (in particular proximity of the Sun), one cannot draw from firm conclusions of these measurements. Indeed, these probes are stabilized thanks to a embarked Gyroscope, as on the Sondes Travelling, they thus underwent several corrections of trajectory intended to maintain the orientation of the communication system towards the Earth. On the other hand, the orientation of the probes Pioneer is stabilized by gyroscopic effect, i.e. it is the rotation of the probes around their longitudinal axis which guarantees the stabilization of their trajectory. Their current speed can thus be calculated by knowing only their initial speed and the acceleration which they underwent in the vicinity of planets that they visited. For this reason the speed of the Pioneer probes is known with more precision.

Assumptions

• a real deceleration:
• by nelles forces Gravitation, exerted by:
• the Belt of Kuiper,
• a brown Dwarf (see Némésis),
• the black Matter.
• the Solar wind or the pressure of radiations (which would however be exerted normally in the other direction),
• frictions with the medium ( drag in English),
• a force of reaction to the radio transmissions,
• a gas leak of the probes (of which the Hélium coming from fission in the generating ) (which as much could thus have made them accelerate, or not to decelerate both),
• a thermal pressure (coming from the generators or besides),
• of the errors, either in measurement, or in calculation;
• a physical phenomenon which had not been observed yet:
• a modification the speed of light which would induce a disturbance of the Doppler effect used to measure the speed of the probe,
• of the corrections to metric of Schwartzschild which governs the space time generated by a mass with spherical symmetry (here Sun),
• a phenomenon equivalent to the Effet Casimir which would connect the inertial mass to the gravitational energy of the vacuum, this one itself affected by the absence of radiation of Unruh big wavelengths (but why?).

All the material causes were quantified and rejected in 2006.

The Pioneer probes do not send any more data, and Galileo was deliberately disintegrated in the atmosphere of Jupiter in 2003. Up to now, the data of the other missions, such as Cassini, did not give anything. One also proposed a mission which would be dedicated to the study of this phenomenon (in particular with the European space agency); this mission should have a hyperbolic solar orbit of a ray higher than 20 UA.

See too

• Program Pioneer

References