But while the Pioneers had reached escape velocity from the Sun and would ultimately leave the solar system, by 1980 a researcher at NASA’s Jet Propulsion Laboratory noticed the Pioneers were slowing down more than the data predicted they would. It was understood that the probes would slow down to some extent due to the Sun’s gravitational attraction. This astonishing accuracy with regards to measuring the acceleration of the Pioneers led to an unusual discovery. The Pioneers are considered the most precisely tracked and navigated spacecraft to date. The Voyager spacecraft, which were not spin stabilized and relied on more frequent use of thrusters, cannot be tracked to this level of precision. The combination of the type of transceiver aboard the spacecraft and ground-based Doppler tracking used on the missions allowed their acceleration to be tracked to an almost unbelievable accuracy of ∼ 10 –10 meters per second squared (m/s 2). Both Pioneers were spin stabilized (which means that they rotate around a central point to keep them from wobbling or changing trajectory) and required very few course corrections that could perturb their motion. The Pioneers had some unique design features that allowed them to be very precisely tracked by Earth-based receiving stations. The Pioneers also famously carried the Pioneer plaque, with a pictorial message for any extraterrestrials who may someday encounter the craft this would give them information as to the origin of the probes. Powered by four plutonium-238 radioisotope thermoelectric generators (RTGs) each, the Pioneer spacecraft carried a plethora of scientific devices that allowed them to take photographs and make detailed measurements of the environments around Jupiter and Saturn and in the outer solar system. Like their successors, the Voyagers and New Horizons, both Pioneers are past the orbit of Pluto and will continue speeding outward from the center of the solar system. Launched in 19, respectively, these spacecraft were the first to transit the asteroid belt and the first to make close observations of Jupiter (both Pioneer 10 and 11) and Saturn (Pioneer 11).
Ref: /abs/0809.Before Voyager 1 and 2 explored the outer solar system, Pioneer 10 and 11 paved the way. But could it really be possible that the Pioneer anomaly is the first evidence of physics beyond Einstein’s version of general relativity? Obviously, more analysis is needed and it always pays to be cautious with these kinds of ideas. Now Christophe and co say that the periodic variations are compatible with the effects on radio signals that some of these modifications might cause. But there has never been a way to test these modifications.
Now Bruno Christophe and pals from the French aerospace lab, ONERA, near Paris and various other French institutions, have carried the most detailed analysis yet on these periodic variations and raise another interesting possibility.Ī number of people have suggested modifications to general relativity that would explain the Pioneer anomaly.
Instead, they think probably the result of something at our end such as a tiny variation in Earth’s orbit. The team at the NASA’s Jet Propulsion Lab who have been collecting the data say that it’s unlikely that this variation is a from the spacecraft. What isn’t so well known is that there is a periodic component to the anomaly. All that has been widely discussed and numerous explanations have been put forward to explain this discrepancy. Both probes appear to be decelerating faster than can be explained by the Sun’s gravity. NASA has been accurately tracking their position and speed using Doppler tracking measurements of radio signals from the craft. Here’s the background: Pioneer 10 and 11 were launched in 19 respectively and, after sweeping past a number of the outer gas giants, have been heading out of the solar system ever since. The Pioneer anomaly grows ever more fascinating. Periodic Pioneer anomaly points to modified general relativity
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