New Theory About the Source of Pioneer Space Probe Deceleration 156
First time accepted submitter deathcow writes "After forty years, a fresh perspective on old Pioneer data leads to new conclusions as to why the Pioneer probes are decelerating. Many theories to the slowing probes have persisted over the years — was it gravity? some type of unforeseen radiation? dark matter? Thanks to the data backup preservation efforts of a NASA Ames Research engineer, mountains of old telemetry data were still available for studying this curious anomaly."
Article too long, let me save you some time (Score:5, Informative)
It's thermal recall force from heat generated by components on Pioneer.
The article is way too long but here's the essential paragraph:
"we estimated the magnitude of the thermal recoil force at different times over the course of the Pioneer missions. After matching the model to the Pioneers’ temperature and electrical readings, we found that the spacecraft did experience a sizable thermal recoil force, corresponding to an excess of about 60 W even after 20 years in deep space. The magnitude of the force was still tiny by Earth standards—about the same as the backward push your car experiences in reaction to the photons spit out by its high-beam headlights. The team found that a good half of the force came from heat from the RTGs (radioisotope thermoelectric generators), which bounced off the back of the spacecraft antenna. The other half came from electrical heat from circuitry in the heart of the spacecraft"
There, you may resume.
I hate IEEE Spectrum (Score:5, Informative)
I hate Spectrum. Not because they have bad articles, but because they never have anything that I haven't already been reading about for the past months, or even years.
Hint to editors. If you ever get a submission with a link to Spectrum, chances are very high that Slashdot has covered [slashdot.org] it before [slashdot.org].
Re:Article too long, let me save you some time (Score:2, Informative)
... wasn't this already determined, around a year ago?
Not so new (Score:5, Informative)
Not so new of a theory, and already discussed here at Slashdot:
http://science.slashdot.org/story/11/07/26/0135234/heat-most-likely-cause-of-pioneer-anomaly [slashdot.org]
Everything from clouds of dark matter, weird gravitational effects, alien tampering and exotic new physics have all been blamed for the 'Pioneer Anomaly' — the tiny, inexplicable sun-ward acceleration acting on the veteran Pioneer deep space probes. However, evidence is mounting for a more mundane explanation. Yes, it's the emission of heat from the spacecrafts' onboard radioisotope thermoelectric generators (RTGs), slowly nudging the Pioneers off course, that looks like the most likely culprit. It's unlikely that this new finding will completely silence advocates of more exotic explanations, however.
Summary (Score:5, Informative)
Re:Regardless - the science is fascinating (Score:5, Informative)
It'll last longer than 88 years. The half life is 88 years... that means it's only halfway done after 88 years. All it's going to do is lose efficiency over the next thousand years or so.
Re:I hate IEEE Spectrum (Score:5, Informative)
Re:Article too long, let me save you some time (Score:5, Informative)
... wasn't this already determined, around a year ago?
Well not positively determined, the new analysis of the data does a better job of confirming it. So yes, as usual the summary is horribly wrong- it's a better proof of an existing theory, not a new theory.
Re:Nah (Score:5, Informative)
This is science kid, leave it for people who can read a full paragraph without needing a red bull.
Err no. Science starts by giving you a brief summary of the theory and conclusions, then proceeds to get into the details. We call it an Abstract. This is a fluff piece which should have been titled "Thermal radiation theory confirmed as source of Pioneer slowdown". Most of the space is spent rambling on about the history of the mission and very little about the methods used to determine the results.
Re:Article too long, let me save you some time (Score:4, Informative)
The most impressive thing is that we can actually measure this minute effect
According to Wikipedia [wikipedia.org], it's 8.74×10^10 m/s^2. If you integrate that over fourty years [wolframalpha.com], that's 17000 km, or 55 ms light-speed delay, which should not be too difficult to detect.
--jch