Rendering the Pioneer spacecraft in 3D has helped solve the anomaly of their strange deceleration as they left the solar system - radiative heat reflecting off the surface pushed them slightly back towards Earth.
Credit: Wikimedia
SYDNEY: It’s not dark matter, multiple universes or weird gravity: the strange deceleration of the Pioneer spacecraft is just waste heat – the trouble is nobody’s looked at it the right way, Portuguese researchers report.
Known as the ‘Pioneer anomaly’, the unexplained deceleration of NASA’s two Pioneer spacecraft, Pioneer 10 and 11 (launched in 1972 and 1973 respectively) has provoked some exotic theories, including errors in Einstein’s theory of gravity or the presence of multiple universes.
More mundane theories including reflection of light from the Sun, or thermal emissions from the spacecraft itself couldn’t explain the small discrepancy in the spacecrafts’ speed, a tiny drop of less than 0.000000001 metres per second.
Now astrophysicist Frederico Francisco from the Institute for Plasmas and Nuclear Fusion in Lisbon, Portugal, and colleagues said they have the answer.
3D solution
The team used a 1970’s software program called Phong Shading, originally developed to create a 3D rendering effect on graphics, to model the reflection of waste heat from the spacecraft on their varied surfaces – the 2.7-metre diameter antenna, and rest of the spacecraft behind it. Then they did the maths.
Scientists had previously calculated the effects of heat loss from the spacecraft accounted for just one to two thirds of the deceleration.
The anomaly was first noticed in 1998 when scientists studied radio signals from the then distant spacecraft and found that they were slowing down faster that theories predicted.
Solved!
In a paper posted on the physics website arXiv, the team said that the new calculations – which take into account how the spacecraft themselves reflect back their internal heat - can account for the deceleration – a tiny 8.74×10−10 ms−2.
“This method provides a simple and straightforward way of modelling the various components of reflection, as well as a more accurate accounting of the thermal radiation exchanges between the surfaces on the Pioneer spacecraft,” the researchers write.
“With the results presented here it becomes increasingly apparent that, unless new data arises, the puzzle of the anomalous acceleration of the Pioneer probes can finally be put to rest.”
While small, the effect was enough to force the spacecraft hundreds of thousands of kilometers from where they were expected to be.
