Study finds heat is source of 'Pioneer anomaly'

Jul 18, 2012 by Jia-Rui C. Cook
An artist's impression of Pioneer 10 heading out of the solar system towards the galactic center. Image credit: NASA Ames

(Phys.org) -- The unexpected slowing of NASA’s Pioneer 10 and 11 spacecraft – the so-called “Pioneer Anomaly” – turns out to be due to the slight, but detectable effect of heat pushing back on the spacecraft, according to a recent paper. The heat emanates from electrical current flowing through instruments and the thermoelectric power supply. The results were published on June 12 in the journal Physical Review Letters.

“The effect is something like when you’re driving a car and the photons from your headlights are pushing you backward,” said Slava Turyshev, the paper’s lead author at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “It is very subtle.”

Launched in 1972 and 1973, Pioneer 10 and 11 are on an outward trajectory from our sun. In the early 1980s, navigators saw a deceleration on the two spacecraft, in the direction back toward the sun, as the two spacecraft were approaching Saturn. They dismissed it as the effect of dribbles of leftover propellant still in the fuel lines after controllers had cut off the propellant. But by 1998, as the spacecraft kept traveling on their journey and were over 8 billion miles (13 billion kilometers) away from the sun, a group of scientists led by John Anderson of JPL realized there was an actual deceleration of about 300 inches per day squared (0.9 nanometers per second squared). They raised the possibility that this could be some new type of physics that contradicted Einstein’s general theory of relativity.

In 2004, Turyshev decided to start gathering records stored all over the country and analyze the data to see if he could definitively figure out the source of the deceleration. In part, he and colleagues were contemplating a deep space physics mission to investigate the anomaly, and he wanted to be sure there was one before asking NASA for a spacecraft.

Pioneers 10 and 11 both carried small metal plaques identifying their time and place of origin for the benefit of any other spacefarers that might find them in the distant future. Pioneer 10 is heading towards the star Aldebaran in the Taurus constellation and will take more than two million years to reach it. Image credit: NASA Ames

He and colleagues went searching for Doppler data, the pattern of data communicated back to Earth from the spacecraft, and telemetry data, the housekeeping data sent back from the spacecraft. At the time these two Pioneers were launched, data were still being stored on punch cards. But Turyshev and colleagues were able to copy digitized files from the computer of JPL navigators who have helped steer the Pioneer spacecraft since the 1970s. They also found over a dozen of boxes of magnetic tapes stored under a staircase at JPL and received files from the National Space Science Data Center at NASA Goddard Space Flight Center and worked with NASA Ames Research Center to save some of their boxes of magnetic optical tapes. He collected over 43 gigabytes of data, which may not seem like a lot now, but is quite a lot of data for the 1970s. He also managed to save a vintage tape machine that was about to be discarded so that he could play the magnetic tapes.

The effort was a labor of love for Turyshev and others. The Planetary Society sent out appeals to its members to help fund the data recovery effort. NASA later also provided funding. In the process, a programmer in Canada, Viktor Toth, contacted Turyshev because he heard about the effort. He helped Turyshev create a program that could read the telemetry tapes and clean up the old data.

On December 4, 1973, excitement rose as the Pioneer 10 spacecraft sent back images of a Jupiter of ever-increasing size as it plunged at high speed toward its closest approach to the planet. PICS (Pioneer Image Converter System) began to show a few spots on the screens, which gradually built up into a very distorted crescent-shaped Jupiter. "Sunrise on Jupiter," exclaimed a scientist excitedly. Subsequent PICS images were of a crescent Jupiter gradually decreasing in size as the spacecraft sped away out of the Jovian system. Image credit: NASA Ames

They saw that what was happening to Pioneer wasn’t happening to other spacecraft, mostly because of the way the spacecraft were built. For example, the Voyager spacecraft are less sensitive to the effect seen on Pioneer because its thrusters align it along three axes, whereas the Pioneer spacecraft rely on spinning to stay stable.

With all the data newly available, Turyshev and colleagues were able to calculate the put out by the electrical subsystems and the decay of plutonium in the Pioneer power sources, which matched the anomalous acceleration seen on both Pioneers.

“The story is finding its conclusion because it turns out that standard physics prevail,” Turyshev said. “While of course it would’ve been exciting to discover a new kind of physics, we did solve a mystery.”

Pioneer 10 and 11 were managed by NASA Ames Research Center, Moffett Field, Calif. Pioneer 10's last signal was received on Earth in January 2003. Pioneer 11's last signal was received in November 1995. JPL is a division of the California Institute of Technology, Pasadena.

Explore further: New countdown for launch of European navigation satellites

Related Stories

TPS Enables Study Of Mysterious Pioneer Anomaly

Jun 09, 2006

There's a mystery at the edge of our solar system: Two spacecraft, Pioneers 10 and 11, which were launched to Jupiter and Saturn more than 30 years ago, are hurtling towards the edge of our solar system - but at a slower ...

Ames celebrates the 40th anniversary of Pioneer 10

Mar 01, 2012

Launched on March 2,1972, Pioneer 10 was the first spacecraft to travel through the Asteroid belt, and the first spacecraft to make direct observations and obtain close-up images of Jupiter. Famed as the most remote object ...

Research team appears to solve the Pioneer anomaly

Apr 18, 2012

(Phys.org) -- Back in the early 70’s NASA launched two exploratory spacecraft, Pioneer 10 and 11. Their missions were to gather information about the solar system as they made their way through it by ...

Mystery force may be due to mirrors

May 05, 2011

Portuguese physicists report that they have identified the unknown force whose influence on outward bound interplanetary space probes has puzzled scientists since 1998. ...

Voyager 2 completes switch to backup thruster set

Nov 15, 2011

(PhysOrg.com) -- NASA's Voyager 2 has successfully switched to the backup set of thrusters that controls the roll of the spacecraft. Deep Space Network personnel sent commands to the spacecraft to make the ...

Recommended for you

SpaceX rocket explodes during test flight

21 minutes ago

A SpaceX rocket exploded in midair during a test flight, though no one was injured, as the company seeks to develop a spacecraft that can return to Earth and be used again.

Amazing raw Cassini images from this week

18 hours ago

When Saturn is at its closest to Earth, it's three-quarters of a billion miles away—or more than a billion kilometers! That makes these raw images from the ringed planet all the more remarkable.

Europe launches two navigation satellites

18 hours ago

Two satellites for Europe's rival to GPS were lifted into space on Friday to boost the Galileo constellation to six orbiters of a final 30, the European Space Agency (ESA) said.

SpaceX gets 10-year tax exemption for Texas site

19 hours ago

Cameron County commissioners have agreed to waive 10 years of county taxes as part of an agreement bringing the world's first commercial site for orbital rocket launches to the southernmost tip of Texas.

Voyager map details Neptune's strange moon Triton

20 hours ago

(Phys.org) —NASA's Voyager 2 spacecraft gave humanity its first close-up look at Neptune and its moon Triton in the summer of 1989. Like an old film, Voyager's historic footage of Triton has been "restored" ...

User comments : 25

Adjust slider to filter visible comments by rank

Display comments: newest first

ScottyB
5 / 5 (3) Jul 18, 2012
so how long before the probe starts a reverse in direction?
ackzsel
5 / 5 (1) Jul 18, 2012
@ScottyB
Maybe it wont because of radiation pressure from the sun or transmissions.
El_Nose
5 / 5 (4) Jul 18, 2012
this story is 3 years old AT LEAST -- they keep rehashing it when its a slow news week

The nuclear fuel used would run out well before radiation slowed the craft enough to stop and then move backwards.

tadchem
5 / 5 (4) Jul 18, 2012
"Nature always sides with the hidden flaw." - Murphy's Law, unnumbered corollary
antialias_physorg
4.5 / 5 (8) Jul 18, 2012
300 inches per day squared

Wow...that gets my vote for the most non-metric (and hard to imagine) unit ever used.

so how long before the probe starts a reverse in direction?

The electrical systems will eventually fail, which should stop the effect. At that point it'll just be residual radiation from the plutonium chamber which should be omnidirectional (i.e. it shouldn't contribute)

...unless the shielding towards the front is weaker than towards the back. In that case the infrared (and occasionally escaping gamma) would still slow it down.

That effect, too, will dwindle as the lump of plutonium grows less and less radioactive.
Tuxford
2 / 5 (11) Jul 18, 2012
As I have commented before, this effect is seen on various Earth flybys, according to a JPL senior scientist I met recently. Yes, likely it is due to thermal effects, but only in part. But the relativist's keep insisting that there is no new physics...what a relief. Delusional studies are so sad....

http://phys.org/n...ors.html

SincerelyTwo
5 / 5 (1) Jul 18, 2012
It's pretty neat that this artifact of humanity will continue on floating through interstellar space for possibly millions of years ... one day some alien civilization will have scouts flying around on survey missions and one of them might accidentally run into this thing and wonder where it came from. :)
antialias_physorg
5 / 5 (2) Jul 18, 2012
one day some alien civilization will have scouts flying around on survey missions and one of them might accidentally run into this thing

That'll have to be one AWESOME accident, as the Voyager probes aren't going anywhere near...well...anywhere in the foeseeable future. And even for the most inquisitive species I'd imagine that just zipping around in deep, deep space would be massively uninteresting.
GSwift7
4.2 / 5 (5) Jul 18, 2012
so how long before the probe starts a reverse in direction?


Never. The amount of deceleration is nothing compared to the velocity of the spacecraft. They will continue into interstellar space until gravity from other objects becomes stronger than the gravity from our solar system. They will be pulled along by the tides of our local cluster and our spiral arm on a slowing changing path through the Milkyway, lacking the velocity to escape our galaxy, but never to return here.
Peter Hent
4.2 / 5 (5) Jul 18, 2012
As I have commented before, this effect is seen on various Earth flybys, according to a JPL senior scientist I met recently. Yes, likely it is due to thermal effects, but only in part. But the relativist's keep insisting that there is no new physics...what a relief. Delusional studies are so sad....



Not as sad as delusional posts.
GSwift7
4.2 / 5 (5) Jul 18, 2012
That'll have to be one AWESOME accident, as the Voyager probes aren't going anywhere near...well...anywhere in the foeseeable future. And even for the most inquisitive species I'd imagine that just zipping around in deep, deep space would be massively uninteresting


Interesting thing to think about. I think it depends on the upper limit of technology to observe from a distance. If it is possible to build an observatory capable of scanning the entire sky and spotting something as small as Pioneer or Voyager from many lightyears away, then maybe. It's probably safe to assume that anyone who would build such a device would be very interested in examining something like Voyager, once they detected it. Actually traveling to intercept it may not be practical for anyone, but looking at it from a distance might be possible. ...If there's anyone else out there to look.
corymp
3 / 5 (4) Jul 18, 2012
My aunt thew a letter in a bottle off the coast of Newfoundland as a child. 27 years later she got a post card from France where it was found. Just sayin, u never can tell where the thing might end up
antialias_physorg
1 / 5 (1) Jul 18, 2012
Just sayin, u never can tell where the thing might end up

Space isn't like oceans with currents and eddies. Space is also a Lot bigger. A LOT. A really, really, really incredibly large amount bigger. Something you can get lost in for trillions of years easily without ending up anywhere.

We know where these probes will end up for the foreseeable future. We can look at the sky, plot the course.
The closest Voyager 1 will get to anything is in 40k years (1.6 light years 'close' to AC 79 3888 - which is not expected to support life). Local gravitational fields aren't gonna play much hob with that course (not at those kinds of distances). It'll stay within this galaxy, though.
Voyager 2 will pass Sirius at more than 4 light years distance in 300k years..and nothing much after that. Sirius is a binary and it's doubtful whether such a system can have stable planetary orbits.
Skepticus
3 / 5 (2) Jul 18, 2012
The effect is something like when you are driving a car and the photons from your headlights are pushing you backward

ha ha no wonder I keep seeing quite a few young turds in their hot wheels driving at night without headlights on-apparently they want decreased resistance and to go faster!
GSwift7
3.7 / 5 (3) Jul 18, 2012
Sirius is a binary and it's doubtful whether such a system can have stable planetary orbits.


That depends on the orbits of the binaries, and their relative sizes. Take our solar system for example. If you replace all the outer planets, from Jupiter out, with a star about the same as the sun, orbiting where Pluto is, then both of the stars would be able to have planets like Mercury, Venus, Earth and Mars. Or, if you have two stars like our sun about the distance to Mercury apart, then you could have an earth-like planet orbiting both of them at a distance farther out than we are now.
GSwift7
3.7 / 5 (3) Jul 18, 2012
I've seen you and others here make that claim before, but observations indicate that binary stars with planets are common. Here's a NASA page that talks about it. There are many examples of binary stars we have observed which have obvious signs of planets around them.

http://imagine.gs...22c.html
elektron
3 / 5 (2) Jul 18, 2012
The effect is something like when youre driving a car and the photons from your headlights are pushing you backward,


I hate it when that happens
Torbjorn_Larsson_OM
5 / 5 (6) Jul 18, 2012
Never mind headlights, the pushback is irritating because the way it makes my flashlight jump around. (O.o)

Good riddance. I remember the crackpots (as Tuxford here) even managed to tie it to timing errors of crafts observed passing close to Earth. Those are all over the place, so it isn't even a systematic error contribution to pin down but more likely measurement problems. :-/

@ ScottyB: The gradual power failure is included in the analysis. The Pu isotope has a halflife of some ~ 90 years, but the system degrades faster @ ~70 years IIRC.

@ El Nose: It was the publication of the paper that prompted JPL to send out a press release, it has nothing to do with media at large.

@ antialias:

Lots of Kepler et al binaries have planets, and the planetary scientists are reworking their models. One early result is that binaries means planets can't be as densely packed as the binary adds tugging. But again, see the Kepler results of densely packed systems, it isn't very limiting!
antialias_physorg
5 / 5 (1) Jul 19, 2012
Lots of Kepler et al binaries have planets

Sirius has already been looked at. To date nothing has been found (although, admittedly, our ability to find Earth sized planets and smaller is still very lacking so this isn't proof positive that there are none)

At 4.6 light years passing distance that's still far out there. That's more than the distance from us to our closest neighboring star (Proxima Centauri). If they have telescopes THAT good then they don't need Voyager to tip them off about us. In that case they can already see individual houses on Earth.
GSwift7
3.7 / 5 (3) Jul 19, 2012
Sirius has already been looked at. To date nothing has been found (although, admittedly, our ability to find Earth sized planets and smaller is still very lacking so this isn't proof positive that there are none)


Sirius and Proxima could both have an "earth" around them, and we wouldn't know it yet. We can still only spot an "earth" if it passes directly in front of its star while we are watching (slim chance of that). In the case of both Sirius and Proxima, the binary orbit isn't aligned with us, and if there are planets there the planets would almost certainly be in the same plane as the binary orbit, so they would not cross in front of their parent star from our point of view.

In that case they can already see individual houses on Earth.


Oh geeez, I should clean up my yard then.
antialias_physorg
not rated yet Jul 19, 2012
It's freaky that Voyager 1 will get to within 1.6 light years of Gliese 445 (which is 17.6 ly distant) in 'a mere' 40000 years whereas Voyager 2 will take almost 300000 years to get within 4.6ly of Sirius (8.6 ly distant).
Even though both have almost the same speed when departing the solar system (17.5 and 16.1 m/s respectively). I somehow can't get that to make any sense at all (???)

As for telescope resolution:
Sirius is 8.6 light years away. Voyager passes it at 4.6 light years distance. Biggest thing on the Voyager is about 3 meters (which is the dish..I actually couldn't find the size specs of the entire craft anywhere, only the dish diamater)
So a telescope that could barely resolve Voyager at 4.6 lightyears could resolve something 12 meters wide on Earth. Unless your yard contains some huge boulders you can sit back and relax.

Parsec
5 / 5 (2) Jul 19, 2012
so how long before the probe starts a reverse in direction?

At .9 nano-meters per second per second deceleration, I strongly suspect the Plutonium source which is driving it will have decaying long before it reverses direction. Remember that as the Plutonium decays, the .9 nano-meters deceleration itself is decreasing.
SleepTech
not rated yet Jul 21, 2012
so how long before the probe starts a reverse in direction?


Never. The amount of deceleration is nothing compared to the velocity of the spacecraft. They will continue into interstellar space until gravity from other objects becomes stronger than the gravity from our solar system. They will be pulled along by the tides of our local cluster and our spiral arm on a slowing changing path through the Milkyway, lacking the velocity to escape our galaxy, but never to return here.


Deceleration is an issue when it comes to traveling at high speeds in space. The Pioneer has stumbled upon a novel way to slow down, albeit near insignificant. Could this means of deceleration be utilized by an interstellar probe if modified for maximum efficiency? Like a "radiation sink" that just kinda sucks in radiation, transforming it to heat which then over time slows down the spacecraft?

Idk I'm not the physicist, that's why I'm asking.
GSwift7
1 / 5 (1) Jul 23, 2012
Could this means of deceleration be utilized by an interstellar probe if modified for maximum efficiency? Like a "radiation sink" that just kinda sucks in radiation, transforming it to heat which then over time slows down the spacecraft?


Probably not in the way you are thinking, but yes in another sense. I assume you are talking about an interstellar probe (something actually targeted towards another star)? With a target that far away, you would want to account for this kind of force in your design and planning (to avoid extra course adjustments). As for slowing down, that depends on your goal and the specifics of the star system you are headed to. If there are planets then you would use them to slow down, with gravity assist and possibly atmospheric drag. I would guess the first goal would be getting into an eliptical orbit around the star, aligned with that star's ecliptic. Then you would manipulate that orbit to arrange fly-by's of planets. Long mission.
antialias_physorg
1 / 5 (1) Jul 23, 2012
Like a "radiation sink" that just kinda sucks in radiation, transforming it to heat which then over time slows down the spacecraft?

Not really. You can tack against solar radiation and use radiation for deceleration - but radiation imparted to your craft from the outside will have to obey conservation of momentum.
Solar sails aren't much of a viable drive
The faster you go the more energetic the photons coming from the front and the less energetic the ones coming from the back (blue/redshift). So they would tend to become even less effective with higher speeds. Especially in interstellar space they are next to useless.

Photonic drives could, in theory, get arbitrarily close to light speed (think of a big flashlight strapped to the back of your craft). But the power needs would be huge and the acceleration pitiful.