As it turns out, standard physics prevailed: Pioneer Spacecraft Anomaly solved.

For your “Just Too Cool” file.

From NASA’s Jet Propulsion Lab comes a fascinating story about the Pioneer 10 and 11 spacecrafts.  When last contacted they were mysteriously slowing down.  Someone figured out why.

It was, as it turns out, rocket science!

Study Finds Heat is Source of ‘Pioneer Anomaly’

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 respectively, 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 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). [NB] 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.

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. [Wow.  I remember making programs with those.] 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, Greenbelt, Md., and worked with NASA Ames Research Center, Moffett Field, Calif., to save some of their boxes of magnetic optical tapes. He collected more than 43 gigabytes of data, which may not seem like a lot now, but is quite a lot of data for the 1970s. [I'll say. I remember my Atari with its massive, what, 64k of RAM? And in my recent cleaning I found a 5" diskette.  Blast from the past.] He also managed to save a vintage tape machine that was about to be discarded, so 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, heard about the effort and contacted Turyshev. He helped Turyshev create a program that could read the telemetry tapes and clean up the old data.

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 heat 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.

[Bottom line...] “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 in Pasadena.

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About Fr. John Zuhlsdorf

Fr. Z is the guy who runs this blog. o{]:¬)
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19 Responses to As it turns out, standard physics prevailed: Pioneer Spacecraft Anomaly solved.

  1. Supertradmum says:

    Love this article, thanks Father. I started on punch cards, computers which were huge and had to be in cold rooms, and thought the big floppies were so cool when they came out. Wow, we have progressed and I am happy those wise guys and gals solved the problem.

  2. chcrix says:

    “He collected more than 43 gigabytes of data, which may not seem like a lot now, but is quite a lot of data for the 1970s. [I’ll say. I remember my Atari with its massive, what, 64k of RAM? And in my recent cleaning I found a 5″ diskette.”

    Your 5″ diskette probably held 360kb of data. So 3 would be a megabyte, 3000 would be a gigabyte, and about 129,000 for the 43 gb.

    In terms of the big iron tech of the time, a 3330-11 (hard drive) would hold 200 mb. 5 would be a gb. So it would take 215 hard drives in what would have been a large data center of the time to hold this data.

  3. chrix, I recall the first time I entered a computer shop to buy some of those 360K floppies to use with my brand new PC. The salesman showed me a box of 10. I asked if I could buy just a half box. Didn’t think in this lifetime I’d ever be able to use a whole box of those floppies, 80-column punch cards having sufficed for most of my previous computing.

  4. robtbrown says:

    Supertradmum says:

    Love this article, thanks Father. I started on punch cards, computers which were huge and had to be in cold rooms, and thought the big floppies were so cool when they came out. Wow, we have progressed and I am happy those wise guys and gals solved the problem.

    I also started with punch cards. We would write code on grid paper, then clerks would transfer it to cards. Then it would go to the system. Sometimes it took a week just to set whether the program compiled–which it usually didn’t.

    A woman I worked with was once called in the middle of night when the trail went down. She went in, found the problem record, wrote a request for a utility scan it off the tape, and took it out to the system. She was standing in front of the drive when the tape was loaded. The scan started . . . and the tape drive caught on fire. She said to hell with it and bid everyone good night.

    And then there was the time when 20,000 premium notices were sent to the same guy–bags of mail at his front door. My team was not involved, Deo gratias.

    Ah, card to tape! Those were the days.

  5. fvhale says:

    This is why I never use a flashlight to see what is ahead of me when I walk on ice at night–those darn photons shooting out the front keep pushing me backward.

  6. robtbrown says:

    BTW, I wrote lots of papers in Rome on an Amstrad PPC 512 that was the length and width of a keyboard but much thicker. It folded open, and there was a pop up screen that was about 6″ x 4″. DOS had to be loaded each time, then the word processing software. If memory serves, the machine cost about $1000.

    http://en.wikipedia.org/wiki/PPC_512

    For the Licentiate tesina I bought a new Dell, partly because I wanted to use more sophisticated WP software that recognized Greek characters–I wanted to insert two Greek words. A year after the STL was finished, a good buddy, the late, great Fr Bob Zylla, was reading the paper and pointed out that I had misspelled one of the Greek words.

  7. robtbrown says:

    Pioneer 10?s last signal was received on Earth in January 2003. Pioneer 11?s last signal was received in November 1995.

    All that money and not even a post card or phone call.

  8. fvhale says:

    Punched cards? That is like praying in the vernacular, and most people punching cards had now idea about the beauties of the underlying binary text. I taught students how to program in binary, the 0′s and 1′s according to ancient tradition, which were communicated to computers by postures of toggle switches (stand up = 1, kneel = 0), and which we discerned the leading of the CPU by carefully trained discernment of the stained glass showing light (1) or darkness (0).

    Real programmers programmed physically, understanding that computers were machines. None of these modern transcendental abstractions like keyboards and clouds–punch cards (and punched paper tape) were the start of a slippery slope leading to our sad times where people think that computers are “community” rather cold, lifeless machines over very, very short service lives.

    (This is part science-liturgical fiction, but based on actual experience programming early IBM mainframes from front panel dials, switches and buttons, and reading arrays of lights; and also PDP-8 systems programmed by front panel switches, and reading arrays of lights.)

  9. Supertradmum says:

    robtbrown, you crack me up. Is it female? Reminds me of the first really bad Star-Trek movie…V’ger

  10. Supertradmum says:

    I also remember the sacred changing of the tapes-very liturgical and only certain vestal virgins were allowed to do it. I was on the cards and could NOT touch the tapes.

  11. Supertradmum says:

    robtbrown, DOS was so ugly….but we thought it was so cool.

  12. Supertradmum, remember the excitement of the DOS 2.0 upgrade? When it arrived, before sticking the new system disk in the floppy drive the first time, I sat down and read the whole manual cover to cover. Back then, we didn’t mess around.

  13. In my experience, the typical student (of whatever age or level) will have little feeling for the magnitude of the “flashlight deceleration” involved here. The Pioneer spacecraft had been traveling at an average speed of 35 thousand mi/hr, and an anomalous loss of velocity about 1 ft/hr was observed to occur every day. Which amounts to a loss of 1 mi/hr of velocity every 15 years or so. So if you were riding on the spacecraft, you might not sense any perceptible change in speed in the first thousand years, during which time your velocity might decrease from 35,000 mi/hr to about 34, 930 mph.

  14. RichardT says:

    “like when you’re driving a car and the photons from your headlights are pushing you backward”

    Isn’t there something in the Captain Aubrey books where they’re chasing a ship, and the men ask him to stop firing the forward guns because the recoil will slow them down? [YES! That's right. I don't recall which book, however, but I remember the exchange. There was also a moment when Dr. Maturin made a facetious remark about how to make the ship sail faster. My memory is scrambled today.]

  15. Supertradmum says:

    Henry Edwards, yes I do and yes we read manuals, which I admit I do not anymore.These youngsters missed all the fun.

  16. Supertradmum says:

    HenryEdwards, remember when upgrades were rare?

  17. Thom says:

    Nothing is ever (and should never be) settled in science , but this explanation is certainly seems plausible. And no wonder it seems like you go faster with the lights off in the dark: photon repulsion.

  18. mike cliffson says:

    “…./… he gave them a law which shall not pass away…../..
    Cool story, father, cooly told.
    And cool that we’re still “on track”!

  19. Kephas says:

    Re: “…At the time these two Pioneers were launched, data were still being stored on punch cards. [Wow. I remember making programs with those.]…”

    Isn’t that “Object-Oriented” Programming Father?
    LOL