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Space Science

Rosetta Fly-By To Probe "Pioneer Anomaly" 89

Posted by kdawson
from the tous-le-mond dept.
DynaSoar writes "On Friday November 13th, ESA'a Rosetta probe will get its third and final gravity assist slingshot from Earth on its way to its primary targets, the asteroid Lutetia and Comet 67P/Churyumov-Gerasimenko. But the slingshot itself will allow ESA scientists to examine the trajectory for unusual changes seen in several other probes' velocities. An unaccountable variation was first noticed as excess speed in Pioneers 11 and 12, and has since been called the Pioneer Anomaly. More troubling than mere speed increase is the inconsistency of the effect. While Galileo and NEAR had appreciable speed increases, Cassini and Messenger did not. Rosetta itself gained more speed than expected from its 2005 fly-by, but only the expected amount from its 2007 fly-by. Several theories have been advanced, from mundane atmospheric drag to exotic variations on special relativity, but none are so far adequate to explain both the unexpected velocity increases and the lack of them in different instances. Armed with tracking hardware and software capable of measuring Rosetta's velocity within a few millimeters per second while it flies past at 45,000 km/hr, ESA will be gathering data which it hopes will help unravel the mystery."
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Rosetta Fly-By To Probe "Pioneer Anomaly"

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  • by Anonymous Coward on Friday November 13, 2009 @11:34AM (#30087986)
    45000km/hr 45 000 km = 45 000 000 meters = 45 000 000 000 millimeters. 1 hour = 60 minutes = 3600 seconds. Rosetta's velocity is thus 12 500 000 millimeters per second.
    • by snspdaarf (1314399) on Friday November 13, 2009 @11:43AM (#30088106)
      Yeah, Mars is one thing, but if this hits Earth, it could wipe out the dinosaurs all over again!
      • by RockDoctor (15477)

        Yeah, Mars is one thing, but if this hits Earth, it could wipe out the dinosaurs all over again!

        This posting seems to suggest that you thing that [something] hitting the Earth had something significant to do with the extinction of the dinosaurs. Why is this?
        Nothing significant is known to have hit the Earth in the quarter-million years (say, around 5000 dinosaur generations) between the Chicxulub impactor and the extinction of the dinosaurs. Whatever killed off the dinosaurs, it's unlikely to have been the

    • Metric only (Score:3, Funny)

      by jbeaupre (752124)
      Could you please tell me what that is in metric time? These crazy 60 second minutes and 60 minute hours are too confusing. It might have been ok for the Summarians, but it's time to use a modern unit divisible by 10.
      • by Zerak-Tul (1654309) on Friday November 13, 2009 @12:14PM (#30088430)
        Wait, 60 isn't divisible with 10 now?
      • by cyn1c77 (928549)

        Could you please tell me what that is in metric time? These crazy 60 second minutes and 60 minute hours are too confusing. It might have been ok for the Summarians, but it's time to use a modern unit divisible by 10.

        12.5 mm per microsecond.

        Thanks for playing.

      • Re: (Score:3, Funny)

        by DynaSoar (714234)

        Could you please tell me what that is in metric time? These crazy 60 second minutes and 60 minute hours are too confusing. It might have been ok for the Summarians, but it's time to use a modern unit divisible by 10.

        Metric and English seconds are exactly the same, if you start at minus 40. You can also use the metric version called Absolute Seconds, which start at minus 273 seconds (minus 4 minutes, 33 seconds). I'm pretty sure this is what NASA is using since they have an automatic hold scheduled into all their count downs at around T minus 4 minutes. It probably takes them that 33 seconds to change the clock faces from 60/60/24 markings to 10/10/10 markings. Actually, the time researcher Vernor Vinge presented a time

        • by Toonol (1057698)
          Swatch tried to fix this confusion with "Internet Time", but they were just too visionary for their own good.
        • Absolute Seconds, which start at minus 273 seconds (minus 4 minutes, 33 seconds)

          Wait, so the difference between relative zero and absolute zero is John Cage [wikipedia.org]? That's spooky.

      • Right. From now on seconds, kilo seconds, and mega seconds only please.
    • Re: (Score:3, Insightful)

      by MozeeToby (1163751)

      I think you mean 3.74698572 × 10^12 Planck Lengths per Planck Time. It's high time we abandonded this archaic 'metric' system for one that more accurately expresses the universe.

    • by PPH (736903)
      Could we all please stick to the FFF [wikipedia.org] system of units?
  • by CheshireCatCO (185193) on Friday November 13, 2009 @11:36AM (#30088026) Homepage

    This isn't the Pioneer anomaly. The latter was seen not in flybys but during extended cruise phases with no maneuvers. As far as I know, it has only been seen in Pioneers, although that may be due to the particular nature of those spacecraft that make them excellent tests for this effect. (Assuming it's not entirely intrinsic to the spacecraft in the first place.)

    This effect is a flyby effect and is different from the Pioneer Anomaly, as the article itself pretty clearly notes.

    • As far as I know, it has only been seen in Pioneers, although that may be due to the particular nature of those spacecraft that make them excellent tests for this effect.

      According to Wikipedia [wikipedia.org] the problem is that other spacecrafts have too much built-in disturbance (e.g. from thrusters) to measure such a small effect.

      However I wonder why no one has built a spacecraft that explicitly avoids all such disturbances so the effect can be checked with the best accuracy possible. Also, put all sorts of additional m

      • Sure, but just launching the spacecraft would cost serious cash. I'd bet around half a billion dollars or more. That's a large investment for this particular effect.

      • by DynaSoar (714234) on Friday November 13, 2009 @12:52PM (#30089016) Journal

        As far as I know, it has only been seen in Pioneers, although that may be due to the particular nature of those spacecraft that make them excellent tests for this effect.

        According to Wikipedia [wikipedia.org] the problem is that other spacecrafts have too much built-in disturbance (e.g. from thrusters) to measure such a small effect.

        However I wonder why no one has built a spacecraft that explicitly avoids all such disturbances so the effect can be checked with the best accuracy possible. Also, put all sorts of additional measurement devices on it (of course only of the sort that doesn't disturb the path measurement, e.g. nothing producing large amounts of heat), e.g. to look at the matter density around (maybe there's simply more gas out there than expected, which is slowing down the space craft by friction). And of course, also measure as much of the internal state as possible, in order to find out about unexpected effects like gas leaks.

        The problem with Voyager data is that they course correct using thrusters and so their exact location is more uncertain. Pioneers and most system bound probes are spin stabilized and so can be measured and predicted more reliably.

        Several probes have been testing some of the relevant effects in Earth orbit for years. LAGEOS I and II detected an effect of relativity called frame dragging. This is an effect which is hypothisized to be greater near a planet, but also noticeable across great solar system distances. Gravity Probe B has measured it to a greater degree, is still collecting data, and is observing some unusual effects within the data. One of the LAGEOS teams is planning another probe, LARES, to be launched within a year or so, looking at this effect (also called the Lense-Thirring effect) with greater accuracy. Getting good numbers on this effect will allow others to determine if the effect is involved in any of the cases noted. It may also help to explain why it is not seen in different instances on the same probe (Rosetta 2005 vs. 2007) if the frame dragging is due to rotation, is asymmetrical, and the probes are found to have passed through the planetary field with vs, opposite the direction of rotation.

        • by CheshireCatCO (185193) on Friday November 13, 2009 @02:17PM (#30090406) Homepage

          The problem with Voyager data is that they course correct using thrusters and so their exact location is more uncertain.

          No, not really. The location is what's being measured. The problem with Voyagers is that since they use thrusters, you don't know precisely enough what impulses were applied to them. If you don't know that, you can't remove it from the tracking data to reveal the small anomaly.

          Also, if it is frame dragging, it doesn't explain Pioneer very well I can't imagine (being really damn far from any rotating mass and all). Additionally, I don't believe it makes sense to ascribe different instances on the same probe being due to passing Earth with rather than against the rotation: unless the probe is going out in the solar system and then, later back in again, the flyby will have the same orientation, albeit at different distances and latitudes. (On the other hand, you'd expect different effects, but not *zero* effect in one case, no matter what the relationship between the flybys is.)

          • by photon317 (208409)

            Also, if it is frame dragging, it doesn't explain Pioneer very well I can't imagine (being really damn far from any rotating mass and all).

            Unless the tiny effects measured on Pioneer are frame-dragging at a much larger scale. Pioneer may not be "near" enough to any of our "big" planets to see those local frame drag effects, but don't forget about the larger context of the movements within, and of, our galaxy as a whole. It may be that Pioneer was the first object we've thrown out there that was in an isolated enough state from local solar system effects to see that.

    • by BadEvilYoda (935532) on Friday November 13, 2009 @12:16PM (#30088456)

      The Planetary Society has an interesting FAQ on this subject: http://www.planetary.org/programs/projects/innovative_technologies/pioneer_anomaly/update_20050720.html [planetary.org]

      Also explains why it is seen with Pioneer 10 and 11 and not Voyager 1 or 2 or other more "modern" spacecraft.

      From the FAQ: The Pioneers are spin-stabilized spacecraft. The Voyagers are three-axis stabilized craft that fire thrusters to maintain their orientation in space or to slew around and point their instruments. Those thruster firings would introduce uncertainties in the tracking data that would overwhelm any effect as small as that occurring with Pioneer. This difference in the way the spacecraft are stabilized actually is one of the reasons the Pioneer data are so important and unique. Most current spacecraft are three-axis stabilized, not spin stabilized.

    • by DynaSoar (714234) on Friday November 13, 2009 @12:28PM (#30088652) Journal

      This effect is a flyby effect and is different from the Pioneer Anomaly, as the article itself pretty clearly notes.

      The situations in which they are measured differ. This is what TFA states. But it is by no means certain that the cause differs, and TFA makes no claims one way or the other. John Anderson of JPL and colleagues published in 1998 and 2002 examinations of the Pioneers, Ulysses and Galileo trajectories and hypothesized a single phenomenon, a time dilation effect due to gravity. The fly by effects may be more pronounced due to greater frame dragging than trajectories more or less straight to the heliopause, but the velocity changes when noted are of the same magnitude. Mbelek's recent paper looks at fly by data to determine whether special relativity may account for the anomalies in fly bys, but does not exclude applying the same to non-fly by situations. If the math proves valid, and sufficient data is obtained, then it may be able to be determined whether the two discrepencies have a single cause. The data collection on Rosetta is being done in part to try to determine whether or not they are the same. If there weren't at least hypothesized 'same or different' consideration, there'd be no mention of Pioneers.

      • Re: (Score:3, Insightful)

        by CheshireCatCO (185193)

        If there weren't at least hypothesized 'same or different' consideration, there'd be no mention of Pioneers.

        Unless they're often confused, which they are. Two anomalies involve spacecraft trajectories are obviously easy to mix up, whether or not there is any reason to suspect a relationship.

    • Re: (Score:2, Insightful)

      by arminw (717974)

      ...This effect is a flyby effect and is different from the Pioneer Anomaly...

      How does anyone know? Everybody assumes (believes) that the spacecraft as a whole are scrupulously electrically neutral. If that is not the case, which is very likely, then the electrical and magnetic fields in space would certainly affect its motion. An electric field, even a very weak one, affects a charged object 36 orders of magnitude more than gravity. Depending on the polarity of the charge, which can sometimes be negative a

      • I wasn't saying that the underlying physics can't be the same. I was say that the effects are different. When we find two phenomenon that aren't obviously the same, we give them different names so we can keep them straight. Calling one the other (whether or not you personally suspect that they're related by the underlying cause) is sloppy terminology and confusing.

        An electric field, even a very weak one, affects a charged object 36 orders of magnitude more than gravity.

        Nonsense. You just quantified something that's not quantifiable. How massive is the test body, whats the charge, what's the strength of the

        • by arminw (717974)

          ...I've often carried a small charge (shuffle your feet on the carpet to try it yourself) and never have I found my weight has noticeably changed...

          That is because you are on the earth with a considerable mass compared to your mass. If you did this experiment of charging yourself up in relation to another object, in a gravity free or gravity neutral environment, you might be surprised how much a small charge can affect the movement of a mass comparable to that of your body.

          (...Macroscopic objects like probe

          • hat is because you are on the earth with a considerable mass compared to your mass. If you did this experiment of charging yourself up in relation to another object, in a gravity free or gravity neutral environment, you might be surprised how much a small charge can affect the movement of a mass comparable to that of your body.

            No, not at all. The acceleration is necessarily the same in both situations. And you're totally dodging the point, which is you're quantization of the intrinsically unquantizable.

            Astronomers and astrophysicists have no or very little training into the behavior of electrically charged objects and fields.

            And now I'm guessing you don't actually know any astrophysics or know any astrophysicists. I am an astrophysicist. I assure you, we have many graduate classes that are rich in E&M. I, for example, had no fewer than three graduate courses that were basically plasma physics (which is basically applied E&M) in different c

            • Aaaand, I see you're an Electric Universe person. Never mind, the above isn't meant for you. This discussion is effectively over.

              "Sometimes the hardest part of being the Mayor is recognizing the one time the village idiot has a flash of genius." Anybody can be correct by accident, not likely but possible.

    • by grshutt (985889)

      The European Space Agency's ESA Portal has a short article on the unexplained variations in orbital energy experienced by these spacecraft.

      See http://www.esa.int/SPECIALS/Operations/SEMUCV3VU1G_0.html [esa.int]

    • by physburn (1095481)
      He's right. The Pioneer anomaly is a slight acceleration towards the sun that seemed to start outside the orbit of jupiter and has a constant magnitude. (Unlike gravity where the acceleration is inversal proportional to distance square.

      The thing the Rosette probe might measure, is called the Flyby anomaly, which is occurs when a spacecraft flys close to a planet, the acceleration on the craft seems subtly different to what is predicted by gravity (Newton or Einsteins).

      Both effects occur in our solar sys

  • But the slingshot itself will allow ESA scientists to examine the trajectory for unusual changes seen in several other probes' velocities.

    Ya, like what happened to John Crichton [wikipedia.org]...

  • by Cliff Stoll (242915) on Friday November 13, 2009 @11:53AM (#30088220) Homepage

    Pioneer 10 and 11, of course (not 11 and 12)

    The Pioneer 10 & 11 spacecraft both flew by Jupiter, and Pioneer 11 went on to Saturn encounter.

    I remember it well - while a grad student at the Lunar & Plantetary Labs, I helped with the Imaging Photopolarimeter during Saturn Encounter.

    The spacecraft, designed in the early 1970's, had essentially no onboard memory, so instructions had to be uploaded in real time. The several hour-long communications delay made for real excitement at encounter (Did the spacecraft survive the ring crossing? Did the instruction arrive? Did the sensor point in the correct direction? Is it returning images?)

    We'd spent months in advance, preparing alternative sequences for the encounter. Each sequence was on punched papertape. Then, at encounter in September 1979, we'd pick the tape, mount it on a teletype, and send the data out over the NASA deep space network, then anxiously wait to see if the instructions worked on Pioneer 11.

    • by psybre (921148)

      Then, at encounter in September 1979, we'd pick the tape, mount it on a teletype, and send the data out over the NASA deep space network, then anxiously wait to see if the instructions worked on Pioneer 11.

      Wooooooh, how do I get access to the deep space network?!!!

    • Re: (Score:2, Funny)

      by Anonymous Coward

      My father worked on some long distance space probes in the 1970s, as well. The excitement you're talking about is very real.

      One day during the summer, when I was maybe 12 or 13, he came home from work early. It turns out the probe he was working with at the time was crossing the asteroid field or positioning itself to take some pictures or something, and well, he got very excited. So excited that he shit his pants while in mission control.

      So he came home, had to change, and went back to work.

    • by Knara (9377)
      I'm pretty sure you mean Voyager 6 [wikipedia.org]
    • Cliff Stoll? (Score:2, Interesting)

      by Anonymous Coward

      Are you the same Cliff Stoll that wrote that Cuckoo's Egg book back in the '80s?

    • by batquux (323697)

      It's not an anomaly. The universe just sucks.

      • by rrohbeck (944847)

        It's not an anomaly. The universe just sucks.

        What else would you expect? It's mostly vacuum.

    • by mbone (558574)

      The spacecraft, designed in the early 1970's, had essentially no onboard memory.

      In the Deep Space Network, where I worked at the time, that was regarded as a perverse feature, not a bug. Those spacecraft had to get tracking time, or the data would be lost forever. That was not regarded as playing nice in the intense juggling of tracking resources that goes on all of the time in the DSN.

  • Here come the tinfoil hats. If they're right for once I'll buy them all new tinfoil!
    • You do realize that every time one of these probes uses the Earth to boost its speed, the Earth slows down, right? That means the Earth will then orbit closer to the sun, resulting in higher temperatures. The proof is in the data. We've been doing gravity assists for the last few decades and the Earth has gotten progressively warmer over the same period.

      Blaming global warming on CO2 is a conspiracy engineered by NASA!

  • A wizard did it.

  • We all asume "space" to be empty, but what if there are pockets of extremely low density gas (low energy plasma?) or dust rotating around the sun at certain spots of the solar system... so sparse that we don't immediately see them with our telescopes, but as the devices flew through the gas, it acted to slow down the craft?

    You would only hit it on certain trajectories out, like a cloud to an airplane, sometimes it's just not in your path...

    • by Gauthic (964948)
      Nah, it's an effect of the Aether pushing against the hull.... I'm bringing it back!
    • Re: (Score:2, Insightful)

      by maxwell demon (590494)

      That might explain the Pioneer slowdown, but I don't think it could explain the energy gain on fly-by.

      • by arminw (717974)

        ....but I don't think it could explain the energy gain ...

        If electric forces are involved, depending on their polarity, there can be either a gain or loss in velocity. It seems that the existence of electric forces in space are seldom if ever discussed.

      • if the gas was massive enough and in the right position, sure it could cause energy gain, no?
    • by PPH (736903)

      How do the various crafts velocity anomalies relate to their direction of travel w.r.t the solar system's orbit around the Milky Way center? Or the direction to that center itself?

      There's already a lot of speculation about why gravity seems to operate differently across the span of galaxies. Perhaps we're seeing this effect here as well.

      You would only hit it on certain trajectories out, like a cloud to an airplane, sometimes it's just not in your path...

      I was thinking of geese, but I suppose the cloud/airplane analogy works just as well.

  • Center of earth... (Score:1, Interesting)

    by McNihil (612243)

    Most likely due to the center of earth wobbling a bit that makes things in a slingshot have increased velocity... AFAIK the earth center would be slushing around a bit and due to rotational inertia most likely have some wobbling... if that wobbling coincides with the slingshot frequency it will have a positive effect if it is in-tune with it.

    But then again IANAGNC (I am not a geoligist nor cosmolog)

    • by tgd (2822)

      If YANAGNC, what makes you think that option is most likely?

    • Re: (Score:3, Interesting)

      by MozeeToby (1163751)

      I would think that such an effect would have been discovered in the various 'gravity maps' that have been made of the Earth. If so, I can't imagine that they forgot to take that into account when trying to solve (or resolve) one of the mysteries of modern physics.

      • by arminw (717974)

        ...I can't imagine that they forgot to take that into account ...

        But they do purposely neglect and forget the effects of electricity in trying to explain the small anomalous effects. Electric forces can act to slow down slightly or as observed in some cases speed the space probe up slightly. I just cannot understand why electricity as the cause of these mysterious effects is never mentioned or investigated.

        • by McNihil (612243)

          I am more inclined to think that the simulation of such a system with a fluid and non homogeneous core and what it does to center of mass is quite heavy and they would simply use a very good approximation. Electrostatic effects especially in vacuum is also an interesting venue, coupled with solar wind maybe? Either way the math involved in this is definitely more than what regular geologists and cosmologists usually have to deal with.

          The more I think about this the more I believe that "we do know" what is c

      • by thejynxed (831517)

        Stranger things have happened. This is physics and space stuff we're talking about here.

  • by SlappyBastard (961143) on Friday November 13, 2009 @12:37PM (#30088780) Homepage
    This sounds like a case for . . . Modified Newtonian Dynamics!
  • Symmetry breaking. Space has a preferred direction. I have no basis for believing this, I just think it would result in the most amusing tizzy.

  • It is all making sense now. Planet X's orbit modified the Pioneer trajectories via gravity assist, and was not in the same orbital position near the other probes when they crossed its orbital path. This completely undeniably confirms the existence of the planet and 2012 hypothesis. In short we're all going to die in 2012.

    • I know its for the lolz, but I can't believe the way pop culture has really spun the whole 2012 thing.

      The Mayans predicted -multiple- events to happen after 2012, some as far as 4600+ A.D., and only one inscription ever, in terrible condition, predicts that anything will happen in 2012. It translates roughly to mean that on Dec 21 2012, There will be something black or dark. And (possibly) the return of many strides...(?) very open to interpretation. The whole thing started in the 70's when this guy wrote a

      • by scorp1us (235526)

        LOL.

        Well I for one, have never seen a calendar end. They just contain cycles... In fact, if it doesn't renew, then its not a calendar!

        The Mayans had the advantage of not having 7 days in a week and 12 months, which creates this idea that the calendar "runs out" so we have to buy a new calendar every year.

        • Except they -DID- have days of the week and they -DID- Have months, just like we did! They had 18 months of 20 days each (and 5 days at the end of the year seperate from the months altogether), and they also had a seperate cycle, like us, for "days of the week" like Sunday to Saturday except not 7 days (I can't recall the correct number right now).

          To put it in perspective, While December 25th occurs each year and every year, it does not always occur on a Friday. Thus, if I wrote down "I got an awesome prese

      • Hey! I read it.

  • Well, as long as the Pioneer Anomaly does not involve dysentery... carry on.
  • ... as a defense against a speeding ticket?
    • by Tablizer (95088)

      Can I use this effect as a defense against a speeding ticket?

      Sure! Let's see, that'll reduce your ticket amount by 0.000000274 cents. Here's the revised ticket. Have a nice day!

  • 1: Global Warming
    2: The Bush Presidency
    ----------------------
    The variation could be due to an interaction between the two.
    The interaction is approximately equal to:
          (New York) Times (M.Moore/(Gore to the power of Soros))

    But then, I'm no rocket surgeon.

  • They are not trying to test Pioneer anomaly, but the flyby anomaly [wikipedia.org]. These are totally separate things, and either could be real or due to systematic errors without affecting the other. This paper by Anderson and Nieto [arxiv.org] describes both anomalies.

    The flyby anomaly [arxiv.org] is an step-function like change in spacecraft velocity that occurs at the moment of closest approach of a Earth gravity assist. (There is not sufficient tracking data to say whether or not it occurs for gravity assists at other planets. There are enou

Never try to teach a pig to sing. It wastes your time and annoys the pig. -- Lazarus Long, "Time Enough for Love"

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