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More Spacecraft Velocity Anomalies
ZonkerWilliam recommends a bulletin from the American Institute of Physics, which discusses a study noting that recent spacecraft, such as NEAR, appear to display velocity anomalies much like those seen in Pioneer 10 (which were observed beginning ten years ago). The anomalies amount to up to 13 mm/sec., with a measurement accuracy of 0.1 mm/sec. Quoting: "A new look at the trajectories for various spacecraft as they fly past the Earth finds in each case a tiny amount of surplus velocity. For craft that pursue a path mostly symmetrical with respect to the equator, the effect is minimal. For craft that pursue a more unsymmetrical path, the effect is larger."
Occasionally this is also quoted as ending with 'Hmm, that's funny'.
Number 857 #2, February 28, 2008 by Phil Schewe
More Spacecraft Velocity Anomalies
A new look at the trajectories for various spacecraft as they fly past the Earth finds in each case a tiny amount of surplus velocity. For craft that pursue a path mostly symmetrical with respect to the equator, the effect is minimal. For craft that pursue a more unsymmetrical path, the effect is larger. In the case of the NEAR asteroid rendevous craft (), for instance, the velocity anomaly amounts to 13 mm/sec. Although this is only one-millionth of the total velocity, the precision of the velocity measurements, carried out by looking at the Doppler shift in radio waves bounced off the craft, is 0.1 mm/sec, and this suggests that the anomaly represents a real effect, one needing an explanation.
Some ten years ago another anomaly was identified for the Pioneer 10 spacecraft (see http://www.aip.org/pnu/1998/split/pnu391-1.htm) and a certain amount of controversy has clung to the subject since then. One of the researchers on that earlier measurement is part of the new study, conducted by Jet Propulsion Lab scientists. John D. Anderson (jdandy@earthlink.net, 626-449-0102) says that the JPL scientists are now working with German colleagues to search for possible velocity anomalies in the recent flyby of the Rosetta spacecraft. (Anderson et al., Physical Review Letters, upcoming article; designated as an editor's suggested articlePhysical Review Letters)
Nasa & JPL determined in late October that the extra push pressure is from slight low energy gamma radiation from the core of our galaxy being red-shifted by going "uphill" (yeah, I know bad rubber-sheet analogy) out of the gravity well of the entire milky way. The spiral rotation factor of the spiral (once every 55 million years), though slight, is conjectured to impart further pressure of about 2.8 mm/sec.
It isn't noticable closer in because the heliopause outweights everything else. Only when you get closer to the outside of our solar system's bubble, does it become noticable.
According to this, the acceleration anomaly can't be accounted for by dark matter.
Equine Mammals Are Considerably Smaller
The precision of the measurements is 0.1 mm/sec, not the accuracy. Those are different things.
Chemists use "un" to describe non-symmetric molecules pretty often- consider the rocket fuel UDMH: unsymmetrical dimethylhydrazine, though chemical reactions lacking symmetry are more often called "asymmetric," like the Sharpless asymmetric epoxidation. Asymmetric reactions can sometimes produce unsymmetrical products. Yes, it is unpossibly confusing. Just make sure to not confuse either "asymmetric" or "unsymmetric" with "antisymmetric."
"FDA staff reviewers expressed concern about the number of patients who were left out of the study because they died."
no. That is wrong. The "particle" part of "wave-particle duality" does not refer to a separate state. Further, it doesn't have mass, either.
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And light does not have a 'particle state'--it can be modeled as a particle, sure, but it really isn't. Light waves do not have "amplitude". And it is a particle and a wave at the same time, as are you. The concept is hard to get around at first. Either way, it can certainly be quantized and a single photon has a finite amount of energy based solely on it's frequency. The intensity is the sum of the total energies of the individual photons. If this were not the case, a lot of spectroscopy would be bunk.
How about MOND?
The range isn't an issue, it's how accurately they can measure doppler. The standard technique is to transmit a special signal to the spacecraft, which retransmits it to the Earth, like an RF mirror. This allows them to use extremely stable ground-based oscillators, like Hydrogen masers. This signal can also be modulated with a PN code to allow precise range measurements.
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The Earth does indeed gain mass continuously from in-falling space dust, captured solar wind, etc., and as a consequence of GR, our clocks should be getting slower over time relative to distant satellites. However, I would think that the effect is not sufficient to account for the observed velocity discrepancy. I am just a lowly programmer, but I would be very surprised if those physicists have not taken this into account or discounted this accordingly.
Life's a tale told by an idiot, full of sound and fury, signifying nothing.
If such a source did exist, and was in fact the cause of the Pioneer anomaly - it wouldn't be be the Pioneer anomaly as we'd have seen it's effects on the outer planets decades ago. This goes 1x10^10 for NEAR which has barely left the inner solar system.
The article has little information about what types of trajectories are affected, so this is just wild guessing. If the orientation of solar panels or dish antennas are markedly different for different trajectories, drag from particles or acceleration from absorbing/reflecting solar radiation can also differ. There's more garbage in the plantary plane, so there's more drag and more blocking of solar radiation.
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The Pioneer 10 and 11 speed-position anomalies, unaccounted drift, were noticed by the late 70's. NASA and the peole involved just didn't discuss it with the public until much later, after many potential sources of error and theoretical possiblities had been analyzed. That is when I first heard it mentioned, in Houston, ca 1977-78.
Just what I'm aware of: the standard formulae for predicting the positions of planets are not very accurate.
This is due to the fact that the differential equation problem for an n-body problem is extremely difficult to get right. That said, there is another, newer method called the Parker-Sochacki solution to the Picard iteration(about 10 yrs old) that develops MacLauren series solutions to the N-body problems.
But if you plug the numbers into that solution, you still find that fairly significant error develops. That said, there error is a lot less. And what there is, problem comes from the many asteroids and planetoids that surround our Sun, as well as from nearby Oort clouds and whatnot.
Well, I wouldn't expect to find this type of an error -- velocity changes (as compared to what you expected) as you leave the equatorial plane -- coming from the nearby oort clouds. However, I would expect this kind of an error to result from both (1) using the older N-body approximations, and (2) the asteroids that are within the solar equatorial plane.
My guess -- if you look at the calculation methods used, they didn't use the PS method. And if you then use the error in planetary predictions under PS, to guess at the mass of in-plane asteroidal matter, you might find an additional reduction in error.
Correct Horse Battery Staple: 72 bits of entropy. Enter "Correct H" into google. When it generates the phrase, that's
I can't speak to this specific case, but someone did a study several years ago of the Voyager anomaly and whether it could be a gravitational effect. The gist of the analysis was the if it were gravitational, it would also affect the distribution of long-period comets, especially the "new" ones from the Oort cloud. They calculated the effect you'd expect and it's much too large relative to what we see in the comets, so whatever is affecting Voyager pretty much cannot be gravitational in nature.
It's also worth noting that even in the mega-analysis by Anderson et al. concluded that although they couldn't determine a source for the anomaly, they still generally felt that it was more likely to be endogenic than exogenic.
What about the angle between the spacecraft's trajectory and the radio signal?
Ordinary telescope tracking of the the direction to the craft taken months apart can tightly define the shape of the orbit and thus tightly define the current direction the craft is going within a fraction of a degree. If you know the craft's trajectory then you know the angle between that and the line-of-sight path to earth, and basic trig will easily convert the line-of-sight velocity figure into the forwards velocity.
The small uncertainty in the precise direction of the craft's travel may indeed be a significant factor for the final +/- 0.1 mm/sec uncertainty in the measurement.
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Normally, the ground station collects data on range, range rate (doppler), and where the antenna is pointing. The antenna has shaft encoders that give high-resolution measurements of the direction it's pointing in. With some complicated mathematics, this data can be used to figure out the exact position and velocity of the spacecraft. To get a more accurate measurement, data from multiple ground stations around the world is collected and processed. In addition, you already have at least a rough idea of the spacecraft's position and velocity, which was used to point the ground antenna in the right direction, so you aren't starting from scratch.
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I don't think so. The spacecraft transmitter's frequency is phase locked to the frequency of the signal received from the ground station. Since it can't transmit on the same frequency as the ground station, there's a circuit in the spacecraft's RF system that takes the incoming signal and multiplies it by a constant to produce the outgoing signal. So it may be receiving at 2.2 GHz and transmitting at 2.0 GHz. That's 20 cycles out for every 22 cycles in. The incoming signal is used as a frequency reference for generating the outgoing signal.
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