NASA Baffled by Unexplained Force Acting on Space Probes

[PraedSt]

The Anderson formula does not have anything to do with the Pioneer anomaly....

Thanks for clearing that up borman. I'm slowly getting the hang of it.

[VanderL]

CDA report on dust between Jupiter and Saturn

Cassini/Cosmic Dust Analyzer in situ dust measurements between Jupiter and Saturn
http://adsabs.harvard.edu/abs/2007JGRA..11207105A

Thanks for this, unfortunately I can only access the abstract. There are many reports on solar system dust (streams, trails and even rings), but so far no detailed data from 20-80 AU.

I recall that there was a report of an anomaly during the cruise phase between Jupiter and Saturn for one of the Pioneers.

Interesting, do you know of any specific references?

Further, a charged dust drag is not reported to affect neither Voyager craft nor New Horizons.

Well, if the Pioneer anomaly is caused by charge drag, the effect is very small. As I understand it, none of the other spacecraft (including Voyager) could possibly yield any relevant data, see below.

The Voyager 1 and Voyager 2 spacecraft, which have now gone even further from the Sun than the Pioneers, are not as helpful as might be expected in contributing to the investigation of the Pioneer anomaly because of the way in which they are stabilized. Unlike the Pioneers, which are spin-stabilized, the Voyagers have what is known as three-axis stabilization. This results in a greater uncertainty in the spacecrafts' theoretical positions. The uncertainty is sufficiently high as to mask any deceleration similar in magnitude to that seen in the Pioneer probes.

Also the measured Pioneer anomaly was different for Pioneer 10 and 11. So one would need to explain how each could see different dust densities to accommodate a dust drag hypothesis if the sea of dust is to be uniform for both craft.

The trajectories of both craft are different, I guess it is easier to imagine variations than a uniform dust distribution. It could also be related to the charging process itself, maybe the amount of charging a spacecraft undergoes is correlated to the amount of charged dust particles?

In my opinion, the hypothesis seems to require too many angels to work plausibly. I don’t see how a uniform density can be maintained while YORP effects exist.

I know the hypothesis is far from proven, but I don’t think there are too many angels for it to work. As I said in an earlier post, the easiest way to get a linear acceleration from a charged spacecraft is a weak but constant electric field. That’s what my earlier question was about, trying to find a simpler mechanism than charged dust. On the other hand, the hypothesis can be tested when data from the New Horizons mission become available.

Eventually, Turyshev and his research team may be able to sort out whether a drag vector is indicated or not over other vectors in order to winnow out some of the various theories.

As I understand it, thermal modelling is expected to solve the problem, but that shouldn’t keep others from trying to find other plausible explanations.

Hope this helps some.

Thanks, it does help to hear other’s thoughts on the matter.

Cheers.

[VanderL]

CDA report on dust between Jupiter and Saturn

Cassini/Cosmic Dust Analyzer in situ dust measurements between Jupiter and Saturn
http://adsabs.harvard.edu/abs/2007JGRA..11207105A

I recall that there was a report of an anomaly during the cruise phase between Jupiter and Saturn for one of the Pioneers.

Further, a charged dust drag is not reported to affect neither Voyager craft nor New Horizons. Also the measured Pioneer anomaly was different for Pioneer 10 and 11. So one would need to explain how each could see different dust densities to accommodate a dust drag hypothesis if the sea of dust is to be uniform for both craft.

In my opinion, the hypothesis seems to require too many angels to work plausibly. I don’t see how a uniform density can be maintained while YORP effects exist. Eventually, Turyshev and his research team may be able to sort out whether a drag vector is indicated or not over other vectors in order to winnow out some of the various theories.

Hope this helps some.

Hi Borman,

I can't find any references about either a different measured anomalous acceleration or any glitches between Jupiter and Saturn, could you (or anyone else) point me to any sources? Thanks.

Cheers.

[borman]

Some references regarding Pioneer Anomaly Onset

The Turyshev et al analysis as of last April:
http://planetary.s3.amazonaws.com/mi...S-20080417.pdf

The press release was cited in a link in post 112 given by Jerry.

One of the goals was to see if a model based on a rather thorough computer simulation that includes telemetry and a larger data set could show if the anomaly might be due to heat flow in the direction that simulates a persistent force in the direction of the sun.

One craft still needs to be modeled, but the apparent upper limit does not account for the total anomaly. The upper limit, however, may be sufficient to account for the disparity noted between the two Pioneers in what could be treated as the main text, now in version 5:

Study of the anomalous acceleration of Pioneer 10 and 11
http://arxiv.org/abs/gr-qc/0104064

On page 19, one can see charts 6 and 7 that show solar pressure and unmodelled accelerations. Note that it appears that the anomaly attains close to 20 percent of its final value between 5 and 10 AU. Solar pressure is quite dominant still in this region relative to the anomaly. So it is a question of whether it is present but difficult to tease out of the data noting that the sign of solar pressure is opposite to the anomaly. Or whether it is present but buried beneath the solar pressure closer in. Remember that the MESSENGER team used this pressure for solar sailing to tack the craft and conserve fuel. Another option is that the anomaly is actually not present within a threshold value presented by solar pressure.


There was this Iorio paper commenting on the Pioneer Anomaly between Jupiter and Saturn:

Jupiter, Saturn and the Pioneer anomaly:
a planetary-based independent test

http://arxiv.org/PS_cache/arxiv/pdf/...712.1273v1.pdf

With regard to New Horizons and the anomaly, suggestions were made by Nieto:

New Horizons and the Onset of the Pioneer Anomaly
http://arxiv.org/PS_cache/arxiv/pdf/...710.5135v2.pdf

Here the onset is treated as starting just short of 10 AU. It is also noted that New Horizons has a larger heat systematic. The RTG is larger presumably to assist in further post encounter missions that flyby other icy bodies beyond Pluto.

This may permit Turyshev et al to perform a further analysis to constrain the heat theory by also simulating New Horizons along the same route used to simulate the Pioneers during the portion that New Horizons is also spin stabilized during hibernation. If there is similarity in design with respect to heat paths and if heat is totally responsible for the Pioneer Anomaly, then one would initially expect the Anomaly to be present in the New Horizons Dopplers and perhaps even in greater magnitude than monitored in the Pioneers since the RTG is bigger. However, the particular differences between the spacecraft need to be modeled before much weight can be attached to the observation. It should be noted that no Pioneer Anomaly has been reported by the New Horizons team even though they have been quite good about regular reports as well as reports of problems. It could turn out that New Horizons constraints may severely limit the role of heat to effectively serve as the counter-example that rules out the heat model as the source of the Pioneer Anomaly.

One should avoid jumping to any conclusions with respect to the November 4th Twitter report about a course correction next year. This is expected to be a Newtonian course correction. The team has been both lucky and good to have not made even more corrections.

Another fine point regards the investigation of a possible relation between the spin anomaly and the main anomaly. In the main Anderson et al text, starting on page 22 with section VI A there is a discussion of the spin rate change that is likely caused by leaks. A drag effect seems quite unlikely as Pioneer 11 spins up rather than down. After chart 14, one sees equation 19 where the observed anomaly is considered the sum the base anomaly minus a correction due to the spin anomaly. Although the assumption of a base anomaly, a_P(0), minus an offset seems natural enough, it should be noted that it is still an assumption that has not been verified independent of spin change. During the monitoring of the Pioneer Anomaly, both craft always had a non-zero value for spin change. So a_P(0) has never been monitored or observed, but so far it has only been assumed. However unlikely it seems, this still leaves to be ruled out that the presence of the Pioneer Anomaly could critically depend on the existence of spin rate change, either positive or negative, to permit the appearance of the main anomaly.

It may be possible to test and rule out this concept with data from New Horizons, either already present or as a post encounter experiment to gather data. It is already noted that New Horizons has not announced the presence of the anomaly even though it has gone through bouts of hibernation where it is spin stabilized. There are no reported spin down or up anomalies yet to be reported, although Murphy no doubt lurks behind the door of each ACO to make something go wrong and start a leak. In the October 25 Twitter, http://twitter.com/newhorizons2015?page=2 , it is noted that the craft is spun up to 5 rpm that suggests a spin rate change. If the anomaly is only present during spin rate changes, it would only be apparent in the Dopplers during the spin up phase. However, it is more likely that if the anomaly is present, that the spin up force due to jetting gas during this brief period totally obscures the anomaly. The craft may be well built and one may have to wait some time until small leaks occur if at all to introduce a small enough spin up or spin down anomaly that does not drown out the main anomaly. Otherwise one could consider asking the craft to perform and simulate a small leak sometime after the main encounter mission with Pluto to see if this experiment assists in acquiring the main anomaly.

[Jerry]

We missed a MAJOR opportunity in the New Horizons probe: We coul have used the final stage (which is also on a fast trajectory out of the solar system); as a new test of the Pioneer anomaly. A simple spin stabilization and phase-lock looped transmitter/receiver would have created an excellent Newtonian vessel at minimal cost.

[Jerry]

http://lanl.arxiv.org/abs/0811.0756v4

The astronomer E.V. Pitjeva, by analyzing with the EPM2008 ephemerides a large number of planetary observations including also two years (2004-2006) of normal points from the Cassini spacecraft, phenomenologically estimated a statistically significant non-zero correction to the usual Newtonian/Einsteinian secular precession of the longitude of the perihelion of Saturn, i.e.
̟˙ Sat = −0.006 ± 0.002 ′′ cy−1; the formal, statistical error is 0.0007 ′′ cy−1. It can be explained neither by any of the standard classical and general relativistic dynamical effects mismodelled/unmodelled in the force models of the EPM2008
ephemerides nor by several exotic modifications of gravity recently put forth to accommodate certain cosmological/astrophysical observations without resorting to dark energy/dark matter.

This series of observations, if they are confirmed, will put rubber teeth in the relativistic positional reckoning theory.

[VanderL]

Some references regarding Pioneer Anomaly Onset

The Turyshev et al analysis as of last April:
http://planetary.s3.amazonaws.com/mi...S-20080417.pdf

The press release was cited in a link in post 112 given by Jerry.

One of the goals was to see if a model based on a rather thorough computer simulation that includes telemetry and a larger data set could show if the anomaly might be due to heat flow in the direction that simulates a persistent force in the direction of the sun.

One craft still needs to be modeled, but the apparent upper limit does not account for the total anomaly. The upper limit, however, may be sufficient to account for the disparity noted between the two Pioneers in what could be treated as the main text, now in version 5:

Study of the anomalous acceleration of Pioneer 10 and 11
http://arxiv.org/abs/gr-qc/0104064

Many thanks Borman, I finally had some time to catch up on your post here. The values I asked for are in the first link,
(8.09 ± 0.20) ×10−8 cm/s2 for Pioneer 10
(8.56 ± 0.15) ×10−8 cm/s2 for Pioneer 11

You are probably correct in your assessment that the difference between the Pioneer craft can be accounted for by the thermal modelling, but not the entire anomaly.

On page 19, one can see charts 6 and 7 that show solar pressure and unmodelled accelerations. Note that it appears that the anomaly attains close to 20 percent of its final value between 5 and 10 AU. Solar pressure is quite dominant still in this region relative to the anomaly. So it is a question of whether it is present but difficult to tease out of the data noting that the sign of solar pressure is opposite to the anomaly. Or whether it is present but buried beneath the solar pressure closer in. Remember that the MESSENGER team used this pressure for solar sailing to tack the craft and conserve fuel. Another option is that the anomaly is actually not present within a threshold value presented by solar pressure.

Interesting, as others have maintained here, this seems to be testable with other spacecraft, but nothing has been published yet.

There was this Iorio paper commenting on the Pioneer Anomaly between Jupiter and Saturn:

Jupiter, Saturn and the Pioneer anomaly:
a planetary-based independent test

http://arxiv.org/PS_cache/arxiv/pdf/...712.1273v1.pdf

With regard to New Horizons and the anomaly, suggestions were made by Nieto:

New Horizons and the Onset of the Pioneer Anomaly
http://arxiv.org/PS_cache/arxiv/pdf/...710.5135v2.pdf

Here the onset is treated as starting just short of 10 AU. It is also noted that New Horizons has a larger heat systematic. The RTG is larger presumably to assist in further post encounter missions that flyby other icy bodies beyond Pluto.

This may permit Turyshev et al to perform a further analysis to constrain the heat theory by also simulating New Horizons along the same route used to simulate the Pioneers during the portion that New Horizons is also spin stabilized during hibernation. If there is similarity in design with respect to heat paths and if heat is totally responsible for the Pioneer Anomaly, then one would initially expect the Anomaly to be present in the New Horizons Dopplers and perhaps even in greater magnitude than monitored in the Pioneers since the RTG is bigger. However, the particular differences between the spacecraft need to be modeled before much weight can be attached to the observation. It should be noted that no Pioneer Anomaly has been reported by the New Horizons team even though they have been quite good about regular reports as well as reports of problems. It could turn out that New Horizons constraints may severely limit the role of heat to effectively serve as the counter-example that rules out the heat model as the source of the Pioneer Anomaly.

One should avoid jumping to any conclusions with respect to the November 4th Twitter report about a course correction next year. This is expected to be a Newtonian course correction. The team has been both lucky and good to have not made even more corrections.

Another fine point regards the investigation of a possible relation between the spin anomaly and the main anomaly. In the main Anderson et al text, starting on page 22 with section VI A there is a discussion of the spin rate change that is likely caused by leaks. A drag effect seems quite unlikely as Pioneer 11 spins up rather than down. After chart 14, one sees equation 19 where the observed anomaly is considered the sum the base anomaly minus a correction due to the spin anomaly. Although the assumption of a base anomaly, a_P(0), minus an offset seems natural enough, it should be noted that it is still an assumption that has not been verified independent of spin change. During the monitoring of the Pioneer Anomaly, both craft always had a non-zero value for spin change. So a_P(0) has never been monitored or observed, but so far it has only been assumed. However unlikely it seems, this still leaves to be ruled out that the presence of the Pioneer Anomaly could critically depend on the existence of spin rate change, either positive or negative, to permit the appearance of the main anomaly.

It may be possible to test and rule out this concept with data from New Horizons, either already present or as a post encounter experiment to gather data. It is already noted that New Horizons has not announced the presence of the anomaly even though it has gone through bouts of hibernation where it is spin stabilized. There are no reported spin down or up anomalies yet to be reported, although Murphy no doubt lurks behind the door of each ACO to make something go wrong and start a leak. In the October 25 Twitter, http://twitter.com/newhorizons2015?page=2 , it is noted that the craft is spun up to 5 rpm that suggests a spin rate change. If the anomaly is only present during spin rate changes, it would only be apparent in the Dopplers during the spin up phase. However, it is more likely that if the anomaly is present, that the spin up force due to jetting gas during this brief period totally obscures the anomaly. The craft may be well built and one may have to wait some time until small leaks occur if at all to introduce a small enough spin up or spin down anomaly that does not drown out the main anomaly. Otherwise one could consider asking the craft to perform and simulate a small leak sometime after the main encounter mission with Pluto to see if this experiment assists in acquiring the main anomaly.

Wow, I can’t see any fault with your logic, and you have it all worked out very well. I’m still very much interested in the idea that the Pioneer anomaly can also be explained as a charge drag. I think all the considerations you presented above would also apply to such an approach.

Cheers.

[Jerry]

If there is a violation of the equivalence principle, there MUST be a slight, though possibly detectable reduction in the energy required during the spin-up. (I have looked for similar reports of variability in the spin-down rates of Cassini's reaction wheels, but as far as I know, they have never released the engineering data.)

[borman]

DAWN will do a Mars flyby on February 17 this year

NASA Dawn Journal 30 December 2008

http://www.spaceref.com/news/viewsr.html?pid=30259

Perhaps another chance to test which model properly predicts the magnitude of the anomaly assuming the cosines do not cancel out.

Both the Anderson model and the McCulloch model have a dimensionless constant of around 10^(-6) to multiply the cosine differences to get the amount of Delta V_hyperbolic.

But there are important differences that will show up in a Mars test. In Anderson, the speed of light appears in the denominator, so the numerator needs to be a velocity, Rw. In McCulloch, the numerator has an acceleration term approximately equal to cH or a_0, so the denominator needs to be an acceleration to make the term dimensionless. After an addition of a weighting factor of about 14 not included in the Anderson formula, both formulas coincide at most values except that it is a bit off for NEAR in McCulloch. It is a coincidence that they happen to agree at Earth and would greatly diverge from each other at Mars. Both have the constant directly proportional to R, the radius of the planet. But Anderson is also directly proportional to radians per second where McCulloch is inversely proportional to the square of the equatorial velocity of the planet. So the effect on Mars would be almost twice as great at Mars according to the McCulloch formula where the Anderson formula would predict a significantly smaller amount for the constant.

It may be important to sort out between these two formulas before Dec 21, 2012 to estimate the strength of any flyby anomaly when the sun passes the galactic plane as it appears from Earth once roughly each 26,000 years. While this represents a neat time for the start of various calendars, Nostradamus has predicted a certain amount of “misbehavior” on the part of gravity from its normal nature during this event that might impart a decision regarding various geological tipping points that may be present during this time.

The McCulloch theory of modified inertia derives from an idea by Haisch in the mid 1990’s regarding the source of inertia where boundary conditions of the universe lead to an estimate of a Casimir type effect:

Can the flyby anomalies be explained by a modification of inertia?
http://arxiv.org/abs/0712.3022

[Jens]

It may be important to sort out between these two formulas before Dec 21, 2012 to estimate the strength of any flyby anomaly when the sun passes the galactic plane as it appears from Earth once roughly each 26,000 years. While this represents a neat time for the start of various calendars, Nostradamus has predicted a certain amount of “misbehavior” on the part of gravity from its normal nature during this event that might impart a decision regarding various geological tipping points that may be present during this time.

What does Nostradamus have to do with any of this?

[borman]

Nostradamus gravity anomaly prediction

What does Nostradamus have to do with any of this?

500 years ago, one might say that modern science had not yet come into its own. Astronomy was mixed with Astrology. Nostradmus also studied what was considered medicine at the time and also explored what might be called sooth-saying and encrypted prophesies into quatrains. Many of these are vague but subsequent historical events have, from time to time, seemed to lend some support that some of the prophesies have been interpreted to have come to pass. Perhaps this is just coincidence or the prophesies are so vague that many different historical events could be interpreted as potential fulfillment of the vague prophesies.

Occasionally, though, Nostradamus actually goes out on limb and makes a prophesy that is more specific. One is the prediction of a gravitational anomaly at the end of what might be called an extended year. This year only happens once every 26,000 Earth years when the sun comes just between the Earth and the galactic center. A number of calendars from earlier civilizations such as the Mayan use this event to mark an extended notion of a New Year. Now it actually takes about 1000 of these "extended" years or 26 million years for the solar system to bounce through the galactic plane and the fossil record indicates a possible rhythm with regard to mass extinctions at this frequency.

Now the year 2012 represents the end of one of these 1000 extended year units. But the chance that solar system is passing the galactic plane at this particular unit of 26000 years is only one in a thousand probability.

With respect to the thread proper, it is reported as a fact of observation on a small scale of only hours that spacecraft with hyperbolic velocity making either a positive or negative momentum exchange with Earth are also noted to have an additional positive or negative Delta V that appears to depend on whether the craft's path, relative to the axis of rotation of the Earth, goes from equator to pole or pole to equator respectively. The effect is minimized for example when the path both enters and leaves along the equator. As simple as this explanation seems, it is not derivable from Newtonian mechanics with full relativistic extensions. It most resembles frame dragging except that it is orders of magnitude too large.

In the event that more flyby anomalies are observed and not only at Earth but elsewhere as well, it should be apparent that the flyby anomaly also appears at different and larger scales as well. As one considers, for example, the motion above and below the galactic equator where the solar system becomes the test craft, then the time units must be in units of 26 million years instead of just hours for spacecraft doing an Earth flyby. When observing anomalies at the galactic cluster scale such as has been recently started in the multiband observations that include Hubble, CHANDRA and the weak lensing k lines associated with the Dark Matter Effect, the time scale for a flyby is in the 100 million year to billion year range.

The similarity between the anomalies in the Delta V of Earth passing spacecraft and the anomalously low M/L ratios seen in some galactic clusters, but absent in others, such as observed in Abell 520 can be related through the observation of whether the spacecraft or galactic clusters do the flyby and stay within the equator to experience little effect of loss of inertia or loss of Dark Matter Halo or travel from equator to pole and suffer a loss of inertia to gain speed or loss of DM halo or a lowering of the M/L ratio for the affected clusters of galaxies. With Abell 520 we get to note that some clusters of galaxies did not lose their Halos and maintained their M/L ratio at the same time that two others show deficiencies that seem to represent a counter-example to the bullet cluster. Meanwhile the core of the nebula shows an excess of M/L of up to 720 which may represent the stripped rammed gas undergoing a polar to equator inertia gain which causes a negative Delta V during Earth spacecraft flybys. It should be noted that the sign of the Delta V of the flyby anomaly depends only on whether the path of the craft changes from polar to equatorial or the reverse and is independent of the much larger gravity assist classical momentum change between the craft and the planet that is well understood. For example one can lose speed due to the assist but still gain positive Delta V due to the anomaly. One can gain much speed from the assist but lose Delta V to the anomaly if the path moved from a polar to an equatorial orbit during the positive speed assist. They can also align in the same direction as well.

Getting back to Nostradamus, there may be a physical justification for his prophecy since it has to do with passing through an equatorial region to initiate a flyby anomaly. But as noted above the year 2012 is but one of a thousand 26000 year units that may actually correspond to a real plane crossing. Also it is to note that orbits that are in the plane have the effect minimized. So, for example, say the solar ecliptic is has zero inclination with respect to the galactic plane during the event. Then the effect would be minimized as regards the planets within the ecliptic. However, long period comets from the Oort cloud are not all within the ecliptic and would be subject to whatever the extent of the inertial change the event causes. Changing the orbital elements of these comets may send a storm of them randomly into the inner solar system along new trajectories that might intersect many planets including Earth. Such comet impacts could lead to some mass extinction.

[Jens]

Can you give me the reference, i.e. what quatrain that is coming from? I've looked around on the Internet, but can't seem to find that (simple) information.

[Ari Jokimaki]

It may be important to sort out between these two formulas before Dec 21, 2012 to estimate the strength of any flyby anomaly when the sun passes the galactic plane as it appears from Earth once roughly each 26,000 years.

Perhaps I'm missing something here, but as I have understood, the Sun will not pass galactic plane in 2012. It seems it will take millions of years to next passing, and Sun is currently travelling away from the plane. See the post #8 of this thread and especially the first reference there. Also, I wonder where that value of 26000 years came from? Is it just one of Milankovitch cycles, the one that has to do with the Earth axis precession? If it is, then I don't see why it is important here, as I don't see it causing any gravity anomalies.

[borman]

Can you give me the reference, i.e. what quatrain that is coming from? I've looked around on the Internet, but can't seem to find that (simple) information.

The requested citation

I think the allusion is usually made to the Epistle to Henry II at around the 25th paragraph:

“This will be preceded by a solar eclipse more dark and gloomy than any since the creation of the world, except that after the death and passion of Jesus Christ. And it will be in the month of October than the great translation will be made and it will be such that one will think the gravity of the earth has lost its natural movement and that it is to be plunged into the abyss of perpetual darkness. “
From:
Epistle to Henry II

http://www.sacred-texts.com/nos/epistle.htm
Recently, History.com and its TV network have been featuring a video called Nostradamus 2012 (About 35 minutes in) where attention to this paragraph has been drawn with respect to some drawings attributed to a lost book of Nostradamus
http://www.history.com/video.do?name...nt_nostradamus

Understand that much of the connections made require a certain amount of imagination on the part of the interpreters to make the connections.

The reference to Nostradamus was not to sidetrack the thread, but to consider the variety of situations where a flyby anomaly might present itself.

While the vague prophecies seem to suggest a number of gloomy and doom scenarios, it might be checked whether a more concrete threat might exist with respect to the flyby anomaly.

Now 3 parts in a million is not much to be a threat to the navigation of craft, but over repeated intervals it can add up over time. Consider Apophis for example. In 2029, it is estimated that there is only a 1 in 45000 chance it can hit a keyhole that will put into an orbit that will collide with Earth a few years later. But the estimates do not take into consideration the use of the Anderson formula and only use Newton’s mechanics with relativistic extensions. Just to be more thorough, the keyhole probability should be calculated including the empirical Anderson formula. At present the inclination of Apophis is only 3.331 degrees, so one would not expect a large contribution due the flyby anomaly. But the anomaly can be treated as an accruing perturbation that, over a number of orbits, may lead to a significant enough error to suggest some form of mitigation. The idea of putting a transmitter on Apohpis to monitor its orbital changes may permit a further study of the flyby anomaly as its effect evolves over successive flybys.

The calculation for Apophis should be done by either the Anderson team or the NEO team and independently verified so as to not raise the Torino number recklessly if it is not warranted.

[borman]

Perhaps I'm missing something here, but as I have understood, the Sun will not pass galactic plane in 2012. It seems it will take millions of years to next passing, and Sun is currently travelling away from the plane. See the post #8 of this thread and especially the first reference there. Also, I wonder where that value of 26000 years came from? Is it just one of Milankovitch cycles, the one that has to do with the Earth axis precession? If it is, then I don't see why it is important here, as I don't see it causing any gravity anomalies.

Thanks for the research. It will be some time before an actual plane crossing is to occur. I believe the precession cycle is what is suggested. The actaul plane crossing cycle is too long a period to be appreciated in terms of human history wheras the shorter precession cycles could have been witnessed about 40 times by humans. However, I am not aware of any history books that go back even to the most recent past cycle.

Of course, one does not have to wait 26000 years to monitor if anything funny is going on with gravity just due to an alignment of the sun with the galactic center. One can draw a line from the galactic center through the sun and fly a craft through the eclipse cone and monitor for any effect upon the craft's trajectory to anticipate anything that might happen on Earth when it passes through the same cone later.

[borman]

Will Stardust-NExT be supplying another data point?

On this past January 14th, the Stardust-NExT spacecraft made an EGA. The closest approach occurred over California and it appeared to exit over the South Pole. The assist was to gain spacecraft speed. Because it exited over a pole, there is a chance that the flyby anomaly will be positive Delta V and may rival the NEAR magnitude. However the exact angles to be used for the cosine functions are known by the team and were not published on the NASA webpage:

http://stardustnext.jpl.nasa.gov/

There was a correction earlier on the 10th, but no indication that propulsion occurred during or after the assist that would bury the anomaly. There was available an artistic rendition of the flyby that shows the general path of the craft during the assist:

http://stardustnext.jpl.nasa.gov/mul...8_complete.wmv

A measurement of the resulting values of the anomaly may allow an additional test of the Anderson formula as well as those developed by others. The closest approach was a rather distant 9200 km which may provide additional information that could test the Adler hypothesis that uses a 2 component Dark Matter concentration to offer an explanation for the anomaly.

[Jerry]

You have pointed out a general problem with trying to nail anomalies down: Since few orbital scientists think there are any real discrepancies, little attention is paid to this issue. I would hope that if Stardust DID bump off coarse: 1) We would learn about this soon. 2) This would germinate broader interest and more careful analysis of both prior and future gravitational assists.

Meanwhile...has anyone seen or heard anything about the new model of the Mar's atmosphere - the model driven by the detailed EDL of the Phoenix lander?

[borman]

The more data points we have, whether giving evidence of a signal or not, the better we can constrain and sort out what theories are on the right path. There are several theories, but they all need further testing by the data. It has not been published whether the Anderson empirical formula has correctly predicted the recent Rosetta flyby of Earth. It was supposed to be small, around 1 mm/sec delta V if the formula has captured what is happening with this anomaly. Stardust-NExt flyby would be another opportunity to test the formula; it was far enough away that there would be no atmospheric drag to cloud the signal and hopefully no Hydrazine leaks. It has a set of sails that can collect solar pressure, but as the signal seems to be near closest approach, this signal can be separated from the background solar pressure with an estimated condfidence. The amount of solar pressure would not vary much over the few hours of interest either side of closest approach.

[nutant gene 71]

You have pointed out a general problem with trying to nail anomalies down: Since few orbital scientists think there are any real discrepancies, little attention is paid to this issue. I would hope that if Stardust DID bump off coarse: 1) We would learn about this soon. 2) This would germinate broader interest and more careful analysis of both prior and future gravitational assists.

Meanwhile...has anyone seen or heard anything about the new model of the Mar's atmosphere - the model driven by the detailed EDL of the Phoenix lander?

Here's a page on Boston.com, Martian Skies, that shows neat pictures of Martian atmospheric phenomena, like dust devils, clouds, other neat stuff. I hadn't realized Martian air is 95% carbon dioxide? E.g. "What more do we know about Mars' atmosphere? It's hundreds of times thinner than Earth's atmosphere and is made of 95% carbon dioxide, 3% nitrogen, 1.6% argon, and contains traces of oxygen, water, and methane. We also know, from observations that it can support dust storms, dust devils, clouds and gusty winds." Isn't Venutian air the same with 97% CO2, but much much thicker, and hotter? Two near-Earth neighbors with such incredible atmospheric discrepancies!

[Ilya]

[i]"What more do we know about Mars' atmosphere? It's hundreds of times thinner than Earth's atmosphere

About one hundred times, actually.

[VanderL]

Meanwhile...has anyone seen or heard anything about the new model of the Mar's atmosphere - the model driven by the detailed EDL of the Phoenix lander?

Actually yes, see the plan before the descent in this PDF (after adjustment as a consequence of the Mars Lander fiasco), and compare it to this PDF that contains the real data.

Have fun,

Cheers.

[nutant gene 71]

Actually yes, see the plan before the descent in this PDF (after adjustment as a consequence of the Mars Lander fiasco), and compare it to this PDF that contains the real data.

Have fun,

Cheers.

Thanks, VanderL, really good reference papers on EDL before and after for Phoenix. I was puzzled by their assessment (tentatively, in later paper) that atmospheric density was lower than expected, since my intuitive sense was that the probe 'hydroplaned' more than expected upon supersonic entry (why it landed downstream of X), which would lead one to think the atmospheric density was higher. However, their F=pV^2/2(CdS)=ma is rather conclusive that p is lower, not higher. This is puzzling, unless other anomalous factors are identified, still under study. Fun!

[Jerry]

Actually yes, see the plan before the descent in this PDF (after adjustment as a consequence of the Mars Lander fiasco), and compare it to this PDF that contains the real data.

Have fun,

Cheers.

Excellent!

My experience with trying to chase down 'final' EDL characterizations is that they rarely happen. (Pathfinder ran out of $$ without finding hard solutions.)

One major disappointment:

In the absence of an onboard air data system to provide direct measurement of dynamic pressure (q = ρV2/2) to separate the density and CD terms in Eq. (1), any errors in the pre-entry predicted value of CD do have a direct impact on the atmospheric density reconstruction.

I didn't think there would be any free parameters, expecting on-board dynamic pressure charting (even Huygens had one). Sigh.

Like every other Mars landing, the attitude numbers upon entry are high; and so was the velocity during the descent. Bad atmospheric model, or is gravity behaving badly?...

[R.A.F.]

...or is gravity behaving badly?...

Oy vey.

I guess some things never change.

[Jens]

Like every other Mars landing, the attitude numbers upon entry are high; and so was the velocity during the descent. Bad atmospheric model, or is gravity behaving badly?...

If gravity were behaving badly, wouldn't we also see the problem when space shuttle reenter into earth atmosphere? I think there must be lots of chances to track things falling to earth. Or are you proposing that gravity behaves differently on Mars than on Earth?

[WalrusLike]

If gravity were behaving badly, wouldn't we also see the problem when space shuttle reenter into earth atmosphere? I think there must be lots of chances to track things falling to earth. Or are you proposing that gravity behaves differently on Mars than on Earth?

Longer, further trip would mean that a slight effect would have a bigger result at the end and so more easily detected than short LEO trip... I think.

[R.A.F.]

Or are you proposing that gravity behaves differently on Mars than on Earth?

IIRC, and Jerry can correct me if I'm wrong, according to Jerry's "theory", gravity works just fine in our "neighborhood", but varies as we move farther from (or nearer to?) the Sun.

Personally, I've seen no evidence to validate that "theory".

[borman]

Two Toth papers regarding the Pioneer Anomaly

Independent analysis of the orbits of Pioneer 10 and 11

Abstract: http://arxiv.org/abs/0901.3466

Thermal recoil force, telemetry, and the Pioneer anomaly

Abstract: http://arxiv.org/abs/0901.4597

Using new software, the Pioneer Anomaly is confirmed. This works against the idea that prior analysis may have suffered from a systematic that was intrinsic to the software used.

Also some limits are set on the size of a “jerk” or a-dot in case the anomaly is not always constant over the interval of measurement.

As the expanded data set becomes available, it will be used with this software.

In the second paper, the role of thermal recoil is discussed as a contributing factor to the anomaly. This is more of an introductory paper outlining the general approach. It had already been suggested that if up to 2% of the onboard heat could be directed in a non-symmetric manner, that this could account for the major portion of the anomaly.

The equations are derived to show a component congruent to the spin axis. There are a couple simplifying assumptions. One is of a Lambertian emitter. The other is the assumption that the spin remains constant. As the magnitude of the spin vector figures into the computation of the anomaly in the spin direction, it will eventually be important ot qualify or state the error introduced by this assumption. The actual data expose a spin anomaly associated with both Pioneers where one is positive w-dot and the other is negative w-dot. The first simple explanation is that there might be a small gas leak that is applying a small torque that alters the rpm of the Pioneers. But it should be noted that Toth mentions the 12 RHUs that give 1W of power that is directed perpendicular to the spin axis. If there is an unsteady output of power from the RHUs they could exert a net torque due to thermal recoil that could account for a portion of the spin anomaly budget to complement or possibly replace the need for a gas leak.

Of interest are the estimated thermal coefficients associated with RTGs and onboard wattage of around 100W. The output from the RTGs is around 20-25 times the onboard heat but the thermal coefficient of the onboard heat is about this factor greater than the RTG coefficient. Usually the argument that the RTGs have spent their fuel so that there is a draw down of power over time seems inconsistent with the observation that the anomaly is constant over time and does not fall in correlation to the RTG decay. But if the RTG energy replenishes the onboard 100W, this source can help to sustain a thermal recoil magnitude that is not tied to the decay of the RTG energy source over the period of observation.

The thermal recoil theory is essentially a drag theory. It should point in the direction of the spin axis, and not generally in the direction of either the Earth or Sun. So further data that can sort out these three vectors can test whether thermal recoil can account for all of the anomaly. Also all spacecraft that are so spin stabilized should also suffer from thermal recoil. This would include New Horizons during its hibernation phases. When the same software is used where the New Horizons design is used instead of the Pioneer design, the theory should make a prediction of how strong the Pioneer Anomaly should be present in the New Horizons craft. The measured value of the anomaly in New Horizons, if any, will then set limits on the magnitude of the contribution to the Pioneer Anomaly budget from thermal recoil.

[Jerry]

If gravity were behaving badly, wouldn't we also see the problem when space shuttle reenter into earth atmosphere? I think there must be lots of chances to track things falling to earth. Or are you proposing that gravity behaves differently on Mars than on Earth?

What has happened quite consistently in the Mars landing probes, that the expected/predicted/plotted attitude-at-entry of all of the successful Mars entry probes has been greater-than-expected. Most of them (both Vikings, Pathfinder and the MERs have iffy EDL reconstructs; that is, they are near or beyond three sigma in such parameters as the calculated drag coeffient of the parachutes, late parachute deployment and they are consistently landing in the 'long end' of the predicted ellipse.

The problem, in determining whether or not this represents an anomalous trend is that each of the landings has been unsufficiently instrumented to constrain all of the necessary parametrics: The Viking probes had good accelerometers, but no doppler. The Pathfinder had good doppler but no useful accelerometers, and so forth.

Of all of the landings, Phoenix, in my opinion, is the best instrumented and it also represents the most 'textbook' landing. Fuel consumption is nominal - (I did not expect to see that.) But the poor attitude during entry seems to be a vexing and dangerous engineering querk. The probe spend more time losing energy at hyposonic velocities; delaying parachute deployment. Something is not adding up.

[Jerry]

IIRC, and Jerry can correct me if I'm wrong, according to Jerry's "theory", gravity works just fine in our "neighborhood", but varies as we move farther from (or nearer to?) the Sun.

Personally, I've seen no evidence to validate that "theory".

I don't look for evidence to validate hypotheses, I look for evidence to disprove them.

I was looking for an explanation for both the anomalous behavior of pendelums during the entry and exit phase of a total eclipse, and the Pioneer anomalies, when I found all of the entries to Mars' atmosphere are marked by probe attitudes that are greater-than-expected; and anomalies during descent that can be interpreted as changes in wind speed, atmospheric density, parachute drag coefficients or motor performance, depending upon which parameter (velocity, acceleration, doppler shift) set is being monitored. The one common denominator is that the gravitational field could come into play if it is non-Newtonian.

When a probe is approaching a planet such as Mars, at a distance many times the diameter, the planet can be considered a point sourch of gravity relative to the center of gravity of the probe. When on the surface, gravity essentially becomes a plane, that is, there are only very minor changes in the gravity field - it always points straight down, regardless of the direction of motion on the surface.

When a probe is in a highly elliptical orbit, the dynamics are such that 'down' depends upon both the moment-of-inertia of the planet and the vector of the probe at any given time. This dependancy on the distribution of mass within the planet during entry effects the attitude of the probe: (Think of body angle of an fast Ice skater during a turn, and how this angle would vary if the center of gravity were moving under the ice.)

If elliptical orbits return the wrong mass or mass distribution for the planet (very non-Newtonian), then the love numbers are wrong too: The calculated distribution of matter within the planet isn't correct. If Mars is over-dense, then the standard Newtonian calculations predict a core that is less-dense and a surface that is over-dense. So both unexpected attitudes during entry and the lower-than-expected atmospheric pressure during the descent are consistent with funny gravity. (Incidently, the attitude of Huygens during entry of Titan's atmosphere was much higher-than-expected, too.) Since all of the entries to Mars atmosphere are marked by higher-than-expected attitudes; you might consider the possibility that this observational fact is inconsistent with the physical laws used to predict the attitude.

For Mercury, the same effects apply (sans atmosphere), but the sign is opposite: Once Messenger has settle into an elliptical orbit, the calculation of the mass distribution using Newtonian phyics (if they are wrong) will favor a highly centralized mass distribution and relatively low surface gravity. Likewise (and opposite Mars), elevated surface features will appear very underdense, while depression will return overdense gravity fields. This is also why I was expecting Messenger to receive less-than-expected gravitational braking during Messengers first two encounters with Mercury. We know the first gravitational assist was 'off'; but I can't find out whether the assist netted more or less gravitational braking than expected. Since corrections were not made after the second assist assist of Messenger by Mercury for at least a half orbit, at this time I can only speculate that the assist was close-to-expectations; or that the most efficient corrections was a half-lap away.