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Pioneer Anomaly, still?


Enthalpy
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Hello everybody!post-53915-0-77061300-1383679507.png

 

The Pioneer anomaly is or was a possibly anormal small deceleration best observed at Pioneer-10.
http://en.wikipedia.org/wiki/Pioneer_10
http://en.wikipedia.org/wiki/Pioneer_anomaly
It was reported by Anderson et al (arXiv gr-qc/9808081v2), Turyshev et al (arXiv gr-qc/9903024v2), and in detail in 2002 by Anderson et al:
http://arxiv.org/abs/gr-qc/0104064
This latter paper studies and rejects possible explanations: everyone should read its sections VII and VIII before suggesting residual gas, dust, Sunlight and heat recoil, leaks, unknown planets, dark matter and many many more.

The 2002 paper explicitly discarded

  • the infrared recoil by Pioneer's central body as too weak, and decaying too much over time to explain the constant deceleration (VIII D)
  • the infrared recoil by the RTG (radioisotope thermoelectric generators) asymmetry (VIII C)
  • the influence of interplanetary plasma on radiowave propagation (VII C) for being tiny

to conclude that the deceleration wasn't explained.

 

But in 2012, Turyshev et al modelled Pioneer's heat transfers with finite elements:
http://arxiv.org/abs/1204.2507v1
and claimed that infrared recoil by Pioneer's central body plus the RTG (and some radio propagation through plasma) sufficed.

So here's how I tried to make my own opinion - and I agree with Turyshev, that is, with the 2002 paper he co-authored. Anomaly, rather.

 

 

Method choices

 

I have no spacecraft data, no means to model the heat transfers within Pioneer - and no desire neither, because this gives "believe me" styled results not open to scientific discussion. Instead, I adjust a fraction of the produced heat radiated forward; at the Sun distances I consider, the louvers are closed, external sources are small, temperatures vary little, and the forward fraction even less so.

I fit the speed curve instead of the acceleration.

  • Speeds being cleaner than accelerations, visual impression can already convince.
  • Error bars on the acceleration accept tolerances regularly of the same sign, but these tolerances cumulate on a speed curve to show a misfit. Or equivalently, the integration reduces the passband available for noise. All important to see if the curvatures of two functions fit.
  • The speed curve I have starts at 40AU. Sunlight pressure is small there, and model details get negligible.

 

 

The speed curve

 

I pinched it from Anderson et al (arXiv gr-qc/9808081v2, bigger there) and added Sun distances on it, which I only found on a Pioneer "artwork" AC97-0036-3 at Nasa's website. Science would deserve better, yes.

 

post-53915-0-35032500-1383679970_thumb.png
(click the picture for full size)

 

The orange straight line is fit by my eyes through my mouse.

Oscillations at the end have 1 terrestrial year period, so I'm confident they can be modelled out. And in case anybody believes the far-off isolated points are valid, he's welcome to explain this bigger anomaly.

 

 

Sunlight pressure, radiocom recoil, heaters

 

I did it as usual, and took also 252kg craft mass.

The RTG add 5% area to the 2.74m antenna which reflects ~80% of Sunlight. The absorbed ~20% are emitted as IR by the read side (e~0,90) and the front side (e~0.03 for cold naked aluminium). I take 2/3 of the reflected and radiated power for their recoil, as in a cosine pattern. Since the incoming Sunlight is 5.2W at 40.4UA, Anderson's factor of 1.77 instead of my 1.66 would change only 0.6W, and a different aluminium emissivity nothing.

The transmitter shall send 8W permanently rearwards. But maybe 0.5W from the source radiation pattern don't reach the primary mirror, which would make 1W difference.

Twelve 238Pu heaters (Turyshev takes eleven) shall deliver 1W at launch and decay with 87.7 years half-life. Pioneer's bus is to radiate forward the same proportion of their heat as for equipment heat.

More to come.
Marc Schaefer, aka Enthalpy

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Robert Foot has suggested mirror matter could be the cause of the Pioneer anomaly... I can't seem to find an article I can access but these links refer to the idea of mirror matter being the causal element in the pioneer anomaly... I do have the book he wrote about Mirror Matter... I've exchanged several e-mails with Dr. Foot about Mirror Matter, the idea leads to some fascinating possibilities... maybe someone else can access the papers in the links...

 

http://www.amazon.com/Shadowlands-Quest-Mirror-Matter-Universe/dp/158112645X

 

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

 

http://www.findanexpert.unimelb.edu.au/display/person14116

 

http://www.findanexpert.unimelb.edu.au/display/publication2924

 

http://inspirehep.net/record/561148?ln=en

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Radiowave propagation through plasma

Section VII C of [Anderson 2002] caps the effect to 1/400th the anomaly. More arguments here indicate a negligible effect.

Over the propagation path, the plasma's density can change with time. The plasma amount gives a delay, its change rate a speed error, the acceleration of the rate an acceleration error. In case an acceleration of the amount change rate, nicely constant over one half Solar cycle, were any credible, millisecond pulsars would disprove it. Their signal measured over a similar time span at similar frequency passes through about the same amount of plasma to reach Earth, and once their spindown and geometric and relativistic effects are compensated, they can show 10-16 stability, much more accurate that Pioneer's unexpected speed of 10-9c.

The steady part of the plasma density at the spacecraft decreases faster than R-2 (distance to the Sun) and influences the Doppler speed measure. The substantially constant craft speed through varying density results in an acceleration error decreasing faster than R-3 - faster than Sunlight recoil as R-2 which makes 10% of the anomaly at 48AU (see future section). If plasma were to explain 20% of the anomaly there, its resulting error would outweigh Sunlight recoil tens of times near 1AU, which knowingly doesn't happen.

Marc Schaefer, aka Enthalpy

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Infrared recoil by the body

Equipment in the craft's body receive electricity from the RTG and transform it to heat, except the radiocomm power. The electric power decays faster than 238Pu does because the converter ages; the measured curve is Fig. 16 page 35 in [Anderson 2002], where 01 Jan 1987 is 5418 days after launch. I've neglected the cable losses. Plethoric power is dissipated in a shunt regulator near the equipment hence needs no distinction.

The heaters decaying as 238Pu does add their output to the equipment power, and the sum's anisotropic radiation can produce a recoil. As opposed to [Anderson 2002], I feel comfortable with gaps between the closed louvers at the craft's front emitting much more heat than all other superinsulated surfaces, so alone the power available in 1995 would explain the anomaly. This needs the cold antenna dish at the rear to be insulated from the body, which I can't see on photographs; at least the twelve struts would leak just 2W if made of 0.64mm aluminium.

This spreadsheet for the free Gnumerics sums the recoils by Sunlight, the radiocomm beacon, and an adjustable forward proportion of equipment and heaters power, without any contribution by the Rtg - or for a future section, an adjustable contribution by the Rtg without asymmetric radiation of equipment heat.

 

BodyRtgRadiation.zip

 

On the speed curve from [Anderson 2002], which puts the speed anomaly to arbitrary zero on 01 Jan 1987, I've superimposed the computed recoil by Sunlight, the radio beacon, and 0.803 times the equipment plus heaters power, adjusted to fit the slope at the beginning of the observed speed anomaly. There is no means here to adjust the curvature.

 

post-53915-0-45272400-1383771906_thumb.gif

(click the picture for full size)

 

Other proportions of forward radiation would meet the straight line at 2000 days, 2859 days... The curvature mismatch is then less spectacular but still convincing to the eye, even over this limited time span. As [Anderson 2002] put, body heat recoil decays too much to explain the constant Pioneer anomaly. Lacking a recoil source that increases with time (as Sunlight recoil is already included), I'd say that infrared recoil by the body can contribute at most 1/4 the anomaly, as limited by the curvature mismatch.

Marc Schaefer, aka Enthalpy

Edited by Enthalpy
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Infrared recoil by the RTG

The Radioisotopic Thermoelectric Generators (RTG) are the other big source of infrared recoil, stronger but designed symmetric.

To observe their contribution without the central body's infrared recoil, the spreadsheet sums the recoils by Sunlight, the radiocomm beacon, and an adjusted 3.6% forward proportion of the RTG heat (2580W at lift-off) minus the extracted electricity (spreadsheet updated, effect imperceptible)

 

BodyRtgRadiation.zip

 

The RTG's heat decays less than the electricity, the curvature is consequently smaller, and the decay of weak Sunlight pressure happens to cancel out the curvature over the considered time interval, so that this curve fits perfectly the anomaly (click the picture for full size):

 

post-53915-0-75643200-1383950133_thumb.gif

 

So can this be the explanation?

 

I don't believe the RTG became asymmetric enough from Solar UV nor wind.

If the 2*2 RTG were to explain all the anomaly on day 1000 after 01 jan 1987, they would radiate together 77.7W forward. 2 of the 6 sectors were directed to the Sun; for 2W emitted less by each of these two sectors, each other would have needed to emit 1W more. I assume perfect conductivity; imperfect would worsen further by hampering the redistribution. So each Sunward sector must emit 25.9W less, each other 13W more. Though, this is the component parallel to Sun's direction.

 

post-53915-0-48117700-1383950195.png

 

Thanks to high emissivity, a hexagonal prism models well the six fins. A cosine emission lets each facet produce a recoil perpendicular to it and equivalent to 2/3 the power it emits, and the 30° tilt reduces it by 0.866, so that each Sunward sector must emit 44.9W less.

From 2580W radioactivity at launch, decay leaves 2210W at 01 Jan 1987 +1000 days, of which 90W leave as electricity, so a total of 6*535W is emitted. But the front sectors emit more due to a higher temperature that acts equally at rear sectors, so the emissivity drop is (44.9+22.5)/535, that is, from 0.90 to 0.73.

It's even worse, because e=0.90 at fins outperforms e=0.90 at a hexagon, thanks to multiple IR paths. If one fin area emits less, it reflects better heat from its neighbour fin, instead of absorbing it. Big effect, but let's neglect it for simplicity.

I don't believe emissivity dropping by 0.17, nor a half or a fourth of that. Space weathering increases the absorptivity of white paints, but changes their emissivity little, and uses to increase it. Nor can the front sectors improve by 0.17 by some Iapetus effect, from already >0.90.

This asymmetry can't preexist launch. It's equivalent to 19% of the area unpainted, or 44% length times 44% width, at two upper sectors of every RTG. But can it result from launch? Neither: it would mean one or two fins completely separated from one or two RTG, which would be obvious on their temperature data.

Marc Schaefer, aka Enthalpy

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Outgassing

It has been suggested as a contribution, but I claim outgassing is negligible.

Take 2m2 for the body's forward face. The multilayer insulation cumulates less than 100µm thickness, and polyimide outgassing 2% of its mass releases 6g.

The emitted gas is mainly water (18g/mol), as independent molecules in high vacuum. The surface being colder than 200K, the kinetic energy perpendicular to it (RT/2) is less than 831J per mole of emitted molecules, or 300m/s mean speed.

The emitted 6g impart <7mm/s to the 252kg craft - as compared to >200mm/s observed over just 9 years.

The antenna's dish is painted only on its rear face. The RTG are smaller than the body, their paint is thinner and mainly ceramic. Honeycomb glue's volatiles stay in the sandwich or, for a tiny fraction, outgas to the sides. The equipment may add volatile materials, but there is more.

Outgassing happens in the first minutes to hours in vacuum. Nearly all gas would have evolved during and just after launch, especially when Pioneer had its equiment baked by Sunlight as it left Earth - not 20 years later at 240K.

Marc Schaefer, aka Enthalpy

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I numerically duplicated (digitized) the methodology in Turyshev report 1204.2507
It is concluded with RMS analysis,
that Pioneer deceleration decays to a constant deceleration rather than zero
analogous of an object passing through a fluid decelerating with Stokes' law.

Aa. time (years after launch)(after AU to time conversion)
Bb. electric contribution to aPelecx10^-10 m/s^2
n = .406 half life 24.5 years regressing Table 1, 1204.2507
aPelec = 7.75E-10*EXP(-LN(2)*time/24.5)
Cc. RTG contribution to aPrtgx10^-10 m/s^2
n = 0.0104 half life 87.72 years (Plutonium)
aPrtg = 3.71E-10*EXP(-LN(2)*time/87.72)
Dd. or Bb + Cc Total contribution to aPx10^-10 m/s^2
Ee. Doppler measured aPx10^-10 m/s^2

Scenario one
Aa Bb Cc Dd Ee
8.79 6.05 3.46 9.51 9.82
10.78 5.71 3.41 9.12 9.33
12.79 5.40 3.35 8.75 8.78
14.82 5.10 3.30 8.40 8.21
16.81 4.82 3.25 8.07 8.21
18.80 4.56 3.20 7.75 7.39
20.81 4.30 3.15 7.45 7.34
22.82 4.07 3.10 7.17 7.23
24.85 3.84 3.05 6.89 7.72
Dd-Ee has RMS = .34

***************************************
Statistical analysis of fin root temperatures
http://arxiv.org/abs/gr-qc/0512121 Figure 20
indicate temperature(T) half life of 130 years
This translates into power half life ~emissivity*T^4
or 130/4 or 32.5 years. This is not reflected
in reported RTG power performance.
Radiation flux during Pioneer 18 Jupiter flyby
(10,000 times that of Earth)
did not cause differential RTG emissivity.
http://arxiv.org/abs/gr-qc/0104064 C
does not provide any further mechanistic origin of Cc
and none presented in 1204.2507
Assuming RTG contribution(Cc) is replaced by
a constant(Ff) the electric(Bb) + constant(Ff) or Gg
yields RMS = .33 (equal to scenario one .34)
when compared to doppler(Ee)

Scenario two
Aa Bb Ff Gg Ee
8.79 6.05 3.33 9.38 9.82
10.78 5.71 3.33 9.04 9.33
12.79 5.40 3.33 8.73 8.78
14.82 5.10 3.33 8.43 8.21
16.81 4.82 3.33 8.15 8.21
18.80 4.56 3.33 7.89 7.39
20.81 4.30 3.33 7.63 7.34
22.82 4.07 3.33 7.40 7.23
24.85 3.84 3.33 7.17 7.72
Gg-Ee has RMS = .33

***************************************
A more detailed model Hh
minimizing RMS at .27
(the best available fit)
assumes aP approaching a constant 5.9
aP = (12.587-5.9)*EXP(-.068*time)+5.9

Scenario three
Aa Hh Ee
8.79 9.60 9.82
10.78 9.14 9.33
12.79 8.74 8.78
14.82 8.39 8.21
16.81 8.09 8.21
18.80 7.83 7.39
20.81 7.60 7.34
22.82 7.40 7.23
24.85 7.23 7.72
Hh-Ee has RMS = .27

There is statistical logic
within the context of 1204.2507 and historical Pioneer reports
for a constant aP contribution.

Richard D. Saam

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Robert Foot has suggested mirror matter could be the cause of the Pioneer anomaly [...]

Hi Moontanman, thanks for your intererst! And apologies for the late answer.

 

Mirror matter would be a form of Wimps contributing to darks matter, isn't it? Knowing nothing about Wimps nor Mond, I can just refer to the subsection XI B on page 44 of [Anderson 2002] titled "Dark matter or modified gravity?":

- Dark matter would need 3*10-4 added Solar mass to explain Pioneer's anomaly, while ephemeris allow a few 10-6 Solar masses;

- Modified gravitation would act on Mars and Earth orbital radii, strongly if it were to explain Pioneer's anomaly, but Viking's measurements did not see it.

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Hi Moontanman, thanks for your intererst! And apologies for the late answer.

 

Mirror matter would be a form of Wimps contributing to darks matter, isn't it? Knowing nothing about Wimps nor Mond, I can just refer to the subsection XI B on page 44 of [Anderson 2002] titled "Dark matter or modified gravity?":

- Dark matter would need 3*10-4 added Solar mass to explain Pioneer's anomaly, while ephemeris allow a few 10-6 Solar masses;

- Modified gravitation would act on Mars and Earth orbital radii, strongly if it were to explain Pioneer's anomaly, but Viking's measurements did not see it.

No, mirror matter is composed of electrons protons and neutrons.

 

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

 

In physics, mirror matter, also called shadow matter or Alice matter, is a hypothetical counterpart to ordinary matter. Modern physics deals with three basic types of spatial symmetry: reflection, rotation and translation. The known elementary particles respect rotation and translation symmetry but do not respect mirror reflection symmetry (also called P-symmetry or parity). Of the four fundamental interactions—electromagnetism, the strong interaction, the weak interaction, and gravity—only the weak interaction breaks parity.

Parity violation in weak interactions was first postulated by Tsung Dao Lee and Chen Ning Yang [1] in 1956 as a solution to the τ-θ puzzle. They suggested a number of experiments to test if the weak interaction is invariant under parity. These experiments were performed half a year later and they confirmed that the weak interactions of the known particles violate parity.[2] [3] [4]

However parity symmetry can be restored as a fundamental symmetry of nature if the particle content is enlarged so that every particle has a mirror partner. The theory in its modern form was written down in 1991,[5] although the basic idea dates back further.[1][6][7] Mirror particles interact amongst themselves in the same way as ordinary particles, except where ordinary particles have left-handed interactions, mirror particles have right-handed interactions. In this way, it turns out that mirror reflection symmetry can exist as an exact symmetry of nature, provided that a "mirror" particle exists for every ordinary particle. Parity can also be spontaneously broken depending on the Higgs potential.[8][9] While in the case of unbroken parity symmetry the masses of particles are the same as their mirror partners, in case of broken parity symmetry the mirror partners are lighter or heavier.

Mirror matter, if it exists, would have to be very weakly interacting with ordinary matter. This is because the forces between mirror particles are mediated by mirror bosons. With the exception of the graviton, none of the known bosons can be identical to their mirror partners. The only way mirror matter can interact with ordinary matter via forces other than gravity is via so-called kinetic mixing of mirror bosons with ordinary bosons or via the exchange of Holdom particles.[10] These interactions can only be very weak. Mirror particles have therefore been suggested as candidates for the inferred dark matter in the universe.[11][12][13][14][15]

 

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Spin, thrusters and leaks

Pioneer 10 and 11 have six 4.5N thrusters at two opposite sites of the main antenna's rim, 1.37m from the center. One spins up, one down, one opposite and simultaneous pair produces a torque and an other the opposite one - keeping in mind that Pioneer 10 spins at 4.8rpm and Pioneer 11 at unwanted 7.3rpm, so the gyroscopic effect lets instead the rotation axis precess. A viscous hinge at the magnetometer's boom lets Pioneer spin flat. I assume the usual 1s pulses from the thrusters, as they fit the precession's +-0.3° accuracy.

Spin thrusters were not activated after Jupiter or Saturn flyby, but precession thrusters were, to keep the antenna's orientation. This caused a few dozen ~1mm/s steps in the radial speed which were modelled out of the anomaly curve; 5% thruster mismatch, like 50ms lag between valves response, explain it. I assume 588kg*m2 from [Anderson 2002], which needs RTG arms shorter than 3m.

Pioneer 11's spinrate curve shows ~500µrad/s steps when the precession thrusters were used, fig.12 p.23 of [Anderson 2002]. 2% nozzle bias can explain them - not huge at the tip of a long light boom. Consecutive pulses were reportedly used, possibly more at the faster spinning Pioneer 11, so the nozzle bias would be less.

Between the precession pulses, Pioneer 11's spinrate curve rises at roughly 0.002rpm/yr = 7prad/s2 ([Anderson 2002] see instead +0.007rpm/yr). 0.5W unbalanced IR emission at the RTG explain it, or 0.001 emissivity clockwise-anti mismatch averaged on all RTG - or less plausible 0.9W at the thrusters from 9W local heaters, or 1.5W asymmetry at the experiments box.

In its interval I, Pioneer 10's spinrate curve drops at 60prad/s2, or 9 times faster than above (fig.11 p.23 of [Anderson 2002]). If thruster mismatch isn't the main cause, 0.01 emissivity mismatch at the RTG may still explain it - the experiments box less so, with very unsymmetric heat leaks.

----------

In its 1.8yr long interval II, Pioneer 10's spinrate curve drops irregularly at mean 330prad/s2. This exceeds the total IR emitted by the experiments and equipment, the thrusters, and would demand 5% mismatch in the RTG's emissivity, varying over time and disappearing later... So a leak fits better - except that the (axial) precess thrusters were used when the leak began and ended, but the speed anomaly (<0.5N*s deviation there) tells that said leak was precisely azimutal (0.018rad/s over the interval need 7.9N*s at R=1.37m), through the de-spin nozzle. A leak triggered by a shock or a water hammer?

4.4g of N2+2*H2 suffice, expanded to 1800m/s from 290K due to the 1W heater. That's 1mm3 hydrazine every 3.6h. Or a bit more if the molecules don't interact, I didn't check.

So could a similar leak in a thruster explain the anomaly? 500mm/s would need 84g of lukewarm N2+2*H2 through a precession nozzle in 20 years, or 1mm3 hydrazine every 2.1h. Arguments against:
- The anomaly is constant, despite the precession thrusters were fired many times.
- The anomaly is the same for Pioneer 10 and 11, as [Anderson 2002] pointed out.

But could a leak near a thruster explain the anomaly? That's not easy. During the interval I, Pioneer 10 lost 90mm/s, to be explained by 23N*s, but it lost just 6.4mrad/s, needing 2.7N*s there. This leaves reduced chances for a random leak angle. It's much worse at Pioneer 11, whose spinup between the precession pulses is 9 times slower.

Or can there be a leak near the hydrazine tank? Individual 32g/R molecules emitted to half-space from 240K would have mean 250m/s forward, so 580mm/s anomaly would need 0.58kg over 23 years, or 1mm3 in 21min. From constant pressure and temperature after Jupiter, the acceleration would be constant. I don't expect radiation in Jupiter's belts to pass through shielding and make polymer joints porous.
- If a sensor monitored the propellant in tank, this leaked amount is easily checked.
- Corrosion by hydrazine in the compartment may be noticed.
- The anomaly is the same for Pioneer 10 and 11.

Marc Schaefer, aka Enthalpy

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Beyond this analysis.

Fitting the anomaly speed curve rather than the acceleration curve constraints more the attempted explanations of the anomaly. Fitting the numbers with statistics tools rather than a curve by eye would be more reliable. Even better: anomaly speed data spanning a longer time would show more clearly if the curvatures fit. Also, an accurate distance versus date would permit to model the Sunlight recoil properly.

I have suggested very simple spacecraft that measure accurately the speed and position under similar conditions.
All3bis_PurposeSpacecraft.pdf
They are powered by battery hence emit very little heat, contain essentially a sort of radar transponder, need no attitude control and have no trajectory control, are dense and can be spherical. A group of them would vary their properties, make differential measurements in 3D... As a university or club project, they'd cost few M$ to build, can be launched as secondary passengers of a bigger Sun-escape launch, or as main passengers of a cheap launcher, like a Vega with an escape stage.

On some deep space probes, a possible flyby anomaly may have been observed - on others not... Spacecraft resembling the ones I described for the Pioneer anomaly can test it accurately.

  • If passing by a planet, they can ride a main probe and be separated before the flyby;
  • Shorter operation, or nearer to the Sun, would enable more power, including for an atomic clock;
  • They can, after the flyby, serve for the Pioneer anomaly, with proper power design;
  • A very eccentric Earth elliptic orbit is almost a hyperbolic one... If this is an acceptable test, many launch opportunities permit to test a flyby anomaly. A launcher can put the main passenger to Geosynchronous Transfer Orbit, then raise the perigee to ~1000km to release the secondary small probes on a clean air-free orbit. The probe(s) could cumulate thousands of passes for accuracy.

Marc Schaefer, aka Enthalpy

Edited by Enthalpy
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5. Conclusion.

Built that way, the project would provide precise data about the still unexplained Pioneer Anomaly, and looks really

simple and cheap. As it may uncover new physics, developing it would be a nice goal.

Not because it is difficult, but because it is simple.

 

Very interesting

I have many times thought the same; and asked myself why it isn’t done long ago

Have you any idea about the cost to build and launch such space probes

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Building the probes is cheap. It takes under ten people, capable of developing unusual technology, for 2-3 years. I built a satellite with 9 people in 3 years' spare time, which meant nearly a full time for three of us. The probes have a similar complexity. Nice project for one university lab. Say, 3M$.

 

The absence of trajectory nor attitude control makes the probes simple. Their thermal design is more extreme, but under more constant conditions, and primary batteries accept more varied temperatures than Ni-Cd when I designed my satellite.

 

----------

 

The cost of launching them is hard to predict, as it radically depends on the scenario. One exclusive Vega launch is rumoured to be sold 32M€, without the needed upper stage:

http://www.spacenews.com/article/vega-expected-be-price-competitive-russian-rockets

 

Prices drop as a secondary passenger, either of a probe or of a launcher. One small side seat on Ariane IV (to Leo, Gto should be the same) cost 2MF then, so count 2M€ now - but Ariane won't raise the perigee. Ask Zenit and Proton instead, as a secondary passenger, for an Earth elliptic orbit to test the flyby anomaly.

 

The deep-space mission would better launch together with a big probe.

 

----------

 

Operating the probes takes big antennas on Earth and a project team. The antennas exist already but cost manpower, from time to time during years. Obscure to me, so ask the Deep Space Network or equivalent directly.

 

It needs some electronics near the ground antennas to produce the query pulse and measure the delays accurately. If, as I imagine, the rest of the DSN has already clearly defined interfaces, means to know the date, easily understandable software (err...) to correct Earth's position and rotation, locate the probes ans direct the antennas, means to record the data... Then the team building the probes can make the additional electronics for, say 1M$.

 

A permanent post-launch team needs several people for continuity but part-time, essentially to observe if the data is meaningful and store it over years. This team must be able to apply the necessary corrections to the data - not necessarily the team that built the probes. Say, 2 scientists putting each half a day every second week once everything runs fine. Over 20 years, say 200k$.

 

This team would better be the science team as well, but this cost should be separated, as did your question.

 

----------

 

Why hasn't it been done? Several other projects have been proposed, but the ones I know are stabilized probes, with radioisotopic power sources, and so on. This makes them 100M$ projects.

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  • 1 year later...

How can we be sure that heat radiation at all will have any decelerating effect on the pioneer space probes.?

Which scientifically prove can support such conclusion ?

 

Are you asking a general question about the momentum of electromagnetic radiation? Or the specifics of the Turyshev analysis?

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Photons emitted or received have the same effect. This is necessary for momentum conservation: light carries some momentum opposite to the emitter's recoil, and transfers it to the target. Other interpretations wouldn't conserve the sum of momentums of the emitter plus the light, the light plus the target, or the emitter plus the target.

 

Even better than a theory or a principle, the momentum of light is observed at spacecraft, with an interesting accuracy. Both received and emitted light, both visible and far infrared. At geosynchronous satellites, radiation pressure uses to be the main external torque, parasitic or useful since many satellites use it to stabilize themselves.

 

Radiation coming from outside the Solar system isn't probable. First, it would need a significant strength to explain the Pioneer anomaly, but we observe radiation at so many wavelengths without noticing that. The anomaly gets significant as compared to our Sun's radiation pressure near Saturn's orbit, where sunlight is still stronger than any lamp.

 

Then, both Pioneers observed the same deceleration (one craft more accurately than the other) despite going to different directions after the Saturn flyby. That makes an explanation by unidirectional radiation more difficult. But if isotropic, radiation towards the Sun would re-emerge at the opposite site, cancelling the effect out - unless it stops at the Sun.

 

In his latest opinion:

"Support for the thermal origin of the Pioneer anomaly", arXiv 1204.2507

Anderson claims (and I don't agree) that 45% of the anomaly is recoil from heat emitted by the equipment, 35% heat emitted asymmetrically by the generators without influence by the antenna, and 20% due to propagation or being within the uncertainties.

 

One basic difference (besides detail arguments) is that I checked if the speed curve could be fit by radiation recoil, while Anderson made a fit on the acceleration curve. The acceleration curve is more tolerant, because it accepts misfits always in the same direction within the uncertainty, while these small misfits accumulate on the speed curve to make it impossible to fit. The curvatures differ, see message #4.

 

So I dont' tell "Turyshev's model is wrong" (I have discrepancies with some paint degradations; things like that) but rather "the model doesn't pass a more stringent test".

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The RTG add 5% area to the 2.74m antenna which reflects ~80% of Sunlight. The absorbed ~20% are emitted as IR by the read side (e~0,90) and the front side (e~0.03 for cold naked aluminium). I take 2/3 of the reflected and radiated power for their recoil, as in a cosine pattern. Since the incoming Sunlight is 5.2W at 40.4UA, Anderson's factor of 1.77 instead of my 1.66 would change only 0.6W, and a different aluminium emissivity nothing.

 

Earth receives energy approximately [math]1360 \frac{J}{s*m^2}[/math] (without counting loses caused by atmosphere).

Distance 1 AU = 149,600,000,000 m

 

Reversing inverse-square law gives energy emitted by Sun per second:

[math] 1360 * 4 * \pi * 149600000000 ^2 = 3.825*10^{26} W[/math] (wiki mentions 3.846*10^26, so we're pretty close).

 

Now if we will calculate energy at distance 40.4 AU = 6,043,840,000,000 m

[math]\frac{3.825*10^{26}}{4*\pi*6,043,840,000,000^2}=0.833251642 \frac{W}{m^2}[/math]

 

5.2 W/m^2 is 2 * PI bigger than 0.8333 W/m^2..

 

5.2 W/m^2 is at distance 16.16 AU from the Sun.

 

Please also notice it's easy to make mistake by calculating distance satellite traveled from Earth 40.4 AU, instead of from the Sun (not saying it's in this case because I didn't verified data).

Edited by Sensei
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We know there is dark matter out there (even though there is no evidense all all)

We know that the universe is expanding (even though it is never proven that cosmological redshift only can be interpreted like this)

Ohh boy I could continue for weeks

 

 

!

Moderator Note

 

Not here you can't. This discussion is about the Pioneer anomaly, and not a platform for railing against science in general.

 

Radiation pressure is well-accepted (and well-documented) physics. People, including myself, have been using lasers to manipulate atoms via conservation of momentum for decades. If you want to discuss details of it, start a new thread.

 

 

EDIT: Upon further review, the whole mess has been split off. Conservation of momentum of EM radiation/photon discussion is here

http://www.scienceforums.net/topic/86724-photons-and-conservation-momentum-split-from-pioneer-anomaly/

 

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!

Moderator Note

 

Not here you can't. This discussion is about the Pioneer anomaly, and not a platform for railing against science in general.

 

Radiation pressure is well-accepted (and well-documented) physics. People, including myself, have been using lasers to manipulate atoms via conservation of momentum for decades. If you want to discuss details of it, start a new thread.

 

 

EDIT: Upon further review, the whole mess has been split off. Conservation of momentum of EM radiation/photon discussion is here

http://www.scienceforums.net/topic/86724-photons-and-conservation-momentum-split-from-pioneer-anomaly/

 

 

As I understand this thread's it about skepticism to whether the Pioneer anomaly really is solved, or not.

And in this context, even proposals to send out other new probes to test whether it really is scientific OK to consider the case as closed..

 

As we all know 18% of the anomaly is still not addressed, as well as it is not addressed why the anomaly first started after the Saturn flyby.

So these open question alone is enough to conclude that this case not is closed based on beautiful science.

In other words there are indeed reasons to be sceptic.

 

One way to express what could be wrong is to doubt the calculation of the radiation, - as mainly none isotropic , and that this perhabs not is properly understood (as Enthalpy did) and the other point of view is whether the theory of radiation can be considered as well documented science, or not.

 

It is fair to start a new thread regarding this issue , but not to give me a warning.

I do not see how skepticism should lead to a warning.

It has notning to do with hijacking to do.

Edited by Bjarne
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As I understand this thread's it about skepticism to whether the Pioneer anomaly really is solved, or not.

 

Feel free to do a detailed analysis of the results and come up with an alternative explanation. Preferably one based on physics, not magic.

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One way to express what could be wrong is to doubt the calculation of the radiation, - as mainly none isotropic ,

Satellites are typically sending data to us what amount of energy its solar panels received per second. So variations from inverse-square law should be easily spotted.

Edited by Sensei
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As I understand this thread's it about skepticism to whether the Pioneer anomaly really is solved, or not.

And in this context, even proposals to send out other new probes to test whether it really is scientific OK to consider the case as closed..

 

As we all know 18% of the anomaly is still not addressed, as well as it is not addressed why the anomaly first started after the Saturn flyby.

So these open question alone is enough to conclude that this case not is closed based on beautiful science.

In other words there are indeed reasons to be sceptic.

 

One way to express what could be wrong is to doubt the calculation of the radiation, - as mainly none isotropic , and that this perhabs not is properly understood (as Enthalpy did) and the other point of view is whether the theory of radiation can be considered as well documented science, or not.

 

It is fair to start a new thread regarding this issue , but not to give me a warning.

I do not see how skepticism should lead to a warning.

It has notning to do with hijacking to do.

 

!

Moderator Note

Challenging the validity of well-established physics or the scientific method is off-topic. Discussions of that sort belong in speculations.

 

Do not further derail the thread by responding to this modnote.

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I didn't write W/m^2. You did. I wrote "The incoming sunlight is 5.2W at 40.4AU".

 

Perhaps an explanation of your calc would be useful. Sensei has provided one possible misroute to the calculation (ie a missing factor of 2 pi) - I can provide yet another

 

 

 

...The RTG add 5% area to the 2.74m antenna which reflects ~80% of Sunlight. The absorbed ~20% are emitted as IR by the read side (e~0,90) and the front side (e~0.03 for cold naked aluminium). I take 2/3 of the reflected and radiated power for their recoil, as in a cosine pattern. Since the incoming Sunlight is 5.2W at 40.4UA, Anderson's factor of 1.77 instead of my 1.66 would change only 0.6W, and a different aluminium emissivity nothing.

 

The area of a circle of radius 2.74m (increased by 5% per above) - then absorbtion of 20% (per above) equals 5.200; again clearly wrong (its metres squared rather than watts) - but unless you provide calcs it is difficult to know if yours is a typo or we just don't understand your logic yet

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