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Craig Markwardt
science forum addict
Joined: 16 Jun 2005
Posts: 66
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 Posted: Tue Jul 18, 2006 5:48 pm Post subject:
Re: Ranging and Pioneer
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"John (Liberty) Bell" <john.bell@accelerators.co.uk> writes:
| Quote: | Oh No wrote:
The position of Pioneer was calculated from Doppler information.
This statement is misleading. The position(s) of Pioneer(s) at any
given time was calculated using classical trajectory dynamics (with GR
corrections taken into account). So was the anticipated velocity hence
Doppler shift of antenna signal at any given time. What was observed by
NASA/JPL was an accumulating deviation from predicted Doppler shift,
which led Anderson et al. to infer an apparent classically anomalous
acceleration of the probes.
These apparent classically anomalous accelerations were tabulated
against predicted positions, not against altered positions inferred
from such apparent classically anomalous accelerations of the probes.
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Your statement is also misleading. While it is true that the
trajectory was "predicted" by classical mechanics, what you don't say
is that the parameters of the trajectory (initial conditions) were
adjusted in order to provide the best possible fit of the model to the
Doppler observations. Thus in a very real sense, the Doppler
observations can be used to "calculate" the position of the Pioneer
spacecraft. Despite the adjustment of all possible classical "knobs"
in the model, the anomaly remains.
CM |
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John Bell
science forum addict
Joined: 31 Dec 2005
Posts: 84
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| Posted: Tue Jul 18, 2006 5:48 pm Post subject:
Re: Ranging and Pioneer
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Jonathan Silverlight wrote:
| Quote: | In message <1153038223.243208.252860@s13g2000cwa.googlegroups.com>,
"John (Liberty) Bell" <john.bell@accelerators.co.uk> writes
Richard Saam wrote:
Oh No wrote:
The position of Pioneer was calculated from Doppler information. Ranging
was not available. Can anyone explain why ranging could not be used? Is
this just a limit on available technology, or is there a more
fundamental reason?
Regards
Here is an extreme case
in terms of Beta Pictoris
at many light years distance
arXiv:astro-ph/0601244 v1 11 Jan 2006
Dynamic motions are inferred from
atomic molecular quantum transitions.
The time (frequency) of such transitions are assumed the same
there and here
from which observed differences in frequencies
are related to dynamic motions.
The problem is the same as you identify.
How does one "range" the motions of Asteroid size objects
(which do not have quantum transitions) in Beta Pictoris
other than observing the gross newtonian gravity motions of the system
as a whole.
The problem could be solved if only a radar signal could be sent,
reflected for obtaining active ranging information.
In fact, with the (still functional) Pioneer, the possibility of
obtaining ranging data is enhanced by the fact that it contains a
narrow beam broadcast antenna directed towards the Earth, which can be
turned on and off via ground control.
Whether or not NASA thought to accuirately design and measure such turn
on/off delays prior to launch, in order to facilitate such a ranging
test, is, of course, another matter.
Even when Pioneer 10 and 11 were fully functional (and contact was lost
with 11 in 1995 and 10 in 2003)
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According to Anderson et al. contact was not lost with Pioneer 10. The
transmitter was switched off via ground control to conserve energy,
thereby allowing it to be switched on again at a later date, for
further tests.
| Quote: | the fact remains that they couldn't do
the type of ranging involving transmitting and receiving a modulated
signal that was done with Galileo and Ulysses. They certainly wouldn't
have used anything as drastic as turning the transmitter on and off.
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No, but they could now, if they knew switch on/off times accurately, in
order to test whether the unexpected apparent anomalous acceleration
had real consequences in terms of resultant reduced elapsed distance.
John (Liberty) Bell
http://global.accelerators.co.uk
(Change John to Liberty to respond by email) |
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John Bell
science forum addict
Joined: 31 Dec 2005
Posts: 84
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| Posted: Tue Jul 18, 2006 5:48 pm Post subject:
Re: Ranging and Pioneer
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Jonathan Silverlight wrote:
| Quote: | In message <1153038223.243208.252860@s13g2000cwa.googlegroups.com>,
"John (Liberty) Bell" <john.bell@accelerators.co.uk> writes
Richard Saam wrote:
Oh No wrote:
The position of Pioneer was calculated from Doppler information. Ranging
was not available. Can anyone explain why ranging could not be used? Is
this just a limit on available technology, or is there a more
fundamental reason?
Regards
Here is an extreme case
in terms of Beta Pictoris
at many light years distance
arXiv:astro-ph/0601244 v1 11 Jan 2006
Dynamic motions are inferred from
atomic molecular quantum transitions.
The time (frequency) of such transitions are assumed the same
there and here
from which observed differences in frequencies
are related to dynamic motions.
The problem is the same as you identify.
How does one "range" the motions of Asteroid size objects
(which do not have quantum transitions) in Beta Pictoris
other than observing the gross newtonian gravity motions of the system
as a whole.
The problem could be solved if only a radar signal could be sent,
reflected for obtaining active ranging information.
In fact, with the (still functional) Pioneer, the possibility of
obtaining ranging data is enhanced by the fact that it contains a
narrow beam broadcast antenna directed towards the Earth, which can be
turned on and off via ground control.
Whether or not NASA thought to accuirately design and measure such turn
on/off delays prior to launch, in order to facilitate such a ranging
test, is, of course, another matter.
Even when Pioneer 10 and 11 were fully functional (and contact was lost
with 11 in 1995 and 10 in 2003) the fact remains that they couldn't do
the type of ranging involving transmitting and receiving a modulated
signal that was done with Galileo and Ulysses. They certainly wouldn't
have used anything as drastic as turning the transmitter on and off.
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Notwithstanding the fact that Anderson et al. claimed (I think in 2004)
that Pioneer 10 was still functional, with its antenna turned off to
conserve energy, the fact remains that, if their reported apparent
anamolous acceleration is real, this should mean that the effect of
turning the antenna on or off should, by now, be observable on Earth
more than 1 second before originally expected.
Knowledge of the antenna turn on/off times to an accuracy better than
this, is, I suggest, not too much to ask for the adequate pre-launch
documentation of a piece of kit (and space program) of this cost.
Performing such a proposed test is hardly drastic, and far from
expensive (if adequate pre-launch documentation exists), given that
NASA/JPL have already turned off the antenna, and plan on switching it
on again at some unspecified time in the future.
John (Liberty) Bell
http://global.accelerators.co.uk
(Change John to Liberty to respond by email) |
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Oz
science forum Guru Wannabe
Joined: 30 Apr 2005
Posts: 155
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| Posted: Wed Jul 19, 2006 7:29 am Post subject:
Re: Ranging and Pioneer
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It seems to me that a repeat test simply requires a modest satellite to
exit the solar system as rapidly as possible.
Since the direction and basic design would appear to be uncritical the
key issue appears to be speed.
I imagine a modern design would be rather small and light and comprise
little more than a small box of electronics, a radioactive power source
and a large dish.
Given the direction is uncritical presumably a multiple slingshot path
could be devised so as to achieve maximum speed despite using a modest
launcher. It is (for example) plausible to do multiple slingshots
skimming (say) mercury, the moon and jupiter?
It would be quite helpful if we didn't have to wait 30 years for a
result....
--
Oz
This post is worth absolutely nothing and is probably fallacious. |
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Oh No
science forum addict
Joined: 06 Apr 2006
Posts: 82
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| Posted: Wed Jul 19, 2006 2:43 pm Post subject:
Re: Ranging and Pioneer
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Thus spake Oz <Oz@farmeroz.port995.com>
| Quote: | It seems to me that a repeat test simply requires a modest satellite to
exit the solar system as rapidly as possible.
Since the direction and basic design would appear to be uncritical the
key issue appears to be speed.
I imagine a modern design would be rather small and light and comprise
little more than a small box of electronics, a radioactive power source
and a large dish.
Given the direction is uncritical presumably a multiple slingshot path
could be devised so as to achieve maximum speed despite using a modest
launcher. It is (for example) plausible to do multiple slingshots
skimming (say) mercury, the moon and jupiter?
It would be quite helpful if we didn't have to wait 30 years for a
result....
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One might have thought the New Horizons mission an ideal opportunity, as
the craft was powered straight into an escape trajectory
http://ccar.colorado.edu/~nerem/zipfiles/hunkins/
Launched in January, New Horizons has already crossed the orbit of Mars
and is now crossing the asteroid belt. It will reach Jupiter next
February. It's the fastest spacecraft ever flown.
Alas, the spacecraft will very likely be unsuitable for Pioneer Effect
experiments for another reason: "Unfortunately, New Horizons suffers
from a similar drawback in this respect to the Cassini spacecraft -
namely, that its RTGs are mounted close to the spacecraft's body, so
infrared radiation from them, bouncing off the spacecraft, will produce
a systematic thrust of a not-easily predicted magnitude, several times
as large as the Pioneer effect."
From:
http://www.daviddarling.info/encyclopedia/P/Pioneer_anomaly.html
I don't know, but this may be a problem with all recently built fission-
powered space vehicles.
Nieto et al have been campaigning for a special mission, but I don't
know if they have even got as far as formally applying for funding.
Regards
--
Charles Francis
substitute charles for NotI to email |
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Oz
science forum Guru Wannabe
Joined: 30 Apr 2005
Posts: 155
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| Posted: Thu Jul 20, 2006 8:59 am Post subject:
Re: Ranging and Pioneer
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Oh No <NotI@charlesfrancis.wanadoo.co.uk> writes
| Quote: | One might have thought the New Horizons mission an ideal opportunity, as
the craft was powered straight into an escape trajectory
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Arrives pluto 2015.
Jupiter slingshot to 32 jovian radii.
Presumably a slingshot that went to say 3 jovian radii would result in a
very significant exit velocity compared to the 11km/s achieved here.
--
Oz
This post is worth absolutely nothing and is probably fallacious. |
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