The Pioneer Anomaly Options

[remcook]

http://www.planetary.org/news/2005/pioneer_anomaly_faq.html

The planetary society may be checking it out...

The Planetary Society has committed to raise the funds to preserve the priceless Pioneer data from destruction.


After years of analysis, but without a final conclusion, NASA, astonishingly, gave up trying to solve the "Pioneer Anomaly" and provided no funds to analyze the data. The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers. The agency is going to scrap, literally demolish, the only computers able to access and process that data in the next few months!

[tasp]

I bet it is not as simple as this, but I will post an idea and watch it be shredded . . .



Any possibility either Voyager craft could be spun at a few revs per hour, with the thrusters turned off, and keep the dish pointed at earth for maybe a year or two?

My thought is if we could get a confirmation of the Pioneer anomaly with a Voyager craft it might help JPL design a more capable or sophisticated 'Pioneer Anomally Probe' someday.

With the 'nodding' motion compensation used at Triton, I am cautiously optimistic that there might still be a new trick for our favorite 'old dog' to learn.

Having a spin stabilised period of flight for a Voyager might yield enough high quality tracking data at what would have to be an attractive price compared to launching another probe designed for the task.

Besides, I'm getting old and would like this mystery cleared up while I am still around . . .

[mchan]

Any possibility either Voyager craft could be spun at a few revs per hour, with the thrusters turned off, and keep the dish pointed at earth for maybe a year or two?

One problem is that something that was not designed to be spin stabilized (like Voyager) would very likely not spin very well. E.g. the spin axis would move around. In the case of Voyager, a stable spin axis (is such exists) may not align with the axis if the high gain antenna.

[ugordan]

One problem is that something that was not designed to be spin stabilized (like Voyager) would very likely not spin very well.  E.g. the spin axis would move around.  In the case of Voyager, a stable spin axis (is such exists) may not align with the axis if the high gain antenna.

Wasn't the spacecraft-solid rocket stack spin stabilized for the duration of the rocket's burn during Jupiter injection or was it also in 3-axis stabilization mode? I would have figured delivery errors would be minimized by spinning up first.

Another possible problem with spin-stabilizing is the star sensor, would it be able to cope with starfield smearing during rotation?

[Bob Shaw]

Wasn't the spacecraft-solid rocket stack spin stabilized for the duration of the rocket's burn during Jupiter injection or was it also in 3-axis stabilization mode? I would have figured delivery errors would be minimized by spinning up first.

Another possible problem with spin-stabilizing is the star sensor, would it be able to cope with starfield smearing during rotation?

If all that's required is a beacon, then setting up a slow spin where the aim point of the antenna nutates around the position of the Earth might be better than a precisely-aimed but data-free arangement. The CG and dynamic behaviour of the Voyagers must be *very* well known by now (unless something has dropped off with the cold). If data is required, that's perhaps another story. Perhaps the lesson here is that future interstellar-precursor probes should be designed with graceful aging in mind, so that as their output of data reduces it still remains - just - there.

Oh, and isn't it good to hear that there's going to be another attempt to reach Pioneer!

Bob Shaw

[ljk4-1]

Can New Horizons participate in this experiment? Or was that another item left off the menu?

[djellison]

Can New Horizons participate in this experiment?  Or was that another item left off the menu?

That's an unfair and unjustified jab at the mission.

From http://www.planetary.org/programs/projects...e_20050720.html

The Pioneers are spin-stabilized spacecraft. The Voyagers are three-axis stabilized craft that fire thrusters to maintain their orientation in space or to slew around and point their instruments. Those thruster firings would introduce uncertainties in the tracking data that would overwhelm any effect as small as that occurring with Pioneer.

This difference in the way the spacecraft are stabilized actually is one of the reasons the Pioneer data are so important and unique. Most current spacecraft are three-axis stabilized, not spin stabilized. It is unlikely another spin-stabilized craft will be sent across the solar system in the foreseeable future.

Doug

[ugordan]

That's an unfair and unjustified jab at the mission.

No - it cant, because it uses thrusters to manouver which would impart a small, but hard to calculate delta-V every time the spacecraft pitches, rolls and yaws.  Same reason that Voyager is of no use either.

Yes, but unlike the Voyagers, NH also has a spin mode which will be used during the long interplanetary cruise. So we might get long intervals when the s/c will be spin-stabilized and use it to get periods of precise tracking data. This will of course not be possible during the Jupiter encounter as well as the Pluto encounter phase, but at all other times (assuming thrusters will be off) it should be possible.
Seven years or so between Jupiter flyby and start of Pluto approach phase is a pretty good sample, IMHO.