Computer Forensics to Help Solve Pioneer Mystery

Matthew Sparkes writes "Launched 35 years ago on Friday, Pioneer 10 was the first spacecraft to reach the outer Solar System and return pictures of Jupiter, closely followed by Pioneer 11. However, the twin Pioneer spacecraft drifted off course (see number 8) by hundreds of thousands of kilometres during their three-decade mission, and NASA eventually lost contact with them. An international team of scientists, including many amatuer hobbyists, are re-analysing the tracking and telemetry data in the hope of discovering the reason."

Comments

Not Really a True "Solution"

[eldavojohn]

Computer Forensics to Solve Pioneer Mystery

No, there's a 50/50 chance they "solve" the mystery.

As the article states:

If the direction is towards the Earth, it almost certainly indicates the anomaly was caused by faulty technology or an artifact of receiving the data at the ground stations. If, however, the direction is towards the Sun, new gravitational physics may be needed to explain the effect.

So if the direction of deceleration is towards Earth, then you might be able to consider the mystery solved and blame it on the process of collecting the data. But if the deceleration is towards the sun or another direction, we have an observation of an unknown effect in physics. If the latter is the case, I think the mystery is just starting to be understood--with a long ways to go and many more observations before we can consider it solved.

Re:Do they have all the original calculations?

[Impy the Impiuos Imp]

> And another guess, but surely the gentlest squirrel's fart as
> the craft left Earth could translate to huge discrepancies by
> the time they get to the other side of the solar system?

Yes, a one-off measurement error at launch would turn into hundreds of thousands of miles difference years later. However, the positions of the craft all along the way show it is still slowing down too fast.

In your terms, the squirrel must be hiding on board and farting from time to time on a reqular basis and in the direction of travel, slowing it.

If you're really interested in this...

[Anonymous Coward]

Here's a link to the cannonical paper on the issue: http://arxiv.org/abs/gr-qc/0104064

Also, if you're interested, and in the New York area, some of the scientists who've been working on this are speaking at the Hayden planetarium in a few weeks: http://haydenplanetarium.org/programs/asimov/

Just to give a feel for what obsessive level of detail we're dealing with, here's a list of the possible causes considered in the paper above. The numbers after each listing are the bias and uncertainty in units of 10^-8 cm/sec^2. Listings with only one number only have an uncertainity, not a bias.

1 Systematics generated external to the spacecraft:
  a) Solar radiation pressure and mass +0.03 ±0.01
  b) Solar wind ± 10^-5
  c) Solar corona ±0.02
  d) Electro-magnetic Lorentz forces ± 10^-4
  e) Influence of the Kuiper belt's gravity ±0.03
  f) Influence of the Earth orientation ±0.001
  g) Mechanical and phase stability of DSN antennae ± 0.001
  h) Phase stability and clocks ± 0.001
  i) DSN station location ± 10^-5
  j) Troposphere and ionosphere ± 0.001
2 On-board generated systematics:
  a) Radio beam reaction force +1.10 ±0.11
  b) RTG heat reflected off the craft -0.55 ±0.55
  c) Differential emissivity of the RTGs ±0.85
  d) Non-isotropic radiative cooling of the spacecraft ±0.48
  e) Expelled Helium produced within the RTGs +0.15 ±0.16
  f) Gas leakage ±0.56
  g) Variation between spacecraft determinations +0.17 ±0.17
3 Computational systematics:
  a) Numerical stability of least-squares estimation ±0.02
  b) Accuracy of consistency/model tests ±0.13
  c) Mismodeling of maneuvers ±0.01
  d) Mismodeling of the solar corona ±0.02
  e) Annual/diurnal terms ±0.32