What's the deal with Pioneer 9/10 ?

[DiggitCamara]

This thread seems to spoof someone’s belief that the Pioneer probes are behaving erratically.

However, NASA in this article seems to be telling us that they have permanently lost contact with the probes.

So, fight my ignorance! Are these probes gone from (current) technological reach? Or is NASA still physically tracking them?

If they are still tracking them, how? And what’s the Straight Dope about that? (Meaning of course:

1. The probes are moving as expected
2. They’re moving faster than expected
3. They’re slowing down
   )

Links would be appreciated!

[Chronos]

Without radio contact, there’s no way of detecting them any more. At those kinds of distances, you’re lucky to find a dwarf planet, much less a probe a few meters across.

Meanwhile, the Pioneer Anomoly (which has been known for rather a while, from back when we were still getting data from the probe) is apparently real, but it’s small enough that there are an awful lot of potential explanations which need to be ruled out before we can go changing the laws of physics.

[DiggitCamara]

@Chronos

Without radio contact, there’s no way of detecting them any more. At those kinds of distances, you’re lucky to find a dwarf planet, much less a probe a few meters across.

Meanwhile, the Pioneer Anomoly (which has been known for rather a while, from back when we were still getting data from the probe) is apparently real, but it’s small enough that there are an awful lot of potential explanations which need to be ruled out before we can go changing the laws of physics.

Thanks. Just to get it straight: We don’t get data from the probe(s) since around 2003?

And this site which reports the facts (breathlessly, in present tense) is not that trustworthy?

[LSLGuy]

When in doubt, try Wiki… Pioneer anomaly - Wikipedia

[user_hostile]

Did I miss something here? What about Voyager 1 & 2? Didn’t they suffer the same anomaly? If not, what’s the explanation?

[Kevbo]

@user_hostile

What about Voyager 1 & 2?

The pioneers use spin stabilization, the voyagers use thrusters to maintain alignment.

From the wikipedia article linked above:

These spacecraft, such as the Voyagers, acquire small and unpredictable changes in speed as a side effect of the frequent attitude control firings.

From the article, the acceleration is sunward, so they are slowing down.

[minor7flat5]

For background, here’s a great article on Pioneer 10 from the Winter 2001 issue of Invention & Technology:
The Spacecraft That Will Not Die

The article predicted the loss of communication by 2002.

I found this bit about the PDP-11 quite intriguing:

Technological progress long ago caught up with Pioneer and left it in the dust. Designed to operate in an age of huge mainframe computers and punch cards, Pioneer 10 can’t be controlled by today’s superfast desktop computers. The project’s remaining original Digital Equipment PDP 11-14 computer, standing like a museum piece in the Pioneer control room at Ames, must be kept running in order to transmit navigation commands. Its operations supervisor, Ric Campo, laments, “The equipment is barely keeping alive. Much of the hardware is maintained by stripping cards and interfaces from similar hardware in the Pioneer control center.” The data telemetry system was reconfigured several years ago to run on a Macintosh, but such a fix isn’t possible for the command system. Present-day engineers can still interpret the data sent by Pioneer’s ancient systems, but Pioneer can’t understand commands not compiled by the computers of its own age.

[mlees]

@user_hostile

Did I miss something here? What about Voyager 1 & 2? Didn’t they suffer the same anomaly? If not, what’s the explanation?

Wiki addresses that:

…the effect is much harder to measure accurately with craft that use thrusters for attitude control. These spacecraft, such as the Voyagers, acquire small and unpredictable changes in speed as a side effect of the frequent attitude control firings. This ‘noise’ makes it impractical to measure small accelerations such as the Pioneer effect.

[Punoqllads]

@minor7flat5

For background, here’s a great article on Pioneer 10 from the Winter 2001 issue of Invention & Technology:
The Spacecraft That Will Not Die

The article predicted the loss of communication by 2002.

I found this bit about the PDP-11 quite intriguing:

…Present-day engineers can still interpret the data sent by Pioneer’s ancient systems, but Pioneer can’t understand commands not compiled by the computers of its own age.

Huh? Have they never heard of a cross-compiler?

Methinks the article writer misunderstood something.

[minor7flat5]

@Punoqllads

Huh? Have they never heard of a cross-compiler?

Methinks the article writer misunderstood something.

Or there are a whole mess of other factors that were left out. The writers in that magazine are fairly thorough; it’s not Popular Science.

[Rysto]

@Punoqllads

Huh? Have they never heard of a cross-compiler?

Methinks the article writer misunderstood something.

Is it possible that the control software was written in assembly? If that’s the case then the only options would be to emulate it or re-write the whole thing.