Pioneer 11 - out of touch...?

[JohnCU]

From what I've found concerning the inability to communite with Pioneer 11:

The Earth's motion has carried it out of the view of the spacecraft antenna.

How is that possible? The earth rotates on its axis, around the sun, and the galaxy we are in is rotating (i think anyway)... but I fail to see how the earth could move in such a way as to block the view of the antenna. Maybe I'm not thinking about it right.

 

[lyssword]

Maybe it's (earth) is not rotating fast enough in a certain direction. Lets say it rotates sideways, but not much up and down type of rotation. Just a thought

 

[PottedMeat]

Wikipedia says:

http://en.wikipedia.org/wiki/Pioneer_11

Earth's motion has carried it out of alignment with the spacecraft antenna. As it cannot be maneuvered to point back at our planet, it's now impossible to establish further communication with the probe and know if it is still transmitting a signal.

I guess when it was designed, the antenna was to have its highest gain towards Earth in the Solar System, so the highest gain lobes would be pretty narrow. So at such a large distance it would be difficult to keep alignment. Maybe in a few hundred years we'll drift back.

 

[Markbnj]

I guess it would be possible to send out a relay, if they thought it was worth it.

 

[Pulsar]

I don't believe this is a signal you can relay - it is so faint they need to use multiple radio telescopes to pick it up. I believe they do some type of differential analysis between the different signals to weed out the background noise.

 

[Markbnj]

Originally posted by: Pulsar
I don't believe this is a signal you can relay - it is so faint they need to use multiple radio telescopes to pick it up. I believe they do some type of differential analysis between the different signals to weed out the background noise.

I guess I was assuming that if you could pick it up on earth, you could pick it up in space using a lot less antenna, since you wouldn't have the earthly interference to deal with.

 

[jagec]

Originally posted by: PottedMeat
Wikipedia says:

http://en.wikipedia.org/wiki/Pioneer_11

Earth's motion has carried it out of alignment with the spacecraft antenna. As it cannot be maneuvered to point back at our planet, it's now impossible to establish further communication with the probe and know if it is still transmitting a signal.

I guess when it was designed, the antenna was to have its highest gain towards Earth in the Solar System, so the highest gain lobes would be pretty narrow. So at such a large distance it would be difficult to keep alignment. Maybe in a few hundred years we'll drift back.

Either that, or the trim thrusters are out of gas.

Or the craft doesn't know where "earth" is (they index it on Canopus and the sun? Don't you need to index on 3-4 stars at least?), so it can't point towards it, and of course we can't communicate with it to give more detailed instructions.