In article <iyZIh.126401$_73.61120@newsread2.news.pas.earthlink.net>,

They're not radiating detectable signals, and that's a fairly strong
statement, given the things that DSN *can* pick up. They didn't just go
out of range; they actually stopped sending.

The relationship between available power and signal output isn't linear.
When available power from the RTGs got too low to run the basic spacecraft
systems, the voltage on the spacecraft power bus would sag below the
minimum needed by the systems. At which point, many of them -- e.g., the
radio transmitter -- would just *stop working*, because they needed a
certain minimum power voltage to function at all.

On Mar 16, 4:48 pm, h...@spsystems.net (Henry Spencer) wrote:

There's obviously a bit of chicken-and-egg problem here, since people
aren't going to commit to missions that need an assembly base if there's
no assembly base. But still, at the very least you'd need to have
ambitious plans that are likely to materialize soon... and while NASA had
no shortage of ambitious plans, ones that had a reasonable chance of
being
funded were in short supply. In particular, after the SEI debacle,
trying
to sell ISS on the grounds that it would be used to assemble a manned
Mars
expedition would have been political suicide.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |
h...@spsystems.net

What about testing deep space probes on a station?
I know that the benefits wouldn't outweigh cost, but at least
experience could be gained and problems like Galileo's antena avoided.
This is just a musing, without the Shuttle and given ISS's orbit it
doesn't make much sense.

"Hyper" <hyperbor...@yahoo.com> wrote in message
What about testing deep space probes on a station?
I know that the benefits wouldn't outweigh cost, but at least
experience could be gained and problems like Galileo's antena avoided.
This is just a musing, without the Shuttle and given ISS's orbit it
doesn't make much sense.

Exactly. In the case you DO have the shuttle, unless you're doing assembly,
you can already do that (check them out in LEO) and it has in fact been
done.

And was to be done on Galileo, except the delay required a different
trajectory that took it closer to the Sun, so the antenna had to say closed
longer.

IIRC Galileo was to be boosted by a Centaur - which got banned from
shuttle flights after Challanger - and the antenna problems stemmed
from spending too much time in storage and being moved from location
to location until flights were resumed. However, because there was no
alternative to Centaur it had to use Venus aand Earth for grav
slingshots.

snip

BTW, to illustrate the silliness of the *establishment*:
...
The COMPLEX team ruled out the option of using gravity to eject
Galileo from orbit around Jupiter, sending the craft into a
heliocentric orbit because of uncertainty where the nuclear-laden
satellite might ultimately go.

Such an option, the panel said, might require a launch-safety review
similar to the one ordered before Galileo was sent aloft by a space
shuttle 11 years ago.

"The reason for this is the very small, but nonzero, chance of
eventual impact with Earth. The anticipated cost of such a review is
so great -- in excess of Galileo's current annual operations budget of
some $7 million -- that NASA has no option but to dispose of the
spacecraft within the jovian system."
...

Wouldn't a close look at Jupiter's Trojans or at Ceres warrant the
"non-zero" risk?

And in any case, if you're doing simple assembly, you could simply do that
from the shuttle anyway.
Launch the probe on one rocket (shuttle or other), launch a upperstage or
two on another, and join them in orbit. Also been done with the Shuttle.

They're not radiating detectable signals, and that's a fairly strong
statement, given the things that DSN *can* pick up. They didn't just go
out of range; they actually stopped sending.

How can you tell the difference? (Seriously not my area of expertise).

And was to be done on Galileo, except the delay required a different
trajectory that took it closer to the Sun, so the antenna had to say closed
longer.

IIRC Galileo was to be boosted by a Centaur - which got banned from
shuttle flights after Challanger - and the antenna problems stemmed
from spending too much time in storage and being moved from location
to location until flights were resumed.

"The reason for this is the very small, but nonzero, chance of
eventual impact with Earth. The anticipated cost of such a review is
so great -- in excess of Galileo's current annual operations budget of
some $7 million -- that NASA has no option but to dispose of the
spacecraft within the jovian system."
Wouldn't a close look at Jupiter's Trojans or at Ceres warrant the
"non-zero" risk?

"Henry Spencer" <henry@spsystems.net> wrote in message
news:JErDJD.95H@spsystems.net...
In article
iyZIh.126401$_73.61120@newsread2.news.pas.earthlink.net>,

They're not radiating detectable signals, and that's a fairly
strong statement, given the things that DSN *can* pick up. They
didn't just go out of range; they actually stopped sending.

How can you tell the difference? (Seriously not my area of
expertise).

One way of detecting weak signals (while giving up the ability to decode
symbols) is to integrate and dump over an interval much longer than a
symbol. In this manner, a weak signal will be detectable, but not decodable.