Heliocentric TDRS?

Has there ever been any proposals for a deep-space TDRS-style
satellite for relaying telemetry from outer-planet missions such as
New Horizons et al?

I was thinking there may be some advantages in putting relay devices
in heliocentric orbit at, say, the orbit of Mars, to pick up telemetry
on those occasions when the Sun is between Earth and the exploring
spacecraft.

Also, wouldn't transmissions be easier to intercept from listening
spacecraft far away from Earth's ionosphere?

TVDad Jim wrote:
Has there ever been any proposals for a deep-space TDRS-style
satellite for relaying telemetry from outer-planet missions such as
New Horizons et al?

I was thinking there may be some advantages in putting relay devices
in heliocentric orbit at, say, the orbit of Mars, to pick up telemetry
on those occasions when the Sun is between Earth and the exploring
spacecraft.

Also, wouldn't transmissions be easier to intercept from listening
spacecraft far away from Earth's ionosphere?

From conversations with one of the Galileo instruments folks
while it was on the way to Jupiter, one of the wild ideas that
was quickly discussed to salvage the mission after the main antennea
failed to deploy in a useful way was whether some kind of light,
relatively cheap relay satellite could be gotten to Jupiter.
The answer (not surprisingly) was no, not in any sensible
way. And for the same reasons it's a tough sell for most other
outer solar-system missions - it would have to have an enormous
transmission power to make up for the relative cheapness of
antenna collecting area on the ground. (Not to imply that the DSN
has always been well enough supported to take full advantage).
Another thing considered by the Galileo folks that may see
future use is covering a dry lake bed (for example) with a big
flat phased array, which works just fine for low-frequency
radio astronomy and would do likewise for data relay.

Relays do make sense for very short-duration missions and surface
operarations where there are competing time/power/size constraints.
That meant that the Galileo and Cassini orbiters acted as
storage and relay depots, and anything orbiting Mars has been
used to relay Spirit/Opportunity data. As you note, if we
get to the point of long-term human operations at Mars, there
would be utility to not losing contact for weeks at a time
during conjunction. Robotic probes can be set to do something
non-hazardous (as far as we can tell...), but you wouldn't
want people sitting around waiting for radio clearance. To avoid this,
the relay wouldn't need to be all that far from Earth, but the
balance between power and mass available would work differently
depending on which was favored. Lots of power means it woulc be farther
from Earth and use a smaller receiving antenna; lots of mass would
let you use a larger receiving antenna and have it farther from the
target world. For outer-system missions, though, the distances
become so large that you might as well pack the gear into probe
itself for all the good an intermediate relay does.

Bill Keel

In article ,
William C. Keel wrote:
...one of the wild ideas that was quickly
discussed to salvage the [Galileo] mission after the main antennea
failed to deploy in a useful way was whether some kind of light,
relatively cheap relay satellite could be gotten to Jupiter.
The answer (not surprisingly) was no, not in any sensible way...

However, as I understand it, the problem was not a technical one.
Technically, the idea made sense. With a modest dish antenna to point at
Earth, and even a small one to point at Galileo, the data rate could have
been vastly higher. The key is that the relay would have been *close* to
Galileo; being a factor of a thousand closer would give it a huge
advantage over even much-larger ground stations.

The problem was the timing. Even with a light spacecraft, getting it to
Jupiter in time for Galileo's primary mission would have required that it
be designed, built, and launched very quickly indeed. Getting the funding
and other resources needed for that, on such short notice, was almost
impossible. It might have been attempted if it had been the only way to
do the Galileo mission, but when people managed to put together a plan to
save much of the mission without it, that killed it.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

"William C. Keel" wrote in message
...
TVDad Jim wrote:
Has there ever been any proposals for a deep-space TDRS-style
satellite for relaying telemetry from outer-planet missions such as
New Horizons et al?

I was thinking there may be some advantages in putting relay devices
in heliocentric orbit at, say, the orbit of Mars, to pick up telemetry
on those occasions when the Sun is between Earth and the exploring
spacecraft.

Also, wouldn't transmissions be easier to intercept from listening
spacecraft far away from Earth's ionosphere?

From conversations with one of the Galileo instruments folks
while it was on the way to Jupiter, one of the wild ideas that
was quickly discussed to salvage the mission after the main antennea
failed to deploy in a useful way was whether some kind of light,
relatively cheap relay satellite could be gotten to Jupiter.

I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions. Pretty soon they will get so far away that
communications will be impossible. But if we launched a chaser
communications relay vehicle that could detect and communicate
with the Pioneer/Voyager spacecraft and with earth, we could extend
both Pioneer/Voyager's deep space capability by a factor of two.

"Rocky Top" wrote in message
news:yXMIh.213$Eg4.29@trnddc03...


From conversations with one of the Galileo instruments folks
while it was on the way to Jupiter, one of the wild ideas that
was quickly discussed to salvage the mission after the main antennea
failed to deploy in a useful way was whether some kind of light,
relatively cheap relay satellite could be gotten to Jupiter.

I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions. Pretty soon they will get so far away that
communications will be impossible. But if we launched a chaser
communications relay vehicle that could detect and communicate
with the Pioneer/Voyager spacecraft and with earth, we could extend
both Pioneer/Voyager's deep space capability by a factor of two.


Which one would you pick?

They're not all in the same place.

http://www.heavens-above.com/solar-escape.asp

I suppose you might pick Pioneer 11 and Voyager 2 since they're in the same
general vicinity though leaving the ecliptic in different directions.






--
Greg Moore
SQL Server DBA Consulting
Email: sql (at) greenms.com http://www.greenms.com

In article . net,
Greg D. Moore \(Strider\) wrote:
I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions...

Which one would you pick?
They're not all in the same place.
http://www.heavens-above.com/solar-escape.asp
I suppose you might pick Pioneer 11 and Voyager 2 since they're in the same
general vicinity though leaving the ecliptic in different directions.

Unfortunately, the Pioneers are dead(*). It's just Voyagers 1 and 2 now,
and they're heading out in quite different directions.

(* Pioneer 11 was last heard from in Nov 1995, although it wasn't being
monitored very often and it may have lasted into 1996. Pioneer 10's last
signal was heard on 22 Jan 2003, and was very weak with no intelligible
telemetry; nothing was heard in the next attempt on 7 Feb. )
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

"Henry Spencer" wrote in message
...
In article . net,
Greg D. Moore \(Strider\) wrote:
I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions...

Which one would you pick?
They're not all in the same place.
http://www.heavens-above.com/solar-escape.asp
I suppose you might pick Pioneer 11 and Voyager 2 since they're in the
same
general vicinity though leaving the ecliptic in different directions.

Unfortunately, the Pioneers are dead(*). It's just Voyagers 1 and 2 now,
and they're heading out in quite different directions.


Well, "dead" or simply too weak for existing technology to pick up.

I'm not sure we can say for sure. I believe they should still be capable of
broadcasting SOMETHING, just nothing we can pick up at this range.

But in any event, I agree, a relay sat is a non-starter.


(* Pioneer 11 was last heard from in Nov 1995, although it wasn't being
monitored very often and it may have lasted into 1996. Pioneer 10's last
signal was heard on 22 Jan 2003, and was very weak with no intelligible
telemetry; nothing was heard in the next attempt on 7 Feb. )
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |





--
Greg Moore
SQL Server DBA Consulting
Email: sql (at) greenms.com http://www.greenms.com

"Henry Spencer" wrote in message
...
Unfortunately, the Pioneers are dead(*).

So, did Commander Kruge destroy Pioneer 10 or 11?

"Greg D. Moore (Strider)" wrote in message
ink.net...
"Rocky Top" wrote in message
news:yXMIh.213$Eg4.29@trnddc03...


From conversations with one of the Galileo instruments folks
while it was on the way to Jupiter, one of the wild ideas that
was quickly discussed to salvage the mission after the main antennea
failed to deploy in a useful way was whether some kind of light,
relatively cheap relay satellite could be gotten to Jupiter.

I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions. Pretty soon they will get so far away that
communications will be impossible. But if we launched a chaser
communications relay vehicle that could detect and communicate
with the Pioneer/Voyager spacecraft and with earth, we could extend
both Pioneer/Voyager's deep space capability by a factor of two.


Which one would you pick?

They're not all in the same place.

http://www.heavens-above.com/solar-escape.asp

I suppose you might pick Pioneer 11 and Voyager 2 since they're in the
same general vicinity though leaving the ecliptic in different directions.


Whichever one is doing the most interesting science or whichever
one could do the most interesting science deeper into the cosmos.

Would the information capable of being collected be of any interest
very much deeper on?

Would it be worthwhile to send out an exo-solar misson with chaser
relays on a dedicated mission?

rt

In article yXMIh.213$Eg4.29@trnddc03,
Rocky Top wrote:
I always thought we should launch a chaser relay vehicle for the
Pioneer/Voyager missions. Pretty soon they will get so far away that
communications will be impossible. But if we launched a chaser
communications relay vehicle that could detect and communicate
with the Pioneer/Voyager spacecraft and with earth...

Unfortunately, if the chaser is at half the probe's distance, the signal
it hears from the probe is only a factor of four stronger than what Earth
hears. And the Earth stations have unlimited weight and power available
for big antennas and elaborate receivers, plus they have human maintenance
when things break. Consequently, good Earth stations are much better
receivers than what you could reasonably put on the chaser -- much more
than a factor of four better. So the chaser doesn't make sense.

Relay satellites only make sense when they are quite close to the probes
they are relaying for. But that won't help you much with sheer distance;
its big advantage is letting the probes (e.g., landers) use smaller
transmitters and antennas.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |