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What Is Soyuz Using For Comm These Days?



 
 
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  #1  
Old May 20th 08, 05:08 PM posted to sci.space.policy,sci.space.history
Rand Simberg[_1_]
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Default What Is Soyuz Using For Comm These Days?

Anyone know? Do they have a TDRSS system as part of the ISS
agreement?
  #2  
Old May 21st 08, 05:21 AM posted to sci.space.policy,sci.space.history
Jorge R. Frank
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Default What Is Soyuz Using For Comm These Days?

Rand Simberg wrote:
Anyone know? Do they have a TDRSS system as part of the ISS
agreement?


No - they have a TDRSS-like system called Altair, and there may be a
satellite or two from that system still running, but Soyuz isn't
equipped with an antenna for it. It relies on ground stations for comm,
and all the ground stations are in Russian territory.

(For that matter, I don't think the Lira antenna on the Zvezda module
intended to communicate via Altair was ever fully deployed.)
  #3  
Old May 21st 08, 01:07 PM posted to sci.space.policy,sci.space.history
Rand Simberg[_1_]
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Default What Is Soyuz Using For Comm These Days?

On Tue, 20 May 2008 23:21:16 -0500, in a place far, far away, "Jorge
R. Frank" made the phosphor on my monitor glow
in such a way as to indicate that:

Rand Simberg wrote:
Anyone know? Do they have a TDRSS system as part of the ISS
agreement?


No - they have a TDRSS-like system called Altair, and there may be a
satellite or two from that system still running, but Soyuz isn't
equipped with an antenna for it. It relies on ground stations for comm,
and all the ground stations are in Russian territory.

(For that matter, I don't think the Lira antenna on the Zvezda module
intended to communicate via Altair was ever fully deployed.)


Actually, I got an email response from Oberg:

"Mir used to have a TDRSS-like system called 'Luch', and a dish
antenna capable of communicating with the GEO relay satellite is
installed on the Service Module now linked to ISS.

But it's never worked. The old system broke down and wasn't replaced
in the 1990's. There are one or two payloads already built, at the
Reshetnev plant in Krasnoyarsk, but they won't deliver them until the
Russian Space Agency pays cash -- and by now, their components have
probably exceed their warranties anyway.

The Russians have a voice relay capability through the NASA TDRSS, but
can't relay TV or telemetry, so they conduct how-criticality
operations such as dockings or spacewalks only when passing over
Russian ground sites. They don't even have ocean-going tracking ships
any more -- all sold for scrap [one is in drydock as a museum]."
  #5  
Old May 21st 08, 08:33 PM posted to sci.space.policy,sci.space.history
[email protected]
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Default What Is Soyuz Using For Comm These Days?

On May 21, 12:47 pm, Damon Hill wrote:

Are there any commercial GEO data link services that could serve
low orbit satellites? Seems like there'll be a market sooner or later
where store-and-dump doesn't cut the mustard.

--Damon


market for what LEO spacecraft?

  #7  
Old May 22nd 08, 12:05 AM posted to sci.space.policy,sci.space.history
Scott Dorsey
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Default What Is Soyuz Using For Comm These Days?

Rick Jones wrote:

I wonder how much of Iridium still works, or how many satellite ISP's
there are around the globe and how well a "base station" moving
across/below them at 17000 MPH would work...assuming the base station
kept a dish pointing at one or another of the ISP's satellites in GEO.
Terrestar perhaps if it manages to launch? (although that would be NA
only I guess)


All of Iridium works. The whole constellation isn't up there, but you
can pick up the phone anywhere in the world and get a call through.
Iridium is pretty heavily used.

There are actually a lot of satellite phone services and ISPs around
the globe, but most of them are using satellites that target only a
very small area. Iridium works anywhere, and it's a hell of a lot cheaper
than INMARSAT.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #8  
Old May 22nd 08, 12:32 AM posted to sci.space.policy,sci.space.history
Rick Jones
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Default What Is Soyuz Using For Comm These Days?

In sci.space.history Scott Dorsey wrote:
All of Iridium works. The whole constellation isn't up there, but
you can pick up the phone anywhere in the world and get a call
through. Iridium is pretty heavily used.


That got me looking them up on the web - the production rate they
achieved with the satelites was impressive if the wikipedia article is
at all accurate. Almost like the satellite equivalent to a liberty
ship 21 days to make a satellite, one coming off the line every 4.3
days. That starts to sound like "responsive" in the context of some
of the other posts in the group.

The 1500 millisecond latency quoted for TCP was equally astounding if
not as positive I wonder how much of that is bandwidth and how much
of that is hopping around. IIRC 1500 milliseconds is enough time for
6 GEO hops - ~250 milliseconds for each up and down to GEO - so that
makes me wonder where all that latency happens to be if the satellites
are only 480 odd miles up. Perhaps it is the baud rate.

rick jones
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where do you want to be today?
these opinions are mine, all mine; HP might not want them anyway...
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  #9  
Old May 22nd 08, 01:09 AM posted to sci.space.policy,sci.space.history
Scott Dorsey
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Default What Is Soyuz Using For Comm These Days?

Rick Jones wrote:

The 1500 millisecond latency quoted for TCP was equally astounding if
not as positive I wonder how much of that is bandwidth and how much
of that is hopping around. IIRC 1500 milliseconds is enough time for
6 GEO hops - ~250 milliseconds for each up and down to GEO - so that
makes me wonder where all that latency happens to be if the satellites
are only 480 odd miles up. Perhaps it is the baud rate.


It's all latency from hopping around, that's not related at all to the
bandwidth limitations. There are some tweaks you have to do with some
TCP/IP parameters (and that includes cranking buffers way up and using
the dynamic window size stuff), but you can actually get some pretty
good throughput for file transfers. It's no fun for a telnet connection,
though.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."
  #10  
Old May 22nd 08, 01:43 AM posted to sci.space.policy,sci.space.history
Rick Jones
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Default What Is Soyuz Using For Comm These Days?

In sci.space.history Scott Dorsey wrote:
It's all latency from hopping around, that's not related at all to the
bandwidth limitations. There are some tweaks you have to do with some
TCP/IP parameters (and that includes cranking buffers way up and using
the dynamic window size stuff),


You mean the RFC 1323 "large window" extensions (window scaling)?

Assuming that 1500 milliseconds is a round-trip latency, the ever fun:

Tput Window/RTT

Would suggest that the classic TCP window of 65535 bytes would limit one to:

Tput 65535Bytes/1.5S

or ~42KB/s (K == 1024) no matter how much more bandwidth there was out
there. Still, I thought the wikipedia article was claiming a rather
lower baudrate than that?

but you can actually get some pretty good throughput for file
transfers. It's no fun for a telnet connection, though.


Indeed.

rick jones
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oxymoron n, commuter in a gas-guzzling luxury SUV with an American flag
these opinions are mine, all mine; HP might not want them anyway...
feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH...
 




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