Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!rutgers!mcdchg!illusion!marcus
From: marcus@illusion.UUCP (Marcus Hall)
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle-ground communication and payloadprices
Message-ID: <386@illusion.UUCP>
Date: 29 Mar 89 17:38:56 GMT
References: <2099@botter.cs.vu.nl> <1989Mar20.191412.23335@utzoo.uucp> <1194@ncrcce.StPaul.NCR.COM> <1989Mar22.175026.1247@utzoo.uucp> <210
Reply-To: marcus@illusion.UUCP (Marcus Hall)
Organization: Magic Numbers Software, Bloomingdale, IL
Lines: 38

In article <2516@phred.UUCP> petej@phred.UUCP (Pete Jarvis) writes:
>In article <2102@botter.cs.vu.nl> wallagh@cs.vu.nl () writes:
>>I still don't understand why you need 3 satelites to cover all the 
>>communication with the Shuttle.
>>Aren't there enough tracking stations on the ground? 
>>There is (at least) a couple in the US, some in Europe and in Australia.
>>That should be enough , I think. But it isn't. Why?
>
>The TDRS satelites are designed to replace the ground tracking stations
>to save NASA $30 million a year.

Well, at $100 million for each TDRS, plus about $250 million in launch costs
(okay, so there were a few other things happening on the mission, but the TDRS
was the primary payload) we'll call it $300 million per TDRS in orbit.  Not
counting TDRS-C at all, the 3 TDRS's come to $900 million.  This would keep
a $30 million per year system of ground stations operating for 30 years.  Is
TDRS likely to last long enough to reach economic payback?  Note that NASA
already is planning for the follow-on advanced communication satellite, so
it doesn't seem like they're waiting for 30 years to replace the TDRSS.

>  They also fill in the gaps that the
>ground stations could not provide. They also provide for more timely
>down-linking of telemetry data from the Shuttles so they don't have to
>"save" it and down-link it later when they are over the appropriate
>ground station. Last, but not least, the TDRS will provide an important
>link to the Hubble Space Telescope allowing image data to be transmited
>to its ground station (Reston, Virginia) on a continous basis.
>
>Peter Jarvis - Physio-Control -- Redmond, WA.

Yes, there are other advantages to the TDRSS, and the ground stations would
need upgrading to get the communication capacity of the TDRSS,  and even then
it would not provide the constant coverage required for efficient use of
the HST, etc.  I think that you have to look at it as an enhancement of the
current capabilities instead of a cost-saving measure.

marcus hall
marcus@illusion.UUCP		..!mcdchg!illusion!marcus