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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!cs.utexas.edu!ut-emx!anita
From: anita@ut-emx.UUCP (Anita Cochran)
Newsgroups: sci.space,sci.space.shuttle,sci.astro
Subject: Re: Future Space Missions
Summary: not a shuttle launch
Message-ID: <20862@ut-emx.UUCP>
Date: 13 Nov 89 18:30:18 GMT
References: <2086@jato.Jpl.Nasa.Gov> <5569@cbnewsh.ATT.COM>
Distribution: na
Organization: The University of Texas at Austin, Austin, Texas
Lines: 41

In article <5569@cbnewsh.ATT.COM>, lmg@cbnewsh.ATT.COM (lawrence.m.geary) writes:
> In article <2086@jato.Jpl.Nasa.Gov> baalke@mars.jpl.nasa.gov (Ron Baalke) writes:
> >                         Future Space Missions
> > 
> >   o Cassini
> >       Possible launch in 1996, orbiter would spend 4 years studying Saturn and
> >       send an atmospheric probe into the moon Titan.
> 
> I have heard that Cassini will also use an Earth flyby to gain speed.
> I assume this means that these probes are using underpowered boosters
> and launching from the shuttle, as was the case with Galileo. This was
> done with Galileo because it was too late - or would cost too much, or
> the probe was too heavy - to refit the probe for launch on an ELV with
> a Centaur upper stage. But WHY in heavens name is JPL sticking to this
> method for probes planned for far in the future? 
> Why aren't there plans to use appropriate boosters?
> 

You are wrong in what you heard about the launch method for Cassini.  Both
CRAF and Cassini are NOT shuttle launches. Since they were being planned
around the time of the Challenger explosion, NASA realized relying totally
on the Shuttle was not a good idea.  Instead, both of these missions
will launch on a Titan IV with Centaur upper stage.  This is not
the most powerful combination we have ever had but it will work.
And yes, there will be an earth flyby to gain velocity.

Galileo would have been fine with a shuttle launch as originally planned.
However, when the Challenger blew, it was decided that the IUS was
potentially too dangerous.  Thus, they went to the Centaur.  That is why
they had the earth flyby on Galileo.  Cassini has another very important
constraint on launch characteristics.  If it launches much later than
scheduled, it will not be able to use the Jupiter gravity assist which
is so important to getting to Saturn since Jupiter will move out of
position with respect to Saturn.


-- 
 Anita Cochran  uucp:  {noao, ut-sally, ut-emx}!utastro!anita
                arpa:  anita@astro.as.utexas.edu  
                snail: Astronomy Dept., The Univ. of Texas, Austin, TX, 78712
                at&t:  (512) 471-1471