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From: hthomas@irisa.fr (Henry Thomas)
Newsgroups: sci.space,sci.astro
Subject: Re: CRAF/Cassini Update - 11/09/90
Message-ID: <1990Nov13.104319.11134@irisa.fr>
Date: 13 Nov 90 10:43:19 GMT
References: <1990Nov11.001924.10302@jato.jpl.nasa.gov> <7034.273fd310@abo.fi>
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Reply-To: Henry.Thomas@irisa.fr
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In article <7034.273fd310@abo.fi>, mlindroos@abo.fi writes:
|> In article <1990Nov11.001924.10302@jato.jpl.nasa.gov>, baalke@mars.jpl.nasa.gov (Ron Baalke) writes:
|> > 
|> >                          CRAF/Cassini Status Report
|> >                              November 9, 1990
|> > ...take the Huygens probe about 3 hours to parachute all the way down to the
|> > surface of Titan; if the probe survives the landing, valuable data will
|> > continue to be transmitted back for about 30 more minutes.  No more data will
|> > be returned to the Cassini orbiter from Huygens on any subsequent orbits, as
|> > the battery onboard Huygens will have rundown by then.
|> > 
|> 
|> 30 minutes! Why can't we send an advanced long-life, Viking-style probe
|> to Titan instead?! The Viking lander was "only" about twice as heavy as the 
|> Huygens probe will be so the lack of a powerful-enough launcher surely cannot 
|> be the reason? Is this just because of financial considerations again, or...?

The reason is maybe that we have NO data of the condition down there: 
	- Is there any *solid* ground ?
	- pressure ?
	- temperature ?
So with no information, it seems difficult to design a long-life probe.
A similar(?) problem occured on Venus, where the probes Venera 11-14 lasted only a few hours. The first ones didn't reached the ground because theirs parachutes where destroyed by the acid atmosphere. 
On mars, the informations where much more complete, because the ground had been observed by many orbital probes: it was visible.

There was an excellent article in the ESA journal (?), some month ago about "Cassini Probe  Huygens Entry techniques" .


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