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RE: Huygens Frequencies - more info



The best part of the story is how they defeated the problem.

By rearranging the mission so as to minimize doppler between Cassini
and Huygens at the time of landing.  They really were seriously
worried because at launch they thought of dumping Huygens off at the
earliest possible moment and when the serious error in the design of
the data receiver onboard Cassini was discovered, it required changing
the geometry of the mission.  Anyway, it could not have worked out
better.

Smeds, the engineering hero of this story, to his great credit had to
fight like hell to get his tests and fixes introduced.  The results, so far
as we are able to see them, are remarkable.  I hope they give him a
huge medal.

Bob
N4HY



-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org]On
Behalf Of Graham Shirville
Sent: Sunday, January 16, 2005 3:10 PM
To: amsat-bb@amsat.org
Subject: [amsat-bb] Huygens Frequencies - more info


I had been looking for some information about the frequencies that were used
by the Huygens Titan lander to communicate back to the Cassini mothership
and found this article about a design error that was found in time.

It is a long article but an interesting detective type story about Mr
Doppler!

http://www.spectrum.ieee.org/WEBONLY/publicfeature/oct04/1004titan.html

The Huygens transmitter was actually on 2040MHz with a carrier power of
around 3.5 watts to a 3dBi antenna. This signal was heard by a number of
Radio telescopes on the earth which will enable them to locate the landing
position to an accuracy of around 1 km and the wind speed during the landing
phase to within 1 metre per sec

All amazing stuff considering the path length is around a billion
kilometres.

cheers

Graham G3VZV
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