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Fw: Press Release Nr 39-2001 - ESA and NASA agree new mission scenario for Cassini-Huygens

In case some on the BB have not seen this...

I wonder who worked out that the problem existed - he/she should get a
prize. Maybe track them down to address an AMSAT Convention! sometime?


Graham G3VZV

----- Original Message -----
From: ESA Media Relations <ContactESA@esa.int>
Sent: 29 June 2001 16:43
Subject: Press Release Nr 39-2001 - ESA and NASA agree new mission scenario
for Cassini-Huygens

> Paris, 29 June 2001
> Press Release
> N° 39-2001
> ESA and NASA agree new mission scenario for Cassini-Huygens
> A new mission scenario has been identified in order to solve the Huygens
> radio communications problem and fully recover the scientific return from
> the Cassini-Huygens mission to Saturn and its giant moon Titan.
> After six months of investigations and analysis by a joint ESA/NASA
> Huygens Recovery Task Force (HRTF), senior management from the two space
> agencies and members of the Cassini-Huygens scientific community have
> endorsed several modifications to the mission. These will ensure a return
> close to 100% of the Huygens science data, with no impact on the nominal
> prime Cassini tour after the third Titan encounter.
> The modifications have been introduced because of a design flaw in the
> Huygens communication system. This problem meant that the Huygens receiver
> was unable to compensate for the frequency shift between the signal
> emitted by the Probe and the one received by the Orbiter, due to the
> Doppler shift (**). This would have resulted in the loss of most of the
> unique data returned from the Probe during its descent through Titan's
> dense atmosphere.
> To ensure that as much data as possible is returned from the pioneering
> Probe, the HRTF proposed a new schedule for Cassini's first orbits around
> Saturn.
> The agreed scenario involves shortening Cassini's first two orbits around
> the ringed planet and adding a third which provides the required new
> geometry for the Huygens mission to Titan.
> In the new scenario, the arrival at Saturn on 1 July 2004 remains
> unchanged. However, Cassini's first flyby of Titan will now occur on 26
> October, followed by another on 13 December. The Huygens Probe will be
> released towards Titan on 25 December, for an entry into the moon's
> atmosphere 22 days later, on 14 January 2005, seven weeks later than
> originally planned.
> To reduce the Doppler shift in the signal from Huygens, the Cassini
> Orbiter will fly over Titan's cloud tops at a much higher altitude than
> originally planned - 65,000 km instead of 1,200 km. This higher orbit has
> the added advantage that Cassini will be able to preserve the four-year
> baseline tour through the Saturn system, by resuming its original orbital
> plan in mid-February 2005.
> "In any complex space mission problems may arise," said John Credland,
> Head of ESA's Space Science Projects Department. "The measure of an
> organisation is the manner in which it recovers."
> The new mission scenario will have some impact on Cassini's propellant
> supply, consuming about a quarter of the Orbiter's reserve fuel by the end
> of the four-year mission. It also involves several modifications to ensure
> maximum efficiency of the Huygens communications system. These include
> pre-heating the Probe to improve tuning of the transmitted signal,
> continuous commanding by the Orbiter to force the receiver into
> non-Doppler mode, and changes in the Probe's on-board software.
> "I am very happy that we have found a good engineering solution," said Kai
> Clausen, ESA's Integral Project Manager and co-chairman of the HRTF. "But
> a lot more work still needs to be done. Now we need to complete the
> detailed design, implementation, validation and testing over the next few
> years."
>  "There are still some uncertainties, for example the exact definition of
> the landing site, but these are minor problems," said Jean-Pierre
> Lebreton, ESA's Huygens Project Scientist. "What is important is that we
> have found the solution. It is now time for fine tuning."
> The ESA Director of Science, David Southwood, and the NASA Associate
> Director for Space Science, Edward Weiler, have jointly agreed to the new
> mission approach and have asked the HRTF to hand over to the project teams
> in July for implementation of the joint recommendations.
>  (**) The Doppler shift is a measure of the difference in tone between an
> emitted and a received wave (e.g. radio) when the transmitting source and
> the receiver move one with respect to the other.
> Note to editors
> Cassini-Huygens is a joint NASA/ESA mission with the participation of the
> Italian Space Agency (ASI) launched by a Titan IVB/Centaur launch vehicle
> on 15 October 1997, that will reach Saturn in 2004. It consists of NASA's
> orbiter Cassini and ESA's probe Huygens. While Cassini continues to
> explore Saturn and its rings, the Huygens probe will be released to
> parachute through the atmosphere of Titan. Shrouded in an orange haze that
> hides its surface, Titan is one of the most mysterious objects in our
> Solar System. It is the second largest moon (only Jupiter's Ganymede is
> bigger), and the only one with a thick atmosphere. It is this atmosphere
> that excites scientific interest, since it is thought to resemble that of
> a very young Earth.
> For further information please contact:
> ESA - Communication Department
> Media Relations Office
> Tel: +33(0)
> Fax: +33(0)
> John Credland, ESA - Head of Space Science Projects Department
> Tel: +31 71 565 3430
> Email: John.Credland@esa.int
> Dolores Beasley, NASA Headquarters, Washington DC
> Tel. + 1 202/358-1758
> Guy Webster, Jet Propulsion Laboratory, Pasadena, CA
> Tel. + 1 818/354-6278
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