>
> ------------------------------
>
> Date: Sun, 28 Jun 2009 21:24:02 -0700
> From: Ron Baalke <baalke@...>
> Subject: Joint ESA/NASA Ulysses Mission to End
>
> http://www.esa.int/esaCP/SEM3C61P0WF_FeatureWeek_1.html
>
> Joint ESA/NASA Ulysses mission to end
> European Space Agency
> 26 June 2009
>
> Upon receipt of the last command from Earth, the transmitter on Ulysses will
> switch off on 30 June, bringing one of the most successful and longest
> missions in spaceflight history to an end.
>
> After 18.6 years in space and defying several earlier expectations of its
> demise, the joint ESA/NASA solar orbiter Ulysses will achieve 'end of
> mission' on 30 June 2009. The final communication pass with a ground station
> will start at 17:35 CEST and run until 22:20 CEST (15:35-20:20 UTC) or until
> the final command is issued to switch the satellite's radio communications
> into 'monitor only' mode. No further contact with Ulysses is planned.
>
> Ulysses is the first spacecraft to survey the environment in space above and
> below the poles of the Sun in the four dimensions of space and time. Among
> many other ground-breaking results, the hugely successful mission showed
> that the Sun's magnetic field is carried into the Solar System in a more
> complicated manner than previously believed. Particles expelled by the Sun
> from low latitudes can climb up to high latitudes and vice versa, even
> unexpectedly finding their way down to planets.
>
> Expanding our understanding of the Sun
>
> This is very important as regions of the Sun not previously considered as
> possible sources of hazardous particles for astronauts and satellites must
> now be taken into account and carefully monitored.
>
> "Ulysses has taught us far more than we ever expected about the Sun and the
> way it interacts with the space surrounding it," said Richard Marsden, ESA's
> Ulysses Project Scientist and Mission Manager.
>
> The shut-down of the satellite is a joint decision of the two agencies and
> comes a year after the mission was expected to end.
>
> Weakened power supply
>
> A year ago, the satellite's power supply had weakened to the point that it
> was thought the low temperatures would cause the fuel lines to freeze up,
> rendering Ulysses uncontrollable.
>
> This didn't happen immediately and spacecraft controllers realised that they
> could keep the fuel warm and circulating by performing a short thruster burn
> every two hours, an ingenious solution that has enabled Ulysses' science
> mission to continue. It was decided to maintain the spacecraft in operation
> using NASA's 70 m-diameter ground station network allocated on a
> 'spare-capacity' basis.
>
> But as Ulysses has moved further from Earth, the communications bit-rate has
> gone down while other demands for the 70 m-diameter Deep Space Network
> stations have gone up. Most importantly, the overall return of scientific
> data has decreased to a level where it is hard to justify the cost of
> keeping Ulysses in operation.
>
> Longevity a tribute to builders and operators
>
> "We expected the spacecraft to cease functioning much earlier. Its longevity
> is a tribute to Ulysses's builders and the people involved in operations
> over the years," says Paolo Ferri, Head of the Solar & Planetary Missions
> Division at ESA's European Space Operations Centre, Darmstadt, Germany.
>
> He added that, "Although it is always hard to take the decision to terminate
> a mission, we have to accept that the satellite is running out of resources
> and a controlled switch-off is the best ending."
>
> Final mission operations will be conducted from the Ulysses Mission Support
> Area (MSA) located at NASA's Jet Propulsion Laboratory in California, USA.
> The joint team will include Nigel Angold, ESA Mission Operations Manager,
> and Ed Massey, NASA Project Manager, as well as a number of engineers and
> analysts from both Agencies.
>
> "Tuesday will be a very sad day when we send the last commands to Ulysses,"
> said Angold. "But I'm very proud that we have overcome the many challenges
> that have come our way over the course of nearly two decades. Its longevity
> is an indication of the desire for international collaboration on space
> missions. ESA and NASA are to be commended for supporting this unique
> mission until the very end," he added.
>
> After shut-off, Ulysses will continue to orbit the Sun, becoming in effect a
> man-made 'comet'.
>
> "Whenever any of us look up in the years to come, Ulysses will be there,
> silently orbiting our star, which it studied so successfully during its long
> and active life," said Marsden.
>
> [NOTE: Images and weblinks supporting this release are available at
> http://www.esa.int/esaCP/SEM3C61P0WF_FeatureWeek_1.html ]
>

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