Andrew Yee[_1_]
June 28th 09, 04:59 PM
ESA News
http://www.esa.int
26 June 2009
Joint ESA/NASA Ulysses mission to end
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 ]
http://www.esa.int
26 June 2009
Joint ESA/NASA Ulysses mission to end
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 ]