Rosetta teams up with New Horizons (Forwarded)

ESA News
http://www.esa.int

2 March 2007

Rosetta teams up with New Horizons

ESA and NASA are mounting a joint campaign to observe Jupiter over the next
few weeks with two different spacecraft. Rosetta will watch the big picture
from its current position near Mars, whilst New Horizons will take close-up
data as it speeds past the largest planet in our Solar System on its journey
to Pluto.

The co-ordinated observational campaign of Jupiter using Rosetta and New
Horizons began this week. Jupiter remains a fascinating world of scientific
mystery. "This is an excellent opportunity to test both spacecraft and to
collect valuable science data," says Gerhard Schwhem, Rosetta's Mission
Manager.

"We couldn't pass up this opportunity to study Jupiter's meteorology, rings,
aurorae, satellites, and magnetosphere," says Alan Stern, Southwest Research
Institute, Colorado, and New Horizon's Principal Investigator.

One of Rosetta's targets will be the doughnut-shaped ring of electrically
charged gas that circles Jupiter. Known as the Io torus, it lies in Io's
orbit and is at its most dense near the volcanic moon, Io.

The best theory for its formation is that Io's volcanoes throw sulphur and
sulphur dioxide into space during their eruptions. In space, the atoms and
molecules are stripped of their electrons, electrically charging them and
turning them in ions. These become trapped by Jupiter's powerful magnetic
field and are pulled around every ten hours by the Jupiter's rotation. The
result is that the Io torus circles Jupiter at Io's orbital radius.

The idea for the joint observations came from Stern. As well as leading New
Horizons, he is also the principal investigator for Rosetta's ALICE
instrument.

ALICE is the ultraviolet imaging spectrometer. Designed to analyse gases
being given off by Rosetta's target comet, it will allow scientists to
deduce the production rates of water vapour, carbon monoxide and carbon
dioxide. For the current campaign, it will be the key instrument used to
observe Jupiter. Joining the observations will be VIRTIS (the Visible and
Infrared Thermal Imaging Spectrometer) and OSIRIS (the Optical,
Spectroscopic, and Infrared Remote Imaging System).

Rosetta will study Jupiter for between 6 and 8 days in total, spread over
the next few weeks. Each time Rosetta opens its eyes to look at Jupiter, it
will do so for several hours at a time, collecting as much light from the
faraway planet as possible. "Rosetta will give us the big picture context in
which to see the up-close data from New Horizons," says Stern. During this
time, New Horizons will be riding the long tail of magnetism that stretches
out behind Jupiter and funnels charged particles away.

Rosetta's ALICE was the prototype for the ultraviolet imaging instrument
flying on New Horizons. At Pluto, New Horizons' ALICE will be used to study
the tiny world's tenuous atmosphere.

ESA's Rosetta was launched on 2 March 2004 and is currently circling the
inner solar system using close fly-bys of the Earth and Mars planets to
alter its orbit and eventually swing it out towards Jupiter's orbit, where
it will rendezvous with comet Churyumov-Gerasimenko in 2014.

Such ventures add value to the science that can come out of the Rosetta
mission. "I am sure that this is fascinating science," says Schwhem.

For more information:

Alan Stern
New Horizons Principal Investigator
and
Rosetta's ALICE Principal Investigator
Southwest Research Institute, Colorado, USA
Email: astern @ swri.edu

Gerhard Schwehm
ESA Rosetta Mission Manager
Email: gerhard.schwehm @ esa.int

Rita Schulz
ESA Rosetta Project Scientist
Email: rita.schulz @ esa.int

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