[meteorite-list] Rosetta Monitors Deep Impact

[Ron Baalke]

http://www.esa.int/SPECIALS/Rosetta/SEMCOZ1DU8E_0.html

Rosetta monitors Deep Impact
European Space Agency 
20 June 2005

ESA's comet chaser Rosetta will take part in one of the world's largest
astronomical observation campaigns - the Deep Impact event - while on
its cruise to Comet 69P/Churyumov-Gerasimenko. Rosetta will be watching
from 29 June to 14 July 2005.
 
Deep Impact is a NASA mission to send a 370 kg copper "impactor" probe
to Comet 9P/Tempel 1 on 4 July 2005. Tempel 1 is a short-period comet,
whose orbit runs between those of Mars and Jupiter. There is scientific
interest in comets because their composition carries important
information about the origin of the Solar System, as they have remained
basically unchanged since then.

Rosetta, with its set of very sensitive instruments for cometary
investigations, will use its capabilities to observe Tempel 1 before,
during and after the impact. At a distance of about 80 million
kilometres from the comet, which will be lying about 90 degrees from the
Sun, Rosetta will be in the most privileged position to observe the
event from space.

The observing geometry will be favourable for observations with
Rosetta's microwave spectrometer, MIRO, and the VIRTIS visual and IR
mapping spectrometer. MIRO will concentrate on the chemical composition
and temperature of the gas. VIRTIS will analyse thermal emission by the
comet to determine the composition of the dust ejected, and thus reveal
the comet's mineralogy.

In addition, Rosetta will be the spacecraft carrying the best available
ultraviolet instrument, ALICE, to monitor the event. ALICE will analyse
the gas coming from the impact and tell about its chemical composition.

The Rosetta OSIRIS imaging system will also provide images of the
comet's nucleus from a far-away distance. Scientists also hope to make a
3D reconstruction of the dust cloud around the comet by combining the
OSIRIS images with those taken from ground observatories.

Rosetta's observations will provide a unique data set complementary to
the observations from the Deep Impact spacecraft and the ground-based
telescopes. Before impact, Rosetta will observe Tempel 1 during three
full rotations of the comet around its axis. This allows characterising
the variations of the comet's state over rotation and time, and
preparing for the observations during and after impact.

Rosetta will look at the comet continuously. In the initial phase
(starting on 29 June 01:34 CEST), when the comet is expected to change
only slowly due to its rotation, Rosetta will take the time to study or
"dwell" on several areas on the coma of Tempel 1.

About fifteen minutes before impact (due at 07:44 CEST), Rosetta will
start observing the comet with shorter dwell time, as fast changes are
expected due to the impact. At 09:19, about one hour and a half after
impact, Rosetta will go back to the monitoring mode as before the impact
for 10 more days.

Rosetta will contribute to the major objectives of the Deep Impact mission.

The spacecraft's instruments will measure the composition of the crater
and its ejected material - a cloud of dust and gas cloud expected to
expand and reach its maximum brightness about 10 hours after impact.
Rosetta will also monitor the changes in the natural outgassing of the
comet following the impact.

With these observations, Rosetta may also help to confirm if the impact
has permanently triggered new activity on the comet.

For more information:
 
Gerhard Schwehm, ESA Rosetta Project Scientist
E-mail: gerhard.schwehm @ esa.int