[meteorite-list] ESO's Comet Wirtanen Images Help ESA's Rosetta Spacecraft Prepare to Ride on a Cosmic Bullet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:54:11 2004
Message-ID: <200202261732.JAA17335_at_zagami.jpl.nasa.gov>

http://www.eso.org/outreach/press-rel/pr-2002/phot-06-02.html

European Space Agency/European Southern Observatory
Press Release
N° 08-2002

Top class images help ESA's Rosetta prepare to ride on a cosmic bullet

Chase a fast-moving comet, land on it and 'ride' it while it speeds up
towards the Sun: not the script of a science-fiction movie, but the very
real task of ESA's Rosetta spacecraft. New observations with the European
Southern Observatory's (ESO) Very Large Telescope (VLT) provide vital
information about Comet Wirtanen - Rosetta's target - to help ESA reduce
uncertainties in the mission, one of the most difficult ever to be
performed.

Every 5.5 years Comet Wirtanen completes an orbit around the Sun. Wirtanen
has been seen during almost all its apparitions ever since its discovery
in 1948, but only recently have astronomers obtained detailed observations
that have allowed them to estimate the comet's size and behaviour. The
most recent of these observations was performed in December 2001 with the
Very Large Telescope (VLT), located at the Paranal Observatory (Chile). As
a result of these observations ESA will be able to refine plans for its
Rosetta mission.

Rosetta will be launched next year and it will reach Comet Wirtanen in
2011. By that time the comet will be as far from the Sun as Jupiter,
charging headlong towards the inner Solar System at speeds of up to
135,000 km/h. To get there and to be able to match the comet's orbit,
Rosetta will need to be accelerated by several planetary swing-bys, after
which the spacecraft - following a
series of difficult manoeuvres - will get close to the comet, enter into
orbit around it and release a lander from a height of about 1 km.

The VLT observations were planned specifically to investigate the activity
of Wirtanen at the time of the landing manoeuvres. These observations have
confirmed that - at the same distance from the Sun at which the landing
will take place (450 million km) - the activity on Wirtanen is very low.
This is very good news for the mission, because it means that there will
not be so much dust ejected as to make the landing dramatically difficult.

Comets are basically small frozen bodies made of ice and dust. When they
get close to the Sun the heat causes ices on the comet's surface to
"evaporate", and gas and dust grains are ejected into the surrounding
space forming the comet's atmosphere (coma) and the tail. In addition to
dropping a lander on the comet's nucleus for detailed in-situ
observations, Rosetta's task is to investigate the evolution of the comet
on its way to the Sun: in fact, Rosetta will keep orbiting around
Wirtanen up to the end of the mission in July 2013, at which time the
comet is at its closest approach to the Sun, at about 160 million km from
it.

VLT observations have also provided Rosetta mission planners with an
accurate measurement of their target's size: Wirtanen is only 1.2 km in
diameter, a true cosmic bullet.

"Rosetta is certainly a very challenging space mission. No one has ever
tried to land on a comet before," says Gerhard Schwehm, Rosetta's Project
Scientist. "We need to learn as much as possible about our target. The new
data will allow us to improve our models and make decisions once we get
there."

Note to editors

Rosetta's prime scientific goal is to unravel the origin of the Solar
System. The chemical composition of comets is known to reflect that of the
primordial nebula that gave birth to the Solar System - in the planets,
that primeval material has gone through complex processing, but not in the
comets. Therefore, Rosetta will allow scientists to look back 4.6 billion
years, to an epoch when the Solar System formed.

Previous studies by ESA's Giotto spacecraft and by ground-based
observatories have shown that comets contain complex organic molecules -
compounds that are rich in carbon, hydrogen, oxygen and nitrogen.
Intriguingly, these are the elements which make up nucleic acids and amino
acids, essential ingredients for life as we know it. Did life on Earth
begin with the help of comet seeding? Rosetta may help us to find the
answer to this fundamental question.

Rosetta carries 21 experiments in total . These are provided by scientific
consortia from institutes across Europe and the United States.

The Wirtanen observations by the VLT fall into a tradition of fruitful
collaboration between the European Space Agency (ESA) and the European
Southern Observatory (ESO). The two organizations are already combining
their efforts in several strategic areas, in order to facilitate the
synergy between space and ground facilities, where mutual sharing of
technology and procedures can result in substantial savings.

For more information please contact:
ESA - Communication Department
Media Relations Office
Paris, France
Tel: +33 (0)1 5369 7155
Fax: +33(0)1 5369 7690

Clovis De Matos - ESA
Science Programme Communication Service
Tel : +31 71 565 3460
Email : Clovis.De.Matos_at_esa.int

Rita Schulz - ESA Rosetta Deputy Project Scientist
Tel: +31 71 565 48 21
Email: Rita.Sculz_at_esa.int

For more information about Rosetta visit the ESA Science website at:
http://sci.esa.int/rosetta
More information on the ESA Science Programme can be found at:
http://sci.esa.int.
Information on ESA can be found at http://www.esa.int
This is a joint press Release by ESA and ESO. The ESO release can be found
at :
http://www.eso.org/outreach/press-rel/pr-2002/phot-06-02.html
Received on Tue 26 Feb 2002 12:32:58 PM PST