Following the decision not to launch Europe’s comet chaser, Rosetta, in
January, scientists and engineers in the programme have been examining
several alternative mission scenarios.

Each has been looked at on the basis of the expected scientific return,
the technical risks related to using the Rosetta design in the new
mission, and the containment of costs.

Of the nine mission scenarios studied by the Rosetta Science Working Team,
three have survived to this point and were presented to the delegations of
the ESA Member States through the Science Programme Committee at its
meeting on 25/26 February. Two mission scenarios (in February 2004 and
2005 respectively) would take Rosetta to a new target comet,
Churyumov-Gerasimenko, while another (in January 2004) would take it to
its original target, Comet Wirtanen.

All three options are now being studied in detail so that the final
decision can be made. A campaign of observations using both the NASA/ESA
Hubble Space Telescope and the instruments of the European Southern
Observatory is under way to study Comet

Churyumov-Gerasimenko. In this way, astronomers will be able to
characterise the comet and perform a mission analysis, also to identify
landing scenarios and make a thorough assessment of any hardware
modification that would be necessary.

In parallel, ESA is assessing the launch requirements for the various
mission scenarios. This will include looking at alternatives to Ariane as
back-up options, such as the Russian Proton rocket.

The final decision on Rosetta’s new mission scenario will be made by the
ESA Science Programme Committee in May.

Note to editors

Following the failure of Ariane Flight 157 in December, with the loss of
two spacecraft, ESA and Arianespace took the joint decision not to launch
Rosetta during its January launch window. This meant that Rosetta’s
originally intended mission to Comet Wirtanen had to be abandoned.

For more information please contact:

ESA Communication Department
Media Relations Office
Paris, France
Tel: +33(0)15369 7155
Fax: +33(0)1 5369 7690

For more information about the ESA Science Programme, visit:
http://sci.esa.int

For more information about ESA, visit:
http://www.esa.int