Rosetta performs ESA's closest-ever Earth fly-by

N° 13-2005 - Paris, 5 March 2005

Rosetta performs ESA's closest-ever Earth fly-by

The European Space Agency's Rosetta spacecraft yesterday performed ESA's
closest-ever Earth fly-by, gaining an essential gravity boost in its
ten-year, 7.1 billion kilometre flight to Comet 67P/Churyumov-Gerasimenko.
At closest approach, at 22:09:14 GMT, Rosetta passed above the Pacific Ocean
just west of Mexico at an altitude of 1954.74 km and a velocity relative to
the Earth of 38 000 kph.

The passage through the Earth-Moon system allowed ground controllers to test
Rosetta's 'asteroid fly-by mode' (AFM) using the Moon as a 'fake' asteroid,
rehearsing the fly-bys of asteroids Steins and Lutetia due in 2008 and 2010
respectively. The AFM test started at 23:01 GMT and ran for nine minutes
during which the two onboard navigation cameras successfully tracked the
Moon, allowing Rosetta's attitude to be automatically adjusted.

Before and after closest approach, the navigation cameras also acquired a
series of images of the Moon and Earth; these data will be downloaded early
today for ground processing and are expected to be available by 8 March.

In addition, other onboard instruments were switched on, including ALICE
(ultraviolet imaging spectrometer), VIRTIS (visible and infrared mapping
spectrometer) and MIRO (microwave instrument for the Rosetta orbiter), for
calibration and general testing using the Earth and Moon as targets.
The fly-by manoeuvre swung the three-tonne spacecraft around our planet and
out towards Mars, where it will make a fly-by on 26 February 2007. Rosetta
will return to Earth again in a series of four planet fly-bys (three times
with Earth, once with Mars) before reaching Comet 67P/Churyumov-Gerasimenko
in 2014, when it will enter orbit and deliver a lander, Philae, onto the
surface.

The fly-bys are necessary to accelerate the spacecraft so as to eventually
match the velocity of the target comet. They are a fuel-saving way to boost
speed using planetary gravity.

Yesterday's fly-by came one year and two days after launch and highlights
the valuable opportunities for instrument calibration and data gathering
available during the mission's multi-year voyage.

In just three months, on 4 July, Rosetta will be in a good position to
observe and gather data during NASA's spectacular Deep Impact event, when
the Deep Impact probe will hurl a 380 kg projectile into Comet Tempel 1,
revealing data on the comet's internal structure. Certain of Rosetta's
unique instruments, such as its ultraviolet light instrument ALICE, should
be able to make critical contributions to the American mission.

About Rosetta
Rosetta is the first mission designed to both orbit and land on a comet, and
consists of an orbiter and a lander. The spacecraft carries 11 scientific
experiments and will be the first mission to undertake long-term exploration
of a comet at close quarters. After entering orbit around Comet
67P/Churyumov-Gerasimenko in 2014, the spacecraft will release a small
lander onto the icy nucleus. Rosetta will orbit the comet for about a year
as it heads towards the Sun, remaining in orbit for another half-year past
perihelion (closest approach to the Sun). Comets hold essential information
about the origin of our Solar System because they are the most primitive
objects in the Solar System and their chemical composition has changed
little since their formation. By orbiting and landing on Comet
67P/Churyumov-Gerasimenko, Rosetta will help us reconstruct the history of
our own neighbourhood in space.


Note for broadcasters:
The ESA TV Service will transmit a TV exchange with images of the fly-by,
together with science results/images from observations as far as available
on 11 March. For further details : http://television.esa.int





For further information please contact:
ESA Media Relations Division
Te: +33(0)1.5369.7155
Fax: +33(0)1.5369.7690

ESA Science Programme Communication Service
Te: +31(0) 71.565.3273
Fax: +31(0)71.565.4101



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Jacques :-)

www.spacepatches.info