Last ion engine thrust puts ESA's SMART-1 on the right track for its Moon encounter

N° 56-2004 - Paris, 18 October 2004


Last ion engine thrust puts ESA's SMART-1 on the right track for its Moon
encounter

From 10 to 14 October the ion engine of ESA's SMART-1 carried out a
continuous thrust manoeuvre in a last major push that will get the
spacecraft to the Moon capture point on 13 November.

SMART-1, on its way to the Moon, has now covered more than 80 million
kilometres. Its journey started on 27 September 2003, when the spacecraft
was launched on board an Ariane 5 rocket from Europe's spaceport in Kourou,
French Guiana. Since then, it has been spiralling in progressively larger
orbits around Earth, to eventually be captured by the lunar gravity and
enter into orbit around the Moon in November this year.

The SMART-1 mission was designed to pursue two main objectives. The first is
purely technological: to demonstrate and test a number of space techniques
to be applied to future interplanetary exploration missions. The second goal
is scientific, mainly dedicated to lunar science. It is the technology
demonstration goal, in particular the first European flight test of a
solar-powered ion engine as a spacecraft's main propulsion system, that gave
shape to the peculiar route and duration (13 months) of the SMART-1 journey
to the Moon.

The long spiralling orbit around Earth, which is bringing the spacecraft
closer and closer to the Moon, is needed for the ion engine to function and
be tested over a distance comparable to that

a spacecraft would travel during a possible interplanetary trip. The SMART-1
mission is also
testing the response of a spacecraft propelled by such an engine during
gravity-assisted manoeuvres. These are techniques currently used on
interplanetary journeys, which make use of the gravitational pull of
celestial objects (e.g. planets) for the spacecraft to gain acceleration and
reach its final target while saving fuel.

In SMART-1's case, the Moon's gravitational pull has been exploited in three
"lunar resonance" manoeuvres. The first two successfully took place in
August and September 2004. The last resonance manoeuvre was on 12 October,
during the last major ion engine thrust, which lasted nearly five days, from
10 to 14 October. Thanks to this final thrust, SMART-1 will make two more
orbits around Earth without any further need to switch on the engine, apart
from minor trajectory correction if needed. The same thrust will allow the
spacecraft to progressively fall into the natural sphere of attraction of
the Moon and start orbiting around it from 13 November, when it is 60 000
kilometres from the lunar surface.

SMART-1 will reach its first perilune (initial closest distance from the
lunar surface) on 15 November, while the ion engine is performing its first
and major thrust in orbit around the Moon. After that it will continue
orbiting around the Moon in smaller loops until it reaches its final
operational orbit (spanning between 3000 and 300 kilometres over the Moon's
poles) in mid-January 2005. From then, for six months Smart-1 will start the
first comprehensive survey of key chemical elements on the lunar surface and
will investigate the theory of how the Moon was formed.

For further information, please contact :
ESA Media Relations Division
Tel: +33(0)1.53.69.7155
Fax: +33(0)1.53.69.7690


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Jacques :-)

www.spacepatches.info