No 30-2006         Paris, 17 August 2006

Europe rediscovers the Moon with SMART-1

Now Europe too can say it has been to the Moon. In the early morning of 3
September this year (at 07:41 Central European Summer Time, as currently
estimated), the European Space Agency's SMART-1 mission will end its exploration
adventure through a small impact on the lunar surface.

The whole story began in September 2003, when an Ariane 5 launcher blasted off
from Kourou, French Guiana, to deliver the European Space Agency's lunar
spacecraft SMART-1 into Earth orbit. SMART-1 is a small unmanned satellite
weighing 366 kilograms and roughly fitting into a cube just 1 metre across,
excluding its 14-metre solar panels (which were folded during launch).

After launch and injection into an elliptical orbit around the Earth, the gentle
but steady push provided by the spacecraft's highly innovative electric
propulsion engine forcefully expelling xenon gas ions caused SMART-1 to spiral
around the Earth, increasing its distance from our planet until, after a long
journey of about 14 months, it was "captured" by the Moon's gravity.

To cover the 385,000 km distance that separates the Earth from the Moon if one
travelled in a straight line, this remarkably efficient engine brought the
spacecraft on a 100 million km long spiralling journey on only 60 litres of
fuel! The spacecraft was captured by the Moon in November 2004 and started its
scientific mission in March 2005 in an elliptical orbit around its poles. ESA's
SMART-1 is currently the only spacecraft around the Moon, paving the way for the
fleet of international lunar orbiters that will be launched from 2007 onwards.

The story is now close to ending. On the night of Saturday 2 to Sunday 3
September, looking at the Moon with a powerful telescope, one may be able to see
something special happening. Like most of its lunar predecessors, SMART-1 will
end its journey and exploration of the Moon by landing in a relatively abrupt
way. It will impact the lunar surface in an area called the "Lake of
Excellence", situated in the mid-southern region of the Moon's visible disc at
07:41 CEST (05:41 UTC), or five hours before if it finds an unknown peak on the
way.

The story is close to ending

After 16 months harvesting scientific results in an elliptical orbit around the
Moon's poles (at distances of between 300 and 3.000 km), the mission is almost
over. The spacecraft perilune has now dropped below an altitude of 300 km from
the lunar surface and will get a closer look at specific targets on the Moon
before landing in a controlled manner on the moon surface (controlled, that is,
in terms of where and when). It will then "die" there.

"With a relative low speed at impact (2 km/sec or 7200 km/h), SMART-1 will create
a  small crater of  3 to 10 m in diameter"â says Bernard Foing, SMART-1 Project
scientist, "a crater no  larger than that  created by a 1kg meteorite on a
surface already heavily affected by natural impacts".

Mission controllers at the European Space Agency's Operations Centre (ESOC) in
Darmstadt, near Frankfurt, Germany will monitor the final moments before impact
step by step.

Final milestones of SMART-1 flight operations

In June, SMART-1 mission controllers at ESOC completed  a series of complex 
thruster firings aimed at optimising the time and location of the spacecraft's
impact on the Moon's surface. They had to be done with the thrusters of the
attitude control system since all the Xenon of the Ion engine had been consumed
in 2005.

The manoeuvres have shifted the time and location of impact, which would
otherwise occurred in mid-August on the far side of the Moon; impact is now set
to occur on the near side and current best estimates show the impact time to be
around 07:41 CEST (05:41 UTC) on Sunday 3 September.

"Mission controllers and flight dynamics engineers have analysed the results of
the manoeuvre campaign to confirm and refine this estimate," says Octavio
Camino-Ramos, SMART-1 spacecraft operations manager at ESA/ESOC. "The final
adjustment manoeuvres are planned for 25th of August, which may still have a
consequence on the final impact time", he added.

Large ground telescopes will be involved before and during impact to make
observations of the event, with several objectives:

-	To study the physics of the impact (ejected material, mass, dynamics and
energy involved).

-	To analyse the chemistry of the surface by collecting the specific
radiation emitted by the ejected material ('spectra')

-	To help technological assessment: understand what happens to the impacting
spacecraft to know better how to prepare for future impactor experiments (for
instance on satellites to intercept meteorites menacing our planet)

Media briefing on 3 September, major press conference on 4 September


31-Aug-2006 12:21:36 UT

SMART-1 Impact Site Visibility from Earth

The SMART-1 spacecraft is currently expected to impact the Moon's surface on 3
September 2006, at 05:41 UT. Due to uncertainties in the detailed knowledge of
the lunar topography, it is possible that SMART-1 will impact roughly 5 hours
earlier on the previous orbit at around 00:36 UT.

The best lunar topographic maps currently available are based on data from the
US Clementine mission in 1994. The laser altimeter experiment (LIDAR) on board
provided the spacecraft altitude over a grid with roughly 1 kilometre intervals.
The values in between have been interpolated by the SMART-1 experts, assuming
there are no peaks.

During SMART-1's last orbits, the perilune altitude naturally decreases by about
one kilometre per orbit. This means that, if encountering unknown peaks in the
terrain between one and two kilometres high, SMART-1 may hit ground one orbit or
even two orbits earlier than the nominal impact orbit.

Impact Visibility

If the impact occurs nominally on 3 September 2006 at 05:41 UT, observers from
North and South America and the East Pacific will be able to see the impact or
listen to its radio signal during night time, with best views from America's
East coasts as well as from Hawaii and the East Pacific.

If the probe impacts one orbit before the nominal one, on 3 September at 00:36
UT, the impact will be easily visible from South America, Canary Islands (Spain)
and the US East coast, and from radio observatories from the US in daylight.

Should the impact occur on 2 September 2006 at 19:33 UT, two orbits before the
nominal one, then Africa and South Europe will have a clear view just after
sunset. Radio observatories from South America can listen to SMART-1's final
signal in daylight.


Further information on the event at ESOC
Jocelyne Landeau-Constantin
Head of Corporate Communication Office ESA/ESOC
Darmstadt, Germany : Tel. + 49 6151 90 26 96 / email: jlc@esa.int