SMART-1 -- the lunar adventure begins (Forwarded)

European Space Agency
Information Note No. 14-2003
Paris, France 5 August 2003

SMART-1 -- the lunar adventure begins

This is clearly Europe's time for interplanetary exploration. Having sent
the first European mission to Mars, ESA is about to launch its first probe
to the Moon. It is called SMART-1 and its goals are both technological and
scientific. It is the first of a series of 'Small Missions for Advanced
Research in Technology'.

On the one hand, SMART-1 will test new state-of-the art instruments and
techniques essential to ambitious future interplanetary missions, such as
a solar-electric primary propulsion system. On the other, SMART-1 will
answer pending scientific questions, addressing key issues such as the
Moon's formation, its precise mineralogical composition, and the presence
and quantity of water. These data will help scientists to understand the
Earth-Moon system and Earth-like planets, and will also provide invaluable
information when considering a long-lasting human presence on the Moon.

On 15 July 2003, SMART 1 was shipped to the European launch base in
Kourou, French Guiana, where it is being prepared for its launch, due to
take place on an Ariane-5 rocket on 29 August 2003 (Central European
Summer Time).

For the first time, SMART-1 will combine the power obtained by
solar-electric propulsion -- never used before by Europe as a main
propulsion system -- with lunar gravity. It will not follow a direct path
to cross the 400,000 kilometres distance between the Earth and the Moon.
Instead, from an elliptical orbit around the Earth where it is placed by
the rocket, SMART-1 will gradually expand the orbit in a spiral pathway
that will bring it closer to the Moon every month. Finally, the Moon's
gravitational field will capture the spacecraft. SMART-1 will not land on
the Moon, but will make its observations from orbit, obtaining a global
view. When it reaches its destination, in December 2004, it will enter
orbit around the Moon and make measurements for a period of six months
possibly extended to one year.

Why the Moon? Water, minerals, and a violent origin

"Our knowledge of the Moon is still surprisingly incomplete," says Bernard
Foing, ESA's SMART-1 Project Scientist. "We still want to know how the
Earth-Moon system formed and evolved, as well as the role of geophysical
processes such as volcanism, tectonics, cratering, or erosion in shaping
the Moon. And, of course, in preparation for future lunar and planetary
exploration, we need to find resources and landing sites."

So, there are many unsolved questions about the Moon, even though six NASA
Apollo missions and three unmanned Soviet spacecraft have landed on it and
brought back rock samples. The far side of the Moon -- the one that never
faces Earth -- and the polar regions remain fairly unexplored. The
existence of water on the Moon has also never been confirmed, although two
orbiters in the 1990s found indirect evidence. We are not even sure how
the Moon was formed. According to the most accepted theory, 4500 million
years ago an asteroid the size of Mars collided with our planet, and the
vapourised debris that went into space condensed to form the Moon.

SMART-1 will map the Moon's topography, as well as the surface
distribution of minerals such as pyroxenes, olivines, and feldspars. Also,
an X-ray detector will identify key chemical elements in the lunar
surface. These data will allow scientists to reconstruct the geological
evolution of the Moon, and to search for traces of the impact with the
giant asteroid. If the collision theory is right, the Moon should contain
less iron than the Earth, in proportion to lighter elements such as
magnesium and aluminium. By gauging the relative amounts of chemical
elements comprehensively for the very first time, SMART-1 can make a
significant contribution in resolving this issue.

As for water, if it exists, it must be in the form of ice in places always
hidden from the Sun. In such places, the temperature will never rise above
-170 C. Dark places like that could exist in the bottoms of small craters
in the polar regions. Peering into these craters is maybe the trickiest
task that the SMART-1 scientists have set themselves. They will look for
the infrared signature of water-ice. It will be difficult because no
direct light falls in those areas, but rays from nearby crater rims,
catching the sunshine, may light the ice sufficiently for SMART-1
instruments to see it.

New technologies to prepare for future interplanetary missions

Future scientific missions will greatly profit from the technologies being
tested on SMART-1. Solar-electric primary propulsion is a new propulsion
technique based on so-called 'ion engines' that feed on electricity
derived from solar panels. It is a technique that has only ever been used
once before. These engines provide a very gentle thrust, but they work for
years while conventional, more powerful chemical rockets burn for only a
few minutes.

Ion engines offer key advantages. They need considerably less propellant
than chemical propulsion, which means less weight at launch and more mass
available for scientific instruments and payload. Ion engines open the
door to truly deep space exploration. They slash the time for
interplanetary flight: although they provide less thrust they can last for
years. The ion tortoise will therefore eventually overtake the chemical
hare. Moreover, another application of the gentle thrust provided by
electric propulsion allows very accurate spacecraft attitude control, a
skill that will be useful for scientific missions that require highly
precise and undisturbed pointing. Future ESA science missions will rely
on ion engines.

SMART-1 will also test new miniaturisation techniques that save space and
economise on mass: in space, less mass per instrument enables scientists
to have more instruments on board, so more science. The SMART-1 payload
consists of a dozen technological and scientific investigations performed
by seven instruments weighing only 19 kilograms in total. For example, the
X-ray telescope D-CIXS, consists of a cube just 15 centimetres wide and
weighing less than 5 kilograms. The ultra-compact electronic camera, AMIE,
weighs no more than an amateur's camera.

New navigation and space-communication techniques will also be tested.
An experiment called OBAN, based on images from the miniature camera
AMIE and the star trackers, is the first step towards future 'autonomous'
spacecraft. In a not-too-distant future, scientific satellites will be
able to 'find their way' with a minimum of ground control, just by using
stars and other celestial objects to guide themselves along predefined
paths.

As for communications, engineers need to develop new and efficient ways to
communicate with Earth from deep space, for interplanetary missions that
are long or go far. SMART-1 will test both very short radio waves (called
Ka band, with the instrument KaTE) and a laser experiment to try to
communicate with the Earth using a laser beam, instead of traditional
radio frequencies. ESA already has laser links with telecommunications
satellites from an optical ground station on Tenerife, in Spain's Canary
Islands. Aiming the beam becomes much more difficult if, like SMART-1,
the spacecraft is far away and moving rapidly. Scientists hope that the
on-board camera AMIE will see Tenerife aglow with laser light.

For more information, please contact:

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

For more information about SMART-1 and the ESA Science Programme visit:
http://www.esa.int/science

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

Related articles

* ESA's SMART-1 ready to fly
http://www.esa.int/esaCP/SEME2GXO4HD_Expanding_0.html
* ESA presents SMART-1: Europe to the Moon, the Moon for Europe
http://www.esa.int/esaCP/SEMKKO8YFDD_Expanding_0.html

More information

* SMART-1 lunar mission
http://www.esa.int/export/esaMI/SMART-1/
* SMART-1 overview
http://www.esa.int/science/smart1
* ESA Science
http://www.esa.int/science

IMAGE CAPTIONS:

[Image 1:
http://www.esa.int/export/esaCP/SEMB...anding_1.html]
SMART-1 scanning the Moon's surface

How three remote-sensing instruments on SMART-1 will scan the
Moon's surface during one pass. Repeated passes will gradually
fill in the picture.

Credits: ESA 2002. Illustration by Medialab.

[Image 2:
http://www.esa.int/export/esaCP/SEMB...html#subhead1]
Scenario of the Moon's origin

If this scenario of the Moon’s origin is correct, iron should be
relatively scarce in the lunar surface, compared with magnesium,
for example. D-CIXS will be able to judge the proportions.

Credits: by AOES Medialab, ESA 2002

[Image 3:
http://www.esa.int/export/esaCP/SEMB...html#subhead2]
Artist's impression of SMART-1 ion engine

How an ion engine works. Electrons attracted into the discharge
chamber collide with xenon atoms from the propellant gas
supply, making charged atoms (ions). Current-carrying coils,
inside and outside the doughnut-shaped discharge chamber,
sustain a magnetic field oriented like the spokes of a wheel.
By the Hall effect, ions and electrons swerving in opposite
directions in the magnetic field create an electric field. This
expels the xenon ions in a propulsive jet. Other emitted
electrons then neutralise the xenon, producing the blue jet.

SMART-1 is the first of ESA’s Small Missions for Advanced
Research in Technology. It will head for the Moon using
solar-electric propulsion and carrying a battery of miniaturised
instruments.

Credits: Illustration by AOES Medialab, ESA 2002