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G.D. Racca, B.H. Foing (ESA/ESTEC)
Deep Space exploration was initiated by a series of fly-by missions that were propulsively and energetically modest. Therefore, the basic energy barrier given by the use of chemical propulsion system was not obstructive. In addition, the use of \emph{gravity assits} has enabled deep space missions with enlarged velocity increments. Unfortunately, multiple gravity assits have the drawback to narrow drammatically the launch windows and the cruise phases are extremely long with obvious impacts on the operation costs. The most promising solution for the future deep space missions is found in the use of the Electric Propulsion (EP). Thanks to its high specific impulse, the EP enables very high velocity increments, higher payload ratios and the use of smaller launchers. In addition it alows to have more flexible launch windows and ultimately reduces the cruise time.
SMART-1 is a mission to test the system aspects of primary EP. It will be launched as an auxiliary passanger in late 2002 by an Ariane 5 rocket into a Geo-stationary Transfer Orbit. The planetry target orbit is around the Moon, polar, elliptical, roughly 1000 \times 10000 km with perilune near the South Pole. The Moon will be reached after a cruise of 15 to 18 months and providing a velocity increment of about 3.5 km/s by EP. The transfer trajectory makes use of \emph{Moon resonances} and \emph{Moon swing-by's} to test these techniques for future deep space missions. The EP engine is a stationary plasma thruster, providing a relatively high thrust of 70 mN with an input power of 1350 W and with a specific impulse of 1600 s. The scientific observations of the lunar surface will be carried out with a novel X-ray spectrometer and a low mass, very compact IR reflectance spectrometer, together with an imaging camera. An X-Ka-band transponder will allow to perform spaceraft tracking with high accuracy and, comined with the camera, to test techniques for measuring from orbt the Moon physical librations. During the cruise phase the natural and induced plasma environment will be measured.
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The author(s) of this abstract have provided an email address for comments about the abstract: gracca@estec.esa.nl