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The highest science priority for Spartan is to determine the rate at which water is broken down (dissociated) by sunlight.  This must be measured indirectly from the spectra of hydroxyl radicals (OH) and atomic oxygen which are the primary and secondary products. The hydroxyl coma of the comet will be more compact than the atomic oxygen coma because of its short life when exposed to sunlight. Hydrogen, the other product, will not be detectable because of the lyman-alpha filters in the spectrometers.

Heavier compounds will be sought by measuring spectral lines unique to carbon, carbon monoxide (CO), carbon dioxide (CO2), sulfur, carbon sulfide (CS), molecular sulfur (S2), nitric oxide (NO)and cyanogen (CN), among others.

Spartan-Halley's spectrometers will not produce images, but will reveal the comet's chemistry through the ultraviolet spectral lines they record.  With these data, scientists will gain a better understanding of how:

* Chemical structure of the comet evolves from the coma and proceeds down the tail;

* Species change with relation to sunlight and dynamic processes within the comet; and

* Dominant atmospheric activities at perihelion relate to the comet's long-term evolution.

Other observatories will be studying Halley's comet, but only Spartan can observe near perihelion.

The Spartan Program

The Spartan-Halley 200 carrier measures 52 by 43 by 51 in. and weighs 2,250 lb. without payload.  The attitude control system and other components use elements from the sounding rocket program. All data are stored on a Bell & Howell MARS 1400 recorder; 500 megabytes of storage are available to the experimenter. The spacecraft sits on the Spartan Flight Support Structure and is held in place by a release-and-engage mechanism.

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