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\centerline{DETERMINATION OF ASTEROID MASSES: (1) CERES}
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\centerline{Z. Kne\v zevi\'c, M. Carpino and M. Kuzmanoski}


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We have made a comprehensive analysis of the most favourable 
close encounters of asteroids with the largest asteroid (1) Ceres, in order 
to determine the mass of Ceres from the changes it imposes in the motion of 
the encountered bodies. We took into account only the well observed bodies 
(including some already used by the previous authors) which approached Ceres 
in the last 25 years.

All the available observations were included in orbital fits, providing
estimates of the observational errors and of the sensitivity of the final
value of the mass with respect to uncertainty in each of the comprised
observations. The observations of particular importance for a succesfull
and reliable mass determination are identified and the need for their 
remeasurement and/or rereduction emphasized. 

Two methods (semianalytical and numerical) were employed in these analyses,
the results being compared both for the reliability and for the
efficiency of their derivation. The robustness of results was tested 
against the assumed errors in the orbital elements, and the associated 
covariance matrices are derived.

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