Estimating the mass of asteroid 433 Eros during the NEAR spacecraft flyby

The Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 3830 kilom eters of asteroid 433 Eros on 23 December 1998. The gravitational perturbat ion on NEAR was evident in the spacecraft tracking data. Ground-based Doppl er and range tracking of the spacecraft as well as spacecraft images of the asteroid's center of figure and surface features were used to determine th e mass and rotation pole of Eros. The mass of Eros is (7.2 +/- 1.8) x 10(18 ) grams and, coupled with a volume estimate provided by the NEAR imaging te am, this mass suggests a bulk density of 2.5 +/- 0.8 grams per cubic centim eter. The rotation pole position is 15.6 (+/-3.7) degrees in right ascensio n and 16.4 (+/-1.8) degrees in declination, which is consistent with ground -based and NEAR imaging team observations.