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[3.03] The Characterization of Eros Using NEAR Radio Science Data

D.K. Yeomans, P.G. Antreasian (JPL/Caltech), J.-P. Barriot (CNES), S.R. Chesley (JPL/Caltech), D.W. Dunham, R.W. Farquhar (APL/JHU), J.D. Giorgini, C.E. Helfrich, A.S. Konopliv (JPL/Caltech), J.V. McAdams (APL/JHU), J.K. Miller, W.M. Owen, Jr. (JPL/Caltech), D.J. Scheeres (U. MI), P.C. Thomas, J. Veverka (Cornell), B.G. Williams (JPL/Caltech)

We have determined the mass of asteroid 433 Eros, its gravitational harmonics through fourth order, and rotation state, using ground-based Doppler and range tracking of the NEAR spacecraft and spacecraft images of the asteroid's surface landmarks. Our Eros shape model was determined using both the optical landmark and laser ranging data. The mass of Eros is (6.687 ±0.003) x 10¹⁸ grams which, coupled with our volume estimate, implies a bulk density of 2.67 ±0.03 g/cm³. The asteroid's true gravity field is nearly identical to a predicted gravity field that was determined by an integration, assuming constant density, over our shape model. Hence the asteroid appears to have a uniform density distribution. The right ascension and declination of the rotation pole are 11.37 ±0.05 and 17.22 ±0.05 degrees respectively and at least over the short term, the rotation state of Eros is stable with no measurable free precession of the spin pole. Escape velocities on the surface vary from 3.1 to 17.2 m/s. Eros' dynamical environment suggests that it is covered with regolith and that one might expect material transport toward the deepest potential wells in the saddle and 5.5 km crater regions.

A portion of this work was carried out at Caltech's Jet Propulsion Laboratory under a contract with NASA.