NEAR's Flyby of Mainbelt Asteroid 253 Mathilde

J. Veverka, J.F. Bell III (Cornell), C. Chapman (Southwest Research Institute), M. Malin (Malin Space Science Systems), L.A. McFadden (U. of Maryland), S. Murchie (APL), M. Robinson (Northwestern), P.C. Thomas (Cornell), D.K. Yeomans (JPL), A. Harch (Cornell), B.G. Williams (JPL), B. Clark (Cornell), R.W. Farquhar, A. Cheng, D.W. Dunham (APL)

On June 27, 1997, the NEAR spacecraft, on its way to Eros, will make a flyby (10 km/sec) of 253 Mathilde, a large C-asteroid 50 tex2html_wrap_inline11 50 tex2html_wrap_inline11 70 km across, with an extremely long rotation period (17.4 days, according to Mottola et al.). NEAR will approach Mathilde at a phase angle of 139 tex2html_wrap_inline15 and depart at 39 tex2html_wrap_inline15 ; at closest approach (1200 km) the phase will be near 80 tex2html_wrap_inline15 . An imaging strategy has been devised in which the spacecraft will obtain over 500 images in about 25 minutes around closest approach. The best resolution expected is 200 meters. Global imaging in seven colors between 0.4 and 1.1 tex2html_wrap_inline21 m will achieve a resolution of 500 meters. On departure a satellite search will be made in which bodies as small as 100 meters across could be detected. The flyby will determine the mass of Mathilde to better than tex2html_wrap_inline23 10%. The Mathilde flyby complements the Galileo flybys of Gaspra and Ida by providing the first-ever closeup study of a C-type asteroid. The NEAR flyby also represents the first time that such a study will be carried out by a spacecraft with no scan platform.