[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

No Subject



                   NEAR EARTH ASTEROID RENDEZVOUS (NEAR)
                    Mathilde Encounter:   June 27, 1997

              The NEAR flyby of Mainbelt Asteroid 253 Mathilde: 
                 Science Objectives and Encounter Strategy

     ------------------------------------------------------------------
     A. Harch, J. Veverka, J.F. Bell, C. Chapman, M. Malin, L.A.
     McFadden, S. Murchie, M. Robinson, P.C. Thomas, D.K. Yeomans, B.G.
     Williams, S. Squyres, R.W. Farquhar, A. Cheng, D.W. Dunham

     On June 27, 1997 the NEAR spacecraft will pass within about 1200
     km of main belt asteroid 253 Mathilde. Complementing the Galileo
     flyby's of S-asteroids Gaspra and Ida, this will be the first ever
     close observation of a C-asteroid. Mathilde has attracted recent
     attention due to its extremely slow rotation period of 17.5 days.

     Primary science objectives during this 10 km/sec flyby include
     high- resolution imaging, as well as albedo and spectral mapping
     of the illuminated surface of the large (50x50x70 km) asteroid.
     The best monochrome images will achieve resolutions of 200
     meters/pixel. Global imaging in seven colors between 0.4 and 1.1
     micron will be carried out at resolutions of 400-500 m/pixel. On
     departure a satellite search will be made in which bodies as small
     as 100 meters across could be detected. A determination of the
     mass of Mathilde to about ±10% will be carried out by the Radio
     Science experiment.

     Due to the encounter geometry (approach phase angle 139°,
     departure at 39°) the best imaging of Mathilde will occur around
     and just after closest approach. Locating Mathilde with sufficient
     accuracy to insure the the highest resolution observations are
     obtained near closest approach requires optical navigation updates
     of Mathilde's position as late as 12 hours before encounter. This
     will be the first ever fast flyby of an asteroid with a
     spacecraft, which unlike Galileo, does not have a scan platform.