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Re: NEAR Flyby on Asteroid 253 Mathilde on June 27

I wrote:
>This will be the first mass determination of an asteroid by a spacecraft
>flyby.  Galileo did not pass close enough to Ida or Gaspra to determine
>their masses.  Also, Mathilde is a rather large asteroid at 38 miles (61 km),
>which is twice the size of Ida and four times the size of Gaspra.  Mathilde
>appears to be a spherical body, while Ida and Gaspra were irregularly shaped.
 
Some additional information on Galileo's flyby of Ida.  Though the mass
of Ida could not be determined by the gravity affect of the asteroid on
the spacecraft, a range of possible densities was determined by using
Dactyl, the new moon discovered orbiting Ida.  Since we have a good idea
what the volume of the Ida is, there is a certain density range of the asteroid
that would support an orbiting satellite.  This density range was determined
to be 1.9 to 3.2 grams per cubic centimeter.  For more details, see the 
following references:


Galileo Messenger, Issue 35, December 1994
http://www.jpl.nasa.gov/galileo/mess35/TOC.html
 
"Dactyl Orbit Determination Analysis," D. Byrnes and L. D'Amario, AAS
95-315, AAS/AIAA Astrodynamics Conference, August 1995.
 
"The Discovery and Orbit of 1993 (243)1 Dactyl," M. Belton et al, Icarus,
1996, Vol. 120, pp 185-199.

Ron Baalke