JET PROPULSION LABORATORY INTEROFFICE MEMORANDUM
IOM 312.F  01  0006
April 11, 2001

TO:  Solar Systems Dynamics Group
FROM:  E M Standish
SUBJECT:  Suggested GM Values for Ceres, Pallas, and Vesta

The Table presents GM values for Ceres, Pallas, and Vesta which represent
the most recent planetary ephemeris adjustments.  The associated uncertainties
are intended to be realistic values as opposed to the formal errors from the
solutions.

It seems as though the various ephemeris solutions during the past half year
have all given GM values which are within the limits of the uncertainties
given here.

GM Values of Ceres, Pallas, and Vesta.
------------------------------------------------------------------------------
       km^3/s^2       sigma(percent) (au^3/d^2)x10^-13    M(ast)/M(sun)x10^-10
Ceres  63.2 +/- 0.2   0.3            1.409 ... +/- 0.004  4.762 ... +/- 0.015
Pallas 14.3 +/- 0.5   3.5            0.319 ... +/- 0.011  1.078 ... +/- 0.038
Vesta  17.8 +/- 0.2   1.1            0.397 ... +/- 0.004  1.341 ... +/- 0.015
------------------------------------------------------------------------------

These values are virtually identical to those of 63.2, 14.3, and 17.9,
presented last November (Standish, 2000), but they do differ a bit from those
of DE405 (62.4, 13.3, and 17.3).  The improvement since DE405 has come from
the addition of a substantial amount of Mars ranging and doppler data 
(Pathfinder and MGS).

In the ephemerides solutions, determinations are also made for the mean
values of the densities of the three major taxonomic classes, C, S, and M
(carbonacious, stony, and metal).  The values for these, however, don't seem
to be as stable as those of the GMs.

Reference

Standis, E.M.: 2000, "Recommendation of DE405 for 2001 Mars Surveyor and for
Cassini", JPL IOM 312.F-00-107.