same conclusion. Indeed, on figure 5, the values estimated since 1991 (Baer and Chesley 2008) of GMs of Ceres, Pallas and Vesta are plotted as well as the values provided by INPOP06, DE414, DE421 and INPOP08 which correspond to the four last points dated in 2008 and 2009. On this graph, are represented (using darked circles) asteroid masses estimated by close-encounters (see for instance Baer and Chesley 2008, Hilton 1999), asteroid and try to estimate its mass only on that arc.

[Figure: Fig. 4. MEX and MGS/MO 1-way residuals with the new INPOP08 fitted to VEX, MEX and MGS/MO data (righthand side plots) and INPOP06 fitted to all MGS/MO and a part of MEX data (left-hand side plots). The improvement of INPOP08 is mainly induced by changes in the asteroid mass determinations and the addition of MEX data. see section 3 in the text. The y-axis unit is meter.]

Such an investigation is presented in (Somenzi et al. 2009).
Interamnia, or (532) Herculina). However, for some others, the differences from previous estimations can reach 500 % as for the case of (9) Metis or even worse (as for (6) Hebe). We estimate to 50% of estimations close to previously published masses (differences below 50 %), 21% of first estimations and 4 very unsufficent estimations (differences greater than 500 %).
5.1.3. Cassini normal points Cassini normal points for Saturn were provided by JPL and are described in details by (Folkner et al. 2008). The impact of these data is not negligeable. They give very important informations about the Saturn orbit itself by providing very accurate estimations of the Earth-Saturn distances and geocentric angular positions of Saturn. Thanks to these, our knowledge of this orbit especially in term of distances from the Earth reduces from about 27 km to 22 meters at the epoch of Cassini normal points.
Such differences can be explained by the differences in the modelisation used to fit the data. For instance, by the differences in the data reduction, the weight used in the fit as well as by fitting individually a different number of asteroids and by absorbing the effect of all the other minor bodies by the fit of the taxonomic classes and the addition of a ring, one absorbs in the fit of individual masses dynamical effects which are not really caused by one particular asteroid but by a group of asteroids inducing effects very similar in amplitudes and periods. The fitted mass for this particular asteroid represents then not only its gravitational potential but also the one induced by other asteroids. This remark can be illustrated by the unrealistic values of some densities deduced from masses and presented in table 3 as well as the almost zero mass of the asteroid (747) Winchester, the perturbations induced by (747) being quite negligible or not clearly separated from another asteroid perturbations like in the case of (6) Hebe. In order to better estimate the real mass value of one particular asteroid, one could isolate the arc of Mars orbit where and when this asteroid has the biggest impact
5.2. AU fixed and rescaled GM of the sun version As a first step to a new generation of planetary ephemerides fitting the GM of the sun and using a fixed value of AU, an alternative version of INPOP08 was built. This version is based of the INPOP08 ephemeris presented in the previous section. However, instead of providing a value of AU fitted to observations, the AU is fixed to the (IERS 2003) value and the change is absorbed by the multiplication of all the initial conditions of planets and asteroids as well as all the masses including the GM of the sun by a factor equivalent to AUfitted over AUIERS03. A new value for the GM of the Sun is then deduced and preOften, users are asking for the accuracy of planet ephemerides.