The following table shows the results of simulated orbital fits , obtained by adding to the set of the astrometric observations which are presently available also a limited number of future observations, distributed around the dates of the oppositions of the asteroids in the years 1997-2004. More precisely, we have simulated 13 new astrometric observations distributed over a period of 120 days around the date of each opposition. It is needless to say that, since the formal RMS is computed in the assumption that all the observations be uncorrelated, it probably underestimates the real accuracy of the result. Improving upon this situation by adding new observations is therefore a very slow process. The set of observations available after the date of close approach is quite meager, so a significant improvement can be obtained by adding more data points in the future.
Future observations can improve significantly the fit.
Ib is correct but misleading, since 5 out of the 6 available pre-encounter observations fall within an interval of 8.9 years from the date of the close approach, and only one predates it by 34.8 years. For this reason, the value of the mass determined from this encounter is very uncertain, since it depends almost entirely on the correctness of this single observation, which is of course impossible to demonstrate from the analysis of residuals. Also in this case, the availability of additional pre-encounter observations is essential. Wasserman Also in this case the astrometric measurements available before the close approach are few and the fit depends critically on a single observation. Future observations are helpful, but only if also additional pre-encounter observations will become available.