3.2 Statistics of one year of operations

The total number of object identifications credited to our group in about one year of operations is 2,528. Out of these, 902 were orbit identifications; moreover, 173 were attributions to the newly identified orbits. Still the majority of the identifications (1,344+109) have been obtained by the use of only the attribution method. The changes from month to month reflect experiments we have been doing with new procedures, different order of operations, and even the use of different computer hardware. They also reflect the changes in the operations of the other groups hunting for identifications since, as mentioned in the previous section, we are not counting the cases in which we had found an identification and then discovered it had been proposed by others and published, often only a few days before. Table 2 does not include a special case of attributions, namely the attributions to numbered asteroids. We have submitted 15 of these and all of them have been published.

  

Figure: Length of observed arcs for all the attributions proposed by our group and published by the MPC between January and May 2000. Above: length of the first arc (the one for which an orbit was computed and propagated). Below: length of the second arc, for which an attributable was prepared.

A more detailed analysis is possible for the identifications we submitted in the last few months, since the protocol for submissions has been followed in a precise way. The results for the 649 attributions submitted by us and published by the MPC between January and May 2000 (excluding the attributions to other identifications; that is, taking only the first column of Table 2) are summarized in Figure 6 as a function of the length of both observed arcs. The cutoff at 10 days for the length of the second arc is the result of our choice of computing attributables only for arcs shorter than 10 days; for longer arcs, the orbit identification method is generally better. The comparatively small number of one night stand attributions published so far depends upon two factors: first, these single night attributions are rated uncertain and most of them are left pending; second, after 1992 the one night stand data have not been published by the MPC and are therefore not available for our search of identifications. Out of these 649 attributions only 123 involved two arcs both observed before 1990; 300 involved two arcs both observed after 1997. These figures suggest that the attributions are mostly found among the new observations made available every month, which are identified with other recent observations. The attribution algorithm appears to be less effective than the orbit identification one for the purpose of finding identifications among the old data, which have been in the archives for years, even decades. An interesting special case is that of identifications involving Near Earth Asteroids (NEA). Only 4 such cases were found by us and published. Out of these, two were attributions to known NEA, $2000 {\rm\ CN}_{101}$ and $1998 {\rm\ MR}_{24}$; another was an orbit identification between two known NEA, $1998 {\rm\ EP}_8 = 1999 {\rm\ RN}_{45}$. The fourth one was an orbit identification of the asteroid $2000 {\rm\ GR}_{127}$, believed to be a NEA (that is, with nominal perihelion distance q<1.3 AU) with a non-NEA asteroid $1997 {\rm\ GG}_3$, but the orbit resulting from the identification was not that of a NEA.