Precision of Ephemerides for Space Missions

Extract

One of the most extensive programs of systematic observations of minor planets currently being conducted is that at the Crimean Astrophysical Observatory. The observed positions, together with the residuals from the predictions in the annual Ephemeris volumes, have been listed in the Minor Planet Circulars for several years now; and inspection of the residuals yields information about the accuracy of minor planet ephemerides as a whole.

The observations are made using a 40 cmf/4 double astrograph, the limiting magnitude being about 18. Between June 1968 and October 1969, corresponding to one synodic period of an average minor planet, about 40 percent of all the numbered objects were observed. These observations may be regarded as reasonably representative of all the planets. Observations were made of 60 of the objects with numbers in the 100’s and only 29 of those in the 1100’s, but in general the distribution was surprisingly uniform.