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Published online by Cambridge University Press: 12 April 2016
If one wants to study the physical characteristics of individual asteroids, he must first find them and be prepared to track them accurately during observation. To make the necessary predictions, the positions of asteroids are measured in reference frames defined by stars of known coordinates as the input information for calculation of orbits and ephemerides. Continuation of positional observations over lengthening arcs provides the basis for improvements of orbits and increased accuracy of ephemerides.