Celestial Reference Frames [chapter]

J. Kovalevsky
1981 Astrophysics and Space Science Library  
A celestial reference frame is based on some dynamical or kinematic approximation of an absolute coordinate system and is materialized by a fundamental catalogue of stars. It is characterized by the accuracy of the system and the precision of its stellar realization. The present situation, marked by the construction of the FK5 system and catalogue, is briefly described. It will be an hybrid system based on the discussion of all existing observations. The prospects for improvement in accuracy
more » ... ment in accuracy are good using lunar laser observations or VLBI determination of the positions of extra-galactic radio-sources. Three procedures that may be used to link such a system to a star catalogue are given. A major improvement in precision is expected from the Hipparcos programme and further extensions include essentially the densification of catalogues with stars of magnitudes 10 to 14 using photoelectric automatic meridian instruments. Conceptually, the simplest reference system is inertial: There, the differential equations of motion may be written without including any rotational term. Such a system is dynamical in character and can be constructed uniquely from the analysis of the motion of one or several celestial bodies such as the Moon or the planets, provided that all 77 E. M. Gaposchkin and B. Kofaczek (eds.j. Reference Coordinate Systems for Earth Dynamics,[77][78][79][80][81][82][83][84][85][86]
doi:10.1007/978-94-009-8456-1_7 fatcat:wozxjbh63jdtfesgpyhu7i3bfe