Hemenway, P. | Search NASA

NASA NTRS1984

A catalog of selected compact radio sources for the construction of an extragalactic radio/optical reference frame

A catalog of 234 strong compact extragalactic radio sources that display optical counterparts is presented. This catalog identifies proposed sources for establishing an almost inertial reference frame against which the motions of the earth, solar system, galactic objects, and spacecraft may be measured. This catalog also defines those sources for which precise optical positions should be determined in order to relate this reference frame with the optical FK 5 fundamental system. The accuracy of the radio source positions of these sources is not greater than 0.1 arcsec with the majority not greater than 0.01 arcsec. Further refinement to not greater than 0.005 arcsec by future observations is expected soon.

Argue, A. N.↗

NASA NTRS1980

A Fundamental System based on observations of minor planets

Astronomers adopt a single system of star positions and motions for reduction of other observations. Relative observations of faint minor planets may make a significant contribution to the evaluation of systematic errors in this Fundamental System, and provide means of deriving a position system in ecliptic coordinates. New techniques, such as observations with the Space Telescope, must be evaluated for possible incorporation into a revision of the Fundamental System. A historical summary of the application of minor planet observations to the formation of astronomical coordinate systems is given. Then a project to investigate the systematic accuracy of the Fundamental System is outlined. Of the four observation types considered, 'crossing point' observations provide a unique stabilizing influence on any coordinate system incorporating them. Finally, some sources of systematic error and some methods of their treatment are discussed.

Hemenway, P.↗