The extra-galactic, radio reference frame at present provides the best tie to inertial space. The U.S. Naval Observatory (USNO) has published a catalog of extragalactic radio sources suitable for the definition of a radio reference frame as part of its Radio Optical Reference Frame (RORF) project. The last year of radio observations coordinated by USNO, in cooperation with the NASA Crustal Dynamics Project, is compared to the RORF radio frame to demonstrate the stability and time independence of the frame. The RORF radio frame is made independant of the earth's orientation by the use of the ensemble of radio sources and their relative positions to define a rigid frame into which any other rigid frame may be rotated. The orientation of the RORF frame is stable to about 2 microarcseconds per year, though individual sources can show apparent proper motions at much higher levels due to changing structure. The catalog as a whole however does not degrade with time.
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1995