The X/Ka-band 2019a Celestial Frame
Abstract
Observations at X/Ka-band are motivated by their ability to access more compact source morphology and reduced core shift relative to observations at the historically standard S/X-band. In addition, the factor of four increase in interferometer resolution at Ka-band should resolve out some extended source structure. Given these motivations, an X/Ka-band (8.4/32 GHz) celestial reference frame has been constructed using a combined NASA and ESA Deep Space Network. In 179 observing sessions we detected 678 sources covering the full 24 hours of right ascension and the full range of declinations. The resulting XKa median precision is now 66 μas in RAcosDec and 94 μas in Dec.
Comparison of 541 X/Ka sources in common with the S/X-band (2.3/8.4 GHz) ICRF3 produced wRMS agreement of 153/ 161 μas in RAcosDec/ Dec. There is evidence for systematic errors at the 200 μas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and terrestrial frame distortions. Actions are underway to reduce all of these errors. In particular, a collaboration between NASA and the ESA deep space antenna in Malargüe, Argentina is reducing weaknesses in the southern hemisphere. By comparing coordinate estimates, we probe the accuracy limits of current celestial frames in an effort to understand the advantages of each frame.- Publication:
-
Proceedings of the 24th European VLBI Group for Geodesy and Astrometry Working Meeting
- Pub Date:
- March 2019
- Bibcode:
- 2019evga.confP.302J
- Keywords:
-
- astrometry;
- ICRF;
- VLBI;
- AGN;
- quasar;
- Ka-band;
- 32 GHz;
- Deep Space Network