The Celestial Reference Frame at X/Ka-band (8.4/32 GHz)

Abstract

We have constructed an X/Ka-band (8.4/32 GHz) celestial reference frame using fifty-two 24-hour sessions with the Deep Space Network. We detected 455 sources covering the full 24 hours of right ascension and declinations down to -45 deg. Comparison of 404 X/Ka sources in common with the S/Xband (2.3/8.4 GHz) ICRF2 shows wRMS agreement of 213 micro-arcsec (mas) in a cosd and 282 mas in d. There is evidence for systematic errors at the 100 mas level. Known errors include limited SNR, lack of phase calibration, troposphere mismodelling, and limited southern geometry. Compared to X-band, Ka-band allows access to more compact source morphology and reduced core shift. Existing X/Ka data and simulated Gaia data predict a frame tie precision of 10–15 mas (1-s, per 3-D rotation component) with anticipated improvements reducing that to 5–10 mas per component.