The JPL 2024b X/Ka Celestial Frame Re-weighting to Reduce Systematics

The X/Ka-band (8.4/32 GHz) Celestial Reference Frame became one component of the ICRF-3 in 2018. In the six years since, the X/Ka data set has increased by a factor of two as well as adding the much needed north-south geometry from Japan to Australia. Median formal precision is now better than 100 micro-arseconds. The accuracy of the frame is limited by systematic errors larger than the formal precision. The limited network geometry allows for geometric distortions—most notably quadrupole 2,0 distortions. This paper will compare the use of two data weighting methods to account for the dominant noise from wet tropospheric fluctuations and the resulting impact on systematic frame distortions:1) white noise weighting2) elevation dependent white noise