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B. Soja, C. Jacobs, T. Runge, C. Naudet, R. Gross, A. de Witt, D. Gordon, J. Quick, J. McCallum, H. Krasna:
"Ionospheric calibration for K-band celestial reference frames";
Talk: 24th Meeting of the European VLBI Group for Geodesy and Astrometry, Gran Canaria, Spain; 2019-03-17 - 2019-03-19; in: "EVGA 2019 Abstract Book", (2019).

The International Celestial Reference Frame (ICRF) has traditionally been composed of radio source coordinates estimated from VLBI observations in S- and X-band. The ICRF3, released in 2018, included for the first time a CRF based on observations at K-band. A major benefit of observations at higher frequencies is that source structure effects are smaller. A disadvantage of the K-band data is that the single-frequency observations require external ionospheric calibrations. If the ionospheric corrections are of sufficient quality, a K-band CRF could have an astrometric accuracy better than the 20-30 μas source-structure-induced noise floor of current S/X-based CRFs.In the case of the ICRF3, the K-band observations were corrected using two-dimensional global ionospheric maps with a two-hour temporal resolution. In this study, we investigate the improvement in the K-band CRF when using calibrations based on ionospheric data with increased resolutions. In particular, we (1) test ionospheric products from JPL with a temporal resolution of 15 minutes and (2) evaluate a potential improvement in spatial resolution by assuming functioning GNSS equipment at all ten VLBA sites (currently, only five have GNSS stations that are contributing to ionospheric products).

http://www.oan.es/evga2019/EVGA2019_PDF/O316_EVGA2019_Soja.pdf