Mirshodjon Makhmudov (Ulugh Beg Astronomical Institute of Uzbekistan Academy of Sciences, Uzbeksitan); Jerome Saunier (Institut national de l'information géographique et forestière, France); Guilhem Moreaux (Collecte Localisation Satellites , France)

The Kitab Observatory of the Ulugh Beg Astronomical Institute of the Academy of Sciences of Uzbekistan is a unique geodetic site in Central Asia, where two independent space-geodetic techniques, DORIS and GNSS, have been operating for more than 30 years. The co-location and complementarity of these techniques make Kitab particularly suitable for inter-technique comparison and regional geodynamic studies. This study examines coordinate time series from the current co-located stations at the observatory: the IDS DORIS station KIVC and the IGS GNSS station KITG. The DORIS series is taken from the IDS combined solution, while the GNSS series for KITG is derived from an independent GAMIT/GLOBK processing. The analysis is performed in a common reference framework with consideration of the co-location geometry of the site. The comparison focuses on the north, east, and up components and includes the assessment of linear trends, seasonal variations, and residual behavior. Particular attention is given to the agreement between the long-term motions derived from the two techniques, the expression of periodic signals in the coordinate series, and the stability of the vertical component, which is especially important in inter-technique comparisons. In addition to the time-series analysis, the study briefly presents the history and current status of the Kitab Observatory, including its contribution to geodesy and the configuration and performance of the KIVC and KITG stations. This work aims to clarify the level of consistency between DORIS and GNSS observations at Kitab and to discuss the potential of their joint use for geodynamic monitoring in Central Asia.