Schnell, Dorothee: Quality aspects of short duration VLBI observations for UT1 determinations. - Bonn, 2006. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc:
author = {{Dorothee Schnell}},
title = {Quality aspects of short duration VLBI observations for UT1 determinations},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2006,
note = {Today geodetic Very Long Baseline Interferometry (VLBI) is the most important technique for the determination of all components of earth rotation. Among all parameters describing the current earth rotation relative to a quasi inertial system the daily earth rotation phase UT1 is the most variable quantity including significant unpredictable variations. Short duration single baseline VLBI sessions, so called Intensive sessions, are carried out regularly since 1985 in order to monitor this phase angle of daily earth rotation with minimized operating expense and contemporary analysis. Due to the importance of a regular and dense UT1 monitoring the International VLBI Service for Geodesy and Astrometry (IVS) established a second baseline for such Intensive observations in 2003. In terms of consistency these two independent Intensive baselines form two unequal UT1 sensors affected by various sources of error. In order to generate a common and consistent UT1 series from both baselines and towards a combination of Intensive UT1 results with those of regular VLBI 24 hours global network sessions, the knowledge of baseline dependent impacts is essential.
In this thesis, the question of consistency and homogeneity of the two independent series of short term single baseline VLBI sessions is approached taking into account the specifics of the VLBI observing technique itself. On the basis of theoretical considerations and empirical studies the error propagation of different impact factors to the final UT1 estimates is verified. Within the framework of these investigations, two special test sessions of parallel observations were designed and carried out in order to allow conclusive empirical studies on the precision of and the systematic effects on the UT1 results from short term VLBI sessions. Although the formal errors of both Intensive series are of equal order of magnitude, significant baseline dependent elements of uncertainty have been identified. These geometry and time dependent impacts affect the relative as well as the absolute accuracy of each Intensive series and have to be kept in mind when merging the results of the two series. At the end, a realistic estimation of the relative and absolute UT1 accuracy of the two different single baseline VLBI series is given. A concise summary of the Intensive specific sources of error helps to detect weak points within the analysis process.},

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