VLBI scheduling strategies with respect to VLBI2010

Abstract

Very Long Baseline Interferometry (VLBI) plays an important role for the realization of global geodetic reference frames. The next generation VLBI system, called VLBI2010, has been developed with a major goal of bridging the gap from the current 5-7 mm level of accuracy for VLBI position determination to the new sub 1 mm requirement. To reach the goals of VLBI2010, various new facets have been investigated within the International VLBI Service for Geodesy and Astrometry (IVS) including small fast-moving antennas, broadband frequency observations (2-14 GHz), and two or more antennas at a site. In order to exploit the full power of the future VLBI2010 system and derive the best possible geodetic parameters, a new scheduling package (VIE_SCHED) will be developed at the Institute of Geodesy and Geophysics (IGG) of the Vienna University of Technology, which is one part of the Vienna VLBI Software (VieVS).<br />Considering a more uniform network and fast moving antennas, one of the new strategies is source-based scheduling, which means that the schedule program selects radio sources from the catalogue without regard for their direct impact on individual stations. The conventional strategy is station-dependent scheduling, i.e., the sky coverage is optimized in short intervals taking into account the rapid atmospheric variability, partly at the expense of the total number of observations. It also includes the considerations of antenna maintenance and power saving mode. Variance and covariance analysis and even a dynamic optimization process will be considered to select the next source, which allows the successful separation of the various geodetic parameters in large multi-parameter adjustments. Schedules of sites with multiple antennas will also be considered. The scheduling software will offer the possibility to the user to optimize the schedule according to different criteria. It writes .skd file, which contains a complete description of the session, the schedule and the additional information used in scheduling the session. The work of developing the graphical interface is also needed to make it easy to use.<br />To test the newly developed scheduling algorithms, thorough and realistic simulations will be carried out. VIE_SCHED is directly connected to VieVS to provide feedback on the quality of the schedule.<br />Different schedules for 24-hour continuous VLBI2010 observations are compared in terms of scheduled sources, number of observations, idling percentage, sky coverage, station position repeatabilities, baseline length repeatabilities, and Earth Orientation Parameters (EOP) to evaluate different scheduling strategies. Within the doctoral thesis, the new scheduling software VIE_SCHED will be developed, implemented and tested according to the requirements of the VLBI2010 system.