Simulations of Different Antenna Velocities in VLBI Networks

Övrigt konferensbidrag, 2009

The new 40-m radiotelescope of the National Geographical Institute (IGN) in Yebes (code Ys) started to participate in IVS geodetic VLBI sessions in 2008. The azimuth and elevation slew velocities cause stress on the structure, and therefore has an impact on the expected life of the instrument; this calls for slow velocities and accelerations. However, high velocities are needed for better network geodetic results because, in principle, they allow more observations to be performed. In order to evaluate the optimum slew velocities for the new antenna, we used the scheduling software SKED and created schedules with different antenna velocities for Ys. We focussed on the two sessions EURO94 and R1331 and analyzed the schedules with SKED itself, and with the VLBI analysis software SOLVE, both with and without introducing simulated atmosphere and clock contributions. We found that the schedules with a fast Ys antenna (3◦/s in az. and el.) give slightly better results than the ones with a slow Ys antenna (1◦/s in az. and el.). For the studied EURO session the standard deviation of the estimated topocentric U-component for Yebes is similar for a fast and slow antenna. For the R1-experiment the standard deviations of all three topocentric station components improve for a fast antenna. The SKED-only results appear to be too optimistic, while the SOLVE results show more realistic estimates for the UEN components and sigmas. We found no significant difference in the UEN sigmas with or without introducing simulated atmospheric and clock contributions, although the wrms fit becomes slightly worse.