Impact of a priori Modeling Errors on the Estimate of UT1 from IVS Intensives.

Abstract:

The IVS Intensive sessions are run with the specific goal of providing short latency estimates of UT1. They typically involve 2 stations with a long East-West baselines and last for 1-hour. The small network size and the short duration means that most Intensives have 20-40 observations. This severely limits the parameters that you can estimate. At the IVS Analysis Center at GSFC we usually estimate an atmosphere offset at each station, a quadratic clock at one station, and a UT1 estimate. We study the impact of of errors in the various models used to calculate the theoretical delay on the estimate of UT1. The models we examined include polar motion, troposphere, atmospheric gradients, station position, etc. If an error in a particular model results in a large change in UT1 than we must be particularly careful that this model is accurate. Conversely, if the change in UT1 is small, then we don't need to be as carefull. We also discuss alternative estimation strategies as a way of improving the accuracy of UT1.