Status Report of the Reprocessing for the ILRS Contribution to ITRF2020

Abstract:

The International Laser Ranging Service (ILRS) Analysis Standing Committee (ASC) plans to complete the re-analysis of the SLR data from 1983 to the end of 2020, by early 2021. This will ensure that our contribution to the next ITRF2020 will be available by February 2021. In preparation for the development of this contribution, the ILRS completed the re-analysis of all data from 1993 to present, based on an improved modeling and a novel approach that ensures the results are free of systematic errors in the underlying data. The new approach was developed after the completion of ITRF2014. The ILRS ASC devoted almost entirely its efforts over the past four years on this task. A Pilot Project initially demonstrated the robust estimation of persistent systematic errors at the millimeter level, leading us to adopt a consistent set of a priori corrections for data collected in past years. The initial reanalysis used these corrections, leading to improved results for the TRF attributes, reflected in the resulting new time series of the TRF origin and scale. The ILRS ASC will use the new approach in the development of its operational products and as a tool to monitor station performance, extending the history of systematics for each system that will be used in future re-analysis. The reprocessing for ITRF2020 benefits also from an improved validated new target signature model for all stations and targets used for this task, as well as improved geophysical models. These improvements will be adopted for the new operational products which will form a seamless extension of the re-analysis series, providing a continuous product based on our best knowledge of the ground system behavior and performance, without any dependence on a priori knowledge of systematic errors (although information provided by the stations from their own engineering investigations are always welcome and taken into consideration). With all years up to mid-2020 included in this product that spans more than 37 years, we now generated the final version of the ILRS contribution and illustrate the benefits to the ITRF from the new analysis approach. The presentation will demonstrate the level of improvement with respect to the previous ILRS product series and give a glimpse of what is to be expected from the development of a preliminary version of the ITRF2020.