GRGS Numerical Simulations for GRASP Mission

The Geodetic Reference Antenna in Space (GRASP) is a spacecraft system designed to build an enduring and stable Terrestrial Reference Frame (TRF) for accurately measuring and understanding changes in sea level, ice sheets and other elements of the dynamic Earth system. This mission was first proposed in 2011 by JPL in response to the NASA NNH11ZDA012O call for Earth Venture-2 missions. Recently, considering the recommendation of the Prospective Scientific Seminar, CNES expressed its interest and the possibility to participate in a next new JPL proposal. To reach the goals for the TRF realization of 1 mm accuracy and 0.1 mm/year stability (GGOS, Meeting the Requirements of a Global Society on a Changing Planet in 2020, Plag and Pearlman, 2009), GRASP will carry very precise sensor systems for all the key geodetic techniques used to define and monitor the TRF (DORIS, GNSS, SLR and VLBI). In this study, we present the results obtained with numerical simulations carried out by the French Groupe de Recherche en Géodésie Spatiale (GRGS). We simulated the measurements of the four geodetic techniques (DORIS and SLR measurements to GRASP, VLBI PPP or interferometric measurements on GRASP and GPS measurements from ground stations and from GRASP) over three years and evaluated the expected accuracy and stability of the TRF provided by the processing of these measurements. We present the expected impact of the on-board instrument calibration on the TRF as well.