Monitoring Site Stability at the Space Geodesy Facility, Herstmonceux, UK

Deformations at the local site level will directly introduce errors both into site coordinates that are determined from individual geodetic techniques and the measured site ties that link those techniques at co-located sites. Such errors will be present in individual-technique solutions and affect their combination in the formation of an International Terrestrial Reference Frame (ITRF). The NERC Space Geodesy Facility at Herstmonceux, UK, operates a highly precise and prolific International Laser Ranging Service satellite laser ranging (SLR) station, two International Global Navigational Satellite Systems Service (IGS) receivers and a permanently-installed absolute gravimeter. As a result, the site remains an important contributor to the maintenance of the ITRF. Site deformation is monitored using a recently-instigated programme of precise digital levelling and by short-baseline GPS analyses using data from on-site and regional GNSS receivers. The stability of the Herstmonceux site will impact on the validity of future comparisons of site height changes observed using the three independent techniques, SLR, GPS and absolute gravimetry.