RF compatibility of VLBI with DORIS and SLR at GGOS stations: An experimental methodology to validate the models

A continuing thrust in the space geodetic community is to deploy instruments using different techniques at common sites. While the close proximity (of order 100 meters) of the instruments to each other affords improved inter-comparison tests, it also increases the potential for interference between instruments. Of present concern to VLBI are DORIS beacons and the aircraft surveillance radars used in conjunction with satellite laser ranging (SLR). Initial numerical studies(1) were conducted to obtain rough estimates of the degree to which the VLBI SNR is degraded for various levels of DORIS and SLR radar interference. Numerical studies are only as good as the models upon which they are based, however, and there is sufficient uncertainty regarding their accuracy that field and laboratory validation is warranted. In this contribution, we present a measurement methodology designed to resolve the major uncertainties in the models. We also summarize the experimental results to date.