On the computation of the path delay in deep space missions applications by means of a scalar radiometric-based indicator

The estimation of the path delay due to water vapor is a crucial aspect for the calibration of the Doppler observables of a deep space probe. The Advanced Water Vapor Radiometer (AWVR), developed by the Jet Propulsion Laboratory (JPL, NASA), already proved its capability to accurately estimate the path delay during the entire Cassini mission. Here, from the AWVR measurements, a scalar Sky Status Indicator (SSI) was developed as a criterion for selecting the radiometric path delay estimations in the orbit determination process. Results indicate that the use of such index allows a reduction of Doppler residual root mean square.