Performance Characterization of ESA's Tropospheric Delay Calibration
System for Advanced Radio Science Experiments
Abstract
Media propagation noises are amongst the main error sources of
radiometric observables for deep space missions, with fluctuations of
the tropospheric excess path length representing a relevant contributor
to the Doppler noise budget. Microwave radiometers currently represent
the most accurate instruments for the estimation of the tropospheric
path delay (or excess path length) along a slant direction. A prototype
of a Tropospheric Delay Calibration System (TDCS), using a 14 channel
Ka/V band microwave radiometer, has been developed under ESA contract
and installed at the deep-space antenna DS3 complex in Malargüe
(Argentina) in February 2019. After its commissioning, the TDCS has been
involved in an extensive testbed campaign by recording a total of 44
tracking passes of the Gaia spacecraft, which were used to perform an
orbit determination analysis. This work presents the first statistical
characterization of the end-to-end performance of the TDCS prototype in
an operational scenario. The results show that using TDCS-based
calibrations instead of the standard GNSS-based calibrations leads to a
significant reduction of the residual Doppler noise and instability.