Abstract
AbstractMedia 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 delay and delay rate 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 a European Space Agency contract and installed at the deep space ground station 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.
Highlights
Precise radiometric tracking is of key importance during operations of interplanetary missions and for advanced radio science applications
When the tropospheric calibrations are included within the orbit determination process, the radiometric measurements will be affected by a variable amount of uncalibrated tropospheric delay and by additional error sources that are introduced as part of the calibration generation process
This work presented the first statistical characterization of the end-to-end performances of the tropospheric delay calibration system (TDCS) prototype that was installed at European Space Agency (ESA)'s deep space ground station in Malargüe, Argentina
Summary
Gaia is an ESA cornerstone scientific mission, whose aim is to measure the three-dimensional position and velocity distributions of stars within the Milky Way using accurate astrometric measurements (Prusti et al, 2016). The overall concept for this analysis was to perform a standard orbit determination process for the Gaia spacecraft, using Doppler measurements collected at the DSA3 complex and a priori information on the dynamical model provided by the Flight Dynamics team at ESA's European Space Operation Center in Darmstadt, Germany (ESOC FD). This process was repeated by keeping all parameters fixed while varying the applied tropospheric calibrations (either generated from dual-frequency GNSS measurements or generated by the TDCS measurements) to allow for a direct comparison of the respective accuracies
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