The Cassini spacecraft and its ground segment are currently testing a novel radio frequency multilink technology to perform radio science experiments. During solar conjunctions, this allows the complete removal of the solar plasma noise from the Doppler observables, with benefits for deep space navigation as well. This is obtained combining the carrier frequencies of three independent downlinks; two of them, at X and Ka band (Ka1), are coherent with an X-band uplink, whereas an additional Ka-band downlink (Ka2) is coherent with a Ka-band uplink. During the June–July 2002 Cassini solar conjunction, this procedure was fully tested for the first time. It is shown that, using the adopted multifrequency plasma calibration scheme, the standard deviation of the Doppler frequency residuals is reduced up to a factor of 200 over the uncalibrated X-band data. This large improvement in the data quality, revealed by values of the frequency stability previously achieved only during solar oppositions, makes the navigation accuracy of deep space probes nearly independent of the solar elongation angle.
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