MORE: an advanced tracking experiment for the exploration of Mercury with the mission BepiColombo

Precise microwave tracking of interplanetary spacecraft has been a crucial tool in solar system exploration. Range and range rate measurements, the main observable quantities in spacecraft orbit determination and navigation, have been widely used to refine the dynamical model of the solar system and to probe planetary interiors. Thanks to the use of Ka-band and multifrequency radio links, a significant improvement in microwave tracking systems has been demonstrated by the radio science experiments of the Cassini mission to Saturn. The Cassini radio system has been used to carry out the most accurate test of General Relativity to date. Further developments in the radio instrumentation have been recently started for the MORE experiment, selected for the ESA mission to Mercury, BepiColombo. MORE addresses the mission's scientific goals in geodesy, geophysics and fundamental physics. In addition, MORE will carry out a navigation experiment, aiming to a precise assessment of the orbit determination accuracies attainable with the use of the novel instrumentation. The key instrument is a Ka/Ka band digital transponder enabling a high phase coherence between uplink and downlink carriers and supporting a wideband ranging tone. The onboard instrumentation is complemented by a ground system based upon the simultaneous transmission and reception of multiple frequencies at X and Ka-band. The new wideband ranging system is designed for an end-to-end accuracy of 20 cm using integration times of a few seconds. Two-way range rate measurements are expected to be accurate to 3 micron/s, thanks to nearly complete cancellation or calibration of the propagation noise from interplanetary plasma and troposphere. We review the experimental configuration of the experiment and outline its scientific goals and expected results.