This paper describes the concept of a low-profile user terminal antenna intended for mobile bi-directional Ka-band satellite communications. The concept addresses a hybrid electronic and mechanical tracking method. The antenna consists of several two-dimensional leaky-wave antenna panels. Each panel is excited by a slotted waveguide feed, composed of a linear array of circularly polarised slots. This structure offers a reconfigurable radiation pattern. As a proof-of-principle, a rectangular antenna panel for the downlink at 20 GHz was manufactured and measured. The paper describes the design of the panel in detail and presents the results of numerical simulation and measurement.