Venus Atmospheric, Ionospheric, Surface and Interplanetary Radio- Wave Propagation Studies with the VeRA Radio Science Experiment
Publication date: 02 Nov 2007
Authors: Hausler, B., et al.
Journal: ESA Special Publication
Copyright: ESAThe Venus Express Radio-Science Experiment (VeRa) is using radio signals at X- and S-band (3.5 cm and 13 cm wavelengths, respectively) to probe the Venus surface, neutral atmosphere, ionosphere and gravity field, and the interplanetary medium. An ultrastable oscillator (USO) is providing a high-quality onboard reference frequency source; instrumentation on Earth is sampling amplitude, phase, propagation time and polarisation of the received signals. Simultaneous coherent measurements at the two wavelengths allow separation of dispersive media effects from classical Doppler shift. The execution of a radio-science experiment involves the precise interaction of many complex spaceborne and ground-based systems. The quality of the measurements depend critically not only on the noise performance of the USO, the quality of the radio link and the performance of the ground station, but also on the precision of the timing, ephemeris data, orbit prediction and the attitude-control manoeuvres that are needed to perform the experiments and to extract the data.