Some consequences of critical refraction in the Venus atmosphere

Mariner V and the three successful Venera probes have shown the density of the atmosphere of Venus to be so high that critical refraction occurs at an altitude near 35 km. Somewhat bizarre optical effects are to be expected in such an atmosphere. Using a spherically symmetric model based upon the measurements of the refractivity at the top of the atmosphere by the Mariner V S-band occultation experiment, the Venera 4 data in its altitude range, and adiabatic extrapolation to the surface, calculations of a variety of ray paths have been made with a double-precision computer program. Phenomena discussed include the magnification of the planet, the elevation of the horizon, the apparent motion and distortion of the sun, and the possibility of ‘seeing’ completely around the planet.