Venus: Long Term Observations from Venus Monitoring Camera on Venus Express Orbiter

Abstract:

The Venus Monitoring Camera on European Space Agency’s Venus Express orbiter imaged the day side of Venus daily (when observations were possible) once routine operations commenced in May 2006 till 27 November 2014 when the data collection ended. The images collected over 13.3 Venus years (12.3 Venus rotations or 25.6 Venus solar) days reveal the changes in the Venus cloud cover over more than three fourth of the solar cycle at 365, 550, 950 and 1050 nm primarily in the southern hemisphere as most of the images were taken in the apoapsis portion of the 0.84 eccentricity orbit of Venus Express with periapsis located at high northern latitudes. Over the entire period the organization of the southern hemisphere cloud cover is organized in a circum polar vortex extending all the way to the equator. The strength of the vortex indicated by the cloud motions varies over the duration. The unit optical depth of the cloud/haze layer varies both with local time and with latitude and is asymmetric across local noon. Significant periodic changes are also seen in the cloud cover in terms of albedo, global contrast.