Calculating Venusian Day: Arecibo Data Reveals Surprising Findings

Nathaniel Fairfield, also known as thandal, used publicly available uncalibrated delay-doppler images of Venus collected by the Arecibo Observatory to estimate the planet's rotation and axis tilt. By aligning and calibrating the raw data, Fairfield found that Venus's revolution appears to be slightly speeding up and his estimates of the orbital axis were within 0.01 degrees of the International Astronomical Union's values. The complex signal processing involved mapping the data onto the Venus geoid and using surface features to estimate rotational speed and tilt. This research is important for better planning future missions.