Amateur estimates of Venus day using Arecibo data

[Nathaniel Fairfield] aka [thandal] Curious about the actual rotation and axial tilt of Venus. He decided to spin GitHub Python repository As one does, read the problem further. The scientific literature shows a wide range of estimates and variations for the planet’s revolution and axial tilt. He wondered if the real answer could be found in A Publicly available package Uncalibrated delay-Doppler images of Venus. The data was collected from 1988 to 2020 by the former Arecibo Observatory in Puerto Rico. [Thanda] He found that the planet’s revolution was slightly accelerating, and his estimates of the orbital axis were within 0.01 degrees of the International Astronomical Union (IAU) values. [Note: Venus is a bit confusing — one planetary revolution, 243 days, is longer than its year, 225 days].

Aligning and calibrating raw data is not a trivial task. You have to consider the position and time of the radar (Earth) and Venus. To further complicate the math, the radar was sometimes operated bistatically, with the Green Bank Telescope in West Virginia as the receiver.

There’s a lot of interesting signal processing going on here. The Doppler-delay data consists of 8091×8092 images with complex values ​​that must be mapped onto the Venus geoid. By using various surface features, one can compare their positions over time and obtain an estimate of rotation speed and inclination. If you are interested in these types of calculations, check [Thandal]s Summary reportAnd take note The poliastro Python Astrophysics Library. Why is this important? A reason to plan future tasks better.