Venera : Venus Planetary Radar Astronomy

Analysis of 32 years of Arecibo planetary-radar observations of Venus (1988–2020) to measure its rotation elements and build a registered global radar image.

Writeup: Amateur Estimates of the Rotational Elements of Venus using 32 years of Arecibo Planetary Radar — note: the linked doc is the Feb 2023 snapshot and predates several retractions and refinements; REPORT.md in this repo is the current system of record (the doc's pole detection and "spin-up" claim are retracted, and its period uncertainty was optimistic — see REPORT §6–§8).

What this is

Planetary radar astronomy maps celestial bodies with active radar. From 1988 to 2020 Arecibo intermittently observed Venus in delay-Doppler mode; the data are archived at the PDS Geosciences Node (Bruce A. Campbell & Donald B. Campbell 2022, Planet. Sci. J. 3 55, doi:10.3847/PSJ/ac4f43). This repository projects each coherent look into a Venus body-fixed frame, finds the spin (period and pole) under which all looks co-register, and stacks them into a global image — the rotation elements and the crisp image are two readouts of the same registration (see project_goal.md).

Results

• Sidereal rotation period: P = 243.0206 ± 0.0007 d, pole adopted from IAU (RA 272.76°, Dec 67.16°) — consistent with Campbell 2019 (243.0212) and Margot 2020 (243.0226), above the Magellan/IAU 243.0185.
• Global stack of all 916 looks, both latitude hemispheres (−85°…+83°), at up to ~1.2 km/px (results/figures/global_*, results/session_stacks/global_*.npz).

Coverage is both north and south but only the Earth-facing ~185° of longitude — Earth-based radar sees only the sub-Earth disk, and the six inferior-conjunction epochs sample a limited longitude range.

See REPORT.md for methods, conventions, validation, and the full result.

Code layout

• venera/ — tested library (cspyce + DE440s geometry, projection, registration, rotation fit, stacking). The durable code; run .conda/bin/python test/run_all.py.
• scripts/ — drivers (project all looks → stack → period estimate → global map); see scripts/README.md.
• PLAN.md — remaining/optional refinements.

Example delay-Doppler image: