← INDEX — FIG. 00 — VENUS, 98% MAPPED THROUGH THE CLOUDS
12.6 cm · 3.7 m · 120–300 m
VEIL
MAGELLAN'S RADAR MAP OF VENUS
From orbit, cameras see Venus's ground only as a blurred glow.
BEGIN — CHAPTER 01 →CH.01 / 07 — WHY RADAR
Light bounces off the clouds; 12.6 cm waves walk through
Clouds scatter light; 12.6 cm passes through.
Pioneer Venus 50–140 km; Venera 15/16 1.2–2.4 km; Magellan 120–300 m.
Resolution ladder and droplet size parameter.
CH.02 / 07 — SYNTHETIC-APERTURE RADAR
A 3.7 m dish that sees like a kilometre-long one
Range: 88 m slant resolution.
Azimuth: Doppler, 120 m.
RADAR GEOMETRY
t = 2ρ/c · δground = 88 m / sin θ · Lbeam ≈ ρ·λ/D · Lsynth ≈ ρ·λ/(2·δaz)
t = 2ρ/c; 88 m / sin θ.
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Model assumptions.
CH.03 / 07 — 243-DAY CYCLES
Let the planet turn underneath
25 km strips; 21 km shift per orbit.
83.7%, 96%, 98%.
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Strip spacing formula.
CH.04 / 07 — WHAT THE MAP SHOWED
Too few craters, scattered at random
842 craters on 89% of the surface.
Random, pristine, about 0.5 billion years.
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Illustration only.
CH.05 / 07 — SURFING THE ATMOSPHERE
The first aerobraking at another planet
1.2 km/s by drag, not propellant.
70 days, 700+ passes, 541 × 197 km.
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Model assumptions.
CH.06 / 07 — LEGACY
Still the map of Venus, thirty years on
The global reference, still.
VERITAS and EnVision.
From orbit, light shows us only the blur of Venus.
CH.07 / 07 — REFERENCES