← INDEX — FIG. 00 — 19 AUGUST 1960, 8,500 FT OVER THE PACIFIC KH-1 → KH-4B · 12.2 m → 1.8 m

BUCKET
CORONA, ZENIT & THE FIRST SPY SATELLITES

For twelve years the United States read the Soviet Union from photographs that fell out of the sky.

BEGIN — CHAPTER 01 →

CH.01 / 09 — 1956–1960

A camera that could not be shot down

The U-2 flew sporadically; Powers was shot down on 1 May 1960 [1].

CORONA, cover name Discoverer [1].

THE GAP, COUNTED

1 May 1960 → 19 August 1960 = 110 days

110 days [1].

CH.02 / 09 — DISCOVERER I–XIV, 1959–1960

Twelve failures, then two firsts in eight days

Twelve launches, no capsule recovered [1].

Discoverer XIII recovered from the sea; Discoverer XIV caught in the air [1][6].

CHECKING THE PRESS RELEASE WITH KEPLER

a = R + (h_p + h_a)/2 = 6,378 + (187 + 808)/2 ≈ 6,876 km · T = 2π √(a³/μ) ≈ 94.6 min

Period check.

CH.03 / 09 — RETRO-BURN TO AIR CATCH

Hitting a box in the Pacific from orbit

The recovery sequence [1].

The zone and the sink rate [1].

AFTER THE BURN: AN ELLIPSE THAT MEETS THE AIR

v₁ = √(μ/r₀) − Δv · v_e = √(v₁² + 2μ(1/r_e − 1/r₀)) · cos γ_e = r₀v₁ / (r_e v_e)

Model notes.

RETRO Δv—

ORBIT HEIGHT AT THE BURN—

Assumptions.

CH.04 / 09 — KH-1 → KH-4B, 1960–1972

A 24-inch lens that sweeps from side to side

24-inch panoramic cameras [1][2][3][4].

Resolution as a line pair; 12.2 m → 1.8 m [1][2][5].

GROUND RESOLUTION: FILM LIMIT AND DIFFRACTION LIMIT

GR_film = H / (f · R) · GR_diff = 1.22 λ H / D, with D = f / N · film-plane limit of the lens = 1 / (1.22 λ N)

Inputs [2][3][4].

ALTITUDE—

FILM + LENS RESOLUTION—

F-NUMBER (FOCAL LENGTH 609.6 mm)—

The lens was never the limit [4].

Panoramic sweep [2].

ALTITUDE—

SWEEP (SCAN ANGLE)—

Notes [3].

CH.05 / 09 — PERIGEE, DRAG AND MISSION LENGTH

Fly low for sharp pictures, and pay in days

Low perigee, rapid decay, drag make-up units [1][3].

The trade [16].

ORBIT-AVERAGED DRAG DECAY (GAUSS'S EQUATIONS)

da/dt = −⟨a² ρ v³⟩ / (μ β) · de/dt = −⟨ρ v (e + cos ν)⟩ / β · β = m / (C_D A)

Model notes [16].

PERIGEE—

APOGEE—

BALLISTIC COEFFICIENT (ASSUMED)—

Assumed β.

CH.06 / 09 — THE SOVIET ANSWER, 1961–1994

Zenit: bring the whole camera home

Zenit-2: a Vostok capsule full of cameras [9][10].

Kosmos 4 and 7; 1,000 mm lenses; 81 launches [9][10][11][12].

SAME SCALE, DIFFERENT ROUTE

CORONA KH-4B: 609.6 mm from 150 km → 1 : 246,000 · Zenit-2: 1,000 mm from 250 km → 1 : 250,000

Scale comparison [9][10][13].

CH.07 / 09 — 1972, 1976, 1995

From buckets to bits — and into the open

Last CORONA 1972; KH-11 1976 [1][7][8].

Declassified 1995; archaeology and glaciology [1][2][14][15].

HOW FINE MUST THE SCAN BE?

160 lp/mm → 6.25 µm per line pair → 3.1 µm pixels to sample it · a 7 µm scan pixel at 1 : 246,000 = 1.7 m on the ground

Scanning [2].

CH.08 / 09 — LEGACY

From a hook over Hawaii to a public archive

The pictures were taken to count missiles.

CH.09 / 09 — REFERENCES