CORONA (satellite)

Overview

The CORONA program started in 1956 under the name Discoverer, as a component of the U.S. Air Force's WS-117L satellite reconnaissance and protection effort, which itself drew on RAND Corporation recommendations and designs. Its main objective was a film-return photographic satellite to take over surveillance of the Sino-Soviet Bloc from the U-2 spy plane, specifically to track the location and production rate of Soviet missiles and long-range bombers.

The program also supplied maps and charts for the Department of Defense and other federal mapping projects. Work accelerated after the Soviets downed a U-2 on May 1, 1960.

CORONA eventually included eight overlapping satellite series, called Keyhole or KH, launched between 1959 and 1972. It was later supplemented and replaced by the higher-resolution KH-7 Gambit and KH-8 Gambit 3 satellites. A related but failed effort was the SAMOS program.

Program history

Before the U.S. government began classifying space launches in late 1961, the early CORONA satellites were hidden behind a cover story. They were publicly presented as part of the Discoverer program, a scientific and engineering effort where film-return capsules supposedly brought back biological samples. To sell this story, some CORONA capsules were designed to carry a monkey, though many test monkeys died during ground tests of the life support system.

The Discoverer disguise became awkward, drawing unwanted questions from scientists. The final mission to use the Discoverer name was Discoverer 37, launched on January 13, 1962; after that, CORONA launches were simply labeled as Department of Defense satellite launches. The first CORONA models were the Keyhole 1 (KH-1) satellites, built on the Agena-A upper stage, which provided housing and an engine for orbital attitude control. The KH-1 carried a single panoramic camera called the C (for CORONA), made by Fairchild Camera and Instrument, with an f/5.0 aperture and a 61 cm focal length, achieving a ground resolution of 12.9 meters.

A single General Electric Satellite Return Vehicle (SRV) brought the film back from orbit, using a small solid-fuel retro motor to deorbit. Recovery involved a specially equipped aircraft catching the capsule in mid-air. Three camera-less test launches occurred in early 1959, none fully successful.

Technology

The CORONA satellites relied on a specialized 70 mm film system paired with a 24-inch focal length camera. Eastman Kodak manufactured the film, which initially measured 0.0003 inches thick and offered a resolution of 170 lines per millimeter with a 2-to-1 contrast ratio. The original acetate-based film was later swapped for a more durable polyester stock better suited to the conditions of Earth orbit. Film capacity changed over the program’s lifetime.

Early satellites carried 8,000 feet of film per camera, totaling 16,000 feet. By the fifth generation, thinner film and additional capsules allowed each camera to hold 16,000 feet, for a combined 32,000 feet. Most footage was black and white. Infrared film appeared on mission 1104, and color film on missions 1105 and 1008, but color’s lower resolution led to its abandonment.

The Itek Corporation built the cameras, which used a 12-inch f/5 triplet lens—7 inches in diameter and closely resembling Carl Zeiss AG’s Tessar design. Camera length started at 5 feet and later grew to 9 feet. Starting with the KH-4 series, the lenses were replaced with a Petzval f/3.5 design. These panoramic lenses swept through a 70-degree arc perpendicular to the satellite’s orbital path, chosen for their wider coverage.

Although peak resolution occurred only at the image center, an automatic reciprocating sweep across the 70-degree arc compensated. The lens rotated continuously to counter motion blur from the satellite’s movement over the Earth.

Operations

The Sunnyvale Air Force Station, now Onizuka Air Force Station, is recognized by the U.S. Air Force as the starting point for the CORONA program. In May 1958, the Department of Defense moved the WS-117L program to the Advanced Research Projects Agency (ARPA). The Air Force provided $108.2 million for WS-117L in FY1958. For the DISCOVERER project, the Air Force and ARPA together spent $132.3 million in FY1959 and $101.2 million in FY1960.

John N. McMahon estimated the total CORONA program cost at $850 million. The CIA handled the procurement and upkeep of the CORONA satellites, using cover arrangements from April 1958 to 1969 to work at the Hiller Helicopter Corporation plant in Palo Alto. There, the Agena second stage, cameras, film cassettes, and re-entry capsule were built and tested before being sent to Vandenberg Air Force Base. In 1969, assembly moved to Lockheed facilities in Sunnyvale, California, to keep skilled workers from leaving as the program wound down.

The CORONA Target Program decided what to photograph. Satellites flew in near-polar orbits, and an on-board computer operated the cameras based on targets, weather, satellite status, and already-captured images. Ground control first operated from Stanford Industrial Park in Palo Alto, then shifted to Sunnyvale Air Force Base.

Did You Know?

• In 1957, the Soviet Union launched Sputnik 1, the first artificial Earth satellite, which prompted President Dwight D. Eisenhower to authorize the Corona program.
• Minoru S. Araki, Francis J. Madden, Edward A. Miller, James W. Plummer, and Don H.