Mission Requirements

Considering the prospect of a nuclear war with the Soviet Union, United States leaders in the 1950s had to know two things. First, what were the Soviets doing in their strategic missile programs? They had already demonstrated a nuclear capability with an atomic detonation in 1949 and a fusion-weapon test in 1953. Could they launch a nuclear weapon on a rocket over intercontinental distances? Second, how effective might Soviet defenses prove to be against US forces? Could the Soviets detect and shoot down US long-range bombers? And could the Soviets counter the developing US missile capability?

Conventional intelligence sources in the 1950s collected bits of data on both of these concerns; spies, or human intelligence, were effective in some areas but encountered significant problems because of the strict security rules inside the Soviet Union. One early attempt to reach deep into the Soviet land mass was by Jim Trexler of the US Naval Research Laboratory (NRL). He pioneered work on and tests of intercepting radar signals using the Earth’s largest satellite, the Moon. He was successful in the late 1950s in collecting intercepts from Soviet [REDACTED EO 13525] (the NATO designator) early warning radars on NRL’s 60-foot parabolic reflector antenna in Maryland, and then, with better reception, on the National Radio Astronomy Observatory’s 150-foot reflector in West Virginia. He proposed building a 300-foot and, at one time, a 600-foot “big dish” to collect weaker Soviet radars. 5 In the early 1960s NSA built a special antenna feed for and successfully tested the 1,000-foot-diameter antenna at Arecibo Ionospheric Observatory, Puerto Rico, intercepting [REDACTED EO 13525] and other signals. 6 This technique also allowed radars to be located with an uncertainty of 50 miles using multiple intercepts on separate days.

Listening to radio communications, or COMINT, was somewhat easier. The Soviets used short-wave radio bands extensively for communications, and the US military intercept stations, expanded from their World War II numbers, heard many Soviet-Union-wide operational military, industrial, and research networks, yielding some understanding of the Soviet threat. US strategic planners, though, needed more specific data on the exact locations and capabilities of Soviet military and industrial installations. Attempts to take pictures with balloon overflights proved generally unproductive, and conventional aircraft reconnaissance was limited to flights around the periphery of the Sino-Soviet bloc of states. For that reason, in November 1954 President Dwight D. Eisenhower approved development of the U-2, a highly secret high-altitude reconnaissance aircraft, which was rapidly engineered and put into use in 1956.

Eisenhower came to believe that the U-2 could overfly parts of Soviet airspace at will. But this would have represented a clear violation of international law, unless the leaders concerned had agreed to such flights. On 21 July 1955, Eisenhower proposed to Soviet leader Nikita Khrushchev that the United States and the Soviet Union provide “facilities for aerial photography to the other country” and conduct mutually supervised reconnaissance overflights. 7 Before the day ended. Khrushchev rejected the plan, which came to be known as the Open Skies doctrine, as an American attempt to “accumulate target information.” Eisenhower said later, “We knew the Soviets wouldn’t accept it, but we took a look and thought it was a good move.” 8 The Soviets were thus forewarned of our U-2 flights and the groundwork was beginning to be laid for the use of reconnaissance satellites. Eleven months later Eisenhower approved the first U-2 overflight of the Soviet Union. 9

Beginning with the first operational flight in July 1956, US analysts found in the U-2 data an extensive Soviet air defense system being built to counter US strategic bombers and reconnaissance flights, including the U-2 itself. They also saw research and development (R&D) installations for long-range missile systems and, eventually, operational missile sites. Soviet short-range missiles had already flown that same year. Soon, near Sary Shagan, U-2 cameras photographed what appeared to be Soviet antiballistic missile (ABM) R&D facilities. Because it had a great effect on major US resource decisions on its own ABM, intercontinental ballistic missile (ICBM), and countermeasures techniques, the “ABM problem” became the US’s top intelligence priority, and eventually became the main focus of effort for SIGINT satellites.

US reconnaissance satellites, the successors to the U-2s, were developed expressly to provide visual and electronic access to the Soviet Union. The very first SIGINT satellites, launched in 1960, were intended to detect and locate air defense radars, to determine the electronic order of battle (EOB), which listed the types and locations of Soviet defense system radars), and thus to assist American bombers to pass through Soviet defenses to military targets in the event of war. The US Intelligence Board (USIB) had not yet begun to issue formally documented requirements, but the US military and intelligence organizations perceived the nations of the world aligning themselves with one or the other of’ the superpowers, each with its respective spheres of influence. Thus, the US Air Force Strategic Air Command (SAC) wanted details on Sino-Soviet targets for attack, data on radars and antiaircraft weapons technical information for design of electronic countermeasures, and exact locations of Soviet defensive installations in order to plan their aircraft penetration routes. The US Navy wanted to determine the threat from Soviet surface ships and submarines, and the US Army and NATO commanders were concerned about Soviet and Warsaw Pact air and ground forces.

Another driving force in the early development of SIGINT satellites was the electronic and rocket engineer’s new technical ability to build more and more sophisticated intercept and recording equipment in lighter packages, place these packages in satellites that circled the Earth, and do really useful reconnaissance jobs for significant durations of time in the vacuum of space. Technology indeed moved rapidly in the 1950s. The transistor, which would replace the cumbersome electronic vacuum tube as an amplifier of weak signals, was invented at Bell Telephone Laboratories in 1948. 10 The first “junction transistor” appeared in 1951. By 1960, solid-state electronics began revolutionizing radio and data processing, the two fields on which SIGINT was based. Electronic hardware suddenly could be designed and built in ever smaller sizes and operated on lower power and would produce much less heat during operation. These advances, coupled with the new advances toward long-range rockets for military purposes, provided both the technology and the lifting capability to make possible the design and launch of SIGINT satellites.

US military reconnaissance satellites, already well along in planning when Sputnik I was launched—and in some cases, even with hardware under development (the Air Force’s Advanced Reconnaissance System, Weapon System 117L [WS-117L] was an example)—would number among the pioneers of orbiting artificial satellites. For its reconnaissance satellites, the Air Force developed a general operational requirement and very specific technical specifications based on intelligence data, as it did for all its weapons systems. Nevertheless, construction of WS-117L and the other early SIGINT satellites turned on issues of what instrument might work, and, among those that did, which might be most useful as preliminary collectors of the needed data. At the time, ELINT seemed to be easier to try than COMINT, although COMINT was in the minds of some from the very beginning. Soon, feedback and cross fertilization networks developed among the groups building, using, and analyzing the ELINT data, from which new priorities would be set. The era of SIGINT satellites was starting and would enjoy many and varied forms and successes. The formal USIB requirements for the intelligence data these systems collected would come later.

5. NRL Memorandum Report 1418, 20 May 1963.

6. [REDACTED EO 13525] “Extending the Radio Horizon for Intercept Purposes by Using the Moon as a Reflector,” NSA Technical Journal, Vol. X. No. 2, spring 1965.

7. “Statement on Disarmament. 21 July,” The Department of State Bulletin, Vol. XXXIII, No. 841, 1 August 1955. p. 174. Abel. Elie, “Eisenhower Calls Upon Soviet Union to Exchange Arms Blueprints,” The New York Times, 22 July 1955, p. 1. See also John Prados, The Soviet Estimate: US Intelligence Analysis and. Russian Military Strength, New York: The Dial Press. 1982, pp. 31-32. The term “Open Skies doctrine” was coined later by the popular press and applied to Eisenhower’s statement on disarmament.

8. Parrnet. Herbert S., Eisenhower and the American Crusades, New York: The MacMillan Company, 1972, p. 406. Rostow, W. W., Open Skies: Eisenhower’s Proposal of July 21, 1955. Austin. TX: University of Texas Press. 1982, pp. 7-8.

9. Ambrose, Stephen E., Ike’s Spies: Eisenhower and the Espionage Establishment, Garden City, NY: Doubleday & Co., 1981, p. 266 and pp. 31-34. Quoted in R. Cargill Hall, The Air Force and the National Security Space Program, 1946-1988, USAF Historical Research Center. 1988. (TS/TK)

10. Encyclopedia Americana, “Transistor,” point contact.

NRO APPROVED FOR RELEASE 10 FEBRUARY 2016
Source: National Reconnaissance Office, The SIGINT Satellite Story