18 January 2010

In the 1950s the United States introduced three different systems to try and solve the problem of conducting electronic intelligence (ELINT) on targets deep in the Soviet Union which couldn't be picked up by the USAF and Navy ferret flights operating on the periphery. The first system was to mount ELINT antennas on giant weather balloons that would be launched in Western Europe and drift over the Soviet Union on prevailing winds before being recovered out in the North Pacific. Approximately 200 "Grand Union" balloons were built for the USAF and only about 20 were actually launched with little to no useful intelligence being recovered. The second system was to use ELINT antennas mounted on Lockheed U-2 spyplanes during overflights of the Soviet Union. Between 1956 and 1959, approximately 30 ELINT overflights were made, but only a handful of those missions were deep penetration missions.

The most productive of the systems and ironically the lowest risk due to its low manpower requirement as well as it could be located in the United States was introduced in 1958 as the PAMOR (Passive Moon Relay) system. Originating from experiments dating back to 1948's Project Diana which determined that communications signals could be bounced off the Moon to receivers beyond the horizon, PAMOR (sometimes referred to Moonbounce) was the natural extension. A CIA engineer, Jim Trexler, postulated that a sensitive receiver pointed at the Moon could pick up radar emissions from sites deep in the Soviet Union.

The first PAMOR dishes were built at the Naval Research Laboratory's Chesapeake Bay Annex on the bay's western shore as well as in California in Palo Alto. The definitive equipment was installed soon after in a valley near Sugar Grove, West Virginia (not far from the radio astronomy observatory at Green Bank). Using 150-foot dishes and sensitive listening and tracking equipment, the system readily produced results as the new early warning radar system code named "Tall King" was discovered. Designated P-14 by the Russians, the Tall King radar was a powerful system used for the detection and tracking at long ranges of airborne aircraft. Using known Moonrise and Moonset times, it was possible to draw a line on a map through the Soviet Union- somewhere along that line would be the transmitting radar. Over several weeks, it was possible to narrow down the precise location as this would be where the Moonrise/Moonset lines intersected.

In the latter half of the 1960s (starting in 1964 when it was first intercepted by a PAMOR dish), the system discovered a new high power advanced radar system that was found to be used by the Soviet ABM system to scan and track incoming ballistic missile warheads. Code named "Hen House" due to the configuration of the antenna, detailed analysis not only revealed the Hen House locations, but also radar characteristics such as frequency, power, dwell time, etc. From this analysis it was determined that the Hen House radar was very sophisticated as it could both track and scan and its dwell times were very short, which suggested a high level of computerization.

As the Soviets upgraded and fine-tuned the Hen House system for its ABM defenses, operators would practice and test the system by tracking the Moon, inadvertently making the job of the PAMOR teams much easier!

The discovery by the PAMOR program of the Hen House ABM system was significant as the characteristics of the system drove the design and planned employment of the US SLBM/ICBM nuclear deterrent. At its height in the late 1960s and early 1970s, the program never employed more than 100 personnel, making it one of the most successful ELINT efforts ever deployed.

Source: The History of U.S. Electronic Warfare, Volume II- The Renaissance Years, 1946-1964 by Alfred Price. The Association of Old Crows/Port City Press, 1989, p157-161.

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