MAR-II phased-array radar

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MAR-II, short for Multi-function Array Radar, was a two-faced phased-array radar with separate transmitters and receivers. The transmitters are the smaller round disks on the lower section of the building on the east side (right), the receivers are located on the larger area above them to the west (left).

MAR was designed to be a highly sophisticated system able to track hundreds of warheads and decoys. One to four faces could be installed, to provide coverage over an area from about 90 degrees to a full 360, as required. Both the transmitter and receiver were "active", allowing the beams to be steered in any direction and split up into multiple parts. The system was enormously complicated and expensive to install.

The prototype MAR-I was built at White Sands Missile Range in a dome with provisions for antennas on two sides. Only one was installed, and that was only partially installed to save money. The original antenna design had 6500 "elements" over a 40 foot diameter circle, but for MAR-I they only installed 2500 elements on the inner 25 feet.

For the MAR-II installation on Kwajalein, the structure was built in the form of a truncated pyramid and was designed from the start to have only two faces, for 180 degree coverage. Like MAR-I, only one of the two faces was intended to be installed. Unlike MAR-I, elements were installed over the complete antenna face, instead of just an inner section. To lower costs , many of the elements were left unconnected so the associated transmitter and receiver modules were not needed. The non-connected antennas and their wiring were installed on both faces, however, in case there was a desire to upgrade the system to full MAR performance.

MAR-II was originally intended to work beside a prototype of the Missile Site Radar (MSR) which would also be built on Kwajalein (on Meck Island, some distance to the north). However, as the construction was continuing, the Nike-X system was abandoned in favor of a "lighter" ABM system, ultimately known as Sentinel. This system was designed to deal with relatively light attacks by China or small accidental attacks by the Soviets, and the massive data processing of the MAR system was not considered important. Instead, the much simpler MSR radar became the primary detector, with a simpler PAR radar providing early warning.

MAR-II was abandoned, partially complete, and is currently used for storage. The prototype MSR was built on Meck Island.