The MAR-I (that is a Roman Numeral one) was the first phased array radar
developed by the US Army. This first version used separate arrays for the
transmitter and receiver. In the photo above, the transmitter array can be
seen on the small dome at the right corner of the facility, while the receiver
array is on the larger dome. The MAR-I was built with only one transmitter
array and one receiver array, with the expansion capability to add a transmitter
array on the other small dome with the array pointing to the left, and a
receiver array in the raised portion
on the left side of the
large dome. The domes were all steel and most of the equipment and
facilities were under ground. There was a Nike Hercules tracking radar on top of the large
dome and one on the tower to the right of the main facility. These radars
were used and instrumentation radars to verify the accuracy of the MAR-I radar.
The large outer fence was referred to as a "clutter fence." It was called
that because it blocked the radar signal reflected from the ground (called
ground clutter) from being received by the radar and displayed.
After several years of Research and Development (R&D) testing of the Nike Zeus Anti
Intercontinental Ballistic Missile system the three different radars used with the Nike Zeus system
were deemed to be inadequate. These radars were limited by mechanical
rotation constraints and became
obsolete as technology advanced and the ability to electronically steer the radar beam
became possible. This brought about MAR-I.
As R&D testing
continued, advances in technology were making even the MAR-I technology
outdated. However, there were may things to be learned from the MAR-I
testing and it remained operational until 1969. The technology advances
had made it possible to consolidate the transmit and receive function into one
array. So, at Kwajalein Island in the Pacific, construction had begun on
the R&D Common Aperture Multi-function Radar (CAMAR). Eventually, as the
technology settled out, the Nike X system concept,
which included the Spartan and Sprint missiles,
was replaced by the Sentinel system (later renamed Safeguard), which also
included the Spartan and Sprint missiles along with two phased array radars
called the Missile Site Radar (MSR) and the Perimeter Acquisition Radar (PAR)
and one site was eventually built in North Dakota. The CAMAR building was
completed, but never populated with equipment.
