English: MAR-I was the prototype Multi-function Array Radar, an extremely complex phased-array radar system built as part of the Nike-X anti-ballistic missile (ABM) project of the 1960s. MAR was able to actively steer and form its radar beams under computer control, allowing it to detect, track and discriminate multiple ICBM warheads at long range. MAR was also extremely expensive, one of the reasons that led to the Nike-X system being abandoned in 1967. A second MAR, MAR-II, was under construction on Kwajalein Island, and abandoned in place at that time. In the later Sentinel and Safeguard ABM systems, MAR was replaced by a much simpler early warning radar known as the Perimeter Acquisition Radar (PAR).

The MAR radar was able to steer its beam through a maximum of 120 degrees, so in order to provide complete coverage of the sky, the system allowed between one and four "faces" to be installed. In most cases only two would be used, covering the area to the north where Soviet ICBMs would approach from. Some sites would add more faces in order to deal with SLBMs and other threats. For this experimental installation, only the northwestern face was installed, which is facing the camera in this image.

The receiver antenna is in the large disk on the larger central dome, the transmitter is the smaller antenna on the smaller dome on the right. For this installation, only a small portion of the antenna elements are installed, about 2,500 of a possible 6,900. The installed elements appear as grey shading in the center of the disks. The building had been constructed to allow a second north-east face to be installed, but this was never used and its transmitter dome is blank. Below each of the antenna arrays is a dark slot, which led to a storage area for covers that slid up the rails on either side of the antennas to protect them and ease maintenance. The covers are in storage in this image and cannot be seen.

Surrounding the entire radar site is a large angled "clutter fence". This was a common feature of very large radars of the era. It was designed to reflect sidelobes up into the sky, where they would not be seen. Without the fence, the sidelobes would reflect off local landforms, in this case, some distant hills, and make the received signal very complex. The fence served the secondary purpose of protecting people walking around the site from the intense microwave signal, which was powerful enough to be a health hazard.

In this image, the camera is looking to the southwest. The small silver building to the west of the radar (to the right in the image, inside the fence) is a tracking radar from the Nike Hercules system, which was used to calibrate MAR. Another is placed on the roof of the main MAR dome. The two towers in the upper-left side of the image, just outside the fence, are part of the power substation. MAR-I had a private power line to the nearest power plant, some distance away. The brown-roofed building is a hanger, with a taxiway leading from it to a small airstrip, which is just off the top of the image. The second building with the white roof is an office.

MAR-I was built at White Sands Missile Range just off Highway 70 about 25 miles north of the main Army missile launch sites. This allowed it to track the many missile launches taking place under different programs, meaning the program did not have to budget as many test launches of its own. After its closure in 1969, MAR was stripped for parts and re-purposed as a fallout shelter for the USAF base to the east. The site was later re-used as the base for the High Energy Laser System Test Facility (HELSTF), home of the MIRACL laser. The fence around MAR has since been removed and the area heavily re-developed, although the original MAR-I building remains in place.