English: Meck Island was developed in the 1960s to test the Sentinel ABM system. Sentinel lasted only 18 months before being replaced by the similar Safeguard. It has seen use on-and-off for various projects since then. This image shows the Missile Site Radar (MSR) built on Meck in the late 1960s and early 1970s. The building on left is the original testbed MSR system. Normally it would be buried so only the angled portion on top was out of the ground, but as Meck is only a few feet over sea level, it was decided to build the entire building above ground. A production MSR would have four angled faces to produce a truncated pyramid, but only two faces were built for this installation. The data processing equipment (computers) were placed in the smaller building extending out the back of the radar to the south, just visible as the dark building projecting to the right. Behind it is another building that controlled launch operations. The original MSR used a "space array" system for its radar. The circular disks on the angled faces contained a number of phase shifter devices with antennas on either end. Inside the building was a single transmitter and receiver which was aimed at the back of the disk. The transmitted signal was picked up by the antenna on the back of the phase shifter, shifted, and then rebroadcast from the front. This allowed a single microwave source to feed all of the elements in the phased array system. It also meant that there had to be considerable room behind the radar face, which is why the building is so much larger than the disk of antennas. Production MSRs reduced this ratio somewhat, and looked more pyramidal, less truncated. The rusted metal rails on either side of the radar face were used to hold a window-washer like servicing platform, and could be extended to the ground with additional rails that plugged into sockets that can be made out on the concrete pad surrounding the building. In this image the antennas have been removed and the openings sealed off with covers, and the lower section of the servicing rails have been removed. Safeguard development on Meck was curtailed with the signing of the ABM Treaty in 1972. Testing continued for a time until a single operational Safeguard base was built in the US and became operational in 1975. This was quickly removed from service in 1976 after less than a year of operation. This did not end Army research into ABM systems, however, and through the mid-1970s they began development of the improved Site Defense Radar as part of a more flexible set of technologies that could be rapidly deployed in case the Soviets "broke out" of the Treaty. The building on the right was built as the prototype of this system. This version is much smaller, although the radar disks are about the same size, which suggests it does not use the space array concept. 1960s photography of the site shows the shoreline approximately at the door into this radar's building, the land it sits on was backfilled in 1977. The image is taken looking towards the south end of Meck. Kwajalein Island can just be made out on the horizon between the two radar buildings. What appears to be a walkway running diagonally across the image is a buried cable conduit to the missile launch sites. The photographer appears to be standing on the southernmost section of the launch site, which is built up and thus explains the slight down-angle shot. This image was taken while the island was reactivated for the Homing Overlay Experiment of the late 1980s. The roof of the MSR now hosts a small shipborne radar on the red mast, as well as a camera pointed at the launch site. Grass is growing on the roof of the former equipment building.