When Zeus was still in the early stages of design, Bell Labs suggested using two similar radars to provide extended range tracking and improve reaction times.
Located at the Zeus bases would be the Local Acquisition Radar (LAR), a UHF monopulse radar able to track between 50 and 100 targets.
The Forward Acquisition Radar (FAR) would be positioned 300 to 700 miles (480–1,130 km) ahead of the Zeus bases to provide early warning of up to 200 to 300 seconds of tracking data on up to 200 targets.
The FAR would broadcast 10 MW pulses at UHF between 405–495 MHz, allowing it to detect a 1 square metre radar reflection at 1,020 nautical miles (1,890 km) or a more typical 0.1 m² target at 600 nautical miles (1,100 km).
Each track would be stored as a 200 bit record including location, velocity, time of measure and a measure of the quality of the data.
Clouds of objects would be tracked as a single object with additional data indicating the width and length of the cloud.
Tracks could be updated every five seconds while the target was in view, but the antenna rotated at a relatively slow 4 RPM so targets moved significantly between rotations.
Each FAR could feed data to up to three Zeus sites.

By the time the Zeus plans were being finalized in 1957, plans for FAR were deemphasized, and LAR had been upgraded to become the Zeus Acquisition Radar (ZAR) which provided wide area early warning and initial tracking information.
This enormously powerful radar was driven by multiple 1.8 MW klystrons and broadcast through three 80-foot (24 m) wide antennas arranged as the outside edges of a rotating equilateral triangle.
The ZAR spun at 10 RPM, but with three antennas it simulated a single antenna rotating three times as fast.
Each target was scanned every two seconds, providing much more data than the earlier FAR/LAR concept.

The signal was received on a separate set of three antennas, situated at the centre of an 80 foot (24 m) diameter Luneburg lens, which rotated synchronously with the broadcaster under a 120-foot (37 m) diameter dome.
Multiple feed horns were used in the receiver to allow reception from many vertical angles at once.
Around the receiver dome was a large field of wire mesh, forming a flat ground plane reflector.
The ZAR operated in the UHF on various frequencies between 495–605 MHz, giving it frequency agility.
ZAR had detection range on the order of 460 nautical miles (850 km) on a 0.1 m² target.

The entire transmitter was surrounded by a 65-foot (20 m) high clutter fence located 350 feet (110 m) away from the antenna, which reflected the signal away from local objects on the ground that would otherwise create false returns.
The ZAR was so powerful that the microwave energy at close range was far beyond the mandated safety limits and potentially lethal within 100 yards (91 m).
In order to allow for maintenance while the radar was operating, the equipment areas were shielded in a partial Faraday cage of metal foil, and a metal tunnel was run from the outside of the clutter fence, which blocked the signal outside the fence line.
The other radars completing the system featured similar protection.
When Zeus was still in the early stages of design, Bell Labs suggested using two similar radars to provide extended range tracking and improve reaction times. Located at the Zeus bases would be the Local Acquisition Radar (LAR), a UHF monopulse radar able to track between 50 and 100 targets. The Forward Acquisition Radar (FAR) would be positioned 300 to 700 miles (480–1,130 km) ahead of the Zeus bases to provide early warning of up to 200 to 300 seconds of tracking data on up to 200 targets. The FAR would broadcast 10 MW pulses at UHF between 405–495 MHz, allowing it to detect a 1 square metre radar reflection at 1,020 nautical miles (1,890 km) or a more typical 0.1 m² target at 600 nautical miles (1,100 km). Each track would be stored as a 200 bit record including location, velocity, time of measure and a measure of the quality of the data. Clouds of objects would be tracked as a single object with additional data indicating the width and length of the cloud. Tracks could be updated every five seconds while the target was in view, but the antenna rotated at a relatively slow 4 RPM so targets moved significantly between rotations. Each FAR could feed data to up to three Zeus sites.
By the time the Zeus plans were being finalized in 1957, plans for FAR were deemphasized, and LAR had been upgraded to become the Zeus Acquisition Radar (ZAR) which provided wide area early warning and initial tracking information. This enormously powerful radar was driven by multiple 1.8 MW klystrons and broadcast through three 80-foot (24 m) wide antennas arranged as the outside edges of a rotating equilateral triangle. The ZAR spun at 10 RPM, but with three antennas it simulated a single antenna rotating three times as fast. Each target was scanned every two seconds, providing much more data than the earlier FAR/LAR concept.
The signal was received on a separate set of three antennas, situated at the centre of an 80 foot (24 m) diameter Luneburg lens, which rotated synchronously with the broadcaster under a 120-foot (37 m) diameter dome. Multiple feed horns were used in the receiver to allow reception from many vertical angles at once. Around the receiver dome was a large field of wire mesh, forming a flat ground plane reflector. The ZAR operated in the UHF on various frequencies between 495–605 MHz, giving it frequency agility. ZAR had detection range on the order of 460 nautical miles (850 km) on a 0.1 m² target.
The entire transmitter was surrounded by a 65-foot (20 m) high clutter fence located 350 feet (110 m) away from the antenna, which reflected the signal away from local objects on the ground that would otherwise create false returns. The ZAR was so powerful that the microwave energy at close range was far beyond the mandated safety limits and potentially lethal within 100 yards (91 m). In order to allow for maintenance while the radar was operating, the equipment areas were shielded in a partial Faraday cage of metal foil, and a metal tunnel was run from the outside of the clutter fence, which blocked the signal outside the fence line. The other radars completing the system featured similar protection.
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