New Generation Radar Focuses on Plasma to Create Agile Mirror

4/19/1996 - 35-96r
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When President Ronald Reagan announced the plan for the Strategic Defense Initiative in the 1980s, it was considered revolutionary.

Reagan's idea was to create a defensive system that would zap enemy ballistic missiles aimed at the U.S. before they got near us. Reagan's announcement implied the use of novel technologies, including sophisticated radars capable beyond anything in existence at the time.

Well, Naval Research Laboratory scientists are working to bring the equally revolutionary dynamics of plasma physics to the world of military radar -- and perhaps beyond.

Meet Agile Mirror, which is quite possibly a part of the radar of the future and is being developed at NRL's Plasma Physics Division in collaboration with the Radar Division.

Agile Mirror consists of a plasma sheet formed in a low-pressure chamber by a gas discharge, explained Dr. Robert Meger, Head of the Charged Particle Physics Branch, Plasma Physics Division at NRL and principal investigator. The present laboratory version measures 60 centimeters by 60 centimeters by one centimeter. The plasma acts just like a conducting metal sheet to the microwaves. It is possible to turn the plasma mirror on and off very rapidly (less than 10 microseconds) and change the orientation of the mirror in between pulses. Multiple high power microwave sources with the same or different frequencies could be combined on a single Agile Mirror, in sequence or simultaneously.

"Its beauty is that it can enable a radar system to follow many independent targets while continuing to search for others," Dr. Meger said.

Agile Mirror, currently in an experimental configuration, is a thing of visual beauty and awesome potential.

Its broad-band capability will enable variable or multifrequency radars as well as use for electronic warfare, telemetry and communications. Moreover, it and related technologies are potentially applicable to a variety of other than military purposes, including weather detection (searching for microbursts, for example), air-traffic control, telecommunications, discharge lighting, and even pollution control.

But the people developing the plasma mirror have a more immediate use in mind -- aboard U.S. Navy ships and aircraft tracking multiple, high-velocity targets, said Dr. Meger.

The plasma mirror, called Agile Mirror because of its ability to change direction rapidly and repeatedly, is a multipurpose, microwave beam director. It represents advantages over existing radar technology including size, weight and cost, but especially electronic steering, wide bandwidth operation, and high power capability, he said.

"Because the plasma mirror is electronically steerable with no moving parts, it possesses the ability to more very fast from one point to another," Dr. Meger said.

Dr. Meger explained that radar redirection (crucial for finding targets) originally depended on moving antennas mechanically. This limited response time. A substantial improvement in response time was achieved with phased arrays, which are used on Aegis cruisers.

Phased array radar, which moves electronically by changing the relative phase of individual elements of the array, is costly and has frequency limitations. Frequencies are important because a target invisible in one frequency may be readily visible in another, Dr. Meger explained.

Agile Mirror differs significantly because it offers a means of electronically directing single-element, high-power, high-frequency microwave beams to a target.

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