COTS technology enables passive ground-based radar

By Wilson P. Dizard III

A darkened DC-9 cargo jet skims at low altitude across the Gulf of Mexico during a night flight north. In the cargo bay, hundreds of neatly wrapped bricks of cocaine lie stacked on freight skids, forming tens of millions of dollars of contraband. In the cockpit the pilot and co-pilot, their faces illuminated by the glow from the instrument panel, check multiple radar warning receivers. They assure the supercargo that the Drug Enforcement Administration`s electronic defenses are inactive or evaded, and the smuggling flight can continue. The pilot lights a cigar as dawn breaks over the Gulf and the DC-9 enters U.S. airspace.

Without warning, two Gulfstream executive jets emblazoned with U.S. DEA markings flank the smuggler`s craft and waggle their wings, signaling the DC-9 to land. But wait. The DC-9`s radar detectors were clear. How did those DEA pilots find the smuggler aircraft, or even know it was there?

The DEA aircraft, had help from a passive ground-based radar system, which used the reflected signals from two country music radio stations and a PBS TV affiliate broadcasting "Sesame Street" to an early morning audience. In Detroit, three days after the drug interdiction, the price of a vial of crack cocaine increases substantially.

GAITHERSBURG, Md. Commercial off-the-shelf (COTS) signal processing hardware and COTS visualization software form essential parts of the Silent Sentry surveillance system, a passive radar product family that Lockheed Martin Mission Systems of Gaithersburg, Md., recently unveiled.

The Silent Sentry System uses commercial TV and radio signals that broadcast in the 40 to 100 MHz frequency range. Silent Sentry detects airplanes, helicopters, cruise missiles, ballistic missiles, re-entry vehicles, and rockets in real time with high accuracy, Lockheed Martin officials say.

Silent Sentry also can detect and track threats as small as remotely piloted vehicles and drones, Lockheed Martin officials say. As a passive system, Silent Sentry transmits no radio frequency "signature" that could attract enemy anti-radiation missiles or trigger countermeasures. "This quality gives it a superior level of security for surveillance operations, and is also an environmentally friendly solution," according to a Lockheed Martin statement.

"Television and radio transmissions blanket the Earth and extend into the far edges of space," says Terry Drabant, president of Lockheed Martin Mission Systems. "They give Silent Sentry broad application for a wide range of surveillance tasks, and unlimited access to broadcast signals for accurate, precise detection of targets."

The Silent Sentry system first was conceived 15 years ago at IBM, says Lorraine Martin, director of command and control technology programs for Lockheed Martin Mission Systems. Subsequently, the Silent Sentry research project transferred to Loral and thence to Lockheed Martin in a series of corporate mergers.

"The first and foremost enabling technology for this system is enhanced signal processing power," Martin says. "We`re using Silicon Graphics XL processors. Another enabling technology is that the processors have come down in price. Previously, we were using [processors] with top-of-the-line capabilities."

Complete Silent Sentry systems range in cost from $3 to $5 million. Because they use COTS technology, users can scale the systems for two, four, or more of the high-capacity Silicon Graphics parallel processors. "We don`t know of any other system doing the job the same way," Martin says. "When we compare it to tracking and scanning radars, its costs compare very well."

She added, "The next enabling technology is that Lockheed Martin has a distinguishing capability in our investment in the algorithms to process the signals in real time. That`s where our proprietary data begins." Martin declined to say what type of signal processing semiconductors or algorithms the Silent Sentry system uses. "We`ve got something special here, and we don`t want to give it away."

Lockheed Martin officials call their technology Passive Coherent Location, and say it uses signals of near-resonant, continuous-wave transmitters such as commercial radio and TV stations. Because radio and TV signals travel close to the ground, Silent Sentry "provides superior illumination of low-flying threats," according to a Lockheed Martin statement.

Silent Sentry is a multi-static illuminator surveillance system, which can use one, two, three, or more commercial broadcast signals to determine precise three-dimensional target trajectories. The system`s signal processors can update more than 200 target tracks eight times per second.

The entire system fits in a footprint of 27 square feet. TV and radio transmissions operate at sufficiently low frequencies so as to avoid adverse influence from the weather, Lockheed Martin officials say.

Because the Silent Sentry system does not emit RF signals, its power requirements are limited: it uses 20 amp, 200-to-240-volt AC power. The system is configured with a high-speed tape data system for target tracking archival, and uses Edge Product Family visualization software from Autometric Inc. of Springfield, Va.

Unlike scanning radars, Silent Sentry provides continuous, "staring" coverage of airspace. The Silent Sentry system output is a three-dimensional tactical display combining digital terrain, imagery, and maps. Some Silent Sentry systems can mount in buildings and fixed structures, while others go in trucks or shelters for rapid relocation. The system is not yet ready to go aboard aircraft.

"We`re in the process of working with vendor organizations on packaging requirements," Martin says. "We expect to get dramatic size reductions in coming years, and ride the curve of [hardware improvements] to increase processing power. Our current system is ground-based. Many technologies go from ground, to air, to space."

The Silent Sentry system works best when it can use reflected signals from three transmitters. However, it can provide a significant amount of information based on the reflected signal from only one emitter, Martin says.

"With one transmitter, you get a two-dimensional track, cross-range and down-range, but not altitude," she says. "The resolution and accuracy are not as good. It gets to be very respectable as you get more transmitters."

Lockheed Martin can provide "cooperating transmitters," which users can locate some distance from the Silent Sentry system to work in tandem with existing commercial radio or TV broadcast signals to help illuminate targets.

"We`ve tested the system against a wide array of targets under varying conditions," Martin says. "The [testing] conditions are classified or sensitive to the customers. The customers have asked to remain confidential. Our target market is the U.S. [government], both civil and military. We will only sell to government-approved customers."

The Silent Sentry system has a range of better than 90 miles. "It`s a wider range than some surveillance systems," Martin says. "Altitude is always the biggest challenge ... It`s an area we expect to improve." Clouds and birds have no effect on the system`s performance. Lockheed Martin declined to comment on the effect of chaff and similar radar-spoofing devices.

Martin added, "Right now, we are projecting delivery of the system six months from receipt of an order. We see a wide variety of applications. It works in concert with other systems in a `system of systems` perspective. It notches up the surveillance capabilities of civil and military users."

The Silent Sentry uses a phased array antenna with digital beam forming, says Sam Crow, Silent Sentry product manager. It can scan an azimuth of 90 degrees to 360 degrees. Producing the receiving antenna are engineers at Lockheed Martin Federal Systems in Owego, N.Y.

Silent Sentry developers also have used Yagi antennas, similar to TV antennas, as receive antennas. "We`re able to leverage off the entertainment industry, that makes a lot of antennas [for signals in the Silent Sentry bandwidth]," Martin says.

Military & Aerospace Photos

Most Popular Articles

Related Products

SBC-K7 Embedded PC for Instrumentation and Control

The SBC-K7 is an ideal platform for embedded instrumentation that combines an Atom PC running Win...

Rugged Mobile Communications Server

Advanced communications server designed to be deployed in environments where it needs to meet cer...

RR2P Removable Canister RAID System

Transportable data storage for mobile field use aboard planes, ships and ground transport. 2U, du...

P317xx Portable Computer System w/ Three 17" LCDs

The P317xx portable " lunchbox" system is unique in offering three 17" 1280x1024 resolution LCD d...

M1U20xx 1U Military-Grade Computer System

The M1U20xx Military-Grade Rack Mount System is a reliable high-performance mil-spec 1U solution ...

M4U20xx 4U Rackmount Military-Grade Computer

A 4U rugged military-grade computer offering the latest long-availability high-performance mother...

TFX-19 Trifold Rackmount LCD

The TFX1-19 is a rugged military grade high performance 2U rackmount LCD panel display offering t...

CCXR-17 Slideways Side Access Rackmount LCD Keyboard

The CCXR-17 is a unique Side Access space-efficient military-grade high-performance 1U rackmount ...

Sensors Unlimited GA1280JSX High Resolution, Mil-Rugged, Extended High Sensitivity InGaAs SWIR Camera

Manufactures a high resolution, mil-rugged, extended high-sensitivity 0.9 Mpixel InGaAs SWIR came...

High Temperature Resistant Linear Position Sensors Perform in Military and Defense Applications with High Accuracy

Macro Sensors has designed a series of high temperature and rugged LVDT linear position sensors t...

Related Companies

Innovative Integration

  Since 1988, Innovative Integration has grown to become one of the world's leading suppliers of DSP and data ac...

Elma Electronic Inc

Who we are...   About Elma Electronic Systems   The Systems division of Elma Electronic Inc. supplies the

Winchester Systems Inc

At its founding in 1981, Winchester Systems introduced its first 5 MB disk system for Intel development system users....

Extreme Engineering Solutions Inc (X-ES)

 Extreme Engineering Solutions, Inc. (X-ES) is a leader in the design, manufacture, and support of standard and ...

American Infrared Solutions (AIRS)

American Infrared Solutions

GE Intelligent Platforms

GE Intelligent Platforms is a leading global provider of embedded computing systems and modules for a wide range of a...

Raycom Electronics

Raycom Electronics, Inc., a subsidiary of Electro Technik Industries (ETI), was incorporated in 1965.  The compa...

Trenton Systems Inc

Designs and manufactures rugged rackmount computers and MIL-STD-810 systems using both standard COTS as well as custo...

Intersil Corp

Intersil is leveraging a deep portfolio of intellectual property, a history of design and process innovation and a sy...
Wire News provided by   

Press Releases

Low Viscosity, One Part Cyanoacrylate Is Non-Toxic and Meets ISO 10993-5 Specifications

Master Bond MB250NT is widely used for a variety of applications ranging from repair to high speed producti...

Thermally Conductive, Two Component Epoxy Passes USP Class VI Tests and ISO 10993-5 Specifications

With biocompatibility and cytotoxicity certifications, Master Bond EP21AOLV-2Med is often selected for bond...

One Component, Snap Cure Epoxy Features High Strength Properties

Suitable for a variety of applications in the electronic, aerospace and OEM industries, Master Bond EP3SP5F...

One Part Epoxy Resists up to 500°F and Meets NASA Low Outgassing Specifications

Master Bond Supreme 12AOHT-LO is a one component epoxy for a variety of bonding and sealing applications in...

VICTORY Shared Processing, Fire Control Computer, and Switch for Ground Vehicles Introduced by Curtiss-Wright

Curtiss-Wright Corporation today announced that its Defense Solutions division has introduced a new fully i...


Curtiss-Wright Corporation’s Defense Solutions division applauds Northrop Grumman Corporation (NYSE: NOC) o...

Curtiss-Wright’s New Rugged Mobile IP Router Subsystem Features an Integrated Cisco® 5915 ESR Router

Curtiss-Wright Corporation today announced that its Defense Solutions division, a Cisco® Systems Solution T...

GE Announces First Sub-Credit Card-Sized Multi-Function High Definition (HD) Video Tracker

HUNTSVILLE, AL.— OCTOBER 13, 2014—GE’s Intelligent Platforms business today announced at AUSA (October 13-...


Meeting the Gen3 backplane challenge with OpenVPX and COTS

Tight Pentagon budgets mean military systems must stay in the field for longer than ever before. This doesn't mean obsolete technology, however. Today's military electronics are being upgraded constantly, an...
Sponsored by:

Design Strategy Considerations for DO-178C Certified Multi-core Systems

Join Wind River to learn how system architecture and design choices can minimize your DO-178C certification challenges.

Sponsored by:

Flying, Sailing or Driving - The Rugged, Embedded Intel-based Server that goes where you need it!Flying Sailing or Driving

Leveraging the power of server-class processors is no longer relegated to the confines of data centers. Through several innovations, Mercury Systems has ruggedized Intel’s server-class chips for deployment. ...
Sponsored by:

All Access Sponsors

Mil & Aero Magazine

April 2015
Volume 26, Issue 4

Download Our Apps




Follow Us On...


Military & Aerospace Electronics

Weekly newsletter covering technical content, breaking news and product information

Cyber Security

Monthly newsletter covering cyber warfare, cyber security, information warfare, and information security technologies, products, contracts, and procurement opportunities

Defense Executive

Monthly newsletter covering business news and strategic insights for executive managers

Electronic Warfare

Quarterly newsletter covering technologies and applications in electronic warfare, cyber warfare, optical warfare, and spectrum warfare.

Embedded Computing Report

Monthly newsletter covering news on embedded computing in aerospace, defense and industrial-rugged applications

Unmanned Vehicles

Monthly newsletter covering news updates for designers of unmanned vehicles