Electronic Intelligence (ELINT & SIGINT)

Precise characteristics and locations of Emitter Signals

Signal Intelligence (SIGINT)

The SR-71's Mach 3 speed during its normal operational mission profiles created a very beneficial side effect which was to stimulate the enemy's radars and missile systems. Their responses to the Blackbird's flight path resulted in jamming, missile system tracking, and other electronic activity. The electronic signals generated during these responses were collected by the SR-71's own Electro-Magnetic Reconnaissance (EMR) System as well as other collection assets propositioned in the area at the time. The enemy's capabilities and frequencies used for each radar or missile site were then recorded and documented revealing the enemy's battle plan. The EMR System was installed in the K and L mission bays.  In the 1970s, funding was available for an improvement to the system, so its replacement was come to be known as the Elint-Improvement Program (EIP) System and was installed in S and T mission bays. This new location enabled the system to be flown on both photo and radar missions.  The manufacturer for the EMR/EIP was AIL Systems. The system & associated recorders were powered on by the RSO via the Power and Sensor Control Panel and worked autonomously.  The RSO could also manually run the AR1700 if he was alerted to a signal of interest on the Universal DEF Control Panel display.

EMR System


Advanced Synthetic Aperture Radar System (ASARS1)

Manufacturer: Goodyear Aerospace in Litchfield Park, AZ. and then Lockheed Martin Corporation

High Resolution Radar Imagery

(Detachable Nose component)

Defense Systems (DEF)

Provides ground-to-air and air-to-air missile protection. Still Classified

Def systems were labeled DEF A,B,C,E and G. Later modifications to the DEF Systems resulted in DEF A2, C2, H and M systems. Nearing retirement of the SR-71, a programmable DEF labeled A2C could defeat all known threats to the Blackbirds.

DEF System Storyboard

(Photos Courtesy of Evergreen Aviation Museum, McMinnville, Oregon)

Photo Courtesy of Buz Carpenter

DEF "A2C" System, Manufacturer ITT, and the DEF "C" System (Right grey vertical Unit) Manufacture: Magnavox.

The DEF A2C, C and H Systems were used during the reactivation period of the program 1994-2000.  The A2C System replaced the DEF A2 System from the earlier years.  The DEF A2C is pictured mounted to the D-Bay mission door for display purposes.  It would normally be hard-mounted in the D-Bay.

DEF "H" System

DEF “H” System, Manufacturer: Northrop, probably one of the highest power jammers of its time, could be installed in the K or P Mission bays depending on mission type, photo or radar.  After the replacement of the EMR with the EIP Elint system, the DEF H would be installed in K-Bay, freeing up P-Bay for the TEOC camera to be used on both photo and radar missions.

AR1700 DEF and ELINT Recorder

AR1700, 14-Track Analog Recorder, Manufacturer: AMPEX, mounted in the M Mission Bay.  Pictured above is the installation configuration used during the reactivation period.  The AR1700 recorded information from the Elint and DEF systems.  It could be turned on by the Elint system or by the RSO via the Power and Sensor Control Panel.  During the earlier operational years, it was paired up with a “Digital Recorder” manufactured by RCA which was the primary Elint data recorder.

AR1700 Recorder Open

Universal DEF Control Panel (UDCP) installed in the aft cockpit for the RSO to operate the DEF systems.  Note that all classified placards have been removed & blacked blank display readouts installed.

Picture of EIP serial number 4Left, 4Right & DEF H serial number 9 recovered from #974 crash off of the Philippine Islands.

Editors Note: Credit goes out to Mike Hull for the correct identification of the DEF units pictured above. Mike worked the DEF/Elint systems for 20 years, including the reactivation period 1994-2000. Through his expertise, he provided Evergreen Museum with the demilled units for public display at the Museum. Additionally, Bill Whittle and Mike Hull provided three other sets of DEF equipment to The Air Force museum in 2000 for eventual display at the SAC, Smithsonian & Air Force museums.

DEF equipment & Digital Recorder

 Mike Hull & Bill Whittle de-militarized these for museum displays in 2000

Mission Recording System (MRS)

Collects and records specific internal aircraft flight and sensor activity data on each mission, together with the functioning of airplane and mission systems. Monitors 650 Parameters to include Engine, Electrical, Hydraulic, Digital Automatic Flight and Inlet Control System (DAFICS), Astro Inertial Navigation System (ANS), ECS, MRS and Sensor data

This is the computer MRS readout for the historic New York to London Speed Run in 1974. This document is on display at Smithsonian Air and Space Udvar-Hazy Museum in Washington D.C. and is courtesy of Buz Carpenter (SR-71 Pilot).

Film Processing

(Photo Buz Carpenter)

Film was downloaded from the SR-71 and rushed to the initial processing facility; packaged in canisters and sent to Japan for processing and evaluation as to the take (PI-Photo Interpreters) and then on the the President of the United States for critical decision making criteria.


Data Link System

Provides near real-time downlink and accelerated dissemination of ASARS, ELINT & Photo data


Sensor Data Transmissions


Go to SR-71 Sensor Web page #1....SR-71 Cameras (Optical)

Go to SR-71 Sensor Web page #2....Radar Imagery

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"SR-71 Blackbirds"  Web Site Navigator
First Created: April 15, 1996 - Last Revised: August 17, 2007
Copyright © 1996 Leland R. Haynes     Email: sr71webmaster@sr71.us

Credits: Mike Hull, Donn A. Byrnes; Russell Harvey, Robbie, David Nolte, Bill Whittle, Jim Fitzgerald, David Dempster, Buz Carpenter, Pima Air Museum, Evergreen Aviation Museum; Don Stein. Tony Landis, Lockheed Martin Corporation

Page #223 of the SR-71 Blackbirds