SIGINT Data Processing and Exploitation

Just as solid-state electronic technology changed the capabilities of SIGINT satellites dramatically, the computer revolution that began in the 1950s, and that is still underway, changed the capabilities of computer processing, almost day to day. The capability to process SIGINT information was especially powerful and quick to develop, because the SIGINT satellites collected electrical signals that, with proper coding, were in a form that computers could work on directly. From 1960 to 1975 the multiplying effect of improved satellite collectors and improved computer processors would provide a many-fold increase in operational capabilities. Developing the processing methodology was the key.

It is fairly easy for a trained photo analyst to recognize missiles and radar structures if the photograph is taken by a properly focused camera with sufficient magnification on a clear day, with observable shadows. Likewise it is easy for the signals analyst or linguist to analyze an electronic signal if the signal structure is known and the signal is collected by a properly tuned receiver with sufficient sensitivity and no interference. Unfortunately, the SIGINT analyst usually encounters noise interference, competing signals on the same frequency, and little or no knowledge of the characteristics of any newly detected signal. Noise or interference impedes signal processing and analysis in much the same way as cloud cover impedes analysis of photo data. The denser the cloud cover in photographic data, or interference in SIGINT data, becomes, the more difficult it is to process or analyze the information: sometimes, analysis is impossible.

Multiple electronic signals intercepted at the same time by SIGINT collectors appear much the same as multiple exposures on a photographic print. Or perhaps a better description would be multiple transparencies of different pictures stacked one on top of the other. Analysis of any one signal or picture is virtually impossible until the competing signals or overlapping pictures are separated out, or, as it is termed by analysts, “deinterleaved.” Analysis of complex, structured signals such as telemetry or Multichannel communications require [REDACTED EO 13525] before the data can be analyzed or processed. This is very much like the adjustment process required to successfully view a television picture. The proper channel must be selected, the horizontal synchronization must be established, and the vertical hold must be set to prevent the picture or frames from rolling.

Encryption of electronic data to disguise their real information content introduces another major problem for the SIGINT processor and analyst. Encryption adds keying material, known only to the users, to the clear or unencrypted data, thus producing enciphered data for transmission. Anyone gaining unauthorized access to the encrypted data cannot read it without a major effort to remove the encrypting-key algorithm, thus permitting one to decipher the data. Solving encryption problems is much more difficult than, but is similar in some respects to, the problems faced by photo analysts when camouflage paint or nets have been used to hide an object from view.

Before electronic signals can be machine processed, extensive manual analysis of the captured signals is needed to clearly define the characters that are to be recognized, identified, and codified in special-purpose equipment or in computer software. This manual analysis involves listening to the signal, making signal measurements (often from hardcopy graphic representations of the signal), and developing an understanding of the signal structure (e.g., pulsewidth, type of modulation, pulse repetition rate). As a major designer, developer, and user of the latest in computer technology, the National Security Agency (NSA), established by President Harry S Truman in 1952 to exercise technical and operational control over US COMINT and communications security activities, eventually employed computers to improve decryption and for handling and screening extremely large volumes of ELINT, COMINT, and TELINT data collected from all sources, including reconnaissance satellites.

Beginning in the 1960s, ELINT data were processed to provide EOB of Sino-Soviet radars for the nation’s strike forces in the Single Integrated Operating Plan (SIOP) and for distribution to the military intelligence community. NSA eventually provided direct reporting of the location of threat emitters to the field within hours of their intercept. ELINT data were also used to tip-off other intelligence collection activities. The technical analysis of ELINT allowed assessments of weapon and radar system capabilities to be made and electronic countermeasures to be designed.

COMINT data, often used by NSA linguists fluent in the native language of the target nation, provided databases on that nation’s economic capabilities, such as manufacturing, technical level of competence, number and types of resources (both civil and military), and personal data on key people. Most important, COMINT provided indications of target country political and military intentions, including military planning, deployment of troops, policy positions, and threats. NSA frequently applied special processing techniques to decrypt enciphered communications of target countries.

TELINT processed by NSA was furnished to the CIA, the Air Force System Command’s Foreign Technology Division (FTD), the Army Missile Command (AMC) and other Intelligence Community customers, which analyzed the data to deter- [REDACTED EO 13525]

By 1975 these intelligence products were being rapidly and routinely reported throughout the Intelligence Community. They represented an enormous capability to collect, sort, and distribute information that could hardly have been imagined as the story began in World War II, or even by the start of the satellite era in 1960. The NRO and the NSA, the satellite operator and the processor of the SIGINT information, respectively, were the organizations that made these things happen.

NRO APPROVED FOR RELEASE 10 FEBRUARY 2016
Source: National Reconnaissance Office, The SIGINT Satellite Story