1.0 F-16C Block 50 Sensors

Harm Targeting System (HTS)

A modern block 50/52 F-16C equipped with HTS is a SEAD platform with a robust capability to expediently detect, locate, suppress, and destroy air defense systems.  The Raytheon AN/ASQ-213 is a small 8” diameter by 56” long pod weighing ~ 82-100 lbs which is mounted on the left check station of the F-16. Very little about this system is available online, however the USAF fact sheet does list some general characteristics.  In 1996 release 5 upgrades included vastly increased ranging speed and improved threat identification.  R6 which was fielded in 2000, increased frequency coverage, search speed, number of targets tracked and identification capabilities. R7 facilitates L16 connectivity, and timely PGM targeting capabilities. The fact sheet also states that the sensor is an interferometer-based system. Other references suggest the HTS may have a frequency sensitivity of 500MHz to 40GHz.

Given the fact sheet, anecdotal evidence, and general understanding of physics and interferometers we can likely make some good guesses on how the HTS works. It is likely that the HTS is composed of a phase comparison interferometer array or perhaps multiple arrays.  This type of system allows for precise measurements of emitter angle of arrival. Additionally, it may be possible that the HTS utilizes a blended system such as amplitude comparison and phased interferometer techniques. Generally speaking, phase comparison interferometer techniques (PCITs) benefit from increased distance between antenna elements. There are a variety of element arrays possible with this technique which would be conformal enough to fit inside of the footprint of an HTS pod. Given the nature of PCITs, the footprint of the HTS and its likely element array we would probably generate the greatest instantaneous AOA measurement accuracies by placing the emitter on the beam (thus increasing the distance between antenna elements). This has several advantages and implications for direction finding techniques, and tactical considerations which are discussed later. While the exact accuracy of AOA measurements depends on a variety of factors theoretical performance from PCIT systems range from 0.1°-11° Given modern data processing capabilities and comparative change detection algorithms we would likely be safe in assuming detection accuracies of 1°-5° degrees with 2°-3° being standard.

Signal Processing

Signal processing is a problem of detection, parameter measurement and correlation, emitter sorting, and identification. The ultimate goal of this processing is to classify radar signals by their unique characteristics and to use this data to identify enemy radars operating in the environment, determine their location or direction, assess their threat to friendly forces, and display this information to the pilot.

Signal Sorting

Typical emitter characteristics which are measured include the following:

1. Radio Frequency (RF)

2. Amplitude (power)

3. Direction of Arrival (DOA) - also called Angle of Arrival (AOA)

4. Time of Arrival (TOA)

5. Pulse Repetition Interval (PRI)

6. PRI type

7. Pulse Width (PW)

8. Scan type and rate

9. Lobe duration (beam width)

Given the tactical value of being able to identify/ classify threat emitters, SIGINT, ELINT, and human intelligence exploitation of enemy emitters systems has been a major priority for western nations. The US has a history of successful exploitations of foreign systems and developing training aids which mimic the emission signature of anticipated threats. Historically, there have been concerns that some systems may have War Emergency Emission Modes which would enable a system to utilize a different frequency / emission pattern during wartime which would inhibits the US’s ability to classify and disrupt emitters through typical EW means (Jamming).