Air Force sought a 360-degree view to strip the cloak from hidden radars
By Miriam Adler ·
Threat radars were stripped of their invisibility as automated filters and high-altitude sensors created a gapless horizon where no signal could hide.
The mission of the RC-135U aircraft, known as COMBAT SENT, is a sterile exercise in geometry and electricity. According to a page mirrored by the FAS Intelligence Resource Program, these planes function as a "Scientific and Technical ELINT Collection System." They do not look for people or cities, but for the invisible signatures of radar and electronic emissions. Based at Offutt AFB and flown by crews from the 38th RS, 343rd RS, and 97th IS, the aircraft are designed to hover at the edges of contested space, turning the air into a giant ear.
The Expert Mission Manager
There is a specific, cold efficiency to the way the Air Force handles the deluge of data these planes collect. The record describes a tool developed by the USAF Rome Laboratory called the Expert Mission Manager. It is a "rule-based" automated system designed to ensure that the human operators on board are not overwhelmed by the noise of the modern battlefield.
The goal of the program, sponsored by the Consolidated Cryptologic Program for ELINT Analysis Techniques, is to apply advanced processing to "automatically processing all the knowns and usuals." By delegating the routine signals to an algorithm, the military intends to leave only the "more difficult signals and unknowns to the on-board personnel."
This is the logic of the filter. By defining what is "usual," the system decides what deserves human attention. The Expert Mission Manager doesn't just collect; it validates, re-identifies, and recommends the best geolocation for the aircraft to achieve "optimum ELINT collection." It turns the act of listening into a curated experience, where the machine decides which ghosts in the machine are worth the time of a human analyst.
Document imagery from irp.fas.org From the files: irp.fas.org
"Vanishing Vendors"
Maintaining the machinery of global surveillance is not merely a matter of physics, but of procurement. The record details a push for "Cockpit Modernization" under the PACER CRAG initiative, which brought GPS, new radar, and multi-function displays to the C-135 fleet. The motivation for this was not just safety or reliability, but the reality of the marketplace.
The file explicitly mentions the need to eliminate "vanishing vendor" problems. In the world of high-stakes military aviation, the state is often held hostage by the lifespan of a private contractor's product line. When a vendor disappears or stops supporting a specific part, the aircraft—and the surveillance it provides—becomes a liability. By forcing commonality with the rest of the KC-135 fleet, the Air Force sought to ensure that the RC-135U would not be grounded by the bankruptcy or pivot of a corporate supplier.
This reliance on the commercial sector extends to the hardware of the listeners themselves. The document notes the installation of "high capacity COTS audio recorders" and "COTS computer systems." COTS—Commercial Off-The-Shelf—is the military's shorthand for buying what already exists in the civilian market. It is a pragmatic choice that creates a permanent cycle of obsolescence.
Document imagery from irp.fas.org From the files: irp.fas.org
360-Degree View
To stay relevant, the COMBAT SENT aircraft had to evolve to meet "modern modulation target signals." The existing hardware was failing; audio distribution systems were producing "unintelligible audio output" because they could not handle the bandwidth of new emitters. The solution was a total overhaul of the RF Distribution System, including the use of fiber optics to allow for "re-engining" of the aircraft with CFM-56 engines.
These new engines did more than save fuel; they allowed the planes to fly at higher altitudes, which increased the "airborne sensor field of view and effectiveness." Combined with the common aperture RF distribution, the goal was a "360° field-of-view." This is the ultimate ambition of the surveillance state: a panoramic, gapless horizon where no signal can hide.
To achieve this, the Air Force deployed the Wideband Acquisition/Frequency Hopping Receiver System (FHRS). This system was designed to exploit "frequency agile threat systems"—radars that jump between frequencies to avoid being detected. The FHRS increases the "probability of intercept for LPI systems," effectively stripping away the cloak of Low Probability of Intercept technology.
The record concludes by noting that the COTS computer systems used in the Emitter Source Van (ESV) and Portable Calibration Van (PCV), essential for ensuring the sensors are accurate, would become unsupportable in the FY05-06 years.