Secret US Aircraft Programs of IGLOO WHITE and the Vietnam War

This thread is to examine the aircraft, systems, and networks that were involved in the 'electronic barrier' that was part of the McNamara Line, a defensive line developed to block North Vietnamese and Viet Cong soldiers from accessing South Vietnam along the Ho Chi Minh Trail. The aircraft known to be involved in the effort was the OP-2E, EC-121, manned and unmanned versions of PAVE EAGLE (Beech Debonair). Other aircraft supporting trail interdiction operations could also be included in this list.


Project CHECO Report on IGLOO WHITE via Wayback Machine

Equipment rack behind cockpit in the QU-22B PAVE EAGLE used along the HCMT.

The Infiltration Surveillance Center (ISC) at Nakhon Phanom Air Base in Thailand. This was central node of operations for receiving data relayed from aircraft flying over the Ho Chi Minh Trail. Radiation (Harris Corp, today) was the contractor that oversaw the service of the installation. The facility was secret when it was built, only known as the Project, and was officially known as the ISC or Task Force Alpha.

Modified Neptune aircraft, AP-2H were flown in support of IGLOO WHITE.

IGLOO WHITE was also supported by F-4 Phantoms dropping sensors where O-2 'Oscar Deuce' Skymasters marked the band of the target with smoke that the F-4's were supposed to drop the sensors into. MACV SOG teams were running operations based on IGLOO WHITE data or supported the operation in the placement of sensors near the trails.

Aircraft that were developed or used for operation along the HCMT:



Black Orion P-3A
"In September of 1966, one of the Black Orions was detached from its operations over China and was assigned to a joint Department of Defense/Defense Intelligence Agency operation via the US Air Force. The aircraft was provided to support an intelligence-collection program in Vietnam codenamed “BENT AXLE.” The program involved gathering intelligence to locate Guerrilla encampments and NVA troop concentrations along the Ho Chi Minh Trail system of Laos and North Vietnam. The Black Orions operated out of Okinawa, Japan, at night and flew over Vietnam, conducting one of the first electronic intelligence gathering missions of the conflict. After 1968-69, the incorporation of electronic surveillance/reconnaissance in the Vietnam conflict commenced under an ever widening program called “IGLOO WHITE.”
"This aircraft was only used for a short time, flying directly from its mission over Vietnam to the United States and the Naval Air Station Alameda in January of 1967. The two other Black Orions followed several months later."

Didn't north vietnamese soldiers learned to recover the parachuted sensors in the jungle canopy, making good use of their batteries ?

Dynoman said:

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If that sketch is correct, then the ground sensors' signals were picked up by the ARR-52A VHF sonobuoy receivers on the Bat Cat. Well, I always thought that more communication sophistication was employed with Igloo White...

I believe VHF frequencies were used because the EC-121 was flying at such a high altitude (usually within 25 miles of the sensors) within the line-of-sight performance of demands of VHF that the signal quality was sufficient for monitoring the sensors. However, the original sensors (Phase I) dropped on the trail were Navy sonobouys with limited battery life. The Phase II sensors were modified for the SEA environment and provided some performance improvement, but their VHF emissions still would create some problems for the EC-121, relay aircraft, and the ISC for processing. About 40-60% of the data was lost in the initial employment of the SIDs on the trail. By early 1969 the loss rate was around 17%.

Right. The sonobuoy radio system framework was likely implemented into the HCM Trail sensors as the technology was already available to the Navy and off-the-shelf. That only makes me wonder if the North Vietnamese and their allies reverse-engineered the captured sensors and realized that their presence can be detected using a VHF receiver.

Furthermore, the Bat Cat was apparently fitted with the powerful ARC-89 UHF radio relays. If used along with the ARR-52, then the presence of these planes and their mission was probably well announced to the PRC and East Pakistan.

In 1966 the AF conducted a study to determine the vulnerabilities of the IGLOO WHITE sensor system to the NVAs ECM efforts along the trail. They found that the most likely threat was from the sensor to the relay aircraft. However, during the programs existence there were only a few times that TFA saw radio frequency interference. They thought that those times correlated with B-52 strikes, which could have been the NVA or friendlies jamming efforts. The NVA certainly found the sensors throughout the IGLOO WHITE program. So much so that some SIDS were installed with boobytraps.

ARPA 1966 Study by JASON, an independent advisory group of elite scientist, that addressed a number of issues on how to effectively conduct the war in Vietnam. This study led to the IGLOO WHITE program. The title of the report is Air-Support Anti-Infiltration Barrier. An interesting account from Seymour Deitchman, an insider's story of the JASON teams focus on Vietnam. https://nautilus.org/essentially-annihilated/an-insiders-account-seymour-deitchman/

Dynoman said:

In 1966 the AF conducted a study to determine the vulnerabilities of the IGLOO WHITE sensor system to the NVAs ECM efforts along the trail. They found that the most likely threat was from the sensor to the relay aircraft. However, during the programs existence there were only a few times that TFA saw radio frequency interference. They thought that those times correlated with B-52 strikes, which could have been the NVA or friendlies jamming efforts. The NVA certainly found the sensors throughout the IGLOO WHITE program. So much so that some SIDS were installed with boobytraps.

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The publicly available information on the Igloo White project does not explicitly say how and if the data received from the ground sensors was relayed by the Bat Cat to the analysis center.

The ARR-52 was just a receiver used on naval sub hunting aircraft to pick up signals transmitted by submerged sonobuoys (and originating from their hydrophones). My understanding is that the ARR-52 system was simply utilized in Igloo White due to its availability. It's difficult to imagine what kind of interference the authors of the document you cited thought about. What precisely was being jammed? The GDB signals that guided the B-52?

The CHECO report that includes the issue of ECM application to the sensors on the trail is too large to upload. The actual documents that reference the studies are identified as SECRET in the reference section.

They reference:

Report (Command Correspondence Staff Summary Sheet), subject:
"IGLOO WHITE Phase III Vulnerability to ECM," 20 October
1970, by 7DOPTS (CHECO Microfilm S436, FR 94).

Memo for Record, "Comments on ECM vs IGLOO WHITE," by
Colonel Joseph H. Wack, Assistant for Electronic Warfare,
23 September 1970 (CHECO Microfilm S436, FR 94)

Message, 553RW Korat RTAB, Thailand to 7DOPT, subject:
Data Channel Interference, 190831Z October 1970 (CHECO
Microfilm S436, FR 101)

Memo for Record, "TFA Sensor Data Link Jamming," from 7DOPT
to 71NTSM, 8 March 1971

"Terrain masking (i.e., karst and mountainous features) prevented direct transmission from the sensors to the ISC. Thus, the need for an orbiting aircraft. The EC-121Rs also had a limited capability to analyze data in the event that (a) the ISC-based IBM main-frame computer was down, or (b) the ISC was unable to receive data from the orbiting aircraft (14-hour missions – one hour out, twelve hours on station, and one hour back)."

This brief article nicely summarizes technical issues related to Igloo White.


Uplink from earth sensors:

The sensors reported their data via radio frequency channels ranging upward from 162 megahertz (MHz) to 174 MHz on the very high frequency band. 31 channels were assigned to each type of sensor with a 375 kHz separation between each channel. Every channel contained 27 identification codes or addresses which could be set in the field prior to emplacement. Thus, a total of 837 individual sensors (27x31) could be deployed at any one time without signal duplication in a single operational zone.

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Clearly, that meets the ARR-52 specs.

Downlink at NKP RTAFB:

The sensor transmitters would relay their data to the second element of the system, an orbiting EC-121R aircraft of the Air Force's 553rd Reconnaissance Wing, based at Korat Royal Thai Air Force Base. The EC-121s would then relay the collected information via a radio link at 2200 to 2300 MHz to Nakhon Phanom. At Task Force Alpha, the last of the three components in the system, the intelligence data (from a variety of sources, not just the sensors) would be entered, collated, retrieved, and stored by two IBM 360/40 (later two 360/65) computers. Technicians at the center controlled the system from a variety of video displays that were also linked to the computers.

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That being said, it seems that ground sensors generally employed some sort of burst data transmission on FM to remain stealth.

I wonder if the 2200 to 2300 MHz link was synchronized with the ARR-52, or whether it acted independently only sending processed data to NKP.

An Igloo White artifact: