TERCOM, System and Symbol: Part Three

From Part Two

Direct Action’s bombing of the Litton factory in Rexdale and its assembly line for cruise missile guidance systems reflected discomfort on the Canadian left with the way the Cold War was heating up again after the years of détente and what they saw as an insufficient willingness to put distance between Canada and US foreign policy. Neither it, nor the anti-cruise missile protests, put much specific emphasis on the technology involved. For them, TERCOM itself was just one particular articulation of the US military-industrial complex.

In fact, TERCOM in general was a dead end in military guidance. No other weapons used the same guidance technique, and both the Tomahawk and conventional ALCM used GPS as their primary guidance as soon as practical. I have yet to see any reference to a commercial spin-off from TERCOM either. The idea was more or less a one-off as a guidance technique. It survived into the twenty-first century in only one niche, the nuclear-armed Tomahawk. Because, unlike GPS or other radionavigation systems, there were no outside signals to be jammed or spoofed, TERCOM-assisted inertial navigation remained the sole guidance system on the nuclear-armed Tomahawks even after the conventional versions switched over using to GPS. The last nuclear-armed Tomahawks were only retired in 2013.

On the other hand, TERCOM did demonstrate the value and cost of good mapping, charting and geodetic data. It wasn’t the first system to make use of it – every US strategic bomber and ballistic missile relied on mapping and geodetic information to some extent – but it was the first to demand not just knowledge about Point A and Point B but also about the terrain along the way. That requirement put the Defense Mapping Agency in a bind, forcing it both to go into overdrive and to triage its TERCOM processing work. Recognising that that sort of crash project couldn’t be repeated for every new weapon, the deputy Secretary of Defense issued Program Decision Memorandum 85 (PDM-85) in 1985, which required early military department to “fund with its own resources the cost of unique earth data products.” Though Larson and Pelletiere wrote in the late 1980s that the rule was proving unenforceable, it was a mark of further recognition that this type of information was a critical war weapon.

After the Cold War ended, the Defense Mapping Agency was merged with many of the intelligence community’s imagery creation and analysis office to create the National Imagery and Mapping Agency (NIMA). In 2003, NIMA was renamed the National Geospatial-Intelligence Agency (NGA), a change that reflected the increasing conceptual consolidation of these kinds of information under the umbrella of geospatial intelligence (GEOINT). The term, as the US Geospatial Intelligence Foundation explains, was only about as old as the agency’s new name. But while The Atlantic’s Marc Ambinder could title as story about the agency in 2011 “The Little-Known Agency That Helped Kill Bin Laden,” NGA was pretty deeply embedded in the US national security establishment. More than thirty years after DMA started weaponizing its digital terrain elevation data (DTED), the idea that the military might not only demand detailed maps of its targets but also the underlying data, to transform into a three-dimensional computer model, a physical mockup, or – bringing us right back to the first uses of the DTED – a flight simulator profile (which was, after all, the first use for, back in the 1970s), is old news.

Source Notes: US cruise missiles are pretty widely discussed, so a lot of these posts were cobbled together from a lot of sources. Jay L. Larson and George Pelletiere’s Earth Data and New Weapons (available from DTIC here) was very useful for understanding how the DMA supported TERCOM, and is one of the few places to mention PDM-85. The explanation of how satellite stereophotogrammetry is done comes mostly from the NRO’s internal history Hexagon Mapping Camera Program and Evolution (as reprinted by the Center for the Study of National Reconnaissance). Information about Canadian protests against cruise missile testing and the Litton bombing in Toronto come from John Clearwater’s 2006 book Just Dummies: Cruise Missile Testing in Canada. Ann Hansen, one of Direct Action’s members, published a memoir after he release from prison. Direct Action: Memoirs of an Urban Guerilla offers more but similar details about the Litton bombing and reprints Direct Action’s communique.

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