Stellar parallax or Cold War espionage?

At the dedication of Van Vleck Observatory on June 16, 1916, the observatory’s first director, Frederick Slocum, outlined an agenda for the new institution: determining the distances of stars. This stellar parallax program constituted the observatory’s main research effort for the majority of the twentieth century.

The parallax program involved researchers as well as many human “computers” who were aided by tools, such as the Millionare mechanical calculator, to perform the necessary calculations. Advances in technology allowed for more accurate measurements and faster computations, changing the kinds of work people did. The Mann comparator, which the Astronomy Department purchased in the late 1950s, was one of the observatory’s most important acquisitions in this regard.

A photo of the Mann Machine

The Mann Measuring Machine. Photo by the Author. Van Vleck Observatory collections, Wesleyan University.

The Mann was an important aid to the people tasked with measuring the distances between the different stars recorded on glass plate images of the sky. The stellar parallax program’s results were contingent on both how the plates were recorded and how they were interpreted, so accurate measurements were crucial for exact results. Previously, plate measurers had worked solely relying on their eyes to gauge the minute distances that would be used in their calculations. With the Mann, the measurers could insert each plate and look into a viewfinder, using a mechanical crank to move the plate very slowly by degrees in order to pinpoint the exact locations of the stars and make measurements between them.  It was still tedious work that required a practiced eye, but the comparator made accuracy easier to achieve.

When you take a closer look at our Mann comparator, you can see that there are two small name plates attached to it. One, close to the crank, indicates the manufacturer and serial number of the device. The other, larger plate is affixed to the base and reads, “PROPERTY OF U.S.A.F – 866477 – DO NOT REMOVE THIS TAG.” What do these two tags tell us?

A close-up of the manufacturer tag

A close-up of the David W. Mann, Inc. tag. Photo by the author.

The first tag gives us information about the makers of this precision instrument. In April of 1959, observatory director Thornton Page wrote to the manufacturer David W. Mann, Inc., to inquire about their comparators. Burton W. Wheeler, Jr., the Chief Engineer of David W. Mann, Inc., responded to Page, enclosing a brochure featuring different precision screw comparators manufactured by his company, including a Mann type 422C comparator, which the department ended up acquiring. The Astronomy Department’s files thus give us a fuller picture of this transaction.

But, as the second tag suggests, there was more to the purchase of this instrument than a simple order from the manufacturer.  The Astronomy Department was clearly not the original owner of this device—the military was.  Further correspondence in the department’s files flesh out the link between David W. Mann, Inc.’s products and the Air Force—and illuminate how Wesleyan ended up with this particular machine.

A close-up of the U.S. Air Force tag

A close-up of the U.S. Air Force tag. Photo by the author.

By the time of Page’s inquiry about the Mann comparators, the Cold War was well underway. The competition between the U.S. and the USSR influenced not only the Astronomy department at Wesleyan but also the larger aims of university-based research in the United States. Following World War II, the national armed services provided the majority of federally-backed university science research. By 1959, NASA had already been enacted and had begun to act as a link between universities and the defense establishments who had the resources and political interests to support scientific research.

Why would the U.S. government have an interest in figuring out the precise locations of objects in the sky in 1959? A 1971 CIA study shows that intelligence organizations in the Air Force and the Navy used photography extensively during the Cold War to measure the sizes of and distances between objects in orbit.  These organizations relied on machines like comparators to assist with this “photogrammetry,” and to analyze and postulate the power and plans of the Soviet Union’s military, specifically surrounding the threat of nuclear war.

Following the Soviet Union’s successful launch of the first artificial satellite Sputnik in early October 1957, the competition to achieve dominance in spaceflight capabilities intensified. The American government and society felt a heightened sense of urgency to launch their own satellite and to send humans into space, and these intelligence organizations tracked the movement of both Sputnik and other potential USSR spacecrafts in order to measure the Soviet Union’s progress. Thus, fast and accurate measurements were vital in order to stay up-to-date on the competition: one wrong calculation or missed observation could potentially change the balance of power in the Cold War.

Facing limitations in their existing tools and methods, the armed forces began to invest money to develop equipment that would cut labor and increase productivity—and comparators like those that Mann made were among the results. In 1956, as the Navy’s Photo Intelligence Division grew from a small handful of people to over forty workers, it also acquired comparators, such as a Mann 621, that were used to record coordinate measurements, which were then used in calculations with hand calculators. Later, encoders were added that would automatically record measurements from the comparator onto punched paper tape that could be read into computers.

Mann Comparator Type 621. Photogrammetrists in the CIA used comparators such as this in 1956 to do their work. Ralph S. Pearse, "What Size is It? The Evolution of Photogrammetry within CIA," Studies in Intelligence 15, no. 1 (Winter 1971), pp. 53–65. Declassified 1994.

Mann Comparator Type 621. Photogrammetrists in the CIA used comparators such as this in 1956 to do their work. Ralph S. Pearse, “What Size is It? The Evolution of Photogrammetry within CIA,” Studies in Intelligence 15, no. 1 (Winter 1971), pp. 53–65. Declassified 1994.

The CIA chartered a specific organization, the National Photographic Interpretation Center (NPIC), in 1961, which included a special division specifically devoted to conducting and developing photogrammetric technique and instruments as well as its own research and development division that helped it replace its older computers and comparators in order to keep up with higher demand for greater detail and accuracy. This allowed them to acquire newer Mann comparators, such as the Mann 1210, to aid in measurements, as well as more powerful computers to process the resulting data.  In order to ensure success in the Space Race, the government invested in physical technology for its spaceships and satellites as well as the tools needed for accurate intelligence. The needs of CIA drove much of the innovation in the area of precision measurement during this time.

As the military continually purchased the most up-to-date devices from companies like Mann, they often sold their surplus at discounted prices to universities. The 422C was one of the smaller and earlier Mann comparators, so it makes sense that Wesleyan was able to acquire it in the late 1950s to assist with a program that also involved photogrammetry: stellar parallax. The Astronomy Department purchased the Mann from the Air Force at a fraction of its original price, allowing them to save money while investing in a powerful tool that would aid their research. And it did so: the comparator served its role as a key part of the measuring and calculating process into the 1990s.

The Mann 422C comparator in the basement of the observatory, November 1963. Astronomy Department collections, Van Vleck Observatory.

The Mann 422C comparator in the basement of the observatory, November 1963. Note the IBM punchcard machine at center, used to automatically record the measurements. Astronomy Department collections, Van Vleck Observatory.

The observatory’s Mann Measuring Machine thus represents the nexus of military interests and scientific research during the Cold War era. Without devices such as Mann comparators, the space race  could have had completely different results. Determining the distances to and locations of objects in space with a high degree of accuracy was not just the object of workaday astronomy—it was a major Cold War project.

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