Buried in a stack of declassified CIA abstracts of Soviet scientific journals is a curious 1957 paper by Professor K.S. Lyalikov of the Laboratory of Aerial Methods at the Academy of Sciences, Leningrad. The title, mangled by mid-century OCR, reads:

"Study of the diffraction method for analyzing aerial photographs of the turbulent ocean surface."

A second entry from the same year adds the tantalizing companion piece:

"The use of electronics and cybernetics in aerial photography."

The CIA's Foreign Documents Division had been quietly tracking Lyalikov because he and his colleague Sharikov were doing something remarkable: instead of having a human squint at a photograph of the sea to interpret wave patterns, they shone a beam of coherent light through the developed negative and read the resulting diffraction pattern to extract wave statistics automatically.

The forgotten physics. A photographic negative of a wavy ocean surface is, in effect, a two-dimensional grating whose spacing encodes the sea's dominant wavelengths. Pass a light through it, and the smeared bright spots on a distant screen form an optical Fourier transform — the ocean's spectrum, extracted at the speed of light with no computer required. Lyalikov's team was doing analog Fourier analysis of remote-sensing imagery a full decade before Cooley and Tukey published the Fast Fourier Transform (1965), and roughly twenty years before SEASAT proved you could measure ocean wave spectra from orbit using synthetic-aperture radar.

Was he ahead of his time? Absolutely. What Lyalikov called "diffraction analysis of aerial photographs" is essentially the operating principle behind:

• Modern SAR (Synthetic Aperture Radar) wave-spectrum products from satellites like Sentinel-1 and the retired ERS.
• Optical coherent processors used by the U.S. Navy in the 1960s–70s to process reconnaissance film before digital hardware caught up.
• The "spatial light modulator" analog computers that briefly reappeared in the 2010s as candidate accelerators for machine-learning inference.

The companion paper on cybernetics in aerial photography is even more startling in hindsight. In 1957 — the same year Sputnik launched — a Soviet photography professor was already publishing on what we would now call automated image interpretation. The Western literature would not seriously take up "computer vision" as a discipline until Larry Roberts' MIT thesis in 1963.

Why we forgot. Lyalikov published in Zhurnal Nauchnoi i Prikladnoi Fotografii i Kinematografii — the Soviet Journal of Scientific and Applied Photography and Cinematography. It was translated by nobody, indexed by nobody outside the CIA's abstracting service, and by the 1970s the whole field had migrated to digital methods that made his elegant analog trick look quaint. The diffraction-analysis technique survives only in a handful of optics textbooks and, apparently, in a CIA microfiche.

Next time you look at a Sentinel-1 wave-height map, remember that a Leningrad professor was doing the same math with a lamp and a piece of film while Eisenhower was still president.