Case · C-031

Lake Cote 1971: a disc in a photo from an official mapping flight

Name: Lake Cote 1971: a disc in a photo from an official mapping flight
Start: 1971-09-04
Location: Lake Cote (Arenal area)

Lake Cote (Arenal area) · Costa Rica · Sep 4, 1971

In flight Photos

Unexplained

What happened: On September 4, 1971, a twin-engine aircraft of the Instituto Geográfico Nacional, on a mapping mission at about 10,000 feet in the Lake Arenal area for the national electric utility, took frame 300 with a downward-pointing Zeiss RMK 15/23 aerial photogrammetric camera, and in it an oval, disc-shaped object appears above Lake Cote. None of the four crew members saw it: it was noticed while examining the prints, and it does not appear in frames 299 and 301, taken a few seconds before and after (20 seconds according to the 1989 article, 13 according to the researcher Esteban Carranza). At the altitude of the lake it would measure about 84 meters, according to the 1:20,000 scale of the shot; the 210 meters given in 1989 do not add up with the focal length and altitude reported in the same article (Mick West, on Metabunk in 2021, saw in this a probable conversion error between feet and meters). If it was higher up it was smaller, and its altitude remains unknown; no shadow of it has been found on the ground. The originals are at the National Archives of Costa Rica (reference NP-002544), from which, according to Carranza, certified copies can be requested. Carranza also owns a contact print of the negative, inherited from an uncle: two ultra-high-resolution drum scans were made from it, in 2022 and in 2026, the second without retouching and made available for download by the makers of the documentary “The Cote Photo,” released on Apple TV in September 2026 with the testimony of the on-board photographer, Sergio Loaiza.
Proposed explanation: No agency has published an official conclusion. Richard Haines and Jacques Vallée (Journal of Scientific Exploration, 1989, with a second article in 1990) ruled out double exposure and manipulation and concluded that the analyses suggested an unidentified opaque object, leaving the case open. In the review published with the first article, Marilyn Bruner, a scientist at the Lockheed Palo Alto Research Laboratory, considered a film defect more probable, such as the pressure mark of a particle trapped in the film roll, noting anomalous grain and sharpness along one edge of the image; the test she suggested, an examination of the original negative under raking light, does not appear to have been published. In 2021 a discussion on Metabunk started by Mick West pointed to an internal reflection in the optics as the most probable, but not certain, hypothesis; in 2022 the participants showed that the first drum scan had been retouched, and Carranza later confirmed that the laboratory had covered the scratches, explaining that this is why the second was made without any intervention. In Vetted's live stream of October 27, 2026, the documentary's director, Adam Pillon, relayed the opinion of the technician who made the scans: the film grain is uniform between the disc and the water and there are no signs of manipulation, points that conflict with Bruner's observations. The technician does not take a position on what the object is; Carranza speaks of an unknown object, while Pillon says he considers it a flying saucer. These are opinions relayed in an interview, not published analyses. In 2026, in the same Metabunk discussion, some participants proposed, also with a 3D model of the shot, that the image is a physical defect of the film, for example an imprint in the emulsion left by a particle, a hypothesis close to Bruner's; this too is a forum analysis, not verified on the negative.

Sources

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Jacques Vallée

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