Hokkaido, Japan, February 1958February 1958

Insufficient Data

Summary

On February 19, 1958, radar operators at a U.S. Air Force site in Hokkaido, Japan, detected an unusual radar return over the Sea of Japan, approximately 80 nautical miles off the Russian coast. The return appeared suddenly at 0059Z (just before 10 a.m. local time) and developed rapidly into a dense cloud that expanded to cover an area roughly 55 miles long and 25 miles across. The radar echo rose from an altitude of 3,000 feet to 46,000 feet over the course of about two hours before fading away at 0300Z (around noon). The radar operators, including the site's operations officer, noted that the return resembled a weather radar signature, except for the striking speed of its development. They described it as most nearly resembling the explosion of a very large ammunition ship.

Five Russian aircraft were operating in the area at the time. When the unusual radar return appeared, all five aircraft tracks shifted toward the phenomenon's location, a reaction that investigators found significant. The radar site operators were experienced and stated they had no previous experience with anything resembling this return. Weather conditions at the site were clear, with a weak low pressure area present in the Sea of Japan.

The investigating officer noted that the rapid development of the return and the apparent reaction of Russian aircraft activity would seem to rule out a natural weather phenomenon or radar equipment malfunction. However, when investigators checked with Japanese meteorological, seismic, and maritime safety authorities, they found no evidence of an actual explosion at the location or time in question. No barometric or seismic changes were detected. There was also a report from fishermen off the coast of Hokkaido who had witnessed three unusual luminous sightings in the same area over the preceding months, though these cases appeared separate from the radar event. The Air Force evaluation for this case was listed as unknown. The complete case file, consisting of seven pages, is reproduced below as held by the National Archives.

Reported location

Hokkaido, Japan, February 1958

Date of incident

February 1958

State / country

? / XX

Page count

7 scanned pages

USAF evaluation

unknown

Microfilm

T1206, Roll 32

3 SE PROJECT 10073 RECORD CARD BE CR ere =r Te TT YT TCE Er E | 1. DATE 2. LOCATION 12. CONCLUSIONS 3 0 Wos Balloon a | 19 February 1958 Hokkaido, Japan 0 Probably Balloon BE | = eee Fee ———————————————10 Possibly Balicon || 3. DATE-TIME GROUP 4. TYPE OF OBSERVATION | : : 0 Was Aircraft 3 | = 7 Fe © Ground- Visual CX 8round-Rodor m] BELAY Aterath i GMT 19/003597 0 Air Visuol 0 Air-Intercept Radar D Possibly Aircraft ia { ee eee a EE TEE Ee Sol = | 75. PHOTOS H 4. SOURCE 0 Was Astronomical £ { O Yeas Sketch OD Probably Astronomical E { Ke tLC FORT i ical 5 | 225 No Military 0 the Salil ny BE | 7. LENGTH OF ORSERVATION 3. NUMBER OF OBJECTS | 9. COURSE BX Other EXDIOSiOQ & { O Insufficient Dota for Evaluation 0 | 1 3 0 Unknown = | 2 hours one | stationary . 110. BRIEF SUMMARY OF SIGHTING : 11. COMMENTS | Radar report from Sea of Japan area, Rapid devslopment and a/c reaction § | Return daveloped rapidly to 2 dense rule out weather phsnomena and | - | cloud that expanded to cover an area equipment malfunction. “anlos on) : | approximately 55 miles long and rose possible cause correlated wach. | | from an altitude of 3,000 ft to 46, IR 1886-58 as explosion. Observed o 000ft. Return similar to weather by fishermen, Also seismic detec i | return except for speedof development. tion of nuclear explosion reportad : | rive aircraft in area all turned towaf from Matsushiro, | = | the return and proceeded to the genera 3 | area, Return resembled explosion of 3 ! == RE a J : iarge munitions sShlp exploding. | : : RE EE EL SI CERES 'S ATIC FORM 329 (REV 26 SEP 52) y . ‘ . FE . 3 a 3