Larson AFB, WashingtonAugust 1951

Unidentified

Summary

On August 26, 1951, at 2:26 a.m., radar operators at Larson Air Force Base in Washington detected an unidentified object. The base had two radar sets in operation: an AN/CPS-4 and an AN/CPS-1 (ground-based radar systems used for air defense). The operators tracked the object continuously for six minutes as it moved across the sky.

During those six minutes, the object traveled roughly 95 miles. This meant it was moving at approximately 950 miles per hour. The radar showed the object on a course of 340 degrees (roughly north-northwest) with only minor changes in direction. The operators obtained an altitude reading of around 12,000 feet, though the file notes this measurement was questionable because the object was only tracked for such a short time. They could not determine the object's size or what it was made of.

The Air Force scrambled two F-86 fighter aircraft to intercept the object. However, radar contact was lost before the jets even got airborne. Pilots then conducted a visual search between 17,000 and 25,000 feet but found nothing. Weather conditions at the time were not favorable for anomalous microwave propagation, a natural phenomenon that can sometimes create false radar targets.

The Air Force's technical analysis concluded the radar return was probably caused by interference rather than an actual aircraft or object. Analysts noted that the radar blip appeared to be heading directly toward the station and showed up only on the low beam of the AN/CPS-1 radar set, both facts pointing toward a technical artifact. However, the official Air Force evaluation for this case remained "unidentified."

The full case file is reproduced below as held by the National Archives and spans 8 pages.

Reported location

Larson AFB, Washington

Date of incident

August 1951

State / country

WA / US

Page count

8 scanned pages

USAF evaluation

unidentified

Microfilm

T1206, Roll 8

i © erm ——————————————— - ; : PROJECT 10073 RECORD CARD : 1 1. DATE : _OCATION ( 2. CONCLUSIONS 26 Aug 51 I: Peobobly Bull ug Larson AFB, Wa ER —— — 3. DATE-TIME GROUP 4 TYPE OF OBSERVATION - Sv ——— an SE RR ROA PRR O Ground-Visvel X Ground-Rodar - a Ed 3 CMT 26/ 16282 0 Air Visvol DO Air-Intercept Radar 0 Possibly Aircraft . 0 Was A ical hore Bob go Ba Military : Bucy Nove vem | : her_=2€C Interferenc | | 7 LENGTH OF OBSERVATION Bs SUT Game | So— 0 i Dota for Evaluation DO Unknown 8 Min 1 ad 10, BRIEF SUMMARY OF SIGHTING 1). COMMENTS Speed 950mph, Object tracked continuously for | Review of this incident by the Electroniks a period of six minutes. Object was on a Section of ATIC concludes that the retu course of 340 deg with only slight deviations | was possibly due to interference. This enroute. Alt 13,000 ft but accuracy of measure was concluded becuase of the apparent ment questionable due to brief length time the| path of the object, directly approachin object was detected, F-86 scrambled but radar | the station, and the fact that the contact with the object was lost before a/c target was observed on only the low were airborne. Visual search conducted with beam of the AN/CPS-l radar set. negative results. Weather conditions were not favorable for ancmalous microwave propogation at time of sighting, ATIC FORM 329 (REV 26 SEP $2)