Japan.Motobu · an army radar sees something hang still, then speed off

In March 1950 Okinawa, in the Ryukyu Islands, was still under United States military administration, with Twentieth Air Force bases and Army anti-aircraft units. At about 1030 on March 27, a corporal of the 65th Anti-Aircraft Artillery (AAA) Gun Battalion was operating an SCR-584 "B" radar, serial number 754, which the report says was "in good condition"; the Blue Book record card calls it a "Gun Radar", a radar for aiming anti-aircraft guns. It stood in the gun park at "Kawasake" (so spelled in the document), at 26° 21′ N, 127° 50′ E. The radar picked up an object over the Motobu Peninsula, in the north of the island, at 26° 37′ N, 127° 57′ E, at an altitude of 13,500 feet (the card says 13,000). The report gives a distance to that first point that cannot be read clearly ("1…"), and the card 18 miles; those coordinates give about 20 statute miles to the north-north-east (our own calculation). The card gives the time as 27/0130Z, the same time with Okinawa nine hours ahead of Greenwich (our own calculation).

When the radar picked it up, the object was stationary. Then it moved on a heading of 220°, to the south-west, at about 507 miles per hour, a figure the report explains as follows: 16.9 miles between the first and last points, covered in two minutes. There was only one object, and the last position was at 26° 26′ N and, as far as can be read, 127° 48′ E, at 1040. According to the report, the object was "observed" for about ten minutes and followed by radar for about two minutes after it started to move. The card says it stayed stationary for ten minutes before moving; with first contact at 1030, the last at 1040 and two minutes of movement, the stationary phase in the report lasts at most about eight minutes (our own calculation).

The card tells how it was lost: the radar followed it south-west to a point over a mountain and could go no further ("to point over a mountain. Could not track beyond this point"). It adds that another radar in the area did not pick it up and that it moved faster than the operator could follow ("Additional Radar in area did not pick up object. Speed faster than Operator could track"). A heading of 220° held for 16.9 miles from the first point ends at 26° 26′ N, 127° 46′ E, close to the report's last position and about 6.6 miles from the radar itself. So by the end the antenna had to turn at about 1.2° per second to keep hold of it, some eight times faster than at the start (our own calculation): a fast object passing close is harder to follow.

The operator's name is blacked out in the report. He was 36 years old, had about fifteen years of military service and had been a radar technician for some twenty-… months (the second digit cannot be read). His commanding officer considered him "a superior soldier and radar mechanic and found at all times to be outstandingly reliable and trustworthy". No photographs were taken. Next comes a sentence that is underlined and marked with an arrow in the margin: five F-80 fighters were flying and the radar could have picked them up ("One F-80C and 4 F-80's were flying and could have been picked up by radar, at time object was detected"). The report ends by saying that the Twentieth Air Force radar station on Yontan Mountain was out of service at the time and that the one on the Motobu Peninsula "did not pick up this object". The weather in the area: stratocumulus covering 8/10 of the sky between 3,000 and 4,500 feet, 20 miles visibility, no precipitation and no clouds at the object's height.

Part I of the report, nearly illegible in the scan, agrees with the card that the radar stopped following the object because of its speed and lost it. It also lists three enclosures: an affidavit from the corporal, a statement by the operations officer of a fighter-interceptor unit, the "51st FI…", and another by the weather officer of a detachment. None of the three survives. The Blue Book record card was filled in years later, on a September 1963 form, and concludes "UNIDENTIFIED" with this comment: "Not submitted to Radar Analists at time of receipt in 1950. Track not consistent with A/C. Weather and other causes not apparent. Not recorded as A.P. or malfunction and Operator is considered reliable". It ticks "Ground-Visual" and "Ground-Radar" as the type of observation and gives "10 Min. (Grnd-Observed)" and "2 Min. (Grnd-Radar)" as its length, but the surviving report mentions no one who saw the object with their own eyes: its paragraph h says "observed" without distinguishing between the screen and the eye.

The documents are few, but their figures agree with each other: 16.9 miles in two minutes is 507 miles per hour, and the heading and distance lead from the first point to the latitude the report gives for the last. The operator had his commanding officer's written backing, and the card notes that the track is not consistent with an aircraft, that no weather causes are apparent and that it is not recorded as anomalous propagation (when layers of air bend the radar beam and make it pick up distant things or show them where they are not) or as a malfunction. All of that weighs in favor of a real object, and it is what led Blue Book to keep it as unidentified.

What weighs against it is in the same papers. Only one radar saw the object. The Motobu station, located on the peninsula over which it was picked up, did not detect it, and the Yontan station was out of service, so no second instrument confirms it. Five F-80s were in the air, and the report itself notes that the radar could have picked them up, a line someone underlined and marked with an arrow. Blue Book's dismissal did not come from an analysis: the same card says the case was not sent to its radar analysts, and it is written on a 1963 form, more than thirteen years later. And the track was lost as the object passed close to the radar, where anything fast is harder to follow.

Against the idea of an aircraft stands the stationary phase: the report says the object was stationary when first picked up, and the 1963 card that it stayed so for ten minutes, which an F-80 does not do, and no one in the documents explains how an aircraft could produce that track. But no record of the period excludes the aircraft: the card's sentence was written in 1963 without analysis, and the operations officer's statement on the flights does not survive. That the thing that hung still and the thing that moved were not the same object is a possibility that no source raises. The three missing enclosures (the corporal's affidavit, the operations officer's statement on the flights and the weather officer's) are exactly the ones that could settle it.