Project Blue Book file, RB-47, July 17, 1957

Read from the scan by GLM-OCR; expect the odd misread word.

prompted by the RB-47 incident. The letter, originally classified, says: "This office knows of no S-band airborne equipment having the characteristics outlined."

I have personally questioned several long-time Elint specialists, including a former official in the USAF's airborne electronic warfare laboratory who would have been responsible for having developed the airborne CPS-6B radar-mimic. Today, nearly 20 years afte such equipment--if it existed--had been developed, it would certainly be declassified. Yet none of the Elint specialists had ever heard of such equipment.

2. A foreign aircraft: Only two countries -- Britain and the USSR -- had jet aircraft large enough to carry a powerful CPS-6B type radar and fly at speeds comparable to that of an RB-47. If either country had built such equipment, it could test the equipment against U.S. air defense radars by flying over the international waters of the Gulf of Mexico, without risking a grave international incident by penetration of U.S. airspace.

If either country had built the equipment for the purpose of spoofing, or "play ing games" with U.S. Elint aircraft, this sort of experiment could have been conducted in West Europe or Asia where numerous RB-47 Elint aircraft were based.

3. An extra-terrestrial (E-T) spaceship: Inasmuch as the signal had all of the characteristics of a CPS-6B/FPS-10, it seems certain that the equipment was specifically designed either for use against American air defense radars or against U.S. Elint-type aircraft.

If the intent was to interfere with (jam) CPS-6B/FPS-10 radars, then clearly the E-T mission of July 17, 1957, was a complete failure for there were no reports of such interference from the radars at Houston, Oklahoma City, Duncanville or at Biloxi. Having gone to so much trouble, it would seem logical for the E-Ts to subsequently modify their equipment and to return to Earth for another attempt hopefully more successful. Yet this has never happened, so far as the record shows.

If the E-T went to the trouble of building a CPS-6B type radar and transporting it all the way to Earth for the capricious mission of playing games with the crew of an Elint airplane, then clearly the mission was a success. But an important question is how the E-T spaceship was able to identify this particular aircraft-- the RB-47--among all of those aloft around the Earth on July 17, 1957, as an Elint aircraft?

Elint aircraft do not radiate any distinctive signal to identify their function. They do carry a number of appendages and antennas, but many other types of military aircraft carry a variety of appendages, such as mapping radar, doppler radar, fuel tanks, etc. In darkness and at high speed, it would be especially difficult even for a U.S. Elint specialist to identify an Elint aircraft.

Another curious aspect is that having gone to all the trouble to build equipment to spoof an Elint aircraft, the E-Ts have never since attempted to play games with such an aircraft, so far as is known.

## CONCLUSIONS:

This analyst believes that the S-band signal with all of the characteristics of a CPS-6B/FPS-10 radar actually came from radars of this type at Biloxi and Duncanville. The signal bearings reported by Piwetz, based on figures hurriedly jotted down by