The RAPCON tape transcript contains the following message to the B-52 timed at 0852 CDT by the tower clock (03:52Z): "The UFO is being picked up by the weathers radar also, should be at your 1:00 position 3 mile now." The aircraft responded that they "do not have anything on airborne radar and we are in some pretty thick haze right now and unable to see out that way." The time of this message would be before the 30/180 turn onto the TACAN initial approach fix and so prior to the start of the ASB-9 radar episode discussed here. The file shows that Lt.Marano from FTD made several attempts to get further information from Col.Werlich about the weather radar but was either rebuffed or ignored. It has not proved possible to find information about the characteristics or location of the weather radar involved. Generally one would expect this sort of radar to operate at X-band (similar to the 3 cm airborne radar) or S-band (up to 10 cm). Weather radar is by no means generically inferior to other types of radar, requiring good accuracy and resolution, and most importantly radar height indication as well.
Another puzzle is a report of a rapid unidentified echo on the B-52 gunnery radar. According to the gunner, at some point during the ASB-9 radar episode a target was picked up on the scope of the rearward facing AN/ASG-1gun control radar. It was aft of the aircraft 30 degrees to port of the centre-line (i.e., at about 7 o'clock, behind the left wing) and moved from 1000 to 12,000 yards range in a few seconds (less than 10). It was a "brilliant target". The gunner was impressed by its size and speed, and noted that there was no clutter or other echoes on the scope. Little information is available presently about this radar, but it appears to have been a multilobe tracking radar employing sum-and-difference circuits for ranging and and target following. Probable wavelength would be under 3cm. Azimuth coverage was 320 degrees, 160 degrees left and right of the tail. But there is no reference at all to this incident in the official file and other witnesses have no memory of it.
There is also uncertainty about the role of ground radars in addition to the weather radar. Col. Werlich states that RAPCON at Minot AFB did not detect the UFO at any time, but he observes that "IFF equipment was operating in the airplane. Its a fairly good size blip. Every time it sweeps it shows the blip. The object would have been covered by the blip." It is unclear whether he is referring to the surveillance radar or the precision approach GCA radar or both. The ADC radar south of Minot "do not remember" seeing any unidentified targets says Werlich, but this is a fairly meaningless statement. FTD's requests for more information on this, and on the RAPCON radars, were no more successful than their requests for details of the weather radar report. Werlich's only response is the inaccurate reassertion that only the B-52 bomb-nav radar was involved. This is very unsatisfactory. Werlich himself indicates that he was denied the technical assistance he requested from SAC to further his investigation, and in the context of SAC's sensitivity about some security implications of the incident this is certainly suspicious.
It has been possible to find the following information on radars operational the the Air Defence Command SAGE [Semi Automated Ground Environment] radar site 16 miles S of Minot in October 1968:
Note the "diversity operation" of the heightfinders - two transmitters of 2.5MW each are operated in tandem with the pulse repetition rate slightly out of phase and the delayed signals recombined at the receiver to give an effective 5MW peak power.
All these radars were also part of the ADC "Frequency Diversity Radar Program". Frequency diversity means that as well as being slightly delayed, multiple channels are assigned slightly different frequencies - usually about 5% or less - which increases probability of detection by receiving different scattering patterns from a single target. The SNR increases like the square root of the number of channels and the practical range performance similarly. Whether this freq diversity applies to all 10 of the surveillance beams isn't certain. The vertical stack probably also gives the FPS-27 a heightfinding capability as well.
Note that the range dimension of the resolution cell, in the surveillance set in particular, is quite poor at 6 microsec., about 0.5NM (0.38NM for the heightfinders). No information is available on beam width. The surveillance peak power of 15MWatt converts to a mean power of 30kW, so this is a powerful transmitter designed for long range. The unambiguous range allowed by the interpulse time would be about 240NM.
A target at the altitudes indicated near Minot should have been above the ADC radar horizon out to a range of well over 100 miles if the ADC antenna is about the same height ASL.