DATE: December 2,
TIME: 1410 local CLASS: R/V ground
LOCATION: SOURCES: Vallee CS 1966 186
RADAR DURATION: 60 mins. approx.
EVALUATION: No official
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Date of Report: 12-02
PRECIS: A French military radar site at Ceuta tracked a target which was simultaneously observed visually by the crew of a fighter in the air. The speeds and altitudes of the target were recorded for a continuous period of about I hour from 1410 to 1510, during which time its altitude varied between ~ km (23.000') and 18 km (59,000') with variations in speed from 10 kph (6 mph) to 220 kph (137 mph). The altitude/speed diagram shows a rate-of-climb of >1500 rpm maintained for some 17 minutes (speed 100 mph slowing latterly to 40 mph) up to an altitude of nearly 59,000', levelling off with speed dropping briefly to near-zero, then accelerating steadily to 137 mph over about 12 minutes at the same altitude before suddenly dropping 20,000' in 1 minute down to 39,000' and again levelling off, still at 137 mph, for about 10 minutes, at which point the target dropped, with a simultaneous rapid deceleration, at a mean rate of about 5000 fpm for 3 minutes down to another level of 23,000' at <60 mph, maintaining this speed and level for some 10 minutes until contact was lost.
NOTES: No information is available on the radar type(s) or the nature of the simultaneous air-visual, nor are ranges and bearings given for the target, and the scope presentation is not described. Evidently at least one nodding-fan height finder was involved, but whether there was a concurrent PPI track is unknown. Nevertheless an aircraft would seem to be ruled out by the combination of altitude, somewhat abrupt manoeuvrability, and speed range. Apparently slow speeds, or even brief hovering, might be displayed on the PPI track of a fixed-wing aircraft dining a radial climb at constant slant range, but not on a height-finder simultaneously (although a height-finder operated alone is susceptible to a related blind effect - see below). An altitude of nearly 60,000' was at the very limits of the state of the art for fixed-wing flight in 1954, and coincidentally it was on December 1 - the day before this incident - that Eisenhower gave his authorisation for the $19 million USAF/CIA program to develop a revolutionary plane - the U-2 - which could exceed it in extended flight. No helicopter could achieve the height/speed domain of the target. In short, if the record accurately reflects target movements, this would seem to be unbelievable performance for any fixed wing or rotor craft known to have been flying in 1954.
It is possible that multiple-trip returns from an aircraft beyond the unambiguous range of the set could display spuriously slow speeds, since the angular rate of the target is preserved but at much less *?: in the true range. True radial velocities would be accurately displayed, but motion with a component normal to the line-of-sight would be displayed at spuriously slow speeds to a degree proportional to the tangential vector. On a PPI display, true tangential motion of a multiple-trip target could be reduced still further by a simultaneous steep climb, since the 2-dimensional display only indicates the change in azimuth. On an RHI scope the situation is a little different and changes in elevation would not enhance the multiple-trip effect. However, because the elevation angle is preserved it is obvious that multiple-trip returns displayed at a given altitude by the RHI scope must relate to a more distant target at a greater true altitude. Therefore an aircraft is a still less likely explanation of the target if detected on the 2nd trip. Additionally, of course, any such hypothesis would be conditional upon the nature of the undescribed air-visual corroboration of the target.
Whether or not the RHI indications cited were supplemented by a PPI track is very important to an interpretation of the altitude/speed diagram. A nodding-fan height finder
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date of Report: 12-02
has a poor azimuth resolution, with good discrimination in altitude and range; a surveillance PPI on the other hand does well with range and azimuth but has essentially no resolution in elevation. If the diagram was derived from RHI indications alone, therefore, it may not reflect the true azimuthal vector of target motion and thus the speeds cited would be minima. This would mean that when the, diagram shows the target slowing to about 6 rnph. this could be merely the rate of change in range - but there could be a simultaneous undisplayed tangential vector in the plane of the resolution cell, which, for a typical beam width of about 4 or 5 degrees, would be on the order of 2 miles across at a slant range of (say) 50 miles. At the highest recorded speed of the target in this case, it would take more than 50 seconds to cross this cell laterally, during which time it would be displayed as stationary. Its echo would then disappear and the operator would be obliged to realign the antenna azimuth left or right to find it again, by which time it could have begun to turn towards a radial heading and would now show indications of increasing speed. In this way the speed diagram might show spuriously abrupt transitions and episodes of near-stationarity . Of course it is normal for a height finder to be operated in tandem with a surveillance PPI, and so it may have been in this case although no track information is presented which positively requires this to be so.
Although angles of elevation cannot be inferred without range data, wide variations in altitude up to nearly 60,000' seem intuitively inconsistent with anomalous propagation. This is not necessarily so, however. For a radar with a range of (say) 200 miles, a target displayed near maximum range with a displayed altitude of 60,000' would represent an elevation angle of only about 3 degrees, and a diminishing amount of trapping or partial reflection might be possible up to about 10 degrees. The altitude variations of the target (representing a couple of degrees at long range) might fairly be described as erratic, and could result from sporadic echoes of ground targets beyond the operating range of the set detected due to superrefractive conditions. Such echoes might be mistakenly interpreted as a single coherent track, and a bright star or planet low on the horizon in the same rough direction - possibly exhibiting abnormal scintillation or perceptible image-wander due to mirage caused by the same atmospheric conditions - could have been seen by the visual observers in the air. Granted, such an hypothesis may not be especially probable and may imply an unusually anisotropic atmosphere (with the targetfs] confined to within a maximum azimuth arc of about 20 degrees for a radar range of 200 miles, giving a track length consonant with average speeds of about 75 mph over 60 minutes), but the limited data available do not definitely exclude it. Again, confirmation that the RHI was operated in tandem with an electronically independent PPI scope - and the detailed track information from that scope - would help in assessing this hypothesis, since different operating frequencies and beam shapes would argue against similar sporadic AP echoes occurring in consistent patterns on both scopes.
In conclusion, this potentially very interesting report deserves further investigation -particularly of radar operating characteristics, the ground track of the target and the visual sighting - but unfortunately does not support any definite interpretation as it stands.
S TATUS : Insufficient information