Common sources of ‘aerial phenomena’ detected by ground and airborne radars
During the 1930s British scientists working on a ‘death ray’ discovered that when radio waves from a transmitter struck targets such as aircraft, ships and buildings they bounced back and could be detected by a receiver. The Air Ministry quickly began to develop a functioning early warning system that could be used to calculate the distance, direction and height of German aircraft by listening for the echoes returned from bursts of radio waves. Originally known as a Radio Direction and Finding (RDF) the term ‘radar’ was adopted during WW2 when the Chain Home system, built around the English coastline, was the key to the success of the RAF during the Battle of Britain. But despite its success early radar systems were cluttered by noise from birds, insects, weather systems and unusual atmospheric conditions. Here are some of the most common explanations for UFOs on radar:
Angels were first mentioned by radar personnel at the dawn of the modern UFO era to describe invisible targets in the clear atmosphere. In March 1941 Chain Home radars detected a formation of blips moving across the English Channel. RAF fighters were sent to intercept but their crews saw nothing and the blips faded. Similar ‘angels’ plagued the more powerful Type 80 centimetric radars that were introduced from 1954 and became a hazard for air traffic controllers. A RAF Fighter Command investigation concluded the majority of these were caused by migrating seabirds and others were the result of ‘anomalous propagation’. Computers filtered out smaller echoes and increased the strength of those created by aircraft. The invention of transponders that transmit an electronic identification signal from aircraft to ground control helped to further reduce clutter on air traffic control radars. This means that ‘aerial phenomena’ appear on radar today only if they intrude upon flightpaths and create a nearmiss of the type occasionally investigated by the Civil Aviation Authority’s Airprox board.
This is caused by unusual meteorological conditions that trap and bend radio waves along the surface of the Earth. AP can result in radio energy being returned from objects at distances far in excess of the radar’s normal range of operation. On occasions moving objects such as cars, ships and low-flying aircraft have been superimposed on the usual radar picture. AP may be the ultimate source of some classic radar UFO flaps including those that plagued Washington DC during the summer of 1952 and RAF Bentwaters-Lakenheath in 1956. Measurements of extreme speed and height of anomalous radar targets is completely worthless if the observer is unaware that AP is present and even experienced operators have been fooled. More recently, clear air radar echoes created by backscattering from fluctuations of the index of refraction in the atmosphere have been detected by scientists using powerful radars operating at several wavelengths.
One of the pioneers of radar meteorology, Dr David Atlas (1924-2015) said these experiments prove ‘the atmosphere will effect radar propagation in almost unbelievable ways and produce virtual targets which have apparently fantastic maneuverability’. In 2002 Dr Atlas said the majority of UFO radar incidents occurred before the results of NASA-sponsored research using extremely sensitive radars to probe extremely thin atmospheric echo layers was widely known.
These experiments at Wallops Island in Virginia from 1967 identified ‘incredibly thin, specular reflecting layers like mirrors at high altitudes…that could account for the exceedingly large apparent speeds of echoes either from ground targets or moving vehicles on the ground’. He added:
‘I am strongly convinced that these mysterious radar echoes are due to anomalous propagation somewhat different than that with which scientists in the 1950s and 60s were familiar’. He believed the large number of UFO radar reports during this period ‘was due to the lack of knowledge of their origin. Once their origin was explained the frequency of the reports decreased’.
On occasions prominent buildings have been reported as potential UFOs when ground controllers have been alerted, in real time, to mysterious visual sightings. A classic example occurred in October 1996 when the 273ft (83m) spire of Boston Stump appeared on civilian and RAF radars at the height of a UFO flap in East Anglia. The presence of the stationary echo was only flagged up as unusual when staff at RAF Neatishead in Norfolk were alerted by police and others who had spotted strange lights in the sky above The Wash.This case even fooled defence intelligence experts. Ron Haddow listed it as the ‘only UK event’ where three radars had simultaneously detected a UFO in UK airspace in the Condign report he produced for MoD in 2000.
Interference from other transmitters
Mysterious moving echoes can appear on radars when two or more transmitters are close together. The MoD’s Flying Saucer Working Party investigated one example in 1950 when a sighting made by a RAF Meteor pilot initially appeared to have strong corroboration from a ground radar station in Sussex. Inquiries found the sighting occurred ten minutes before the radar detection and traced the interference to a naval radar in the English Channel. Some of the hypersonic targets detected by Belgian Air Force F-16s in March 1990 were caused by the aircraft’s own radars interfering with each other in a similar manner.
ECM: jamming and spoofing
Electronic Counter Measures are techniques developed by military intelligence agencies to fool enemies. Early crude examples include dropping ‘chaff’ – strips of reflective foil – to jam defence radars during air raids. In 1998 the CIA revealed the existence of a formerly top secret project, code-named Palladium, that was developed alongside the U2 spyplane in the 1950s to insert phantom aircraft into enemy radars. It was used during Cuban crisis and later during the Vietnam war. Project leader Gene Poteat said it allowed them to ‘simulate an aircraft of any radar cross-section from an invisible stealth airplane to one that made a large blip on Soviet radar screens – and anything in between, at any speed and altitude, and fly it along any path’.
A secret CIA-MoD experiment with Palladium might explain the radar UFO reported by USAF F-86 pilot Lt Milton Torres who was sent to investigate a blip detected by RAF radars in East Anglia one night in 1956-57. Torres’s airborne radar locked onto the ‘object’ that appeared to be the size of a B52 bomber and he was ordered by the ground controller to open fire with his salvo of rockets. But ten seconds before he received authentication the ‘bogey’ broke away and disappeared at great speed. There was no visual sighting. On return to base Torres was debriefed by a secret service agent and told his mission was Top Secret. He did not discuss it again until 1986 after retirement from USAF.
‘Specials’: Black project aircraft.
According to intelligence expert Richard Aldrich during the Cold War air defence radars in the West were frequently triggered by incursions by Black Project aircraft developed by the CIA and USAF. Incursions by ‘friendly’ Black Projects have continued with the deployment of the radar-invisible F-117A Stealth and B2 bombers in the Europe from the 1970s. Speculation has continued about the hypersonic Aurora spy-plane that was linked with a series of anomalous radar detections in southwest Scotland during the early 1990s. The existence of the Aurora has been denied but declassified MoD files reveal that intelligence officers declared they ‘would not be surprised’ if covert visits were the source of some unexplained UFO incidents reported in the UK.
This image of a RAF track-tracing sheet is possibly the nearest we have to an official record of unidentified aerial phenomena in the sky above the British Isles. During the Cold War RAF radars scanned the North Atlantic and North Sea for Soviet intruders 24 hours every day of the year. Radar operators routinely made manual records of unknowns tracked on radar by marking their movements, in pencil, on tracing paper.
These UFOs were designated as ‘X-raids’ and, if they could not be identified as friendly aircraft, RAF fighters were scrambled to intercept them. This tracing sheet was produced by Flt Lt J.S. Hassall to record the movements of strange aerial phenomena tracked by radars at RAF Ventor, Isle of Wight, on the afternoon of 29 July 1957.
In his report to the Air Ministry’s UFO branch, DDI (Tech), Hassall said his Type 80 radar first plotted ‘X-raid 422’ moving at speeds between 1000-1400 knots at a height of 42,000 feet above the English Channel. Minutes later Hassall tracked another similar echo, moving at a similar speed, then a third and a fourth. By then he had begun to doubt the tracks were genuine. His report concludes:
‘It was finally decided these were spurious responses, but as they had been designated X-raids, recordings and reports were made’. [TNA AIR 20/9994]