Spain.Noia · the motionless echo on the Iroite radar

At 18:48 UTC on 5 December 1989 (19:48 local time), the air surveillance and countermeasures officer of Air Surveillance Squadron No. 10, the EVA 10, whose radar stands on the summit of Mount Iroite in the Barbanza range above Noia, reported the presence of a UFO 'in the area between Santiago de Compostela and La Coruña'. Two minutes later the operations room spoke by telephone with the duty controller at Santiago tower, who passed on what had reached him from the Civil Guard: the Castro post had reported 'the presence of a possible U.F.O. in an area between Castro and Sada', 'lenticular in shape', which 'travels at low speed and has a great display of lights with bright tones and changing lights'. The report gives no witness's name and does not say how many there were.

At 19:00 UTC, 'once the area had been carefully examined', the operators saw on two displays, the RAPPI and the UPA-35, a 'blitz', an echo, 'in primary and secondary', at position 060/32 NM, that is, some 59 kilometres east-north-east of the station, with a height of 57,000 feet on the RHI, the height-finder display. They measured it continuously: the height varied up to 75,000 feet, about 23 kilometres, with 'few positional variations with respect to the first detection'. Santiago tower coordinated through Nécora, the squadron's call sign, the 'indication of civil aircraft near the U.F.O. for visual confirmation', 'without positive results being obtained'. At 20:00 UTC, according to the tower, its alarms went off on the emergency frequencies, 121.5 and 243.0, with 'interference and radio confusion' between Santiago, the Madrid control centre and Nécora. At 20:40 UTC a direction finder placed the source of that alarm between 160 and 167 degrees from Santiago, to the south-south-east, and at that moment the UPA-35 showed 'several objects', three of them at flight levels 290, 320 and 420. At 20:45 UTC the pulse repetition frequency of the duty channel was changed, and a change of the channel itself was also requested, 'without any variation being observed in the radar presentation'. At 21:02 UTC the tracking and the link with the tower ended. The report's last sentence says that the echo 'remained on the RHI until 08:30z on the 6th of this month without any kind of variation being observed': more than thirteen hours in the same place.

That report, a single page signed by the sergeant on duty in the room as anti-jamming operator, stayed at the squadron. It did not leave the squadron until 23 October 1992, when the lieutenant colonel commanding EVA 10 sent the Air Operations Command, which logged it in on 30 October, a photocopy 'requested in a telephone conversation' by a lieutenant colonel of the command's Intelligence Section. According to the researcher Vicente-Juan Ballester Olmos, that call was made by Lieutenant Colonel Ángel Bastida after he himself had warned in 1992 that the event was missing from the official archives. The command's intelligence officer proposed declassifying it in September 1996, since he saw no 'aspects that make it advisable to maintain the condition of "classified material"', and the file entered the Air Force Central Library on 15 October 1996. The command's summary contains two copying errors: it writes 'Sade' for Sada and gives 1987 as the year of the sergeant's report, which is from 1989. Neither the report nor the summary proposes an explanation.

In 2005 Ballester Olmos reconstructed the civil side; for part of it he cites the notes of the Labacolla tower controller, who wrote no formal report. According to that account, a local resident phoned the Civil Guard post at Sada because he was seeing a strange white light near the south-south-west horizon; some guards saw it too; the Civil Guard alerted the airport at 18:43 UTC and, fourteen minutes later, at 18:57, reported that the light had lost much of its intensity; it disappeared after about fifteen minutes of observation, as if hidden by the trees on the horizon. The radar did not detect the echo until 19:00 UTC. The same account adds that the Madrid control centre at first saw no unidentified objects on its screen, that afterwards both the civil and the military radar showed anomalous echoes, with 'an unusual and repeated change of position and height' between 6,000 and 23,000 metres, unlike the military report, which speaks of 'few positional variations', and that the search and rescue service placed 'according to the satellite' the distress beacon that had set off the alarms some 22 kilometres north-east of Labacolla, in a direction that, according to Ballester, corresponded to the echo's. That position does not match the direction finder in the report, which put the source of the alarm south-south-east of Santiago.

The case matters for the instrument, not for the light. An air surveillance squadron recorded in writing, minute by minute, an echo with primary and secondary returns more than 17 kilometres up, measured by the height-finder, searched for with civil aircraft, subjected to a change of pulse repetition frequency and channel, and present on the display for more than thirteen hours. But the record does not match what the witnesses saw. Plotting the report's bearing and range from Mount Iroite on the map, the echo lay some 15 kilometres north-east of Santiago airport and some 40 kilometres south of Sada, at a height that, seen from Sada, would have put it some 20 to 30 degrees above the horizon; the Civil Guard's object was, according to the report, 'between Castro and Sada' and, according to the controller's account recorded by Ballester, near the south-south-west horizon. No civil aircraft saw it, and the ground witnesses come second-hand, without names. There is a radar with its operators and first-hand official documentation, but the echo does not match the visual observation.

For the light, Ballester Olmos and the analyst Manuel Borraz propose Venus: that evening the planet was low over the south-western horizon and set at about 20:58 local time. An ephemeris calculation confirms it: from Sada, at 18:48 UTC, Venus was about 10 degrees high, at azimuth 224, at magnitude -4.5, the brightest object in the sky after the Moon. The report's 'changing lights' fit the scintillation of a low star-like object; the object that 'travels at low speed' fits less well, although the description arrives through two intermediaries. For the echo, Borraz proposes anomalous propagation of radio waves due to atmospheric conditions, which would also explain the interference and the alarms on the emergency frequencies; Ballester presents it as 'merely a theoretical scenario, but one that seems to fit the complex sequence of radar tracks and associated phenomena'. Against it weighs one fact from the report itself: the echo had a secondary return, the reply a transponder gives when interrogated. That it did not change with the new pulse repetition frequency rules out a second-trip echo, but not an echo from atmospheric ducting, which does not depend on that setting. In its favour, an echo that barely moves in more than thirteen hours looks more like an artefact than like something flying, and the report documents that there was radio interference in the area that night.

An almost motionless echo between 57,000 and 75,000 feet is at the float altitude of a stratospheric balloon, but none of the sources consulted proposes one, and the Stratocat flight catalogue records no scientific launch in Europe between 12 October 1989, when one left Aire-sur-l'Adour, and the end of that year. A drifting balloon, moreover, would hardly stay at the same point for thirteen hours. The three objects on the UPA-35, at flight levels 290, 320 and 420, are at the cruising heights of commercial aviation; the report does not identify them.

The file is also an example of how many Spanish cases were recovered: the report spent almost three years filed away at the squadron and reached the command only because a civilian researcher asked about it. Read in full, it preserves both the technical detail that makes the echo interesting and the facts that weaken it.