Mysterious ... a colour-enhanced photo of a UFO seen from Bendigo. One caller dismissed it as a rock band's laser show. Credit:National Archives of Australia Senior air controllers at Mascot said the contacts were mostly located between 70 and 150 nautical miles north of Sydney at ''alleged speeds of 1100-6500 km/h that suggested high altitude''. The papers state that no scramble was to occur in the round-the-clock operation unless confirmation of any reported tracks was made on the radar screens at RAAF Williamtown or any radar other than Sydney. At the same time, three senior air defence controllers were dispatched to Sydney to investigate and plot every contact and ''control interceptors against these contacts if a reasonable chance of interception presented itself''. But then one of the defence controllers, a squadron leader, asked whether a comparison had been made of the contacts on the screens of Mascot's Area Approach Radar Centre and those in a ''workshop across the corridor''. Soon after, tests showed that the ''unidentified objects reported by Sydney were generated entirely by radar interference known colloquially as 'running rabbits' ''. Squadron leader K. Keenan, in his six-page report, said operation Close Encounter cost 66½ days of overtime, 1000 kilometres was travelled by a staff car and a C130 Hercules transport aircraft ''may have been diverted to Sydney airport'' to deliver one of the defence controllers.

He wrote: ''The lines of communication, extending as they did across the width of an entire corridor, seem to have been insufficient for the purpose.'' He added rather dryly: ''Fortunately there was no temptation to launch aircraft and add to the fuel bill occasioned by use of the RAAF Datsun.'' A cautiously worded statement was released as a result ''in a manner that would not embarrass departmental personnel'' which blamed ''random atmospheric conditions''. Other reports in the X Files give details of an ''unidentified physical feature'' of circles on Milo Station at Adavale, Queensland, in 1982. The file refers to photographs that apparently were taken, but they were not among the papers. Constable Geoffrey Russell, from the local police station, visited the site and wrote a report for RAAF Base Amberley near Ipswich. The officer saw depressions in the ground and thought they were caused by a motorcyclist doing donuts but then dismissed the idea. He wrote: ''I strongly feel this [is] no hoax even though I do not know the cause of this 'feature'.'' He described a large circle of 2330mm in diameter with one inner circle of 2010mm which were 160mm in width and about 15-20 mm deep. The soil around the outer circle appeared to have been ''blown away'', he said.

Elsewhere in Queensland, dairy farmer Robin Priebe phoned Imbil police at 5.30am in July 1983 to report seeing a strange object in the sky to the north of the town. The papers state that a Sergeant Waterson then went to his back verandah and saw ''a large white light with several flashing lights around it'' which did not appear to be a normal aircraft. A similar sighting was made by Constable R. Keys from a separate position. He was also of the opinion that it wasn't a normal aircraft. Mr Priebe said both he and his wife saw a bright red glow gradually change to a white light which then started to move slowly east. Through binoculars, ''the light was disc shaped with a very bright light around the perimeter of the disc with two flashing lights in the front and one to the side'', he said. The only photographs in the X Files were of unusual lights over Bendigo, witnessed by hundreds in May 1983. An interim report by the RAAF stated that Mike Evans, a 17-year-old disc jockey with the Bendigo radio station 3BO, received calls from listeners, then saw the lights himself and took photos. One anonymous caller to the RAAF said the lights were caused by a rock group experimenting with laser lighting. The report said they were probably caused by train headlights or lasers or from planets or stars. There had been unusual weather atmospherics on the night.

Zoe¨ D'Arcy, director of digital and online access at the National Archives, said: ''Where you and I might think UFO - a spaceship - the RAAF and other agencies were probably wondering if there was a security threat. ''Most of the files you read and you think that most probably was a meteorite, but there are ones that you read and you think - well, what could that have been? ''I can't explain that from my knowledge. ''So what was it that these people have experienced? It has that open-ended question to it that I find really intriguing.''