VERLORT Radar

Revision as of 08:15, 8 May 2007

The VERLORT radar at Muchea:
Photo - ???

The VERy LOng Range Tracking (VERLORT) S-band radar (2700 t0 2900 MHz) was an extended-range version of the SCR-584 - often credited as "the radar that won WW II".

For Mercury, the radar range was increased from 650 Km to 4000 Km; the dish diameter from 1.8 m to 3 m and it was given a long name befitting its new space-tracking capabilities. The Red Lake (Woomera) Mercury tracking station used the more accurate AN/FPS-16 radar installed at Woomera for previous space activities.

The VERLORT radar reinstalled at Carnarvon just beside the AcqAid antennas:
Photo - Alan Gilham

The Verlort radar performed reliably for the six Mercury orbital missions at Muchea. It was then relocated to the new Gemini tracking station at Carnarvon as an acquisition aid and back-up for the even more accurate FPQ-6 radar to be installed there.

Although the Verlort was kept operational at Carnarvon for the first few missions it was soon operationally delisted once the FPQ-6 proved its reliablility and other acquisition methods also proved sufficient.

Some technical descriptions

Helical scan mechanism:
Image – ‘Electronics’; Fig 2, Dec ’45, p.104

The SCR family of radars, developed at the MIT laboratories, was remarkable for the innovative MIT solutions to radar operations that are now met in modern radars by electronic methods.

The Verlort Plan Position Indicator (PPI) was driven by a mechanical computer. Once target acquisition occurred, the radar operator needed to keep a ‘hairline’ indicator manually centred on the target’s echo to maintain track.

Even more intriguing were the target acquisition techniques.

For targets where only crude position information was available, a helical scan was used to acquire the target. The dish was swung in a circle at 6 rpm along the expected path with the reflector tilted to and fro about 4° per dish revolution to create a helical spiral about 20° wide along the expected track path - see 'Helical scan mechanism' diagram on right.

Where there was more certainty about the target path, a nutating scan mode was used where the slightly offset dipole feed was rotated rapidly to produce off-axis radiation to increase the effective beam width from 2.5° to about 5.5° . The nutation was switched off when the target was acquired. See ‘conical scan beam’ diagram below left and ‘nutating antenna dipole feed’ below right.

Nutating antenna dipole feed:
Image – ‘Electronics’; Fig 5, Dec ’45, p.107

A conical scan beam:
Image – ‘Electronics’; Fig 1, Nov ’45, p.104

For a detailed technical description of the SCR-584 radar see the November & December 1945 issues of ‘Electronics’ magazine at http://www.hamhud.net/darts/scr584.html.