(also known as the TT&C antenna)
The first OTC (Australia) Earth Station antenna was a fully steerable 42 foot aperture cassegrain-fed
folded-horn antenna, with interacting parabolic and hyperbolic reflectors.
The design of the dish was pioneered by the Aero Geo Astro Corporation. It had a number of advantages over the larger horn antennae. Details here.
The structure was built by the Rohr Corporation of California for Page Communications. (Rohr
were well known in building similar structures – they won the contract to build
the 64m Mars dish at Goldstone. The project was overseen, and the electronics installed by Page Communications Corp.
Five of the CassHorn antennae were built:
Four were built under contract to COMSAT Corporation, for installation at Andover, Maine; Brewster Flats, Washington; Carnarvon, Australia; and Paumalu, Hawaii. However, Australian authorities required that the Carnarvon station be owned and operated by OTC (Australia).
A fifth 42-foot station was built and assembled as a spare at Page Communications’ Taylors Island test site in Maryland. When RCA won the bid to supply an Earth Station for Thai PTT (even though RCA did not have an Earth Station they could sell!), the fifth station was sold to RCA and was installed at Sattahip, Thailand.
(Above information courtesy William Lightfoot, Program Manager for the 42-foot stations.)
The OTC Carnarvon 42-foot Casshorn is the last remaining example of this design of antenna anywhere in the world.
The first – though unscheduled – assignment for the Carnarvon antenna was to test links to the UK through Intelsat-2A on 29 October 1966. Three weeks later, when the satellite was again in a favourable position, it was used for the Down Under Comes Up Live broadcast.
The antenna began communicating through the Pacific-1 (Intelsat-2B)
on 11th January 1967 – three weeks after that satellite’s launch.
Three weeks later, in February 1967, it commenced its role as satellite relay station in support of the NASA MSFN Carnarvon Tracking Station.
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Assembly of the OTC(A) Carnarvon 42 foot cassegrain horn begins.
Photo: Jim Harte. |
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The 42 foot cassegrain horn begins to take shape.
Photo: Jim Harte. |
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The ungainly looking 42 foot cassegrain horn and associated support
vans.
Photo: Jim Harte. |
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The original 42 foot casshorn.
Photo: Graham Watts. |
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The 42 foot cassegrain horn.
Photo: John Lambie. |
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The completed 42 foot cassegrain horn.
Photo: OTC. Scan: Colin Mackellar. |
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The 42 foot cassegrain horn.
The crane in the background may be the beginning of work on the 97 foot parabolic antenna.
Photo: John Lambie. |
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The 42 foot cassegrain horn.
This early 1970s photo, found in an OTC Carnarvon photo album, shows the “Manufactured by” plaque. Image processed by Colin Mackellar.
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Detail from the above photo.
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