Attachment 5
Early OTC Satellite Earth Stations

by
Cyril Vahtrick

This is an account of the history of establishing the first Australian satellite telecommunications relay earth stations to operate with the INTELSAT global satellite system.

Going back in history, experimental earth stations had been established early in the 1960’s by the American Telegraph and Telephone Company (AT&T) at a remote unpopulated spot at Andover, Maine in USA and also by the British Post Office at Goonhilly Downs in Cornwall. The Andover antenna was a giant horn (30 metre aperture) enclosed in a radome because of winter snow. The BPO antenna was a conventional 30 metre parabolic dish with no outer weather protection. These experimental earth stations and others which were established in France and Germany were used to conduct tests across the Atlantic with the AT&T Telstar and other experimental telecommunications relay satellites.

All of these earth stations originally used ruby MASER detector/amplifiers which operated at the extremely low cryogenic temperatures which required the periodic application of liquid hydrogen. While the MASER performance stretched the state of the art in terms of sensitivity, the liquid hydrogen exercise was hardly suitable for a continuous 24-hour telecommunications system.

Nevertheless, given the obvious problems of introducing greater complexity into spacecraft, earlier satellite communications system designs sought to limit complexity in space and conversely, earth station design was expected to be at the best available technological performance in order to maximize the overall telecommunications capacity available via the satellite.

For OTC’s first earth station, because of the very tight time constraints put on us by the NASA Apollo program, OTC decided that an order for our Carnarvon earth station would be placed in USA as an extension to the COMSAT order for four such stations which they planned to install for themselves for the same Apollo program. These earth stations had somewhat smaller antennas than those at the foremost of technology and overall their performance was at a somewhat lower level than that of the very high performance results of the experimental installations mentioned above.

The Carnarvon earth station receiver used parametric amplifiers which needed to be cryogenically cooled to the temperature of liquid nitrogen. This had to be achieved with an on-line cryogenic system to maintain operational continuity. OTC Carnarvon staff had to become proficient in coping with this technology.

The earth station installation was ready for the attempted launch of the first INTELSAT II spacecraft (F2) in October, 1966 but the apogee kick solid state rocket motor malfunctioned and the satellite failed to reach synchronous orbit.

Attachment 4 provides a narrative of what turned out to be an historical event for Australia with the first exchange of television signals from an overseas destination.

The Carnarvon earth station first started full time service for the NASA Apollo project with the successful launch of INTELSAT II F2 in January, 1967.

When it came to planning an eastern Australian earth station to access a Pacific Ocean satellite, OTC faced a quandary. There was still no decision from INTELSAT as to the type of system it would finally choose, and with COMSAT at that stage favouring a multiple satellite random orbit system, it was still possible that OTC may need fast tracking 360 degree earth station antennas.

In line with the international convention requiring no interference to domestic microwave systems, the PMG insisted that it was necessary for OTC to go far afield to Moree to install a satellite earth station in NSW in order to avoid possible interference to possible planned domestic microwave systems. Since the PMG were also the communications regulator, they made sure that OTC was well out of the way of any possible future land microwave links.

OTC immediately realized that it needed to establish a culture among potential earth station contractors to understand that the station needed to be totally and continuously operational all the time. This culture was not necessary, for example, in previous antennas which had been designed and installed around the world for deep space communications in connection with NASA space projects. These antennas could be regularly taken off service for maintenance and adjustments as the earth station site, with the earth’s rotation, moved away from the direction of the deep space target and another antenna, at a different geographic location, took over.

It was not until after OTC had already been committed to the site at Moree that INTELSAT decided to abandon the random orbit option. Nevertheless, this still left the possibility of the phased equatorial orbit as an option, albeit looking less likely. Therefore the specification OTC wrote for the Moree station did not include fast tracking over 360 degrees but still allowed for tracking for a phased equatorial orbit if this was to prove necessary.

Cyril Vahtrick, helped by Barry Lancaster, wrote a comprehensive specification for the Moree earth station, drawing on parallel criteria applying to the COMPAC submarine cable system to emphasise extremely high reliability as well as high performance. Designers of large antennas, whose previous experience rested with space research systems, had to come to terms with the requirement for a continuous 24-hour operation and no time off for routine maintenance and repairs. This entailed full duplication of essential equipment, no-break power supplies, etc. (for reasons of cost, this did not initially include on-site duplication of the actual antenna structure but this did come some time later).

After tenders were called, a system embodying an unusual “polar” antenna mount was chosen for Moree, keeping an eye on the possibility still, that INTELSAT may decide on a phased equatorial orbit.

OTC contracted with an American company… Collins Radio to build and erect the antenna and to provide the transmit and receive system. The station was rigorously tested by OTC staff before it was accepted as our first major international satellite earth station.

The Moree earth station was formally opened by the Postmaster-General on 29 March, 1968 with a television program exchanged with KDD in Japan. This was the beginning of the first regular overseas public satellite communications service from Australia, providing service initially to Japan and USA via the INTELSAT II F2 satellite located over the Pacific Ocean.

The next step was to look westwards for a link across the Indian Ocean to UK and Europe. By 1968, INTELSAT had firmed up on the first fully global satellite system based on the INTELSAT III series.

To permit access to the satellite by UK at its Goonhilly site, INTELSAT calculated that the extreme easterly location of the Indian Ocean INTELSAT III satellite should be at 62.5 degrees East Longitude. This also just gave eastern coverage from this satellite for Japan. Unfortunately, this coverage did not extend to the main international traffic centres in eastern Australia.

Since the vast majority of Australia’s overseas telecommunications traffic came from our eastern States, this posed a problem for the location of a suitable earth station for this traffic. Our experience with the PMG on landline extension costs, led us to the conclusion that we should choose a site as far east as the satellite coverage would allow, to minimize landline extension costs.

This, of course, led us to Ceduna in South Australia. Even with Ceduna’s remoteness, the PMG still had its say on the precise location. By now, INTELSAT had decided that the global satellite system would be based entirely on synchronous satellites, so the possibility of all round rotation of the antenna was gone. Nevertheless, because of the very low angle at which the antenna would need to operate at Ceduna, the PMG said they were concerned about possible interference to some of their possible future microwave links across the Nullarbor plains. So they insisted that the Ceduna earth station should be well out of town.

When it came to OTC establishing an earth station at Ceduna, INTELSAT had by then established key performance values for their “Standard Earth Station”. The concept of a “Standard” earth station was originally put to INTELSAT by OTC, supported by Britain and Canada. The performance requirements of such an earth station was directly linked to the space segment charge to earth station operators, of a CCITT standard telephone circuit carried via satellite.

With the publication of specifications for a “Standard Earth Station” by INTELSAT and the growth of demand for earth stations around the globe, there was a considerable increase in commercial interest for tendering for the establishment of these stations. We in OTC still prepared our own specifications in detail, but made sure that the end result would meet the INTELSAT specification.

We had some very interesting experiences at Ceduna with the selected Japanese contractors. This was a new venture with Japan needing to seek Australian Government approval for Japanese engineers to work in Australia, albeit for a specific project. This produced some interesting experiences with the diversity of cultures.

In the end, the finished product at Ceduna met our specifications and the earth station entered into service in 1969. The Ceduna and Moree earth stations strongly ushered OTC and Australia into the international telecommunications service via satellite.

This story ends here, as an account of the early stages. As with all technology, advances continued to occur. That is another story for somebody else.