Communication Minsiter Flora MacDonald |
accepts a Technical Emmy on behalf of
the Department of Communications. The
Emmy was jointly awarded to NASA and DOC
recognizing their joint role in developing
the Ku band satellite technology through
the Hermes program.
HERMESDemonstration Satellite that Opened the Door to New Services that now Benefit Canada and the World.
Canada's entry into space with the Alouette satellites was at a time when HF radio was the only means of communication for people in many remote locations. With the Alouette and ISIS satellites, scientists learned much about the upper atmosphere, which helped to predict the behaviour of HF communications. In the meantime, engineers in the USA were developing satellite communications. In 1967, John Chapman conducted a study to determine the direction Canadian space research should take. The recommendations, published in a report, "Upper Atmosphere and Space Programs in Canada", were that Canada should solve its communications problems by developing its own satellite network, research should focus on communications satellites and the last scientific satellite, ISIS C, should be cancelled.
Hermes was an experimental satellite built to test a new concept for communications satellites; that is, high power in the satellite and small dishes on earth. Early communications satellites adapted technology already in use for microwave systems (at 6/4 GHz) and hence were limited to transmitting at low power to avoid interfering with the terrestrial systems already in place. As a result very large dish antennas were required on the ground to pick up the weak signals. Hermes transmitted with high power so that TV broadcasts could be received by low-cost earth stations small enough to be used at individual homes. This concept, called a Direct Broadcast Satellite (DBS), was championed by John Chapman as a means of delivering high quality TV transmissions to Canadians outside urban centres.
New technical approaches were required to achieve the goals:
Large flexible panels of solar cells generated the high power (1200W) required for the transmitter (panels provided by ESA). The power of earlier satellites was limited by the number of solar cells that could be placed on the surface of the spacecraft.
A system to stabilize the satellite body in three axis enabled the solar panels to face the sun at all times and ensured that the narrow transmit beams could be kept accurately pointed towards the earth. Earlier satellites were "spinners". The whole body spun to stabilize the satellite.
The high power transmitter was equipped with a new design traveling wave tube (TWT) that generated 200 watts of power (NASA provided the TWT).
A new, higher frequency band (14/12 GHz) did not interfere with microwave systems on earth and hence earth stations could be used in urban environments.
On April 20, 1971, Canadian Department of Communications (DOC) and NASA announced a joint mission to build an experimental satellite - the Communications Technology Satellite (CTS). Communications Research Centre Canada (CRC) would build the satellite and NASA would launch it. CTS was successfully launched on January 17, 1976 from Cape Canaveral. On May 21, 1976, it was officially inaugurated and named Hermes by Madame Jeanne Sauvé. Designed for a two-year life, it was used for an extensive program of experiments until November 1979.
DOC was responsible for the overall management of the project. It designed and built the spacecraft at CRC. Eighty percent of the industrial contracts, by value, went to Canadian industry. The David Florida Laboratory was built with facilities to integrate and test the satellite. NASA provided an experimental, high-powered (200-watt) transmitting tube, conducted pre-launch testing and launched the satellite from Cape Canaveral. The European Space Agency also provided the low noise receiver and the 20 watt Ku-band traveling wave tubes.
When Hermes was launched, it was the most powerful communications satellite in the world with a 200 watt transmitter. It was also the first to operate in the Ku band. Hermes was intended to be a geostationary satellite. After reaching the 116W longitude, spacecraft control was transferred to DOC. The transition between the spin mode and three-axis mode of control was complex and constituted a significant mission hazard particularly since this maneuver had not yet been successfully demonstrated for a geosynchronous satellite. The necessary technology for this operation was developed within Canada. The CTS/Hermes satellite occupies an important place in the evolution towards high-power satellites, because it permitted future communications systems to realize the resulting benefits of small, low cost ground stations and incidentally opening the way to a variety of direct broadcasting applications.
The transponder design allowed several types of experiments to be carried out, including:
- TV broadcast to small communities in remote areas;
- TV transmission, using a transportable terminal, of special events from a remote region to a central area for network distribution or for retransmission to other remote regions. This introduced the term Satellite News Gathering (SNG);
- Broadcast of radio program material to small earth stations;
- Telephone service including voice, facsimile and data, to and between small transportable earth stations;
- Digital data transmission and exchange;
- Investigation of high-speed satellite data transmission;
- Investigation of time division multiple access (TDMA) techniques.
In 1987, an Emmy was awarded to the Department of Communications and NASA recognizing their joint role in developing the Ku band satellite technology through the Hermes program. Communications Minister Flora MacDonald referred to the Hermes satellite as "one of the most important milestones in Canadian space history" when she loaned the award for engineering achievement to the National Museum of Science and Technology. Hermes was the first satellite to operate in remote areas by people with no technical training. In 1976, John Day designed a way to connect telephones via Hermes.
After the success of Hermes, Telesat Canada acquired the world's first hybrid satellite, Anik B, to provide service in both 14/12 GHz and 6/4 GHz bands. Telesat has continued to provide service in both bands. Field trials of social services initiated with Hermes were continued with Anik B. Several of these trials were continued as operational services. These included education networks in Ontario (TVO), BC (Knowledge Network), Alberta and Saskatchewan.
courtesy of Friends of CRC, www.friendsofcrc.ca/