Communication Satellites (4th Ed.)

Donald Martin

Chapter 1: Experimental Satellites (cont.)

Communications Technology Satellite

The Communications Technology Satellite (CTS), formerly called Cooperative Applications Satellite C (CAS-C), was a joint effort of the Canadian Department of Communications and NASA [1–21]. The main purpose of CTS was to demonstrate advanced spacecraft techniques that were applicable to higher power transmissions in the 12- to 14-GHz band, including a high power transmitter, a lightweight extendable solar array with an initial output above 1 kW, and a three-axis stabilization system to maintain accurate antenna pointing. Canada developed the satellite. NASA provided the primary experiment, which was a 200-W output, 50-percent efficient 12-GHz TWTA. NASA also had the responsibility for launching the satellite. The European Space Research Organization (ESRO), now known as ESA (European Space Agency), participated in the CTS program by supplying one of the TWTAs, a parametric amplifier, and some other items.

Communications Technology Satellite

The satellite body was roughly a cylinder 6 ft in height and diameter, which was injected into a synchronous equatorial orbit in a spinning condition. After it was despun, two 51 X 244-in. solar panels were deployed from opposite sides of the body. The solar panels rotated about their long axis to track the sun continually. The antennas were mounted on gimbals on the front (Earth-viewing) end of the body and required no deployment. Satellite details are as follows:

Satellite

Body 72-in. diam, 74-in. height with two solar arrays 51 in. wide and 20 ft, 4 in. long; total satellite span 52 ft, 9 in.
738 lb in orbit, beginning of life
Sun-tracking solar array and NiCd batteries, 1360 W initially, approximately 930 W minimum during last year (1979)
Three-axis stabilization using a variable-speed momentum wheel, ±0.1 deg about pitch (north-south) and roll (velocity vector) axes, ±1.1 deg about yaw (radial) axis
Solid rocket motor for apogee maneuver, hydrazine thrusters for on-orbit use

Configuration

Two 85-MHz bandwidth single-conversion repeaters

Transmitter

11.843 to 11.928 GHz and 12.038 to 12.123 GHz
Normal configuration 20-W TWTA on low band and 200-W TWTA on high band, alternately both bands share the 20-W TWTA (at reduced capability)

Receiver

14.010 to 14.095 GHz and 14.205 to 14.290 GHz
Two preamplifier chains (one on, one standby)

Noise temperature:

Approximately 2000 K with tunnel diode preamplifier
Approximately 1350 K with parametric amplifier
G/T: 6.4 dB/K on-axis with parametric amplifier

Antenna

Two 28-in.-diam antennas, 36.2-dB gain on axis for transmit and receive, 2.5-deg beamwidth, steerable over ±7.25 deg, linear polarization

Telemetry and command

Telemetry: 2277.5 MHz, 2-W transmitter
Beacon: 11.7 GHz, 200-mW transmitter
Command: 2097.2 MHz

Design life

Two years

Orbit

Synchronous equatorial, 116°W longitude, (142°W last half of 1979) ±0.2°E-W stationkeeping, inclination 0.8 deg through mid 1979

Orbital history

Launched 17 January 1976
Delta 2914 launch vehicle
In use until turned off (November 1979)

Management

Developed by Canadian Department of Communications

CTS Communication Subsystem

The communication equipment included 20- and 200-W TWTAs. Two 85-MHz channels were available. Normally, one of the redundant 20-W TWTAs was the power amplifier for one channel as well as the low-level driver for the 200-W TWTA on the second channel. In a backup mode, the 200-W TWTA was bypassed, and the output of the 20-W TWTA was divided between the two channels. Some characteristics of the 200-W TWTA, as demonstrated during the first six months in orbit, were

Construction: coupled cavity, multistage depressed collector, conduction cooling
RF output at saturation: 200-W continuous-wave minimum over the operating band, 240-W peak, 30-dB gain, 3-dB bandwidth 85 MHz
Center frequency: 12.080 GHz
Efficiency: 45% at 224-W output (including power supply)

The CTS had redundant receivers, one with a tunnel diode preamplifier and the other with a parametric amplifier. Both receiver chains were single conversion and had a tunnel diode amplifier (TDA) following the mixer. The receivers fed redundant field effect transistor amplifiers that provided the input signals for the TWTAs. The satellite had two narrowbeam antennas, one directed toward a control terminal and the other toward remote terminals. The two channels were used for two-way communications. The high-power TWTA was used for transmission to the remote terminals that used relatively small antennas.

Canada, NASA, and other United States Government agencies started conducting communication experiments with the CTS following its launch on 19 January 1976. Canada had its control terminal at Ottawa and remote terminals in the north. The capability of the CTS allowed the remote terminals to be relatively small, as indicated by the characteristics given in Table 1.2 . The CTS could support several simultaneous links with these terminals. For example, the 8-ft terminal noted in Table 1.2 could receive a television signal transmitted with only a quarter of the total CTS power. In May 1976, the CTS was renamed Hermes in Canada. By mid-1978, thirty-two experimental programs had been completed or were in progress and seven more were planned. These experiments were in the fields of propagation, communications engineering, television broadcasting, education, medicine, government, and community affairs. The operational viability of many of these projects was studied further using the 12- and 14-GHz channels on Anik B. CTS was used until November 1979, at which time it was turned off.

******

C. Franklin and E. Davison, "A High Power Communications Technology Satellite for the 12 and 14 GHz Bands," Paper 72-580, AIAA 4th Communications Satellite Systems Conference (April 1972). Reprinted in Communications Satellite Systems, Progress in Astronautics and Aeronautics, Vol. 32, P. L. Bargellini, ed. (1974).
V. O'Donovan, "Design of a 14/12 GHz Transponder for the Communications Technology Satellite," Paper 72-734, CASI/AIAA Meeting: Space—1972 Assessment (July 1972).
P. L. Donoughe, "United States Societal Experiments via the Communications Technology Satellite," International Conference on Communications: ICC '76 (June 1976).
L. J. Ippolito, "Characterization of the CTS 12 and 14 GHz Communication Links—Preliminary Measurements and Evaluation," International Conference on Communications: ICC '76 (June 1976).
L. D. Braun and M. V. O'Donovan, "Characteristics of a Communications Satellite Transponder," Microwave Journal, Vol. 17, No. 12 (December 1974).
J. Day, "CTS Communications Experiments," Paper 35B, National Telecommunications Conference: NTC '72 (December 1972).
D. L. Wright and J. W. B. Day, "The Communications Technology Satellite and the Associated Ground Terminals for Experiments," Paper 75-904, AIAA Conference on Communications Satellites for Health/Education Applications (July 1975).
E. F. Miller, J. L. Fiala, and I. G. Hansen, "Performance Characteristics of the 12 GHz, 200 Watt Transmitter Experiment Package for CTS," EASCON '75 Convention Record (September 1975).
G. H. Booth, "The Canadian/U.S. High Power Communications Technology Satellite," Satellite Systems for Mobile Communications and Surveillance, IEE Conference Publication No. 95 (March 1973).
J. Kaiser, "Experiments in Satellite Communications with Small Earth Terminals," Paper 80-0535, AIAA 8th Communications Satellite Systems Conference (April 1980).
H. R. Raine, "The Communications Technology Satellite Flight Performance," Acta Astronautica, Vol. 5, No. 5–6 (May–June 1978).
Journal of the British Interplanetary Society, Vol. 29, No. 9 (September 1976), p. 608.
R. E. Alexovich, "On-Orbit Performance of the 12 GHz, 200 Watt Transmitter Experiment Package for CTS," Paper 1.3, International Conference on Communications: ICC '78 (June 1978)
N. G. Davies, J. W. B. Day, and M. V. Patriarche, "The Transition from CTS/Hermes Communications Experiments to Anik-B Pilot Projects," EASCON '78 Conference Record (September 1978).
A. Casey-Stahmer, "From Satellite Experiments to Operational Applications: Canadian Experiences and Plans," Acta Astronautica, Vol. 8, No. 1 (January 1981).
N. G. Davies et al., "CTS/Hermes—Experiments to Explore the Applications of Advanced 14/12 GHz Communications Satellites," Proceedings of the XXIXth International Astronautical Congress (October 1978).
C. A. Siocos, "Broadcasting-Satellite Signal Reception Experiment in Canada Using the High-Power Satellite Hermes," International Broadcasting Convention, IEE Conference Publication No. 166 (September 1978).
H. R. Raine and J. S. Matsushita, "Hermes Satellite (CTS): Performance and Operations Summary," Paper 80-0578, AIAA 8th Communications Satellite Systems Conference (April 1980).
J. W. B. Day, N. G. Davies, and R. J. Douville, "The Applications of Lower Power Satellites for Direct Television Broadcasting," Acta Astronautica, Vol. 7, No. 12 (December 1980).
D. R. Glover, NASA Experimental Communications Satellites , (10 June 1999).
B. C. Blevis, "The Pursuit of Equality: The Role of the Ionosphere and Satellite Communications in Canadian Development," chapter 14 in Beyond the Ionosphere: Fifty Years of Satellite Communication, A. J. Butrica, ed., NASA History Office, Washington, D.C. (1997).

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