Communication Satellites (4th Ed.)
Donald Martin
Chapter 1: Experimental Satellites (cont.)
Japanese Satellites
Japan built and launched several low-altitude satellites in the early 1970s, but its first communications and broadcasting satellites were built in the United States and launched by NASA. At the same time, Japan was developing smaller synchronous orbit satellites and a launch vehicle for them. The launch vehicle was the N rocket, which was based on the 1970 design of the United States Thor-Delta. An improved version, the N-2, was based on the mid-1970s Delta. The first synchronous orbit mission for this launch vehicle was the Engineering Test Satellite-II (ETS-II), described in a later chapter. The successor to ETS-II was the satell Experimental Communication Satellite (JECS), which was also launched by the N rocket. Japan continued the development and test of satellite bus and payload technologies and the demonstration of improved launch vehicles with a series of Engineering and Test Satellites, also known by the name Kiku. This section describes the Engineering and Test Satellites that have or had a communications or broadcasting payload.
Japanese Experimental Communication Satellite
The objectives of the Japanese Experimental Communication Satellite (JECS) program [1–4] were to develop techniques for launch and on-orbit control of synchronous satellites, propagation measurements, and communications experiments. The satellites were launched on the Japanese N rocket. JECS was based on the Skynet I design, because the Skynet was sized to the Delta launch vehicle from which the N rocket was developed; both satellites were built by the same manufacturer. Like Skynet, JECS was spin-stabilized with a mechanically despun antenna. The solar array was mounted around the outside of the spinning body, and other subsystems were attached inside the spinning body on both sides of an equipment platform. The despun section had two parabolic antennas whose beamwidth was sized to cover Japan while minimizing radiation on adjacent nations. The larger antenna was for C-band (4 and 6 GHz), and the smaller was for K-band (31 and 34 GHz). There was also a 128-element C-band array mounted around the top end of the satellite body, which provided nearly onmidirectional coverage. The C-band equipment could be switched between the two C-band antennas. Technical details of the satellite are as follows:
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Japanese Experimental Communication Satellite |
Satellite
Cylinder, 55.7-in. diam, 37-in. height (64.8 in. overall)
Approximately 290 lb in orbit, beginning of life
Solar cells and NiCd batteries, 118 W maximum at beginning of life, 99 W minimum after one year
Spin-stabilized, 80 to 115 rpm
Configuration
Single transponder with selectable bandwidth of 10, 40, or 120 MHz, input and output independently switchable to either C-band or K-band
Transmitter
C-band: 4.08-GHz center frequency, redundant 5-W TWTAs (one on, one standby), 23-dBW EIRP
K-band: 31.65-GHz center frequency, single 2.5-W TWTA, 34-dBW EIRP
Receiver
C-band: 6.305-GHz center frequency, tunnel diode preamplifier, -12 dB/K G/T
K-band: 34.83-GHz center frequency, mixer followed by transistor amplifier, -5 dB/K G/T
Antenna
C-band: narrowbeam parabola, 22-in. diam, measured minimum gain with rotary joint loss 20.5/23.6 dB (transmit/receive), beamwidth approximately 9/6.5 deg
C-band: array composed of 128 cavity-backed crossed dipoles mounted in a band around the satellite body, pattern nearly uniform in array plane and ±45 deg from the plane
K-band: narrowbeam parabola, 12-in. diam, measured minimum gain with rotary joint loss 34.7/34.9 dB (transmit/receive), beamwidth approximately 2.5 deg
All antennas use circular polarization
The two narrowbeam antennas are despun together
Telemetry and command
Telemetry: approximately 136 MHz, via four monopole antennas
Beacon: 3.94 GHz, via either C-band parabola or array
Command: approximately 148 MHz, via 4 monopole antennas
Design life
Approximately 1.5 years
Orbit
Synchronous equatorial, 145°E longitude planned, both satellites actually are drifting in near synchronous elliptical orbit
Orbital history
A: launched 6 February 1979, destroyed by collision with launch vehicle third stage during apogee motor firing
B: launched 22 February 1980, destroyed by apogee motor failure
Japanese N launch vehicle
Management
Developed by Mitsubishi (prime), Ford Aerospace and Communications Corporation (spacecraft and antennas), and Nippon Electric Company (transponder) for National Space Development Agency of Japan
JECS Communication Subsystem |
The communication subsystem of the JECS had five basic sections: C- and K-band receivers (left side of the figure), an intermediate frequency section (middle), and C- and K-band transmitters (right side). The IF section handled only one signal at a time. By ground commands, either transmitter and either receiver could be connected to the IF section, giving a total of four possible configurations. The bandwidth of the IF section could be switched to 10, 40, or 120 MHz. The 10-MHz option was intended for range and range rate measurements and the wider bandwidths for the communications experiments.
JECS was launched in early February 1979 but was destroyed during apogee motor firing, apparently due to a collision with the launch vehicle third stage. The spare JECS was launched a year later and was destroyed by a failure of the apogee motor.
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- M. Hirai, et al., "Development of Experimental and Applications Satellites," Acta Astronautica, Vol. 7, No. 8–9 (August–September 1980).
- T. Ishida, "Program of Experimental Communication Satellite (ECS) of Japan," Paper 78-614, AIAA 7th Communications Satellite Systems Conference (April 1978).
- M. Ohara, "The Satellite Transponder Performance for the Experimental Communications Satellite (ECS)," Paper 78-563, AIAA 7th Communications Satellite Systems Conference (April 1978).
- E. W. Matthews, L. F. Brokish, and G. F. Will, "The Communications Antenna System on the Japanese Experimental Communications Satellite," Paper 78-584, AIAA 7th Communications Satellite Systems Conference (April 1978).
