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CS (Communications Satellite) Sakura

The Japanese CS (Communications Satellite) series was highly successful since its debut in 1977. The Communication Satellites Sakura(CS) was used to conduct a variety of communications experiments aimed at actualizing practical satellite communications systems in Japan. The prototype satellite CS (also known as Sakura) was operational from 1977 to 1985. The second generation, operational spacecraft, CS-2a and CS-2b, were launched in 1983 and continued to function until 1991 and 1990, respectively.

The Japanese Medium-Capacity Communications Satellite for Experimental Purposes (CS) was an experimental communications satellite launched 1977-12-15. It consisted of a 90 rpm, spin-stabilized cylinder with its curved surface covered with solar cells. The cylinder height was 2.18 m with the antenna extending another 1.31 m along the axis. The spin axis was perpendicular to the orbit (earth's equatorial) plane, but the K- and C-band antenna was despun with a pointing accuracy of better than 0.3 deg. This small, disk antenna was mounted on the end of the cylinder and was oriented at an angle of about 45 deg to the spin axis.

The satellite had a designed lifetime of 3 years on location near 135 deg e. Experiments used 2.1, 2.3, 4, 6, 20, and 30 gHz frequencies for telephone and TV. Experiments studied equipment characteristics, signal transmissions, propagation characteristics, communcations system operation, and spacecraft control/operation. Joint experiments with the ECS satellite in Feb. 1979 was one of the objectives.

Communications Satellite-2A (CS-2A) was launched by the National Space Development Agency of Japan (NASDA) from the Tanegashima Space Center 1983-02-04. The national name for the spacecraft was Sakura-2A. It was a business communications satellite, placed in a geostationary orbit at 132 deg E. It was part of the establishment of domestic satellite telecommunications network mainly for natural disasters, emergencies and for remote islands submillemetre wavelength and microwavelength signals.

CS-2B (Communications Satellite 2B) was launched by Japan 1983-08-05. It is also known as Sakura-2B and provided a reserve satellite on the orbit of CS-2A.

CS-3A (Communications Satellite-3A) was launched by the H-I launch vehicle (H18F) from the Tanegashima Space Center of the National Space Development Agency of Japan 1988-02-19. The satellite was nicknamed "Sakura 3-A". CS-3B (Communications Satellite 3B) was launched from the Tanegashima Space Center, Japan 1988-09-16. It was placed in an elliptical orbit and was moved at a later stage to a stationary orbit above the equator at 136 deg east longitude over the western part of New Guinea.

By 1994 the constellation was comprised of CS-3a and CS-3b (launched in 1988) and stationed at 132 degrees E and 136 degrees E. These spin-stabilized, drum-shaped (diameter of 0.2 m and height of 0.3 m) spacecraft possess an on-orbit mass of 550 kg (compared to the 350 kg CS-2 satellites) and are based on U.S. Ford Aerospace designs. The communications payload consists of 10 active plus five spare 30/20 GHz transponders and two active plus one spare 6/4 GHz transponders. The primary contractors are Mitsubishi and NEC Corporation. CS-3a finished its programmed operation on November 30,1995. CS-3b finished its programmed operation on May 31, 1996. (References 175 and 182)

By the time the design lives of CS-3a and CS-3b are reached in 1995, the next generation of satellites in the series are scheduled to be launched. Known as CS-4 or N-Star, the new spacecraft will be procured by the Nippon Telegraph and Telephone company from the U.S. and will be based on Loral's FS-1300 platform. The N-Star payload will consist of eight 14/11GHz, eleven 30/20 GHz, and five 6/4 GHz transponders and should be operational for ten years. Aerospatiale is under contract to provide unique 2.6 m by 4.5 m composite antennas for the C-band and Ku-band transponders. The N Star spacecraft may also be able to satisfy some of the objectives of the hampered ETS VI (References 175, 183-185).


  • 175. NASDA. National Space Development Agency of Japan, 1994, pp. 19-20.
  • 176. B.I. Edelson, op. cit. p. 270-277.
  • 177. S. Mansfield, "Japanese Make Progress on Experimental Comets Program", Space News, 27 June - 3 July 1994, p.8.
  • 178. "Optical Communications Tests", Aviation Week and Space Technology, 27 July 1992, p. 13.
  • 179. "Agencies Forge Pact", Space News, 12-18 December 1994, p. 23.
  • 180. "Optical Inter-Orbit Communications", Spaceflight, April 1995, pp. 116-117.
  • 181. B.I. Edelson, op. cit., pp. 259-268.
  • 182. NASDA Report No. 1, August 1988, p. 2-3.
  • 183. "French Build N-Star Units", Aviation Week and Space Technology, 4 January 1994, p. 54.
  • 184. "Japan Looks to N-Star To Recover Experiment", Space News, 30 January - 5 February 1995, p. 2.
  • 185. "NTT's N-Star-A Spacecraft To Be Complete in January", Space News, 9-15 January 1995, p. 12.
  • Adapted from: Europe and Asia in Space 1993-1994, Nicholas Johnson and David Rodvold [Kaman Sciences / Air Force Phillips Laboratory]

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Page last modified: 15-05-2014 19:17:39 ZULU