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COMETS - Communications and Broadcasting Engineering Test Satellite

Already in development before the ETS VI accident was the Communications and Broadcasting Engineering Test Satellite (COMETS), also sponsored by NASDA, designed to test inter-satellite and advanced mobile satellite communications. With an overall mass and spacecraft bus similar to ETS VI, COMETS, to be launched in 1997, would carry a variety of Ka-band and S-band transponders and would be stationed at 121 degrees E. Gallium arsenide solar cells will provide increased power (up to 5.5 kW) as compared to ETS VI. Eventually a 2-satellite Data Relay and Tracking Satellite (DRTS) network is envisioned with full compatibility with its American and European counterparts (References 173-177).

Kakehashi (COMETS), a two-ton geostationary three-axis stabilized satellite, was created to develop the new technologies required for future fields in communications and broadcasting. Relay satellites in geostationary orbit will be used to develop the following technologies: Inter-orbit communications technology for relay of communications between observation satellites or space stations in low-altitude circular orbits and earth stations. Advanced satellite broadcast technology for broad-band region-specific broadcasts and high definition television broadcasts using K-band frequency bands. Development of advanced mobile satellite communications technology possessing reproduction relay and inter-beam connection functions by employing K-bands and miliband frequencies.

The Communications and Broadcasting Engineering Test Satellite (COMETS) was a research and development satellite aimed at developing new technology in communications and broadcasting fields such as inter-orbit communications, advanced satellite broadcasting, advanced mobile satellite communications, and upgrading large geostationary satellites. It was to be used for conducting experiments and verifying these subjects.

The COMETS was launched by its 5th H-II Launch Vehicle on February 21, 1998 (JST). Though the first burnig was normal, the second burning time period of the second-stage engine was shorter than scheduled which resulted in injection of the COMETS satellite to lower orbit than the geostationary transfer orbit. Due to successful seven orbital controls, COMETS has been moved to recurrent orbit. It was used for conducting scheduled experiments on the orbit as possible. The planned lifetime of the mission was to be three years, but the failure in the second stage of the H-II launch vehicle resulted in a highly eccentric orbit and prevented the spacecraft from attaining its planned geostationary orbit. The routon operetion phase of the COMETS was bought to an end on January 31,1999, and its extcnded phese started. NASDA terminated its operation on August 6, 1999.


  • 173. N. W. Davis, "Japan Expands Research on Communications Satellites", Aerospace America, August 1992, p. 22-24.
  • 174. NASDA Report, No. 2, November 1988, pp. 4-5.
  • 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.
  • 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 19:17:40 ZULU