ETS 8 (Kiku 8)

ETS 8 [NASDA]

ETS-VIII (Engineering Test Satellite) is to be launched in 2006, with the main purpose of dealing with the increasing demand for digital communications, such as mobile phones and other mobile devices. The satellite, with a gross weight of around three tons and a diameter of 40 meters, has two Large Deployable Antenna Reflectors (LDAR) and two Solar Array paddles. One LDAR, about the size of a tennis court, is one of the world's largest geostationary satellites. Its size will enable direct communications with a geostationary satellite that covers all of Japan, making mobile communications more reliable. Currently under development are Large Deployable Antenna Reflectors with metal-mesh, high-power transponders and on-board processors. The technologies used in the development of these LDARs will be applicable to other large space structures. A subscale test of the LDARs was flown as the LDREX experiment.

The mission of ETS-VIII is not only to improve the environment for mobile-phone-based communications, but also to contribute to the development of technologies for a satellite-based multimedia broadcasting system for mobile devices. It will play an important role in the provision of services and information, such as the transmission of CD-quality audio and video; more reliable voice and data communications; global positioning of and broadcasting to moving objects such as cars; faster disaster relief, etc. Experiments in the fundamental technology for satellite-positioning, using a high-precision clock system, will be conducted between ETS-VIII and GPS, through the reception of signals transmitted from the clock.

The ETS-VIII measures 40 meters long by 40 meters wide when deploying two solar array paddles and two large deployable antennas. The satellite is to verify the following four technologies in geostationary orbit.

• An advanced 3-ton-class spacecraft bus
  Major features of the ETS-VIII demonstration include a light body structure to improve the payload to bus system ratio to 40%, an increase in bus power supply voltage to 100 V, and use of CCSDS-compliant packet transmission and MIL-STD-1553B data bus. In addition, the satellite's heat pipe, which connects the north and south panels, expands effective radiation surface while the attitude control system is equipped with fault tolerant functions and in-orbit programming capability.
• Large-scale deployable antenna reflectors (size: 19 m×17m)
  The larger the satellite antenna, smaller the size required for the groundbased antenna. The ETS-VIII is equipped with two Large Deployable Antenna Reflectors (LDRs), enabling us to establish a communication link with a cellular phone sized ground tarminal. The LDR uses a modular structure to meet the requirements of reflector surface preciseness and antenna diameter expandability. The LDR will be deployed on orbit by expanding its 14 hexagonal umbrella-like modules simultaneously while connecting each other by cables. Once deployed, the reflector forms a parabola Surface with expanding metal mesh (19 m × 17 m in outside dimension). Each module has a deployable truss structure. The LDR will be packed in a 1 m (diameter)× 4 m (length) cylindrical shape during launch.
• Communication technology to link geostationary satellite with hard-held terminals
  The ETS-VIII will conduct orbital experiments on mobile satellite communications and high-speed packet communications, providing voice/data communications with hand-held terminals in the S-band frequency. For these experiments, a 31-element active phased array feeder of 400W gross output and beam forming networks have been developed to synthesize signals into several beams to cover the entire nation. The onboard processor switches links of cellular phones and high-speed packets, enabling us to establish a single-hop communication link with the ETS-VIII without ground switchboards along the path.
• Basic technology of geostationary satellite positioning system
  The ETS-VIII is equipped with high accuracy atomic clock and time transfer equipment, thereby generating extremely accurate time signals. Combining the clock signal with GPS data, the ETS-VIII will conduct positioning experiments to obtain basic satellite positioning system technology.