PALAPA B4

Palapa-B is the second generation of communications satellites designed and built for Indonesia by Hughes Space and Communications Company. The series of four satellites was produced for Indonesia's state-owned telecommunications company, Telkom.

All the Palapa-B spacecraft are Hughes HS-376 models, the world's most popular line of satellites. Palapa-B1 was launched in June 1983 on board the Shuttle [PAM-D]. Palapa-B2 also was launched aboard a Shuttle [PAM-D], in February 1984, but it was placed in an improper orbit when the perigee kick motor, provided by an outside vendor, failed. In November 1984, a space Shuttle crew recovered Palapa-B2 and returned it to Earth for the insurance underwriters. Hughes refurbished the satellite, which eventually was sold back to Indonesia. Renamed Palapa-B2R, the satellite was successfully relaunched in April 1990 aboard a Delta-6925-8 rocket.

After the 1984 launch attempt, a third Palapa-B satellite was ordered. It was successfully launched as Palapa-B2P aboard a Delta-3920 PAM-D rocket in March 1987. Palapa-B4 was launched May 1992 on a Delta-7925-8 rocket.

The Palapa-B spacecraft are twice as large and have twice the capacity and about four times the power of the Hughes-built Palapa-A satellites they replaced. Each Palapa-B spacecraft, like all HS-376 models, has two telescoping cylindrical solar panels and an antenna that folds for compactness during launch. Once the satellite is in synchronous orbit 22,300 miles (36,000 km) above the equator, the antenna is erected and the outer solar panel extended. This configuration more than doubles the satellite's height and power output.

The 24 transponders on Palapa-B are each capable of carrying 1,000 two-way voice circuits or a color television transmission. In addition, Palapa-B carries six spare traveling-wave tube amplifiers, providing a 5-for-4 redundancy.

The Palapa-B satellites operate in the C-band, receiving from 5.925 GHz to 6.415 GHz and transmitting from 3.7 GHz to 4.2 GHz. The effective isotropic radiated power over the 36 MHz bandwidth is a minimum 34 dBW to Indonesia and most of the land mass of the other ASEAN countries and Papua New Guinea. Signal strength in the remaining ASEAN-member areas is a minimum 32 dBW. The satellites use 10 watt traveling-wave tube amplifiers.

Palapa-B has a diameter of 7 feet 1 inch. It is 9 feet 4 inches high in the stowed position. With the 6-foot-wide antenna erected and the outer solar panel extended, the spacecraft is 22 feet 10 inches high. It weighs 1,525pounds at beginning of life in orbit. Four thrusters using hydrazine propellant provide stationkeeping and attitude control during the satellite's life. Two panels of solar cells generate 1,100 Watts of electrical power at beginning of life in orbit. Four thrusters using hydrazine propellant provide stationkeeping and attitude control during the satellite's life. Two panels of solar cells generate 1,100 Watts of electrical power at beginning of life in orbit. Two nickel cadmium batteries provide full power during eclipse when the spacecraft passes through Earth's shadow.

The satellite is stabilized by spinning at 50 rpm. Both the communications antenna and electronics shelf are despun with respect to Earth and achieve a pointing accuracy better than 0.05 degrees. The transmit and receive beams are created by a shared aperture and antenna with two polarization selective surfaces that are slightly offset from each other. The front surface is sensitive to horizontally polarized beams; the rear surface is sensitive to vertically polarized beams. Each polarization reflects signals to separate feed horn networks.