Expanded Communications for Japan
||4.9 m (16 ft)
||2.8 m x 3.8 m (9.2 ft x 12.3 ft)
|Solar Arrays deployed
||26.2 m (86 ft)
||7.5 m (24.6 ft)
|Weight, beginning of life
||1841 kg (4060 lb)
Foreseeing the growth of the communications business, Japan Satellite Systems, Inc., (JSAT) of Tokyo signed a contract in October 1993 for a Hughes 601 satellite from Hughes Space and Communications International, Inc. The satellite, JCSAT-3, was designed to relay voice, data, and television signals via Ku-band to eastern Asia, Australia, New Zealand, and India; and via C-band to eastern and southern Asia and Hawaii. In December 1995, JSAT returned to Hughes for another spacecraft, JCSAT-4, with similar coverage and increased power. In October 2000, HSCI became Boeing Satellite Systems International, Inc.
JCSAT-3 and 4 are among more than 81 Hughes-now Boeing-601 satellites ordered since the body-stabilized model became available in 1987. Hughes also built JCSAT-1 and JCSAT-2, which are Hughes 393 model spin-stabilized spacecraft. Launched in 1989, these were Japan's first commercial communications satellites.
Hughes contracted with Lockheed Martin for launch of JCSAT-3, which took place successfully on Aug. 28, 1995, aboard an Atlas IIAS rocket from Cape Canaveral, Fla. JSAT contracted separately with Lockheed Martin to launch JCSAT-4 on another Atlas IIAS, on Feb. 16, 1997.
Like others in the Boeing 601 series, JCSAT-3 and 4 consist of a cube-shaped center payload section, with solar wings and an antenna array. The Boeing 601 is composed of two modules. The primary structure carries all launch vehicle loads and contains the propulsion system, bus electronics, and battery packs. The payload module holds communications equipment and isothermal heat pipes. Reflectors, antenna feeds, and solar arrays mount directly to the primary module, and antenna configurations can be placed on three faces of the bus. Such a modular approach allows work to proceed in parallel on both structures, thereby shortening the manufacturing schedule and test time. The satellites are built at Hughes Space and Communications Company facilities in El Segundo, Calif.
Stowed (left); In Orbit (right)
Both JCSAT-3 and 4 have a pair of four-panel sun-tracking solar array wings. Each wing extends 11.9 meters north and south from the body for an overall deployed length of 26.2 meters. These panels are designed to generate approximately 5,000 watts with the wings deployed, using K-4 3/4 solar cells. Additionally, a single 30-cell, 200 Amp-hr, nickel-hydrogen battery provides power during eclipse periods.
Both JCSAT-3 and 4 have a C-band payload consisting of 12 active transponders operating at 36 MHz, powered by 34-watt solid-state power amplifiers. JCSAT-3's Ku-band payload has 12 active transponders operating with 36 MHz of bandwidth, and 16 active transponders operating with 27 MHz, each using 63-watt linearized traveling-wave tube amplifiers (LTWTAs). JCSAT-4 also has a total of 28 active Ku-band transponders, but the configuration is different. There are eight transponders with 36 MHz of bandwidth and 16 with 27 MHz, powered by 63-watt LTWTAs. In addition, there are four transponders using 95-watt LTWTAs, operating with 36 MHz of bandwidth. Also, four of the 27 MHz transponders can be switched by ground command to 54 MHz with 125 watts.
On both spacecraft, the flexibility of the communications payload design allows the interconnection of up to 10 C-band uplink channels to Ku-band downlink channels, and 10 Ku-band uplink channels to C-band downlinks.
Each satellite has four octagonal reflectors, one each on the east (for Ku-band) and west (for C-band) and two on the Earth-facing, or nadir, surface (for Ku-band). Each of these reflectors makes use of Hughes' patented shaped reflector technology, which eliminates the need for complex feedhorn arrays. With east and west reflectors deployed, the satellites measure 7.5 meters in width.
The primary on-station beam pointing control is provided by means of a tracking beacon from either of the two Japanese ground control stations, using upgraded equipment provided by Hughes. The main station is in Yokohama, with backup control at Gunma.
For launch, the solar wings and reflectors fold alongside the spacecraft bus, forming a box 2.8 meters by 4.9 meters by 3.8 meters. The booster places the spacecraft into a super-synchronous transfer orbit of about 167 km by 80,000 km. The super-synchronous orbit optimizes use of the satellite's own propellant during the transfer to geosynchronous orbit. After separation from the launch vehicle, the satellite's on-board 490-Newton (110 lbf) liquid apogee motor is fired to circularize the orbit at the 36,000 km geosynchronous altitude. The liquid bipropellant subsystem provides 12 thrusters of 22 Newtons (5 lbf) for stationkeeping. Once on-station, the satellites weigh approximately 1841 kg, including fuel required for 12 years of life. JCSAT-3 operates from 128 degrees East longitude. JCSAT-4 operates at 124 degrees East.