A More Powerful Communications Platform
| Diameter | 3.7 m (12 ft) |
|---|---|
| Height stowed | 3.4 m (11 ft 2 in) |
| Height deployed | 10 m (32 ft 11 in) |
|---|---|
| Weight | 1484 kg (3265 lb) beginning of life |
When the demand for its communications capacity increased dramatically in 1985, Satellite Business Systems (SBS) chose to purchase a larger, more powerful platform from Hughes Space and Communications Company, today known as Satellite Development Center. SBS became the first customer to order the Boeing 393 spin-stabilized model.
The satellite, designated SBS 6, was built to complement SBS 4 and SBS 5, both Boeing 376 models. SBS 6 expanded on the popular Boeing 376 design, offering twice as much power per channel.
SBS 6 was launched from Kourou, French Guiana, aboard an Ariane rocket October 12, 1990, as part of a dual payload for Hughes Communications, Inc. (HCI) -- the Hughes subsidiary that bought the three Ku-band satellites earlier in the year from SBS. SBS 6 entered service in November 1990. It is in geosynchronous orbit 22,338 miles above the equator at 95 degrees West longitude.
SBS 6 provides data, voice, and video communications services to private satellite network customers in the continental United States. Switchable offshore coverage is available on two transponders.
Although SBS 6 was the first Boeing 393 model ordered from SDC, it was the last launched. Two other versions were built and launched, both for Japan Communications Satellite Co. (JCSAT).
SBS 6 spins at 55 rpm. It carries 30 Ku-band channels, 19 operating and 11 spares. Each channel operates in the 43 MHz bandwidth powered by 41-watt traveling-wave tube amplifiers. By comparison, a channel on SBS 4 or SBS 5 produces 20 watts of power. Each SBS 6 channel transmits on a frequency range of 11.7 to 12.2 GHz and receives on a frequency range of 14.0 to 14.5 GHz. The satellite has a signal strength of 46.5 dBW over densely populated areas of the United States. The satellite uses a 2.4-meter parabolic antenna with a multihorn feed array, an omnidirectional command and telemetry antenna.
When it was launched, SBS weighed 5390 pounds. After using fuel during transfer orbit maneuvers, the satellite had an initial on-station weight of 3265 pounds. Fully deployed, the 12-foot diameter spacecraft is 33 feet tall. Like its smaller Ku-band siblings, SBS 6 has a spun section containing its propulsion system and solar drums. Its despun section contains the satellite's communications payload and its antennas.
Two axial and four radial 5-lbf thrusters are used for stationkeeping, spin control, and attitude control. In addition, SBS 6 used two 110-lbf thrusters for apogee maneuvers and satellite reorientation.
SBS 6 was placed into a geosynchronous transfer orbit by its Ariane launch vehicle. About a minute before separation from the booster -- about 20 minutes into the flight -- the satellite's omni command antenna was deployed and the spacecraft started spinning at 5 rpm. Following separation, the satellite's thrusters were fired and its spin rate was increased to 20 rpm. Four separate firings of the two 110-lbf thrusters raised the satellite's perigee to 22,338 miles. After it drifted to its orbital slot, the SBS 6 communications platform was despun, its solar drum was extended, and its parabolic antenna was raised.
SBS was formed in late 1975 by Communications Satellite Corp., IBM, and Aetna Life and Casualty to provide private business communications to corporate customers. It ordered three C-band HS 376 satellites from Hughes in December 1977 -- all have exceeded their contract lives and one has been retired. SBS expanded its fleet with the addition of three Ku-band spacecraft -- SBS 4 was launched August 30, 1984, and SBS 5 was placed into orbit September 8, 1988. HCI purchased the three satellites in early 1990.
HCI was a wholly owned subsidiary of Hughes Aircraft Company. It operated the world's largest fleet of privately owned commercial communications satellites. Services include radio and cable television distribution, as well as customized voice, video, and data communications.
In October 2000, The Boeing Company acquired three units within Hughes Electronics Corporation: Hughes Space and Communications Company, Hughes Electron Dynamics, and Spectrolab, Inc., in addition to Hughes Electronics' interest in HRL, the company's primary research laboratory. The four are now part of Boeing's newest subsidiary, Satellite Development Center.
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