General · EdgepediaOctober 15, 20265 min read

HS-376

HS-376 is a commercial communications satellite bus built by Hughes, carrying digital data, digital and analog voice, and television in geosynchronous orbit.¹^•² Spin-stabilized at 50 rpm, it featured a telescoping cylinder covered with solar cells topped by a despun Earth-facing antenna, with body-mounted and telescoping solar cells providing about 990 W to recharge two NiCd batteries.⁴^•¹^•⁴ Fifty-eight satellites were ordered, built, and launched on the bus between 1980 and 2003, making it one of the most-purchased commercial communications satellite models of its era; the platform is now retired.³^•¹

Key fact	Detail
Stabilization	Spin-stabilized at 50 rpm, with the antenna and communications payload despun at the top of the cylinder⁴^•¹
Power	Body-mounted and telescoping solar cells provided about 990 W, recharging two NiCd batteries⁴
Production total	58 satellites ordered, built, and launched³
Service span	Continuous launches into geostationary orbit from 1980 to the last launch in 2003; the platform is now retired¹

Design and origin

The bus grew out of two competitive procurements in the late 1970s, most likely 1977: Canada's Telesat planned a K-band comsat (ANIK-C), and the newly formed Satellite Business Systems (SBS), a joint venture of Comsat Corp. and IBM, was planning its first satellite purchase, also at K-band. The power these missions required far exceeded the older HS-333 configuration, Hughes's first product line.⁵

Under the leadership of Harold Rosen, the team developed a spin-stabilized configuration with a large circular solar panel sized to the diameter of the soon-to-launch Space Shuttle bay. When SBS's chief executive told the Hughes team that relying on the Shuttle schedule was too risky, quoting a cost in the millions for every month of delay, Rosen proposed the key innovation on the walk afterward: a second cylindrical solar panel built around the basic panel, deployed downward once in orbit. Hughes invested internal research funds to demonstrate the deployment, and the resulting design could fly on a Delta booster or from the Shuttle using the McDonnell Douglas Payload Assist Module (PAM).⁵

Hughes divided the non-recurring development cost across three anticipated procurements, ANIK-C, SBS, and a future customer, and won both initial awards within weeks of each other. The company later sold the design to AT&T, Western Union, Canada's ANIK-D program, Galaxy, Mexico, Indonesia, and Brazil, among others, and reported a return on investment above 30 percent within a few years.⁵

Structure and operation

The spacecraft is a dual-spinner: a spinning rotor section and a despun platform carrying the antennas and communications payload. Attitude control and station keeping used four hydrazine thrusters with about 136 kg of propellant.⁴

A typical satellite measured 2.16 m in diameter and 6.6 m high when deployed, 2.84 m when stowed, with a 1.82 m receive-and-transmit antenna assembly; launch mass ranged from about 550 to 700 kg dry, boosted to geostationary orbit by a solid apogee kick motor such as the Thiokol Star 30.⁶ The HS 376 series transmitted digital data, digital and analog voice, and television in typical geosynchronous applications.²

Versions

HS-376: the original version, first launched in 1980, with a mass between 1.1 and 1.45 t.
HS-376W: the wide version, launched from 1990, with a diameter of 3.43 m, more power, and modernized electronics; it was a joint development with Brazil's INPE.
HS-376L: the longer-life version, launched from 1991, with reduced power of 700 W and reduced electronics weight that allowed more station-keeping propellant, extending the design life to 13.5 years. Thaicom 1, an HS-376L launched in December 1993, measured 2.8 m stowed and 6.7 m deployed with a launch mass of 1,080 kg including its rocket motor.⁷
HS-376HP: the higher-power version, launched from 1995, with a mass between 1.45 and 1.55 t. Bonum-1, Hughes's first commercial satellite contract for Russia, awarded in October 1997, used a high-power HS-376HP and provided service until 2010.⁸

Customers and notable missions

The bus served a wide range of domestic and regional operators. Similar satellites based on the HS 376 flew for the SBS system, the Telesat system, the Indonesian Palapa satellites, AT&T's Telstar satellites, and the Western Union satellites; the Galaxy spacecraft used the same bus, relaying video, voice, data, and facsimile communications in the contiguous United States.⁹ Canada's Spar Aerospace was awarded a $125 million contract to build two satellites under license based on the HS-376 design, similar to Anik D.⁴ A 1994 sale to Malaysia priced a typical HS 376 satellite between $50 million and $100 million.¹⁰

The bus also figured in early on-orbit servicing. In 1985 the Space Shuttle retrieved Westar-IV (Westar 6) and Palapa-B, both HS-376 dual-spinners, using the manned maneuvering unit and the shuttle's Canadarm; both were still spinning when captured and were returned to Earth.¹¹ The Mexican Morelos-A was also a version of the HS 376, deployed from the Space Shuttle with a PAM upper stage firing about 45 minutes after spring-ejection from the cargo bay.¹³

Record and retirement

Launches of HS-376 spacecraft into geostationary orbit ran continuously from 1980 through 2003, and the platform is listed as retired.¹ A 20-year observational study of primarily non-operational HS-376 spacecraft, using the United Kingdom Infrared Telescope on Mauna Kea with multi-band near-infrared photometry, examined space-weathering effects on the fleet.¹ The telescoping solar array developed for the small HS-376 domestic satellites was later borrowed for the much larger Intelsat VI spin-stabilized design.¹⁴

References

Topic: Encyclopedia › Technology and the built world › Transport and spaceflight › Spaceflight › Satellites › Satellites by country, orbit, and bus › Western commercial satellite bus families

Initially written Oct 15, 2026 · Edited: Oct 25, 2026

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