The Hughes 393 (sometimes referred to as the HS-393) is a

communications satellite A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

introduced in 1985 by

Hughes Space and Communications Company Hughes may refer to: People * Hughes (surname) * Hughes (given name) Places Antarctica * Hughes Range (Antarctica), Ross Dependency * Mount Hughes, Oates Land * Hughes Basin, Oates Land * Hughes Bay, Graham Land * Hughes Bluff, Victoria La ...

. It was a spin-stabilized bus that had twice as much power as the

HS-376 The Boeing 376 (sometimes referred to as the BSS-376, and previously as the HS-376) is a communications satellite bus introduced in 1978 by Hughes Space and Communications Company. It was a spin-stabilized bus that the manufacturer claims was th ...

platform.

Design

The satellite bus was designed and manufactured by

Hughes Hughes may refer to: People * Hughes (surname) * Hughes (given name) Places Antarctica * Hughes Range (Antarctica), Ross Dependency * Mount Hughes, Oates Land * Hughes Basin, Oates Land * Hughes Bay, Graham Land * Hughes Bluff, Victoria La ...

. It had a launch mass of , a mass of after reaching

geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...

, and an 8-year design life. When stowed for launch, its dimensions were in height and in diameter. With its solar panels fully extended its height was . Its power system generated approximately 2,350

watts Watts is plural for ''watt'', the unit of power. Watts may also refer to: People *Watts (surname), list of people with the surname Watts Fictional characters *Watts, main character in the film '' Some Kind of Wonderful'' *Watts family, six chara ...

of power at beginning of life and 2,200 at end of life, thanks to two cylindrical solar panels. These panels used K7 and K4-3/4 solar cells, with more than twice the number of cells than on the

. The bottom panel was retracted around the body and top panel for launch, and extended downwards for operation. It also had two 38 Ah NiH₂ batteries. Its propulsion system was composed of two

R-4D The R-4D is a small hypergolic rocket engine, originally designed by Marquardt Corporation for use as a reaction control system thruster on vehicles of the Apollo crewed Moon landing program. Today, Aerojet Rocketdyne manufactures and markets m ...

liquid apogee engines with a thrust of . It also had two axial and four radial

bipropellant The highest specific impulse chemical rockets use liquid propellants (liquid-propellant rockets). They can consist of a single chemical (a monopropellant) or a mix of two chemicals, called bipropellants. Bipropellants can further be divided into ...

thrusters for station-keeping and

attitude control Attitude control is the process of controlling the orientation of an aerospace vehicle with respect to an inertial frame of reference or another entity such as the celestial sphere, certain fields, and nearby objects, etc. Controlling vehicle ...

. It included enough propellant for orbit circularization and 8 years of operation. Its payload was composed of a antenna that fed K_u band

transponders In telecommunications, a transponder is a device that, upon receiving a signal, emits a different signal in response. The term is a blend of ''transmitter'' and ''responder''. In air navigation or radio frequency identification, a flight trans ...

Satellites

The HS-393 was a more powerful platform than the

, being able to supply 2,200 kW of power versus the 1,400 kW of the HS-376HP. Only three were ever built.

References

{{Hughes satellites Satellite buses

Design

Satellites

See also

References