BSB - United Kingdom's First Direct Broadcast Service
The info on this page has been adapted from info on the Boeing Space website.
In July 1987 British Satellite Broadcasting Ltd. (BSB), a privately owned and operated company, selected Hughes Space and Communications Company, (today known as Boeing Satellite Systems Inc.), to design and build two Hughes 376 satellites for the first television Direct Broadcast Service (DBS) in the United Kingdom. Hughes would also build the telemetry and monitoring equipment for the ground station located in Southampton, and train BSB ground station personnel. Additionally, Hughes agreed to purchase and handle all aspects of the launch and insurance and to deliver the satellites only after they had been thoroughly tested in orbit.
In an agreement that inaugurated the commercial launch industry in the United States, Hughes contracted with McDonnell Douglas to supply two Delta rockets. A Delta I model boosted the first BSB satellite, named Marco Polo 1, on August 27, 1989, and a Delta II launched Marco Polo 2 on August 17, 1990.
cutaway diagram of the launch configuration of the Delta 2 rocket
Key to the BSB direct broadcast scheme was having a satellite with enough power to be received by very small (35cm/13.5 inch diameter), low-cost dishes, thereby making DBS both environmentally friendly and affordable for the public. Each satellite was equipped with three 110-watt channels. With a footprint that covered the United Kingdom, the satellites broadcast a mix of news, sports, current affairs, light entertainment, children's daytime TV, and a subscription nighttime movie channel.
An artists impression of one of the BSB satellites operating into Britain
BSB's sister company, Data Vision, provided communications services for business. The D-Mac transmission system used by BSB allowed for large amounts of data to be transmitted alongside the television signals.
The popular spin-stabilized Hughes 376, (now the Boeing 376), spacecraft has proven to be highly reliable and adaptable. The basic bus accommodates a wide range of customized payloads, as demonstrated by the versions ordered and built for a dozen customers on six continents. Marco Polo 2 was the 32nd of this model to be launched and put into service.
The BSB satellite design represented the first high-power DBS use for the 376. Innovative communications electronics and a new Hughes developed super nickel-cadmium battery made the high-power conversion possible. The battery provided sufficient power to maintain uninterrupted DBS coverage during eclipse, a condition caused when the earth's shadow prevents the sun from shining on the satellite's solar cells. To achieve the necessary 110 watts per channel, Hughes engineers linked two proven 55-watt traveling wave tubes (TWTs) in parallel to a common power supply. Such a paralleling arrangement allows TWTs to be reconfigured by telecommand to either high or low power. The satellite contained five Ku-band transponder channels, but only three could be at full power at the same time. With both Marco Polo spacecraft on orbit, five channels were beamed at full power.
To further accommodate high power requirements, the BSB spacecraft used longer solar panels covered with large area solar cells and a single bus system rather than the typical dual bus. The solar cell output at beginning of life was 1100 watts.
The satellite received the TV, radio, and data transmissions, which were broadcast by the 254 by 173 cm (100 by 68 inch) elliptical reflector to homes and business sites throughout the United Kingdom. The antenna provided a signal strength of 59 dBW. A precision antenna pointing system, proven on previous Hughes 376 satellites, maintained the antenna pointing accuracy at better than 0.05 degree.
Compactly stowed for launch, with antenna reflector folded down and cylindrical solar panels telescoped together, the BSB satellites measured 2.7 m (9 feet) in height and 2.16 m (7 feet, 1 inch) in diameter. After the Delta rocket injected the spacecraft into orbit, an apogee kick motor attached to the spacecraft was fired to circularize the orbit at 36,000 km (22,300 miles), geosynchronous altitude. As the satellite moved into its test position, its solar panels were extended and the antenna reflector raised, bringing the satellite height to 7.2 m (nearly 24 feet). Both satellites shared the orbital position of 31 W.
By the end of 1991, BSB had got into severe financial trouble, and a merger with arch rivals Sky took place. However, effectively BSB had been taken over by Sky, and operation of the Marco Polo satellites ceased. BSB rapidly disappeared into history.
Marco Polo 1 was acquired in-orbit by Nordiska Satellitaktiebolaget in 1993, and operated until 2000 as Sirius 1 in the 5 E orbital slot. It was then moved to 13 W, and renamed Sirius W. Although it is not currently transmitting any services, and is operating in an inclined orbit, Nordic Satellite AB expect it to be servicable past 2006.
(Update December 2003: BSB 1 was sent up to the junk orbit in May 2003)
Marco Polo 2 was acquired in-orbit by Telenor of Norway in 1992, and renamed Thor 1. It was located at 0.8 W until it was switched off in January 2002. However, in November 2002, it was moved to 7.4W, and reactivated with digital test signals broadcasting towards Scandanavia.
(However, the end was near, and poor old Marco Polo 2 was sent up to the junk orbit in early January 2003)
Height deployed:
7.2 m (24 ft)
Weight in-orbit:
Marco Polo 1 - 660 kg (1450 lb)
Marco Polo 2 - 662 kg (1500 lb)
Diameter:
2.16 m (7 ft 1 in)
Width stowed:
2.7 m (9 ft)
More on the BSB - Sky merger can be found here.
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