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GBS

UHF Follow-On Global Broadcast Service

UFO satellite modifications for GBS GBS Payloads satellite animation (Neg#: 97PR-00187)

High resolution image available here

To meet the demands of a rapidly deployed, widely dispersed and highly mobile force structure, today's warfighter requires easy access to vast amounts of information. This information flow must be reconfigurable to quickly adapt to ever-changing scenarios on the ground, and must be delivered to theaters of operation worldwide. This is the mission for the DoD's Global Broadcast Service (GBS).

The U.S. Navy's Program Executive Office for Space, Communications and Sensors contracted with Hughes Space and Communications Company (HSC), now Boeing in 1996 to add GBS communications payloads to UHF Follow-On (UFO) satellites 8, 9, and 10. These satellites are three in a series of 10 that were built and launched under a total $1.9 billion contract with the Space and Naval Warfare Systems Command's Communications Satellite Program Office.

The Ka-band GBS payload was derived from Boeing's experience with commercial Ku-band satellite broadcast systems. The first GBS package on UFO F8, was placed into operation in June 1998, only two years after contract award. With the launch of the F10 satellite in late November 1999, the three-satellite constellation provides the DoD with near-global broadcast coverage.

The GBS payload includes four 130-watt, transponders operating in the military Ka-band (30/20 GHz). Each transponder handles 24 mega-bits-per-second (Mbps), resulting in a total throughput of 96 Mbps per satellite. The figure on the reverse side shows the types of services that can be provided by just one 24 Mbps satellite transponder. These data delivery rates represent a vast increase over prior military communications satellite capabilities.

A broadcast management center (BMC) in each satellite's operating region performs information packaging and scheduling functions, and generates the uplinks to the satellite on up to four carriers. The BMC also responds to user information requests from the field. Typical information products include video, mapping, charting and geodesy, imagery, weather, and other digital data. The GBS satellite's high-power wideband transponders enable high-speed data transmission to the selected broadcast areas. Information is disseminated to a variety of mobile and tactical users, via very small aperture terminals.

The BMC serves as the primary injection point (PIP) for each satellite. Data from the PIP is received by the satellite through a fixed, narrow-beam antenna. A separate steerable receive antenna on the satellite is used to receive uplink signals from within a theater of operations. Transportable uplink equipment can be positioned anywhere within the satellite field of view to serve as theater injection points (TIPs). Any of the four transponders can be accessed through either of the satellite's receive antennas, as configured by ground command.

On the downlink side, data is transmitted to users from the satellite via three steerable spot beam antennas. Two of these spot beams each covers an area of 500 nautical miles in diameter. These narrow spots support a nominal data rate of 24 Mbps per transponder. The third downlink is a wide spot beam that covers an area of 2,000 nmi in diameter, supporting a data rate of at least 1.5 Mbps. One of the transponders can be switched from a narrow spot to the wide spot by ground command.

Several UFO satellite modifications were required to integrate the GBS payload. A larger radiator panel with imbedded heat pipes was added to accommodate the increased thermal dissipation associated with the GBS high-power amplifiers. The power subsystem was modified to provide additional capacity for the GBS payload. A fourth silicon-cell solar panel was added to each wing, and the battery capacity was increased from 123 to 164 amp-hours to support eclipse operations. The new GBS fixed receive antenna, together with the forward SGLS omni antenna, were mounted on structure that previously supported SHF antennas (the SHF payload was removed from the satellite because its mission was phased out with the advent of EHF on the satellites). The GBS steerable receive antenna was mounted on a deployable boom. A new pallet structure was added to accommodate the three GBS transmit spot beam antennas. The satellite bus changes were based on commercially proven space hardware from other Boeing programs.

These new payloads on three UFO satellites constitute the space segment for the DoD's Phase II GBS. The associated GBS ground systems were provided for under a separate government contract. Boeing supported the GBS ground segment work in the areas of systems engineering, integration and test.

Now providing UHF, EHF and GBS communications services on a worldwide basis, the UFO satellite system plays a vital role in meeting the DoD's voice, data and video transmission needs.

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