FLTSATCOM SHOREBASED TERMINALS

with a basic understanding of how they operate. But first, we need to discuss FLTSATCOM Shorebased Terminals. FLTSATCOM SHOREBASED TERMINALS SATCOM installations at shore terminals operate from existing naval communications centers and certain command operations centers. Four Naval Computer and Telecommunications Area Master Stations (NCTAMS) have primary responsibility for naval communications via satellite. They are: NCTAMS LANT, Norfolk, Virginia NCTAMS MED, Naples, Italy NCTAMS WESTPAC, Finegayan, Guam NCTAMS EASTPAC, Wahiawa, Hawaii The Naval Computer and Telecommunications Station (NCTS), San Diego, California, as part of TADIXS, provides connectivity between NCTAMS EASTPAC and NCTAMS LANT. Ten NCTSs are used to retransmit Fleet Broadcast message traffic via hf links. In addition, an rf terminal at Yokosuka, Japan, transmits SSIXS and Secure Voice communications to the western Pacific and Indian Oceans. Also, there is landline connection between Japan and NCTAMS WESTPAC to support TADIXS and OTCIXS transmissions. Within these facilities, each subsystem consists of two parts: the baseband equipment (used to collect and control the transmitted or received communications) and the rf terminal (used by the baseband system to transmit and receive via satellite link). Some subsystems have the baseband equipment and rf terminals in the same building, while others have the baseband equipment installed at a remote facility located some distance from the rf terminal. Most subsystems use a common rf terminal. However, the Fleet Broadcast has an rf terminal specifically designed for that subsystem. FLEET SATELLITE BROADCAST SUBSYSTEM The Fleet Satellite Broadcast Subsystem provides the capability to transmit Fleet Broadcast message traffic in a high-level jamming en- vironment. The subsystem has 15 subchannels of encrypted message traffic at an input data rate of 75 bps per channel. These subchannels are time- division multiplexed and are transmitted in a one- way rf transmission at 1200 bps. The shore terminal transmits this data on a direct-sequence, spread- spectrum shf signal to the satellite, where the signal is translated to uhf and down-linked to the subscriber. Figure 3-2 shows a block diagram of the Fleet Satellite Broadcast Subsystem. The High-Speed Fleet Broadcast (HSFB) is a planned upgrade to the Fleet Satellite Broadcast Subsystem. This upgrade will improve broadcast transmission speed, information through-put (capabil- ity of equipment to process or transmit data during a specific period of time), and flexibility. Message Traffic Input The Fleet Satellite Broadcast message traffic is queued and/or channel selected by two processor- controlled message switching systems before transmission. These systems are the Naval Com- munications Processing and Routing System (NAVCOMPARS) for general service message traffic, and STREAMLINER for special intelligence message traffic. Fleet weather data from Naval Oceanographic Command Centers is also transmitted on nonprocessor controlled channels. Rf Transmission The FLTSATCOM satellites have two rf channels allocated for Fleet Satellite Broadcast message traffic. The primary channel is configured for an shf uplink to the satellite and for translation within the satellite for transmission as uhf in the downlink. The second rf channel is designed for backup use only. Since two channels are available, and several different modulation techniques are used for the uplink, there are seven different modes in which the rf link can be transmitted. In modes 1 through 6, the shf transmissions are made by the Satellite Communications Terminal AN/FSC-79. Mode 7 operates the rf uplink and downlink at ultra-high frequencies and uses the uhf transceiver AN/WSC-5(V). Reception Subscribers receive the uhf downlink signal through the AN/SSR-1 receiver system, which demodulates and demultiplexes the signal. The demuxed signal is decrypted and read into the 3-4