FLEET  SATELLITE COMMUNICATIONS T h e    F l e e t    S a t e l l i t e    C o m m u n i c a t i o ns (FLTSATCOM)   System   provides   communications, via  satellites,  between  designated  mobile  units  and shore  sites.  These  links  provide  worldwide  coverage between  the  latitudes  of  70  degrees  north  and  70 degrees  south.  Three  satellites  are  currently  in  use  with a fourth to come online soon: GAPFILLER, LEASAT, FLTSATCOM,  and  UHF  Follow-on  (UFO). System   installations   are   located   on   ships, submarines,  mobile  vans,  aircraft,  and  shore  stations. Though  these  installations  could  operate  separately, integrating  the  system  provides  message  traffic  and voice   communications   to   all   DOD   long-range communications  networks.  In  addition,  certain  shore stations provide a back-up capability to other users in case  of  an  outage  of  any  kind,  which  maintains  net connectivity. The   Navy   SATCOM   system   consists   of information   exchange   subsystems   that   use   the satellites as (1) relays for communications and control, and  (2)  quality  monitoring  subsystems  that  provide data   required   to   manage   satellite   resources.   Each subsystem   is   structured   for   specific   naval communications   requirements.   The   following subsystems  make  up  most  of  the  Navy’s  FLTSATCOM system. Fleet Satellite Broadcast Subsystem. This is an expansion  of  the  “Fleet  Broadcast,”  which  has been  the  central  communications  medium  for operating naval units. Common   User   Digital   Information   Exchange Subsystem   (CUDIXS)   and  Navy  Modular Automated    Communications    Subsystem (NAVMACS).   These  two  installations  form  a communications   network   for   transmitting general-service  message  traffic  between  ships and shore installations. Submarine   Satellite   Information   Exchange S u b s y s t e m   (SSIXS).   T h i s    s u b s y s t em compliments   other   communications   links between SSBN and SSN submarines and shore terminals. Secure Voice Subsystem. This is a narrowband uhf subsystem that links voice communications between   ships   and   connects   with   wide-area shore voice networks. 3-3 Tactical Intelligence Subsystem (TACINTEL). This   subsystem   is   specifically   designed   for special  intelligence  communications. Teletypewriter Subsystem. This subsystem is an extension   of   terrestrial   teletypewriter transmission  networks. Tactical Data Information Exchange Subsystem (TADIXS).   This  is  a  one-way  broadcast  of tactical  information  from  command  centers ashore  to  afloat  units  primarily  in  support  of over-the-horizon  targeting  (OTH-T). Officer   in   Tactical   Command   Information Exchange   Subsystem   (OTCIXS).   T h is subsystem continues to provide inter-and intra- battle  group  communications  and  is  now  also designated  as  the  return  path  for  ship-to-shore OTH-T  communications. Demand  Assigned  Multiple  Access  (DAMA) Subsystem.  This  subsystem  was  designed  to multiplex several subsystems, or users, on one satellite   channel,   allowing   more   satellite circuits to use a single uhf satellite channel. Control   Subsystem.   This   subsystem   is   a communications  network  that  provides  status reporting and management of system assets The   installation   of   subsystem   baseband equipment  and  rf  terminals  aboard  ships  is  driven  by communications   traffic   levels,   type   of   com- munications,  and  mission  requirements.  For  example, Fleet  Broadcast,  a  common  subsystem  in  naval  com- munications,  is  received  by  many  different  types  of ships. Atypical suite on a large ship may include Fleet Broadcast,   CUDIXS,   NAVMACS,   Secure   Voice, TADIXS,   OTCIXS,   Teletypewriter,   and   TACINTEL equipment. Most   subsystems   have   very   rigid   control   and accountability  of  message  and  data-link  traffic.  All subsystems  have  some  form  of  backup  mode.  Within the   constraints   of   equipment   capability,   each subsystem  addresses  the  unique  requirements  of  the user  and  the  environment  in  which  the  user  operates. On board your ship, you may not use all these systems, but during your career you will probably come across all of them. Now that we have identified the satellite communications subsystems, we need to provide you