SATELLITES In 1976, three satellites were placed into orbit over the  Atlantic,  Pacific,  and  Indian  Oceans.  These satellites,  called  MARISATs,   were  procured  by  and are  managed  by  the  COMSAT  General  Corporation. Each  satellite  has  three  uhf  channels  for  military  use (one  wideband  500-kHz  channel  and  two  narrowband 25-kHz  channels).  The  uhf  section  of  each  satellite  is leased to the Navy for communications. To distinguish the   special   management   and   control   functions   for communications  on  these  uhf  channels,  the  Navy  has given  the  leased  MARISAT  satellite  assets  the  name GAPFILLER. Current   planning   calls   for   no   Navy   use   of GAPFILLER  satellites  after  the  mid-1990’s.  Satellite coverage  will  then  be  provided  by  a  combination  of F L T S A T    and  L E A S A T    until   the   new   U H F FOLLOW-ON   (UFO)   satellites   are   placed   into service.  The  Navy  plans  to  have  two  operational satellites in each of four satellite coverage areas. Each satellite coverage area can be terminated in at least two NCTAMS,   allowing   around-the-world   connectivity. You can see this connectivity in figure 3-16. FLTSATCOM SATELLITE The  FLTSATCOM  satellite  consists  of  two  major parts: a payload module that includes the antennas and a  space  craft  module  with  a  solar  array.  The  payload module  contains  the  uhf,  shf,  and  S-band  (tracking, telemetry,  and  command)  communications  equipment antennas.  The  communications  equipment  is  mounted internally on side panels that cover this section of the satellite. The  space  craft  module  contains  nearly  all  other subsystem  equipment,  including  sensors,  attitude  and velocity   control,   telemetry,   tracking   and   command, and   electrical   power   distribution.   The   spacecraft   is stabilized  on  three  axes,  and  the  body-fixed  antennas are   kept   pointing   at   the   sun   by   a   clock   drive.   A FLTSATCOM satellite is shown in figure 3-17. E a c h    F L T S A T C O M    s a t e l l i t e    c a n    r e l ay communications  on  23  separate  uhf  channels.  Of  the 23  channels,  10  are  25-kHz  channels,  12  are  5-kHz channels,  and  one  is  a  500-kHz  channel.  The  ten  25- kHz channels are dedicated for Navy use. Each 25-kHz uhf  down-link  channel  has  a  separate  transmitter. Channel one, used in primary mode for Fleet Broadcast transmissions,   incorporates   signal   processing   within the satellite (the shf up-link signal is translated to uhf Figure  3-17.—FLTSATCOM  satellite. for  down-link  transmission).  In  addition,  two  of  the FLTSATCOM  satellites  have  ehf  packages  attached. FLTSAT Extremely-High-Frequency Package (FEP) The   Fleet   Satellite   (FLTSAT)   Extremely-High- Frequency   (EHF)   Package   (FEP)   provides   ehf communications  capability  for  Army,  Navy,  and  Air Force   ground,   airborne,   and   ocean-going   terminals. Two  FEPs  are  currently  in  orbit,  carried  aboard  two modified uhf FLTSATs, numbers seven and eight. FEP operates at ehf frequencies of approximately 20-GHz on the down-link and 44-GHz on the up-link. It  has  two  antenna  beams:  (1)  a  dual-frequency  spot beam steerable by ground command, and (2) an earth coverage  beam  that  uses  separate  horn  antennas  for transmit and receive. LEASAT SATELLITE The  LEASAT  satellite  has  seven  25-kHz  uhf down-link channels, one 500-kHz wide-band channel, and  five  5-kHz  channels.  One  of  the  seven  25-kHz down-link   channels   is   used   for   Fleet   Broadcast. The   broadcast   up-link   is   shf,   with   translation   to uhf   taking   place   in   the   satellite.   The   remaining 3-21