electronics.    Because of this, the 52C has significant improvements over earlier versions of the 52 radar in the areas of detection, reliability, and maintenance. The antenna assembly (fig. 2-1) is a planar array, tilted back at an angle of 25 degrees. This 25-degree tilt allows the antenna to provide high-elevation coverage. The array is a collection of rows of slotted waveguides and is fed RF from a feed system running the length of one side of the total array assembly. This antenna scans in   the   vertical   plane   by   transmitting   different frequencies, as selected by a digital computer. The   AN/SPS-52C   radar   has   four   modes   of operation:  high angle, long range, high data rate, and MTI  (Moving  Target  Indicator). The operator selects the appropriate mode, depending on the threat type and environment. The primary mode is  high angle. In this mode,   the   radar   provides   coverage   to   a   range   of approximately   180   miles   and   an   elevation   of approximately  45  degrees.    In  the  long-range  mode, t h e    r a d a r    p r o v i d e s    c o v e r a g e    t o    a    r a n g e    o f approximately   300   miles   and   an   elevation   of approximately  13  degrees.  The  high  data  rate  mode provides  a  range  of  approximately  110  miles  and  an elevation of approximately 45 degrees. This mode is used  because  of  its  unique  ability  to  acquire  pop-up and close-in targets quickly. The MTI mode is useful in a high-clutter environment (such as weather in extreme sea-state conditions) where targets are normally hard to  locate.  Coverage  is  about  70  miles  and  up  to  an elevation of 38 degrees. The 52C radar is used with the SYS-1/SYS-2 radar system.   The   SYS-1/SYS-2   system   coordinates   all radar sensors on a ship into a single system. It does this by   using   a   processor   designed   around   integrated automatic   detection-and-tracking   (IADT).   The advantage  of  using  such  a  system  is  that  the  unique characteristics   of   the   various   ship’s   radars   can   be integrated,   resulting   in   more   accurate   and   quicker detection   of   threats.   This   is   part   of   a   program   for non-AEGIS  class  ships  called  New  Threat  Upgrade (NTU). The AN/SPS-52C radar is presently found on the WASP  (LHD)  class  and  the  TARAWA  (LHA)  class amphibious assault ships. It will eventually be replaced by the AN/SPS-48E. AN/SPS-48 RADAR The   AN/SPS-48   radar   is   a   complete   system upgrade of the AN/SPS-52C including all component elements — transmitter, receiver, computer (radar and automatic   detection   and   tracking),   frequency synthesizer  and  height  display  indicator.  Figure  2-2 shows  an  antenna  for  the  SPS-48  radar  on  the  USS Boxer  LHD-4 (see arrow). The   SPS-48   radar   is   a   long-range,   three- dimensional,   air-search   radar   system   that   provides contact  range,  bearing,  and  height  information  to  be displayed  on  consoles  and  workstations.  It  does this   by   using   a   frequency-scanning   antenna, which  emits  a  range  of  different  frequencies  in the  E/F  band.  The  SPS-48  radar  has  three  power modes: high, medium, and low. An upgrade was needed because the 52C radar’s single elevation beam could not dwell long enough in any particular direction. To solve this problem, the 48 series uses a process that stacks nine beams (a train of n i n e    p u l s e s    a t    d i ff e r e n t    f r e q u e n c i e s )    i n t o    a pulse-group.  The  nine  beams  simultaneously  scan  a 5-degree elevation area, allowing the stack to cover 45 degrees of elevation. Two versions of the SPS-48 are currently in use: the  48C  and  the  latest  version,  the  48E.  Maximum elevation has increased somewhat, 65 degrees versus 45 degrees for the 52C. The “E” version has twice the radiated  power  of  the  “48C”,  developed  by  reducing the sidelobes and increasing the peak power. Receiver sensitivity  is  increased  and  the  48E  has  a  four-stage solid state transmitter. The main operating modes are:    EAC   (Equal   Angle   Coverage)—The   radar’s energy is concentrated at a low angle.    MEM (Maximum Energy Management)—Both high and medium power are regulated.    AEM (Adaptive Energy Management)—Allows the radar to be adapted to a priority target radar 2-2 Figure 2-1.—AN/SPS-52 radar antenna.