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AN/SPS-49 Very Long-Range Air Surveillance Radar

The Radar Set AN/SPS-49 is an L-band, long-range, two-dimensional, air-search radar system that provides automatic detection and reporting of targets within its surveillance volume. The AN/SPS-49 performs accurate centroiding of target range, azimuth, amplitude, ECM level background, and radial velocity with an associated confidence factor to produce contact data for command and control systems. In addition, contact range and bearing information is provided for display on standard plan position indicator consoles. The AN/SPS-49 uses a line-of-sight, horizon-stabilized antenna to provide acquisition of low-altitude targets in all sea states, and also utilizes an upspot feature to provide coverage for high diving threats in the high diver mode. External control of AN/SPS-49 modes and operation by the command and control system, and processing to identify and flag contacts as special alerts are provided for self-defense support. The AN/SPS-49 has several operational features to allow optimum radar performance: an automatic target detection capability with pulse doppler processing and clutter maps, ensuring reliable detection in normal and severe types of clutter; an electronic counter-countermeasures capability for jamming environments; a moving target indicator capability to distinguish moving targets from stationary targets and to improve target detection during the presence of clutter and chaff; the Medium PRF Upgrade (MPU) to increase detection capabilities and reduce false contacts; and a Coherent Sidelobe Cancellation (CSLC) feature.

The AN/SPS-49 long range 2-dimensional air surveillance radar used for early target detection. The long-range AN/SPS-49 radar operates in the presence of clutter, chaff, and electronic counter-measures to detect, identify, and control low-radar-cross-section threats traveling at supersonic speeds. AN/SPS-49 provides the front-end element for successful target identification, designation, and engagement with either long range (SM-1 or SM-2) missiles and/or short range local defense missiles. A key feature of the most recent version of the radar, the SPS-49A(V)1 is single-scan radial velocity estimation of all targets allowing faster promotion to firm track and improved maneuver detection. This is done using unique signal processing techniques originated and tested by the Radar Division of NRL using 6.1 and 6.2 Office of Naval Research (ONR) funds.

The AN/SPS-49(V) radar is a narrow beam, very long range, 2D air search radar that primarily supports the AAW mission in surface ships. The radar is used to provide long range air surveillance regardless of severe clutter and jamming environments. Collateral functions include air traffic control, air intercept control, and antisubmarine aircraft control. It also provides a reliable backup to the three-dimensional (3D) weapon system designation radar.
     Band                    L
     Frequency Band:         850 to 942 MHz
                             three selectable 30MHz bands
                             48 discrete frequencies
     Transmitting Power:     360 kW peak
                             280 kW specified peak power
                             12-13 kW average power
     Antenna Parameters:
                             Parabolic Reflector stabilized for roll and pitch 
                             7.3m/24 ft wide, 4.3m/14.2 ft high 
          Rotating Clearance 8.7m/28.4 ft diameter
          Beamwidths:        3.3°-3.3° azimuth 
                             11° elevation
          Cosec2          to 30°, csc2 to 20° elev 
          Gain               28.5 dB 
          Scan rate          6 or 12 rpm 
          Line-of-sight mechanical stabilization to ± 25 deg roll 
          IFF antenna (AS-2188) mounted on boom 

     Range                   250 nm
     Minimum Range :         0.5 nmi 
     Frequency Selection:    Fixed or frequency agile 
     Range Accuracy:         0.03 nmi 
     Azimuth Accuracy:       0.5 deg
     PRF                     280, 800, 1000 pps
     Pulse width             125 microsecond

The AN/SPS-49(V) radar operates in the frequency range of 850 - 942 MHZ. In the long range mode, the AN/SPS-49 can detect small fighter aircraft at ranges in excess of 225 nautical miles. Its narrow beamwidth substantially improves resistance to jamming. The addition of coherent side lobe canceller (CSLC) capability in some AN/SPS-49(V) radars also provides additional resistance to jamming/interference by cancelling the jamming/interference signals. The moving target indicator (MTI) capability incorporated in the AN/SPS-49(V) radar enhances target detection of low-flying high speed targets through the cancellation of ground/sea return (clutter), weather and similar stationary targets. In 12 RPM mode operation, this radar is effective for the detection of hostile low flying and "pop-up" targets. Features of this set include:


There are currently nine configurations of the AN/SPS-49(V).



Ship Class


Developed in the early 1970s. Included sidelobe cancellation and digital MTI, with Coherent Sidelobe Canceller (CSLC) that electronically cancels jamming. Video outputs provided to PPI displays.

CV, CVN, CG, DDG 993, LHD1, DD997, LSD41


Without CSLC



(V)1 system modified to interface with a Radar Video Processor (RVP)



(V)2 system modified to interface with RVP



(V)1 system modified to provide an automatic target detection (ATD) capability and improved ECCM features. Developed in the early 1980s. Added automatic detection and Doppler processing. Digital outputs provided to an associated tracker.

New Threat Upgrade (NTU)


(V)3 system with double shielded cables and a modified cooling system

CG 47


(V)5 system with a (V)6 cooling system

AEGIS Platforms


(V)5 system enhanced to include the AEGIS Tracker modification kit

AEGIS Platforms


Developed in the mid 1990s. Added radial speed determination on each target, each scan. Improved clutter rejection

The Navy operates the AN/SPS-49(V) as a shipborne radar on board approximately 115 ships and shore installations. Operation in the 902-928 MHz band is critical because it offers unique propagation characteristics that permit detection of small, fast moving targets over water, referred to as sea skimmers. A sea skimming missile or aircraft poses a particular problem, since at normal target tracking frequencies in smooth sea conditions there is a tendency for the radar return to be reflected back off the sea surface, causing confusion to the radar resulting in gross errors in assessment of speed and range. This problem has been largely overcome by using frequencies in the 902-928 MHz band. The Navy maintains that continued access to the 902-928 MHz band is essential to meet national defense requirements. Relocating the AN/SPS-49(V) radar to another band may not be possible. Moving it to a lower frequency range could severely degrade the accuracy of the radar and compromise its mission. Moving it to a higher frequency range could significantly degrade the radar’s capability to detect very small targets. Based on this unique frequency requirement, reallocation of the entire 902-928 MHz band is not considered a feasible option. Reallocation of a portion of the band for non-Federal use would reduce available spectrum resources to conduct Naval exercises in coastal areas. The resulting increase in radar-to-radar interference would limit the size of combined task force formations to as few as two or three ships, a situation incompatible with Navy mission requirements. Redesign, procurement and installation of a replacement radar to operate in a different band would cost on the order of $1.66 billion. In 1994 the NTIA stated "The DoD considers that continued access to the full 902-928 MHz band on a primary basis is essential to meet national defense requirements. Based on this stated requirement, reallocation to exclusive non-Federal use is not considered feasible."

The AN/SPS-49(V) radar is, or will be, installed in most medium to large naval ships. Ship classes with AN/SPS-49 include 70 U.S. Navy, Australian, Spanish, and Taiwanese Frigates (FFG-7); 12 Canadian Patrol Frigates (CPF Program); 10 ANZAC Patrol Frigates; 3 Korean KDX; 27 AEGIS Cruisers CG-47 Class; 26 TARTAR and Terrier Class Cruisers; 15 Destroyers; 19 Aircraft Carriers; 4 Battleships now decommissioned; 16 Amphibious ships LSD-41 and LHD, and 6 Battle Spares/training units.

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Updated Wednesday, June 30, 1999 4:31:35 AM