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AN/SPS-74(V) Radar Set

 
Description
The AN/SPS-74(V) radar is an X-band, 480 MHz bandwidth high resolution sensor that rapidly sweeps the surface to the horizon at three hundred Revolutions per Minute (RPM).

The high range resolution and high scan rates and a processor dedicated to processing the ocean surface, provide a system capable of early detection and tracking submarine periscopes at tactically significant ranges in highly cluttered environments.

Advanced signal processing technology is used to analyze the radar data to correctly discriminate periscope detections from sea clutter and confusable targets with high probability while maintaining a low probability of false alarm.

The AN/SPS-74(V) radar consists of two air-cooled below-deck cabinets, the Receiver/Transmitter (R/T) and the Radar Data Processor (RDP); one above-deck Antenna Group; and four Ruggedized Operator Display (ROD) Tactical Workstations. The system is designed to meet all MIL-STD-901D Grade B shock requirements for Nimitz-class ships.

The AN/SPS-74(V) system is manned by an Analysis Operator, a qualified Operations Specialist, during periods of potential submarine threat. Maintenance users are qualified Electronics Technicians. Preventative maintenance is scheduled for less than one hour per week.

AN/SPS-74(V) training will be established and a Navy-approved curriculum published in the Catalog of Navy Training Courses. The basic operation and maintenance training will be provided to shipboard technicians during system installation and as requested by the fleet prior to deployment. Contrary to customary training policies and processes, this training is developed, delivered and maintained by the Program Office and the In-Service Engineering Agent.

The AN/SPS-74(V)1 Advanced Development Model (ADM) is currently installed on four Nimitz-class ships: CVN 70, CVN 73, CVN 74 and CVN 76. The program was terminated in POM-14 endgame decision with Periscope Detection capability being transitioned to AN/SPQ-9B.

 
Features
The AN/SPS-74(V) Periscope Detection Radar (PDR) provides high resolution and fast scan capability, enabling detection of low Doppler, small cross section submarine periscopes presenting limited exposure opportunities for radar detection. PDR significantly enhances the Anti-Submarine Warfare picture and decreases the response time to effectively mitigate enemy submarine threats. The AN/SPS-74(V) consists of a High Range Resolution (HRR) Radar subsystem that detects periscope exposures and a RDP subsystem that analyzes the radar data to correctly classify periscope detections with high probability while maintaining a low probability of false alarm.

The HRR Radar subsystem consists of an above-deck Antenna Group and a below-deck R/T unit. The Antenna Group consists of a stabilized pedestal, rotodome, pedestal electronics assembly (PEA), radome and mechanically-stabilized reflector antenna. The antenna assembly is the primary means of transmitting and receiving the radio frequency (RF) signals that are used to detect submarine periscopes. The antenna assembly, which consists of a reflector and vertically polarized feed horn, is supported on a 300 RPM azimuth rotator with resolver. The roll axis drive and pitch axis drive are used to maintain platform stability to the horizon. The antenna and its associated rotodome are mounted together on top of the pedestal assembly and rotate at 300 RPM. The rotodome eliminates turbulence inside the radome from rotating the reflector at 300 RPM. This helps the pedestal maintain a stable antenna beam position free from vibration.

The primary purpose of the PEA, which is part of the antenna assembly and is mounted inside the radome, is to route the transmitted and received RF signal to and from the antenna. The PEA routes the RF transmit signal from the RF amplifier of the R/T unit to the antenna and routes received RF signals from the antenna to the receive portion of the R/T. A low noise amplifier (LNA) amplifies the received signal to maximize radar sensitivity. The R/T provides 28 Volts Alternating Current (VAC) to the PEA for its space heaters and 28 Volts Direct Current (VDC) to the redundant +15 VDC power supplies to support the LNAs, Built-In Test (BIT) and interface circuit card assemblies, noise source assembly and test target generator assembly.

The R/T unit contains the trigger timing circuits, RF generation and transmission functions and waveguide switching and receiver functions necessary for transmitting and receiving radar pulses. The transmit portion of the R/T unit generates the 480 MHz Non-Linear Frequency Modulated waveform, amplifies it and transmits it to the antenna via the PEA. The receiver portion of the R/T unit receives the RF signal, demodulates it, converts it from an analog signal to a digital signal and then sends it to the RDP unit for processing. The R/T unit receives 440 VAC 60 Hz 3 phase power from the ship and provides power and control for antenna orientation and antenna assembly platform stabilization. The R/T unit also provides a relay closure to signal the RDP unit to power up so that there is a single power on/off control for the entire system. The R/T unit receives navigation (roll, pitch and heading) data from the ship's Navigation Sensor System Interface via an optical Ethernet connection and distributes navigation information to the RDP unit.

The RDP subsystem consists of the RDP unit and the Display Group. The RDP unit, which is comprised of hardware and software configuration items operating within a rugged enclosure, receives and processes data from the R/T unit. The RDP unit receives 115 VAC 60 Hz power from the ship. RDP power up is controlled from the R/T unit through a 28 VDC relay closure. The RDP utilizes advanced signal processing techniques to minimize false alerts while maintaining the ability to track and classify short periscope exposures. System automation allows for minimal operator interaction and provides the capability to alert only upon detection. The RDP is operated from any of the four Display Group RODs, which provides the human-machine interfaces to analyze and validate periscope alerts, monitor and control the system, set system configuration parameters, review automatic system fault detection results and perform troubleshooting and maintenance procedures.

Operation of the AN/SPS-74(V) is determined by user accounts. The Analysis and Maintenance user accounts allow an operator or maintainer to remotely restart system software processes, manage contacts and troubleshoot system faults. Tactical user accounts provide display capability only so other watch sections in the Combat Direction Center can monitor the PDR system's contacts and system status. The Tactical user account cannot modify any system setting, other than local display settings.

The AN/SPS-74(V) has a one-way digital interface to the Navigation Critical Distribution System (NCDS) Local Area Network (LAN) in order to support reporting validated periscope alerts to the shipboard AN/UYQ-100 Undersea Warfare Decision Support System. The AN/SPS-74(V) provides pulse trigger data to the AN/SLA-10B system in order to support shipboard Electronic Support Measures/Electronic Countermeasures receiver systems.

The AN/SPS-74(V) provides a scaled Red-Green-Blue stream of the video displayed at the operator console to the Shipboard Video Distribution System. The AN/SPS-74(V) receives the OD-19 navigation message from NCDS in order to geographically locate its contacts and apply the Inter-Range Instrumentation Group (IRIG-B) time from the ship's services in order to time align the contact data to the ship.

The AN/SPS-74(V) also includes a separate two-way digital interface to/from the Integrated Shipboard Network System LAN for Distance Support. The AN/SPS-74(V) receives and applies updates to its shipboard training curriculum, BIT knowledge base, maintenance procedures and assigned maintainer tasks using updates received over Distance Support. In response, the AN/SPS-74(V) provides maintenance task status, maintainer inputs and system status to a shore-based facility via the Distance Support system.
 
Background
The capability of the PDR is a key operational requirement for aircraft carriers due to the evolving global circumstances and advances in threat submarine technology. PDR technologies were successfully demonstrated under the Office of Naval Research-funded Automatic Radar Periscope Detection and Discrimination (ARPDD) brassboard prototype, but attempts to bring this system into the Fleet proved unaffordable. The AN/SPS-74 program was initiated by the Program Executive Office for Integrated Warfare Systems (PEO IWS) as an Advanced Technology Demonstration (ATD) effort in FY06 to demonstrate an affordable, operationally effective PDR capability with performance comparable to the ARPDD brassboard.

The Resources, Requirements Review Board (R3B) met in August 2006 and determined that the AN/SPS-74 PDR capability was required for all CVN aircraft carriers. The R3B decision and the subsequent approval and designation as a Rapid Deployment Capability (RDC) modified the initial program objective from an ATD to an Advanced Development Model (ADM) with follow-on Production systems. The Navy authorized a total of four PDR systems based upon the AN/SPS-74(V)1 ADM design and eleven Production systems, including ten for installation on Nimitz-class carriers plus one Land Based Test Site.

The AN/SPS-74(V)1 ADM RDP subsystem was developed by 3 Phoenix, Inc. under a Small Business Innovation Research Phase III contract sponsored by PEO IWS. The HRR Radar subsystem was developed by Northrop Grumman Electronic Systems under a competitive Broad Agency Announcement award.

The AN/SPS-74 Program was canceled in POM 14. An/SPQ-9B assumes Periscope Detection requirement. 4 Fielded systems will remain in service until the SPQ-9B PDD capability can be fielded on those hulls.
 
Point Of Contact
Office of Corporate Communication (SEA 00D)
Naval Sea Systems Command
Washington, D.C. 20376
 
Last Update: 17 January 2017