Radar Digital Signal Injection System (RDSIS)
Models and simulations are essential throughout the entire lifecycle of product development. Hardware-in-the-Loop (HWIL) simulations enable testing of system software running on a subset of the system’s fielded hardware. Within HWIL simulations, models are used to replicate or emulate natural and man-made systems as a substitute for products or effects that are difficult or cost prohibitive to use or create, including environmental effects, threats and system hardware. HWIL simulations provide cost-effective options for evaluating design and development trade-offs for “what if” scenarios. Additionally, HWIL simulations perform parametric analysis used for operational planning, preand post-test analysis, and as an input to system-of-systems performance testing. As a system or product evolves, HWIL simulations need to be flexible and adaptable to respond to maturing system requirements and use cases.
The Ballistic Missile Defense System (BMDS), developed and tested by the Missile Defense Agency (MDA), is a globally distributed multibillion dollar system made up of complex elements (Figure 1) that have different communications protocols and interfaces developed by multiple contractors, and that are owned and operated by different branches of the government and military. The BMDS requires continuous upgrades to meet evolving threats, putting a heavy burden on the development and sustainment community. This development includes the need to test and validate new system capabilities on a wide range of threat scenarios. Flight tests provide a reliable venue for testing out the new capabilities, but such tests can also be prohibitively expensive and provide only a small sample of the required data. This necessitates system-level testing through the use of high-fidelity models and simulations of individual elements and validation by flight testing. As more and more BMDS elements are deployed and brought on-line, models and simulations become more important. Simulations provide a cost-effective test and assessment capability that can emulate a near-infinite number of scenario variations that affect critical system performance.
RDSIS is a radar signal processor injection driver developed by Raytheon along with Dynetics and TecMasters Inc. (TMI). RDSIS provides a real-time, high-fidelity test capability for the AN/TPY-2 Radar. The RDSIS simulates the in-phase and quadrature (I&Q) output from the receiver/exciter (REX) and injects these radar returns into the AN/TPY-2 Radar Signal and Data Processor (SDP). This unique approach provides a test capability to exercise the complete signal and data processing functionality in a real-time, tactical configuration. The RDSIS simulates radar return data for targets, associated objects, launch and separation debris, and man-made and natural environments. Simulated radar return data are injected into the SDP at the appropriate time instants, and are packaged in the required formats to support AN/TPY-2 radar operations. Figure 2 shows the current RDSIS configuration.
The RDSIS consists of three primary software configuration items running on two primary hardware configuration items. The RDSIS Executive Controller (REC) provides initialization and scenario truth during testing. During every radar resource period the RDSIS processes radar REX, Signal Processing and Beam Steering Generator (BSG) commands and computes the required parameters of the signal to be injected into the SDP. An x86-based IBM x3950 M2 hosts control functions (REC) and data processing on radar actions (RDP). Once computed, the signal injection parameters are passed to a Mercury Impact RT 3200 computer, consisting of multiple digital signal processing (DSP) boards that execute the RDSIS Signal Injector (RSI) software module. The RSI produces the sampled digital signal that simulates the output of the radar’s REX. This time-sampled, baseband signal is supplied to the SDP through packet digital communications, which closes the control loop with the radar’s scheduling and control software.
RDSIS has evolved from a system engineering integration and test tool to an X-Band Simulator Tester (XST), a deliverable product that integrates with multiple radar systems (forward and terminal modes of AN/TPY-2, along with the X-Band Radar [XBR]). Initially RDSIS development focused on providing a high-fidelity threat modeling capability to stimulate radar discrimination algorithms for verification of radar requirements. Successful demonstrations of the RDSIS throughput capability led to additional investment to provide pre-flight risk reduction simulation testing and to integrate RDSIS as part of the BMDS Single Stimulation Framework (SSF) for participation in integrated system test events with multiple BMDS elements.
For element integration, RDSIS is used for requirements verification at the prime item development specification (PIDS) level for the radar (specifically for requirements that need high-fidelity threat representation and the tactical signal and data processor). For flight test pre-test analysis, RDSIS is used for HWIL performance analysis within the lab environment in support of test event milestones (e.g., scenario certification). RDSIS is also used for post-flight reconstruction to recreate the performance observed on the test day and to anchor data with live mission results to provide evidence for simulation validation and accreditation. Finally, the ground test use cases integrate RDSIS into the SSF with other elements to support BMDS HWIL system performance testing.
RDSIS, when integrated with a Radar Interface Unit (RIU), also supports virtual over-live signal injection. The RIU is modified commercial-off-the-shelf hardware that merges the simulated I&Q from the RDSIS with the live output of the tactical REX. This application of RDSIS provides a greater threat complexity by enabling the tactical software to be exercised with outputs from natural and simulated radar environments.
RDSIS Verification and Validation
RDSIS undergoes thorough integration and testing prior to its use within the radar laboratory environment. This includes verification testing of new requirements and regression testing with each formal release. Test cases are used to test RDSIS functionality; radar interfaces; threat models; and antenna pattern models, receiver characterization (e.g., signal-to-noise ratio, range accuracy and angle accuracy), processing throughput, and SSF interfaces.
RDSIS has been validated through comparison with live radar data including measurements from radar cross section (RCS) signature satellites and high accuracy ephemeris (HAE) satellites, as well as radar data collected during flight tests. Results from these validation activities resulted in initial accreditation of RDSIS by the Operational Test Agency (OTA) in 2011.
Recently, RDSIS has added the capability to interface with the XBR and to model and inject unresolved fuel debris chuff to test new radar capabilities and reduce risk associated with future missile defense flight test events. The Cobra Judy Replacement (CJR) program is leveraging RDSIS to provide an X-band stimulation capability to reduce the risk associated with an upcoming demonstration. RDSIS is also re-hosting the RDSIS Signal Injection (RSI) software item from the Mercury 3200 to an x86 platform with a Linux® operating system. This re-host reduces the overall RDSIS cost and provides a platform-independent solution aligned with the AN/TPY-2 radar signal and data processor hardware migration.
As systems and threat complexity continue to evolve, HWIL simulators, including RDSIS, will develop in parallel to meet simulation and test needs within the laboratory environment. Software architecture studies for RDSIS have already been completed and provide a long-term incremental roadmap for improvements in system throughput, increased scalability and platform independence.
Gregory Hoppa and Rich Powers
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