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Simulator for Moving Target Indicator System

Final Report Summary - SIMTISYS (Simulator for Moving Target Indicator System)

Executive Summary:
The SIMTISYS Software (SW) simulator for Spaceborne GMTI Performance Analysis Simulator will be summarized according to the following main points based on the methodology for “Instrument Performance Specification & Measurement” described by Dr. Simon Watts1:
• Instrument
• User Needs
• Specifications on Performance
• Measuring Performance
• Modeling Scenario

The Simulator is a SW Tool whose functionality is a Simulation2 of Maritime Surveillance Performance from SBRs on a PC Workstation. The Core Engineering Issue is related to the Radar Problem: “Spaceborne GMTI in Sea Clutter.”
Two types of SBRs can be taken into consideration: Type II Radars and Type III Radars. Accordingly Type II Radars are Spaceborne Synthetic Aperture Radars (SARs) providing imaging functionalities (e.g. radars used for mapping). On the contrary Type III Radars are nonimaging Spaceborne Surveillance Radars providing (not necessarily yet coveatingly Early Warning) MTI functionalities e.g. Real Aperture Radars (RARs) which resemble airborne, shipbased, and ground-based surveillance radars against pop-up targets. Only Type II radars have been instantiated in the SIMTISYS project.
Spacecraft constellations and orbital mechanics have been constrained to those Low Earth Orbits (LEO) orbits suitable for Type II Radars operations3 e.g. TerraSAR-X (~ 500 Km height), Cosmo Skymed (~ 620 Km height), Radarsat 2 (~ 800 Km height). Surveillance Areas have been tailored to those European hot spots requiring a maritime watch dog (e.g. vessels in the Mediterranean Sea, the English Channel, the Black Sea, the Barents Sea,…). The SW infrastructure complies to standard policies of system design & development i.e. Flexibility, Modularity, Interoperability, and Efficiency. The Efficacy (i.e. adequacy) relies on the core engineering issue which has not been faced completely by the scientific and technical community especially for the technological capabilities of SBRs, the thorough applicability of SBR-GMTI techniques to the marine environment, as well as sea clutter modeling. Specification on Performance has been based on Moving Target Indicator (MTI) requirements w.r.t. an Optimization Criterion (i.e. the Neyman Pearson Criterion).
The Measuring Performance has been based on comparing Analytical Results with Monte Carlo Simulation Results (wherever possible) based on MTI requirements w.r.t. Decision Theory (i.e. Binary Hypothesis Testing). Due to the complexity of analytic models for the electromagnetic (EM) scattering from hydrodynamic surfaces and from complex targets, the Modelling Scenario has been characterized via a signal processing approach with both deterministic and stochastic parameters.

Project Context and Objectives:
4. SW SIMULATOR DATA RESULTS SUMMARY

The SW Simulator architecture has been envisaged as a set of subsystems interfaced by a Bus where each subsystem characteristics is outlined by a Qualitative Model via a Conceptual Description in [RD-01]. Such an approach has allowed different researchers to instantiate different Quantitative Models by expanding and/or improving key Information Structures i.e.

• Advanced SBR FoV

• Viewing Environmental Geometry

• RX Baseband Signal(s)

The following table summarizes the Compliance Table for the SIMTISYS SW Simulator Validation w.r.t. the requirements outlined in [RD-01] and clarified in [RD-03].

Object Validation Type of Requirement Method Verification Statement
Architectural Concept Functional (R), (I) Compliant
Subsystems Functional, SW-related (R), (A) Compliant
SW Architecture SW-related (T), (I), (R), (A) Compliant

Indeed the SW Simulator Subsystems Qualitative Requirements were described by the word “should” and “could” instead of “shall” and do not represent strict rules to be followed by researchers and developers but only a guiding compass for research lines within the framework of feasible future modern SBR payloads.

The Validation Phase is hereby defined as the Verification of Requirements as part of the SIMTISYS research project WBS which have been organized in a comprehensive framework traceable to high level functional aspects, scientific aspects, and SW-related aspects.

Indeed such requirements have been harmonized by the SIMTISYS consortium as per a round-table under TASI coordination. Given the research nature of the project encompassing the core engineering issue “Spaceborne GMTI in sea Clutter,” the requirements have not been outlined in order to strictly freeze a consolidated and recurrent instrument to be developed, yet as a means to unleash creativity (albeit preserving prudent margins to mitigate risks and accommodate data and models uncertainties) under a neat compass of strategic research & development for a modern SW Simulator to be entirely designed and developed from scratch by researchers with a concurrent heterogeneous expertise.

5. SW SIMULATOR MODELS RESULTS SUMMARY

Indeed the SW Simulator Subsystems Quantitative Models have been defined by each partner within the SIMTISYS consortium as a foreground allocated to the individual company/university concerned in terms of:

• neat descriptions
• executive summary;
• internal block schemes and related signal processing flow;
• analytical formulas and related derivations;
• references to proofs of statements;
• major modeling assumptions and approximations;
• SW code in case of any numerical computation result;
• tables and figures;
• conclusions and way forward.

A summary on the adopted models is reported in the bullets sketched hereafter:

• Although current SAR imagery from LEO spacecrafts has a well defined, mature, and flight proven non-real time system engineering framework with an operative Swath vs Resolution trade-off, MTI techniques are manifold and, for SBRs, are still experimental in terms of both statistical detection assessments and operative temporal responsiveness.

• Sustainability Studies allowed outlining a roadmap where, for the time being, mathematical analysis and computer stochastic simulation appear as the cornerstone for addressing this low-TRL engineering-framework and eventually for simplifying algorithms and operative solutions while key space-qualified enabling-technologies evolve (namely phased array antennas, onboard processing & storage capabilities, downlink telecom infrastructures) with a tremendous impact on possible signal processing techniques to be adopted.

• The SIMTISYS project supports mathematical analysis with stochastic simulation by exploiting the processing & storage capabilities of modern multi-core PC workstations, modern programming languages, COTS and aerospace development tools. Moreover the SIMTISYS project interprets and inevitably frames the possible "responsiveness" concept for SBR MTI with respect to original ground-based MTI heritages where pop-up targets must be faced with a quick procedural cascade made of "detection-tracking" spanning an amount of time on the order of seconds.

• The SW infrastructure complies to standard policies of system design & development i.e. Flexibility, Modularity, Interoperability, and Efficiency. The Efficacy relies on the core engineering issue which has not been faced completely by the scientific and technical community especially for the technological capabilities of SBRs, the thorough applicability of SBR-GMTI techniques to the marine environment, as well as sea clutter modeling.

• The off-line MTI performance Characterization database represents an important aspect of the SIMTISYS project. In summary such a database is a preliminary version based on classic approaches based on DPCA, ATI, STAP and stochastic assumptions (e.g. Gaussian distributions for Interference and Swerling 0 Targets) whereas current heuristic combinations or ad-hoc extensions of the aforementioned techniques (e.g. taking as a reference EUSAR 2012 proceedings on Radarsat2 MODEX GMTI results and techniques) have not been considered.

• A post-detection autofocusing technique has been investigated over a sub-region of the SAR image. It has been based on the 2-Dimension Product-High-order-Ambiguity-Function (2D-PHAF) for estimating the coefficients related to induced moving-target-scattering-centers phase-modulation and range-migration modeled as a superposition of 3rd order 2D Polynomial Phased Signals (PPS).

• The current SIMTISYS project focused on Space-Time Techniques for Multichannel SAR solely (i.e. without RAR KA MIMO STAP approaches). Limited resources, constrained times, prudent engineering design, partial and non-exhaustive availability of public results of spaceborne test campaigns still do not allow SAR system engineers to design Spaceborne SAR Payloads according to a “consolidated moving target detection performance” in the maritime domain for moderate to large sea states in terms of statistical detection assessments.

• Significant steps have been made forward for an improved awareness of the current limits. Accordingly the Reference Study Case adopted during the Validation Phase has been adopted as similar to the MODEX mode experimental payload incidence angles and confirmed the de-facto experimental evidence of current difficulties in single-channel SAR image interpretation for scenarios comprising small vessels in high sea states. Exploiting multi-channel SAR configurations, the Reference Study Case has also highlighted the correct matching obtained from CFAR Detector visual telemetries, and the order of magnitude of related Estimated Detection Probabilities. Finally the Spaceborne GMTI Performance Analysis applied to the Reference Study Case has pinpointed the significant impact on GMTI performance of the statistical clutter amplitude distributions and related temporal correlations as well as the adopted multichannel baselines physical extent, the SAR noise Equivalent Sigma Zero, and the RCS-related parameters associated to target vessels scattering centers models. The impact of ambiguities (in terms of AASR and RASR) on the Spaceborne GMTI Performance Analysis have been neglected.

• Further investigations and matching of experimental data (e.g. taking as a reference Radarsat2 MODEX MTI results and techniques) appear of paramount importance.

Project Results:
3.3 Foreground Identification and IPR
The Consortium agreed on holding the first Program Steering Committee meeting within the second reporting period during the phase of major risks for the final outcomes of the project and during the main dissemination activities. To clearly identify the Property Information and evaluate the rules and the policies for the dissemination of Foreground, the Consortium agreed on the identification of two levels of foreground: the first level is at SW models while the second is at overall simulator. In section 3.2 the individual foreground will be reported while in the present section, the approach to the jointly foreground identification and exploitation is reported.

3.3.1 Jointly Foreground
It is intended as Jointly Foreground the outcome in which there is the participation of two or more parties of the Consortium. In order to regulate the access to the jointly Foreground the RD[05] applies.

3.3.2 Intellectual Property Rights Management
To better regulate the jointly foreground and the access rights to the simulator, the Partners agreed to sign an informal paper in which the access and the regulations are included and detailed, for each Partner.

3.4 Dissemination and Exploitation
The Exploitation plan is widely detailed in RD[06]. In this section the Dissemination Plan is reported.
The PSC decided to share the dissemination approach into a Dissemination Plan, in order to: support each other in the preparation of the publications; optimise the resources for the participation of events; optimise and share the participation to other project (European or International). The dissemination Plan also contains the approach for the participation of all the Parties to:
-main yearly European and International Events on topics related to project contents,
-main initiatives at European Commission Level
-specific initiatives to technical topics related to the project’s contents
Moreover being each partner involved in other FP7 projects, the exchange of information shall be regulated. The European Commission recognised a very key feature the cooperation among several project and the cross fertilization of the results obtained, contribute to the clearly identification of a whole picture of Service and features for the final User. This implies that each project must actively participate to working groups and initiatives for the same purposes.
In the table below the shared Dissemination events where SIMTISYS was introduced as a whole.

List of dissemination activities
NO Type of activities Main leader Title Date/Period Place Size of audience
1 Periodical Meeting Involved Projects Project Steering Board Twice per year Brussels Limited
2 Periodical Meeting European Commission MARSUR Twice per year Brussels Limited
3 Workshop Italian Space Agency Workshop on GMES June 2012 Rome >50
4 Conf. European Commission Let’s Embrace Space 2012 November 2012 Cypro >80
5 Conf. Ministry of Maritime Transports and European Commission European Maritime Day 2013 May 2013 Malta >80

To improve and better support the Dissemination, the Consortium decide to build up a website (www.simtisys.eu) containing all the news, the last issues the events related to the project. The description of this website is detailed in RD[03]. This tool was used as a communication channel with the users and stakeholders but also it was considered as a window of the project where all the main outcomes obtained and discussions, are transmitted to the interested users.

3.5 Foreground
In this section the identified Foreground of each Partner is reported; the exploitation of the whole simulator, and of the SW modules will be detailed in D50.3 – Exploitation Plan (RPT-ECS-SMTI-0021-TASI), as agreed during the PSC meeting is reported.

3.5.1 TASI
TASI has not developed any IP SW code.
TASI does not own the two SIMTISYS workstations.

3.5.2 DIET
In SIMTISYS, DIET has developed several signal processing algorithms aimed at detecting moving targets using single/multiple antennas from single/multiple satellite observations. In particular, DIET has produced the following algorithms.
1. An extended chirp scaling algorithm has been implemented. The algorithm is able to form the SAR image at high squint angles and compensates the range cell migration induced by the satellite motion with respect to a fixed point on the ground.

2. A two-dimensional CFAR detector is realized through the use of a 2D-window that slides over the SAR image with the goal of detecting moving targets while enforcing a constant false-alarm probability.

3. An autofocusing technique based on two dimensional product of high order ambiguity function (2D-PHAF) has been proposed and applied to the high resolution imaging of moving targets from synthetic aperture radars. Using the 2D-PHAF, we have proposed an algorithm that compensates jointly for the range cell migration and the phase modulation induced by the relative radar-target motion in order to produce a focused image of the moving target.

4. A Space Time Adaptive Processing technique has been implemented by combining the complex images produced by SAR processing applied to the signals received by different antennas at different time instants. Two optimal approaches were proposed for deriving the coefficients of the STAP filters.

The previous algorithms have been combined in order to produce three different simulators, which are listed in the following.

1. Multiple Satellite STAP and CFAR detection. This module contains several algorithms aimed at simulating the detection of moving targets against a sea clutter background using a constellation of satellites. The implemented processing algorithms include: raw data generation, image formation, clutter cancellation, and adaptive detection. Alternative observation scenarios can be selected for simulation: single/multiple satellite using single/multiple antenna processing.

2. Map of Detection Probability. This simulator produces a map of theoretical detection probability, obtained applying a 2D CA-CFAR detector, for any position of a moving target on the observed swath. The simulator takes into account the possibility to use STAP techniques, for clutter cancellation, and considers the presence of multiple satellites, to exploit the angular diversity of the target scintillation. It can also be tailored to different sea reflectivity models.

3. Adaptive Focusing of Moving Targets. The simulator implements an autofocusing technique applied to the high resolution imaging of moving targets from synthetic aperture radars. The implemented algorithm compensates jointly for the range cell migration and the phase modulation induced by the relative radar-target motion in order to produce a focused image of the moving target. The result is compared to what it would be obtained by forming the image with the traditional chirp scaling algorithm.

3.5.3 UPC
UPC has developed the Space Borne Radar (SBR) module which delivers multichannel SAR images and Moving Target Indication (MTI) SW module which deliver MTI images and detection Maps including Probability of detection Maps.
For development efficiency reasons both SW modules have been developed using IDL (Interactive Data Language) programming and analysis software. As agreed in the project Consortium Agreement only the compiled executable code has been delivered which can be run on the freely available IDL virtual machine or using an IDL license.
A MTI performance database which allows a fast estimation of vessels probability of detection has been included in the delivered SW

3.5.4 DEIMOS
In the frame of the SIMTISYS simulator, DEIMOS developed two modules, namely SS-QoS and SS-MTI, which DEIMOS declares as foreground.
Both modules consist of an executable file (namely ssQoS.exe and ssMTI.exe) and ancillary files (binary sea map Default Sea 720x360.png constants files, data model files, input files).
A copy of the DEIMOS modules will be provided to each Partner as component of the SIMTISYS Simulator infrastructure, and a licence is granted to each partner for the use within the simulator. However, each Partner shall be responsible for the compliance to licensing aspects of included OSS software.

3.5.5 SISTEMATICA
In SIMTISYS, Sistematica supplied the software infrastructure (BUS) and the GUI. The related software source code is not part of the supply, as per Consortium agreement, so modification of the provided components outside Sistematica control is not possible.
Usage of software components executables (BUS, GUI) supplied to the Partners as part of the SIMTISYS simulator is allowed to each Partner. However, each Partner shall be responsible for the compliance to licensing aspects of included COTS (Oracle) and OSS software (Apache Tomcat, java, xerces, hdf5, NASA World Wind, curl, Filezilla FTP server), needed to run the infrastructure and GUI executables.
Usage of software sub-systems which are part of the integrated simulator but are supplied by the other Partners (ssMTI, ssQoS, ES, SBR, MTI, FFMTI), shall be used under the licensing rules established by the Manufacturers.

3.5.6 Telespazio VEGA
Telespazio VEGA UK has developed the Earth Scenario Module for the SIMTISYS simulator. This module is used to generate representative terrestrial scenes that will be imaged by the virtual SAR system implemented in the other modules. The module receives inputs describing the satellite orbit. Location, dynamics and radar reflecting / scattering properties of the surface and objects (both vehicles and static objects) are modelled. From these, combined with the geometry of the satellite pass, a radar target scene is generated representing the ‘radar’ appearance of the scene from the observation perspective of the satellite. The scenario is modelled in both time and space. Vehicles / vessels can rotate as well as translate on pre-determined trajectories. This allows (e.g.) modelling of representative movement of ships on rough seas, with pitching / yawing / rolling motion. The sea state is configurable, including its effect on background radar scatter. Modelling of objects in the scene is configurable, through the use of ‘canonical’ component objects with well-characterised general radar scattering properties (e.g. cylinders, dihedrals, tri-hedrals, etc).
The model uses an underlying COTS component (Satellite Toolkit) to support the scene generation, and to create animations of the evolving scenario.
A user license for the embedded STK software is required to use the Earth Scenario Module. A single instance of this license is available for each of the consortium partners. Each partner is responsible for conformance to the terms of this license, which may not be reproduced. Permission is granted by Telespazio VEGA UK for each partner to use the software in its executable form, for internal research and development purposes.
Source code for the Earth Scenario Module remains the sole property of Telespazio VEGA UK. Telespazio VEGA UK asserts IPR ownership over the source code, concept and design of the Earth Scenario Module.

3.5.7 D’Appolonia
In SIMTISYS, D’Appolonia supplied the Web-site and bought a workstation used for the dissemination activities and for validating the system.
The Web-site is developed using an open-source platform “Wordpress”. The Web-site contains also a Enterprise Content Management for organizing and storing an organization's documents.
D’Appolonia has not developed any IP SW code of the simulator.

Potential Impact:
European strategies for the homeland protection are aimed at extending national policies, laws, operations, and technical capabilities within the framework of a harmonized i.e. coherently standardized transnational management. For the time being such a strategy is still intertwined to non-optimal tactics in terms of fragmented policies or duplicated efforts thus resulting in an inefficient use of resources.
Promoted by major European institutions such as European Commission, European Space Agency and European Defence Agency (EDA), several programs and projects are being issued encompassing further developments of existing EU systems as well as enabling technologies and related techniques. Copernicus constellation represents a clear step towards such enhanced European capabilities whereas significant advances towards a true European political integration can definitely speed up such a process. More specifically such a program (comprising satellites, ground stations, airborne and ground based ancillary support data, data standardizations…) is aimed at providing services based solely on Monitoring & Forecasting capabilities related to six remote sensing thematic areas:

• Marine Services (ship routes, state of the oceans, oil spill pollution, ice monitoring…);
• Land Services (soil sealing, water quality and availability, spatial planning, forest monitoring and global food security…);
• Atmosphere Services (carbon dioxide, methane, carbon monoxide, ultraviolet radiation, ozone layer…);
• Emergency Services (floods, fires, natural disasters, accidents, humanitarian aid…);
• Climate Change Services (historical data comparison, heat transport…);
• Security Services (monitoring illegal activities, border control, nuclear capabilities and infrastructures, critical assets...).

Additionally Space Borne Radars for real-time surveillance is still a technical challenge in terms of required economical budget for the analysis, design, development and testing. Nevertheless there are gaps between governmental needs and low-TRL resources to overcome such technical challenges.

It is in this framework that SIMTISYS was performed, trying to answer the important question: in which circumstances the Space component can undoubtedly and actively support the emergency response? In which circumstances the Space component has limits?

Several parallel activities during SIMTISYS duration were conducted in Europe on this topic, in some cases also experiments were successfully performed, demonstrating the efficacy of the contribution to early warning the monitoring and controlling authorities by means of Change Detection method, duly performed by the state of the art Space constellations (both commercial and Dual-Use). SIMTISYS’s mandate was relative to the investigation of the limits of the actual Space capabilities to indicate the way to proceed for the future Space constellation constellations.
SIMTISYS obtained the expected results having elaborated a simulator of the techniques and technologies performances required to comply with the user requests. Moreover SIMTISYS elaborated a tool targeting the Research Community for the further technical investigation requested in a pre-operational service for the processing of the received images and, in parallel, in a first phase of future constellation design to improve limiting parameter of the actual constellation.

List of Websites:

www.simtisys.eu

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