Numerical modeling of the expansion of electric thruster plumes provides direct means for predicting spacecraft surface contamination and erosion due to plume ions. A software package named COLISEUM that is capable of self-consistently modeling plasma propagation and interactions with arbitrary 3-D surfaces is being developed by a national team of researchers. Despite much research and development in modeling plume expansion, it is necessary to continuously validate these codes using laboratory based experimental data. It is well-established that vacuum chamber facilities affect the plume of these devices. Thus, the models must not only describe the plume expansion, but also effects of the vacuum chamber. COLISEUM has been designed to simulate both vacuum chamber configurations and spacecraft geometries. This work presents a study that compares results from a hybrid particle-in-cell model (AQUILA) with Monte Carlo collisions to data obtained from the plume of Busek 600W Hall thruster (BHT-HD-600). This data includes current density, ion velocities, and energy distribution data. Also contained in this work is a source derivation description from laser induced fluorescence (LIF) data.

To better characterize the potential impacts on a spacecraft during operation of a Busek Company, Inc. BHT-HD-600 laboratory Hall thruster, a number of plume properties have been measured. These measurements include current density using a Faraday probe, ion energy distribution using a retarding potential analyzer and ion species fractions using an E×B probe. Developed by Busek Co., Inc. for the U.S. Air Force Research Laboratory, the BHT-HD-600 Hall thruster is a nominally 600 W xenon Hall thruster. Plume characterization of Hall thrusters is required to fully understand the impacts of thruster operation on spacecraft. Much of these plume data are vital inputs for numerical models that can then be applied to estimate the effect of the energetic plume on complex spacecraft geometries. Early measurement of plume properties, such as plume divergence, ion energy distribution and species fractions, aids the timely transfer of Hall thruster technology to the user. The plume’s ion beam was characterized by measurement of ion current density radial profiles, ionic energy spectra and ion species fraction distributions. Measurements were recorded ±90 off thruster centerline at 60 cm from the discharge. It was determined slight variations in anode potential and mass-flow produced a measurable effect on ion current density and plume divergence, experimentally showing an increase or decrease of 15 − 20%. Ionic energy spectra demonstrated both inelastic and elastic scattering within the plume. The measurements reveal significant populations of multiply-charged ions in the plume. E×B probe measurements show surprisingly ion species fraction angle dependence.

When a nonlinear integral with respect to a signed fuzzy measure is used in multiregression, people face a serious problem that, comparing to the number of variables (attributes), there are exponentially many unknown parameters in the model. However, in many real-world problems, the higher-order interactions among the variables can be omitted, and then only consider the second-order one with an acceptable small error in the result. Thus, a 2-additive measure based on the Mobius transformation and its inverse can be used to replace the signed fuzzy measure. In such a way, the complexity of the computation will be significantly reduced.

This paper presents the technical and policy issues, architectural considerations, ongoing assessment results, and plans for Distributed Mission Operations Network (DMON) multi-level security (MLS) implementation. In this paper, the Combat Air Force (CAF) Distributed Mission Operations (DMO) Operations and Integration (O&I) team builds on previous Combat Air Force Distributed Mission Operations Multi-Level Security feasibility research and recommendations. Combat Air Force Distributed Mission Operations involves simulations built from components provided by independent vendors for different training communities. The Combat Air Force Distributed Mission Operations MLS problem comes when not all participants have the appropriate clearances for all information. There is a need for aircrews with different capabilities at different security levels, need-to-know, and categories to train together. MLS for simulation is a very challenging problem, not yet solved globally, yet critical to accurate representation of war fighting to distributed audiences at different security levels

Effects Based Operations (EBO) analysis tools are important in assisting the analyst in determining whether or not a Course of Action (COA) will meet the stated Commander's intent and whether it is having negative, unintended consequences. Currently, assessment efforts are focused more on combat effects, than they are on overall campaign effects. In addition, current COA Analysis tools are limited in their ability to integrate effects across domains - from power to water, or gas to transportation for example. In this paper, we describe an open architecture EBO assessment capability that may be used in either a planning role or as a real-time operations assessment tool to address the needs described above. Our research is based on SPARTA's modeling framework - the Net-Centric Effects-based operations MOdel (NEMO). NEMO treats the opponent's infrastructures as a system of networks representing the critical domains, such as electrical power, telecommunications, transportation, gas, water using 'Best-of-Breed' industry standard simulations. NEMO also uses Net-Centric enterprise service approaches (e.g., discovery, messaging, software agents, Geospatial Information System (GIS) Shape files and is built using the Commercial Joint Mapping Toolkit (CJMTK)) to capture and model the relationships between various parts of these networks that represent their real-world interdependencies.

In this paper, we discuss NETE -- a Net-Centric Warfare (NCW) End-to-End model. NETE is a medium fidelity constructive simulation of the Global Information Grid (GIG) infrastructure, Service networks, and their integrated operations in support of definable mission areas. For example, NETE represents netted fires and other mission threads, and the enabling C2 as supported by the 'network of networks'. NETE includes representation of Internet Protocol (IP) based GIG infrastructure and interoperability with current tactical networks, like Link-16. The NETE model provides a means to assess the ability of a defined network to support a concept of operations with resource management to allow the assessment of latencies under varying loads. System loading is accomplished by a generation of background traffic or through sensitivity analyses where the threat level is adjusted. NETE also calculates the impact of network 'jitter' on mission timelines. The fidelity and specific nature of the model is extensible by the operator. To date, we have modeled Transformational Communications supporting missile search operations, missile defense engagement operations, architectures for Responsive Space Operations and Homeland Security. NETE provides a new tool to assess future C2 concepts and architectures as supported by emerging GIG infrastructure and Service NCW networking capabilities.

Today's military operates almost exclusively through coalition operations. The reality of operating in coalitions poses increasing operational, managerial and security issues. This mandates effective, efficient and assured information sharing among coalition partners, while preserving security for sensitive information. New group security protocols have been developed which provide full end-to-end (publisher-to-consumer) information security. Current point-to-point protocols only provide connection-level security, resulting in a loss of end-to-end security services when used with multiparty servers. These point-topoint systems only secure data between users and servers, with no rigorous method to define or enforce synchronized group security policy, or to provide secure end-to-end associations directly between users. In this paper, we will discuss a new generation of group security protocols and standards that have caught up with the requirements for 'Assured Sharing', while simultaneously enabling flexible group key management. The Group Secure Association Key Management Protocol (GSAKMP) provides a standard for distributing cryptographic keys as well as a trustable architecture for defining and enforcing group security policy. With this functionality, a new class of secure group applications for content-based approaches, such as Secure Group Objects (SGO) can provide end-to-end security services to coalitions, resulting in increased network infrastructure performance while simultaneously enhancing overall security.

Net-Centric Operations (NCO) require highly distributed data, applications and personnel across the military Services and agencies. The vision is that data will seamlessly pass between multiple levels of security as warfighters search for and publish/subscribe to services and data. At the center of this new enterprise architecture is the discovery of services. Discovery is one of the "core services" identified for the Global Information Grid (GIG) and is an essential element for legacy applications to migrate from stovepipes to services. It also enables runtime integration and self-assembling networks, which are critical for ad hoc communities of interest (COIs). The most challenging problem in Discovery is in the discovery of services (vice people or data), which relies on the technology of Universal Description and Discovery Integration (UDDI) registries. In this paper, we discuss the gap between vision and reality and describe our research and testing of technology options for Discovery. We begin with a description of the three most common discovery methods (e.g., centralized, decentralized and semi-centralized). We then address interoperability among various UDDI vendors and application program interfaces (APIs) and identify the strengths and weaknesses of each discovery method. Finally, we recommend an approach for a near-term, robust system.

Implementing an effective Missile Defense plan in a Network Centric environment requires a robust collaboration scheme compatible with multiple military models and simulations. Many technology breakthroughs have occurred allowing defense plans to be rapidly exchanged with C2 systems distributed around the Globe. However, the issue of interpreting the data properly within each C2 model or simulation component remains a stumbling block to effective planning. This paper describes a global collaboration approach using the eXtensible Mark-up Language (XML) to create and validate the plans. Experimentation performed using this approach, by allowing plans to be distributed using a Java Message Service (JMS) or provided by web services, is described to highlight the issues with netted sensors and weapons in military planning. An approach to resolving this issue through a higher level NCW model of the architecture supported by tactical element web services is shown.

Scientists at the National Institute of Standards and Technology (NIST) And SPARTA Inc. (Rosslyn, VA) have developed a technique that uses far-infrared radiation to identify bulk or airborne materials inside sealed paper or plastic containers. Applications in homeland security include detection of explosives in the mail and other non-metallic portable containers. A far-infrared light source is directed at a sample in a closed container. After the light transmitted through the materials is detected, the light absorbed by the sample is analyzed. Adjustments are made for light absorbed by the container. The two instruments employed, one using a pulsed laser and the other a glowing filament, are tabletop-sized and work at room temperature. The pattern of light frequencies, or spectra, absorbed by a material depends specifically on the vibrations of the material's atoms and its crystalline structure. The technique detects aerosols, pharmaceutical powders, gases, several explosives, and other materials. The researchers have also compiled a database of spectral characteristics for more than 100 materials, and developed an automated software tool for rapidly identifying bulk materials based on their absorption spectra.