Naval Research Laboratory Space Systems Development Division

The high temperature superconductivity space experiment (HTSSE) program, initiated by the Naval Research Laboratory (NRL) in 1988, is described. The HTSSE program focuses high temperature superconductor (HTS) technology applications on space systems. The program phases, goals, and objectives are discussed. The devices developed for the HTSSE-II phase of the program and their suppliers are enumerated. Eight space-qualified components were integrated as a cryogenic experimental payload on DOD's ARGOS spacecraft. The payload was designed and built using a unique NRL/industry partnership and was integrated and space-qualified at NRL.

The Mobile Imaging and Spectroscopic Threat Identification (MISTI) system developed to locate radiological threats in urban and rural environments is currently undergoing characterization activities. MISTI is a mobile source detection and imaging system designed to identify and localize a radiological source to within +/- 10 m in range. This requirement is based on a 1 mCi Cs-137 source at 100 m in 20s, while maintaining a false alarm rate of less than one per day. MISTI utilizes the cost effective collection power of NaI for imaging and the sensitivity of high resolution HPGe for spectroscopy. MISTI's data acquisition system was developed with the latest commercially availed hardware that met MISTI's requirements. The performance of crucial software and hardware components is presented along with overall system performance. A synopsis and example of the initial characterization results are presented here.

The paper presents a methodology for optimizing the design of large, complex, real-time systems in distributed and parallel processing environments. It can be used as a front-end component in a prototyping process providing increased capabilities for system engineers. The method incorporates various optimization approaches including: heuristic, probabilistic, deterministic, and hybrids. These approaches are applied to the system design structuring techniques and resource allocation techniques to perform optimization and trade-off based on the classes of rules, classes of objective functions, classes of algorithms, sets of analytical equations, and sets of probabilistic reasoning, This method optimizes the system design structure and generates a near-optimal allocation of the logical systems functions onto the implementation resources to meet the overall system requirements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characteristic gamma-radiation can be used to identify radiological threats, however gamma-ray detection and imaging is extremely difficult due to the low interaction probability and inability to focus high energy photons. MISTI’s hybrid system combines the exceptional spectroscopic capabilities of germanium with the cost effective collection power of a large volume sodium iodide imaging array. The system is a mobile, self contained, gamma-ray spectroscopy and imaging system for detecting radiological threats. While moving, the MISTI system is designed to detect sources of nuclear materials, such as a 1mCi Cs-137 source at distances up to 100m in 20s. The spectroscopic identification is performed using a 28 detector germanium array, which in turn triggers imaging using a 10x10 sodium iodide array, when a source is detected. The project is composed of commercial off the shelf technology, allowing a quicker transition from the design phase to the construction phase, reducing total cost. The data from the sensor will be analyzed in real time on board the vehicle and is combined with images and data from other instruments to provide users with a visual location of the source. MISTI’s unique design reduces false alarms, while improving weak source location and identification in urban and rural environments.

The view of a complex real-time computer-based application system as one in which not only automated machine components are embedded but also human servers, especially those who perform time-sensitive tasks in close interaction with machine components, are "embedded" as components, is adopted. Efforts for optimal scheduling of executing components can then be applied not only to the machine components but also to embedded human operators, preferably in a uniform integrated fashion. The notion of the risk incursion function (RIF) introduced earlier by the authors is advocated as the guide for optimal allocation of both machine and human resources. Also, an approach to uniform representation of application environments, machine functions and components, and human functions and components in the form of a uniform network of real-time objects is advocated.

The Naval Research Laboratory (NRL) has developed a multi-channel, multi-mode, multi-band modular communications terminal called the Joint Combat Information Terminal (JCIT). The JCIT is the heart of the communications system for the Army Airborne Command and Control System (A2C2S). The production-ready JCIT has been field tested by the US Marine Corps (USMC) in command and control variants of the Light Armored Vehicle (LAV) and Amphibious Assault Vehicle (AAV). The functionality, expandability, and modularity of JCIT provide state-of-the-art communications for military and civil agencies. Interoperability with SINCGARS, HAVE QUICK, HF, National Satellite Intelligence Broadcasts, military precision GPS, IEEE-802.11, direct broadcast by satellite (DBS/GBS), air traffic control, police, fire, and civil maritime has been demonstrated in the field and in the laboratory. The JCIT architecture was designed to meet current and future military command, control, communications, computers, and intelligence (C41) requirements. It provides a total communications system solution from the antenna to the user the modules developed for the JCIT are not proprietary. The architecture is built from a common set of hardware and software modules. Software allows the hardware to interoperate with other legacy or future radio systems on operator command hardware and software insertion to meet future requirements is supported by the architecture. The architecture is readily adaptable to new platforms, utilizing unchanged hardware and software modules. Although the architecture is not considered "open" by the industry standards, full Government owned interface control documents exist that allow any third party to build hardware or software components for the system. Eight-channel vehicular/airborne units and two-channel vehicular/manpack units have been built. These units share hardware modules and software applications without modification.

Successful satellite operations often depend on the ability to precisely determine the satellite's position throughout it's operational lifetime. Often, simplified models are used to reduce the computational complexity when producing an orbit determination solution. One example is the use of lower order gravitational terms when computing the state transition matrix. The US Naval Research Laboratory's Orbit Covariance Estimation and Analysis software is used to characterize the affects of using the full order geopotential terms when calculating the state transition matrix. Orbit solutions are calculated for several geodetic satellite using satellite laser ranging data. The RMS of the error residual and number of iterations needed for convergence are used as metric to evaluate the difference of using the full order geopotential to calculate the state transition matrix. It is found that typically the RMS error is the same when the higher order gravitational terms are used; however, the number of iterations needed for convergence are often lower. Additionally, the difference in the orbit solution between both methods is examined. Surprisingly, these orbit solutions may differ by up to several meters. This indicates that the higher order gravitational terms should always be considered when calculating the state transition matrix. Because fewer iterations are often needed, this can result in an overall decrease in computational time required.