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NASA NTRS1994

Agent oriented programming

The goal of our research is a methodology for creating robust software in distributed and dynamic environments. The approach taken is to endow software objects with explicit information about one another, to have them interact through a commitment mechanism, and to equip them with a speech-acty communication language. System-level applications include software interoperation and compositionality. A government application of specific interest is an infrastructure for coordination among multiple planners. Daily activity applications include personal software assistants, such as programmable email, scheduling, and new group agents. Research topics include definition of mental state of agents, design of agent languages as well as interpreters for those languages, and mechanisms for coordination within agent societies such as artificial social laws and conventions.

Shoham, Yoav↗

NASA NTRS1994

Lunar base heat pump

A heat pump is a device which elevates the temperature of a heat flow by a means of an energy input. By doing this, the heat pump can cause heat to transfer faster from a warm region to a cool region, or it can cause heat to flow from a cool region to a warmer region. The second case is the one which finds vast commercial applications such as air conditioning, heating, and refrigeration. Aerospace applications of heat pumps include both cases. The NASA Johnson Space Center is currently developing a Life Support Systems Integration Facility (LSSIF, previously SIRF) to provide system-level integration, operational test experience, and performance data that will enable NASA to develop flight-certified hardware for future planetary missions. A high lift heat pump is a significant part of the TCS hardware development associated with the LSSIF. The high lift heat pump program discussed here is being performed in three phases. In Phase 1, the objective is to develop heat pump concepts for a lunar base, a lunar lander, and for a ground development unit for the SIRF. In Phase 2, the design of the SIRF ground test unit is being performed, including identification and evaluation of safety and reliability issues. In Phase 3, the SIRF unit will be manufactured, tested, and delivered to the NASA Johnson Space Center.

Goldman, Jeffrey H.↗

NASA NTRS1995

Stellar Interferometer Technology Experiment (SITE)

The MIT Space Engineering Research Center and the Jet Propulsion Laboratory stand ready to advance science sensor technology for discrete-aperture astronomical instruments such as space-based optical interferometers. The objective of the Stellar Interferometer Technology Experiment (SITE) is to demonstrate system-level functionality of a space-based stellar interferometer through the use of enabling and enhancing Controlled-Structures Technologies (CST). SITE mounts to the Mission Peculiar Experiment Support System inside the Shuttle payload bay. Starlight, entering through two apertures, is steered to a combining plate where it is interferred. Interference requires 27 nanometer pathlength (phasing) and 0.29 archsecond wavefront-tilt (pointing) control. The resulting 15 milli-archsecond angular resolution exceeds that of current earth-orbiting telescopes while maintaining low cost by exploiting active optics and structural control technologies. With these technologies, unforeseen and time-varying disturbances can be rejected while relaxing reliance on ground alignment and calibration. SITE will reduce the risk and cost of advanced optical space systems by validating critical technologies in their operational environment. Moreover, these technologies are directly applicable to commercially driven applications such as precision matching, optical scanning, and vibration and noise control systems for the aerospace, medical, and automotive sectors. The SITE team consists of experienced university, government, and industry researchers, scientists, and engineers with extensive expertise in optical interferometry, nano-precision opto-mechanical control and spaceflight experimentation. The experience exists and the technology is mature. SITE will validate these technologies on a functioning interferometer science sensor in order to confirm definitely their readiness to be baselined for future science missions.

Crawley, Edward F.↗

NASA NTRS1994

From neural-based object recognition toward microelectronic eyes

Engineering neural network systems are best known for their abilities to adapt to the changing characteristics of the surrounding environment by adjusting system parameter values during the learning process. Rapid advances in analog current-mode design techniques have made possible the implementation of major neural network functions in custom VLSI chips. An electrically programmable analog synapse cell with large dynamic range can be realized in a compact silicon area. New designs of the synapse cells, neurons, and analog processor are presented. A synapse cell based on Gilbert multiplier structure can perform the linear multiplication for back-propagation networks. A double differential-pair synapse cell can perform the Gaussian function for radial-basis network. The synapse cells can be biased in the strong inversion region for high-speed operation or biased in the subthreshold region for low-power operation. The voltage gain of the sigmoid-function neurons is externally adjustable which greatly facilitates the search of optimal solutions in certain networks. Various building blocks can be intelligently connected to form useful industrial applications. Efficient data communication is a key system-level design issue for large-scale networks. We also present analog neural processors based on perceptron architecture and Hopfield network for communication applications. Biologically inspired neural networks have played an important role towards the creation of powerful intelligent machines. Accuracy, limitations, and prospects of analog current-mode design of the biologically inspired vision processing chips and cellular neural network chips are key design issues.

Sheu, Bing J.↗

NASA NTRS1995

The determination of the constitutive parameters of a medium with application to a reinforced concrete pad

This report describes the experimental and analytical efforts performed to determine the constitutive parameters of a reinforced concrete pad on which an aircraft (the NASA Boeing 757) was parked while its internal electromagnetic environment was measured. This concrete pad is part of the Large Electromagnetic System-Level Illuminator (LESLI) test facility at the Phillips Laboratory, Kirtland Air Force Base, New Mexico. The relative dielectric constant, conductivity, index of refraction, and reflection coefficient have been determined over the frequency range of 0 to 300 MHz and are presented.

Poggio, A. J.↗

NASA NTRS1994

Experience report: Using formal methods for requirements analysis of critical spacecraft software

Formal specification and analysis of requirements continues to gain support as a method for producing more reliable software. However, the introduction of formal methods to a large software project is difficult, due in part to the unfamiliarity of the specification languages and the lack of graphics. This paper reports results of an investigation into the effectiveness of formal methods as an aid to the requirements analysis of critical, system-level fault-protection software on a spacecraft currently under development. Our experience indicates that formal specification and analysis can enhance the accuracy of the requirements and add assurance prior to design development in this domain. The work described here is part of a larger, NASA-funded research project whose purpose is to use formal-methods techniques to improve the quality of software in space applications. The demonstration project described here is part of the effort to evaluate experimentally the effectiveness of supplementing traditional engineering approaches to requirements specification with the more rigorous specification and analysis available with formal methods.

Lutz, Robyn R.↗

NASA NTRS1995

The performance and calibration of WFPC2 on the Huble Space Telescope

The Wide Field Planetary Camera 2 (WFPC2) was installed in the Hubble Space Telescope (HST) in 1993 December. Since then, the instrument has been providing high-quality images. A significant among of calibration data has been collected to aid in the understanding of the on-orbit performance of the instrument. Generally, the behavior of the camera is similar to its performance during the system-level thermal vacuum test at JPL in 1993 May. Surprises were a significant charge-transfer-efficiency (CTE) problem and a significant growth rate in hot pixels at the original operating temperature of the CCDs (-76 deg C). The operating temperature of the WFPC2 CCDs was changed to -88 deg C on 1994 April 23, and significant improvements in CTE and hot pixels are seen at this temperature. In this paper we describe the on-orbit performance of the WFPC2. We discuss the optical and thermal history, the instrument throughput and stability, the Point Spread Function (PSF), the effects of undersampling on photometry, the properties of cosmic rays observed on-orbit, and the geometric distortion in the camera. We present the best techniques for the reduction of WFPC2 data, and describe the construction of calibration products including superbiases, superdarks, and flat fields.

Holtzman, Jon↗

NASA NTRS1995

Mississippi State University Center for Air Sea Technology FY95 Research Program

The Mississippi State University (MSU) Center for Air Sea Technology (CAST) evolved from the Institute for Naval Oceanography's (INO) Experimental Center for Mesoscale Ocean Prediction (ECMOP) which was started in 1989. MSU CAST subsequently began operation on 1 October 1992 under an Office of Naval Research (ONR) two-year grant which ended on 30 September 1994. In FY95 MSU CAST was successful in obtaining five additional research grants from ONR, as well as several other research contracts from the Naval Oceanographic Office via NASA, the Naval Research Laboratory, the Army Corps of Engineers, and private industry. In the past, MSU CAST technical research and development has produced tools, systems, techniques, and procedures that improve efficiency and overcome deficiency for both the operational and research communities residing with the Department of Defense, private industry, and university ocean modeling community. We continued this effort with the following thrust areas: to develop advanced methodologies and tools for model evaluation, validation and visualization, both oceanographic and atmospheric; to develop a system-level capability for conducting temporally and ; spatially scaled ocean simulations driven by or are responsive to ocean models, and take into consideration coupling to atmospheric models; to continue the existing oceanographic/atmospheric data management task with emphasis on distributed databases in a network environment, with database optimization and standardization, including use of Mosaic and World Wide Web (WWW) access; and to implement a high performance parallel computing technology for CAST ocean models

Yeske, Lanny↗

NASA NTRS1996

New Antenna Deployment, Pointing and Supporting Mechanism

On ITALSAT Flight 2, the Italian telecommunications satellite, the two L-Ka antennas (Tx and Rx) use two large deployable reflectors (2000-mm diameter), whose deployment and fine pointing functions are accomplished by means of an innovative mechanism concept. The Antenna Deployment & Pointing Mechanism and Supporting Structure (ADPMSS) is based on a new configuration solution, where the reflector and mechanisms are conceived as an integrated, self-contained assembly. This approach is different from the traditional configuration solution. Typically, a rigid arm is used to deploy and then support the reflector in the operating position, and an Antenna Pointing Mechanism (APM) is normally interposed between the reflector and the arm for steering operation. The main characteristics of the ADPMSS are: combined implementation of deployment, pointing, and reflector support; optimum integration of active components and interface matching with the satellite platform; structural link distribution to avoid hyperstatic connections; very light weight and; high performance in terms of deployment torque margin and pointing range/accuracy. After having successfully been subjected to all component-level qualification and system-level acceptance tests, two flight ADPMSS mechanisms (one for each antenna) are now integrated on ITALSAT F2 and are ready for launch. This paper deals with the design concept, development, and testing program performed to qualify the ADPMSS mechanism.

Costabile, V.↗

NASA NTRS1995

Averting Denver Airports on a Chip

As a result of recent advances in software engineering capabilities, we are now in a more stable environment. De-facto hardware and software standards are emerging. Work on software architecture and design patterns signals a consensus on the importance of early system-level design decisions, and agreements on the uses of certain paradigmatic software structures. We now routinely build systems that would have been risky or infeasible a few years ago. Unfortunately, technological developments threaten to destabilize software design again. Systems designed around novel computing and peripheral devices will spark ambitious new projects that will stress current software design and engineering capabilities. Micro-electro-mechanical systems (MEMS) and related technologies provide the physical basis for new systems with the potential to produce this kind of destabilizing effect. One important response to anticipated software engineering and design difficulties is carefully directed engineering-scientific research. Two specific problems meriting substantial research attention are: A lack of sufficient means to build software systems by generating, extending, specializing, and integrating large-scale reusable components; and a lack of adequate computational and analytic tools to extend and aid engineers in maintaining intellectual control over complex software designs.

Sullivan, Kevin J.↗

NASA NTRS1996

Report on Alternative Devices to Pyrotechnics on Spacecraft

Pyrotechnics accomplish many functions on today's spacecraft, possessing minimum volume/weight, providing instantaneous operation on demand, and requiring little input energy. However, functional shock, safety, and overall system cost issues, combined with emergence and availability of new technologies question their continued use on space missions. Upon request from the National Aeronautics and Space Administration's (NASA) Program Management Council (PMC), Langley Research Center (LaRC) conducted a survey to identify and evaluate state-of-the-art non-explosively actuated (NEA) alternatives to pyrotechnics, identify NEA devices planned for NASA use, and investigate potential interagency cooperative efforts. In this study, over 135 organizations were contacted, including NASA field centers, Department of Defense (DOD) and other government laboratories, universities, and American and European industrial sources resulting in further detailed discussions with over half, and 18 face-to-face briefings. Unlike their single use pyrotechnic predecessors, NEA mechanisms are typically reusable or refurbishable, allowing flight of actual tested units. NEAs surveyed include spool-based devices, thermal knife, Fast Acting Shockless Separation Nut (FASSN), paraffin actuators, and shape memory alloy (SMA) devices (e.g., Frangibolt). The electro-mechanical spool, paraffin actuator and thermal knife are mature, flight proven technologies, while SMA devices have a limited flight history. There is a relationship between shock, input energy requirements, and mechanism functioning rate. Some devices (e.g., Frangibolt and spool based mechanisms) produce significant levels of functional shock. Paraffin, thermal knife, and SMA devices can provide gentle, shock-free release but cannot perform critically timed, simultaneous functions. The FASSN flywheel-nut release device possesses significant potential for reducing functional shock while activating nearly instantaneously. Specific study recommendations include: (1) development of NEA standards, specifically in areas of material characterization, functioning rates, and test methods; (2) a systems level approach to assure successful NEA technology application; and (3) further investigations into user needs, along with industry/government system-level real spacecraft cost benefit trade studies to determine NEA application foci and performance requirements. Additional survey observations reveal an industry and government desire to establish partnerships to investigate remaining unknowns and formulate NEA standards, specifically those driven by SMAs. Finally, there is increased interest and need to investigate alternative devices for such functions as stage/shroud separation and high pressure valving. This paper summarizes results of the NASA-LaRC survey of pyrotechnic alternatives. State of-the-art devices with their associated weight and cost savings are presented. Additionally, a comparison of functional shock characteristics of several devices are shown, and potentially related technology developments are highlighted.

Lucy, M. H.↗

NASA NTRS1996

Use of the Collaborative Optimization Architecture for Launch Vehicle Design

Collaborative optimization is a new design architecture specifically created for large-scale distributed-analysis applications. In this approach, problem is decomposed into a user-defined number of subspace optimization problems that are driven towards interdisciplinary compatibility and the appropriate solution by a system-level coordination process. This decentralized design strategy allows domain-specific issues to be accommodated by disciplinary analysts, while requiring interdisciplinary decisions to be reached by consensus. The present investigation focuses on application of the collaborative optimization architecture to the multidisciplinary design of a single-stage-to-orbit launch vehicle. Vehicle design, trajectory, and cost issues are directly modeled. Posed to suit the collaborative architecture, the design problem is characterized by 5 design variables and 16 constraints. Numerous collaborative solutions are obtained. Comparison of these solutions demonstrates the influence which an priori ascent-abort criterion has on development cost. Similarly, objective-function selection is discussed, demonstrating the difference between minimum weight and minimum cost concepts. The operational advantages of the collaborative optimization

Braun, R. D.↗

NASA NTRS1995

Development and Application of the Collaborative Optimization Architecture in a Multidisciplinary Design Environment

Collaborative optimization is a design architecture applicable in any multidisciplinary analysis environment but specifically intended for large-scale distributed analysis applications. In this approach, a complex problem is hierarchically de- composed along disciplinary boundaries into a number of subproblems which are brought into multidisciplinary agreement by a system-level coordination process. When applied to problems in a multidisciplinary design environment, this scheme has several advantages over traditional solution strategies. These advantageous features include reducing the amount of information transferred between disciplines, the removal of large iteration-loops, allowing the use of different subspace optimizers among the various analysis groups, an analysis framework which is easily parallelized and can operate on heterogenous equipment, and a structural framework that is well-suited for conventional disciplinary organizations. In this article, the collaborative architecture is developed and its mathematical foundation is presented. An example application is also presented which highlights the potential of this method for use in large-scale design applications.

Braun, R. D.↗

NASA NTRS1995

Reengineering the JPL Spacecraft Design Process

This presentation describes the factors that have emerged in the evolved process of reengineering the unmanned spacecraft design process at the Jet Propulsion Laboratory in Pasadena, California. Topics discussed include: New facilities, new design factors, new system-level tools, complex performance objectives, changing behaviors, design integration, leadership styles, and optimization.

Spacecraft Design Reengineering JPL↗

NASA NTRS1994

Flight System Testbed for Low Cost Spacecraft Interface Evaluation

A world leader in space technology, JPL has over 30 years experience in developing spacecraft systems and managing deep space missions for NASA. Future scientific missions will require the rapid development of small, lightweight, high-technology, low-cost spacecraft. JPL is developing a method of meeting these requirements: a test facility specifically for supporting a rapid prototyping development environment that creates a virtual (simulated) spacecraft in which system-level evaluations of components can be carried out very early in the development cycle, long before an actual spacecraft is built.

flight system testbed component evaluation reengin↗

NASA NTRS1994

Initiating Formal Requirements Specifications with Object-Oriented Models

This paper reports results of an investigation into the suitability of object-oriented models as an initial step in developing formal specifications. The requirements for two critical system-level software modules were used as target applications. It was found that creating object-oriented diagrams prior to formally specifying the requirements enhanced the accuracy of the initial formal specifications and reduced the effort required to produce them. However, the formal specifications incorporated some information not found in the object-oriented diagrams, such as higher-level strategy or goals of the software.

requirements specifications↗

NASA NTRS1994

Experience Report: Using Formal Methods for Requirements Analysis of Critical Spacecraft Software

Formal↗

NASA NTRS1993

Recent Progress in Deep Space Optical Communications

Progress in the NASA-funded optical communications program at the Jet Propulsion Laboratory (JPL) is decribed. This decription includes a system-level breadboard for an optical communications flight package, the planning for the Earth-reception facilities, and the results of a recent optical communications experiment to deep space with the Galileo spacecraft.

Voyager↗