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DOE OSTI2025

Complete definition of 𝑁 →Δ transition generalized parton distributions

We revisit the definition of the leading-twist chiral-even generalized parton distributions (GPDs) for 𝑁 →Δ baryon transitions. We identify and address deficiencies in previous definitions of the transition GPDs inspired by the transition form factors of the vector and axial vector currents. Through systematic analysis of all possible covariant structures, respecting discrete symmetries and the baryon spinor equations of motion, we derive complete sets of independent structures for the transition matrix elements of the vector and axial vector partonic operators. They contain additional structures proportional to the light-cone vector, corresponding to transition GPDs of vanishing first moment, which were not included in previous parametrizations. Their presence is confirmed independently by the light-front multipole expansion and the cross-channel SO(3) partial-wave analysis of the transition matrix elements. Our analysis provides a complete definition of the 𝑁 →Δ transition GPDs for use in theoretical and phenomenological studies.

baryons↗

NASA NTRS1972

Atmosphere explorer missions C, D, and E. Spacecraft experiment interface definition study

The Atmosphere Explorer Missions C, D, & E Spacecraft/Experiment Interface Definition Study is discussed. The objectives of the study included an analysis of the accommodation requirements of the experiments for the three missions, an assessment of the overall effect of these requirements on the spacecraft system design and performance, and the detailed definition of all experiment/spacecraft electrical, mechanical, and environmental interfaces. In addition, the study included the identification and definition of system characteristics required to ensure compatibility with the consolidated STADAN and MSFN communications networks.

Source record↗

NASA NTRS1972

Astronomy sortie missions definition study. Volume 2, book 1: Astronomy sortie program technical report

The work performed to arrive at a baseline astronomy sortie mission concept is summarized. The material includes: (1) definition of the telescopes and arrays; (2) preliminary definition of mission and systems; (3) identification, definition, and evaluation of alternative sortie programs; (4) the recommended astronomy sortie program; and (5) the astronomy sortie program concept that was approved as a baseline for the remainder of the project.

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NASA NTRS1977

Feasibility and systems definition study for microwave multi-application payload (MMAP)

There were three Shuttle/Spacelab experiments: adaptive multibeam phased array antenna (AMPA) experiment, electromagnetic environment experiment (EEE), and millimeter wave communications experiment (MWCE). Work on the AMPA experiment was completed. Results included are definition of operating modes, sequence of operation, radii of operation about several ground stations, signal format, foot prints of typical orbits and preliminary definition of ground and user terminals. Definition of the MOD I EEE included conceptual hardware designs, spacelab interfaces, preliminary data handling methods, experiment tests and verification, and EMC studies. The MWCE was defined conceptually for a steerable high gain antenna.

Horton, J. B.↗

NASA NTRS1981

Satellite Power Study (SPS) concept definition study (Exhibit D). Volume 1: Executive summary

Efforts concentrated on updating of the Rockwell reference concept, definition of new system options, studies of special emphasis topics, further definition of the transportation system, and further program definition. The Rockwell reference satellite concept has a gallium arsenide (GaAs) solar cell array having flat concentrators with an effective concentration ratio of 1.83at end of life. Alternatives to this concept includes solid state power amplifiers or magnetrons for dc/RF conversion and multibandgap solar cells for solar to dc energy conversion. Two solid state concepts were studied. It was determined that the magnetron approach was the lowest mass and cost system.

Hanley, G. M.↗

NASA NTRS1981

Satellite Power Systems (SPS) concept definition study (Exhibit D). Volume 7: System/subsystems requirements databook

This volume summarizes the basic requirements used as a guide to systems analysis, and is a basis for the selection of candidate Satellite Power Systems (SPS) point designs. Initially, these collected data reflected the level of definition resulting from the evaluation of a broad spectrum of SPS concepts. As the various concepts matured, these requirements were updated to reflect the requirements identified for the projected satellite system/subsystem point designs. Included is an updated version of earlier Rockwell concepts using klystrons as the specific microwave power amplification approach, as well as a more in-depth definition, analysis and preliminary point design on two concepts based on the use of advanced solid state technology to accomplish the task of high power amplification of the 2.45 GHz transmitted power beam to the Earth receiver. Finally, a preliminary definition of a concept using magnetrons as the microwave power amplifiers is presented.

Hanley, G. M.↗

NASA NTRS1981

Definition of optical systems payloads

The various phases in the formulation of a major NASA project include the inception of the project, planning of the concept, and the project definition. A baseline configuration is established during the planning stage, which serves as a basis for engineering trade studies. Basic technological problems should be recognized early, and a technological verification plan prepared before development of a project begins. A progressive series of iterations is required during the definition phase, illustrating the complex interdependence of existing subsystems. A systems error budget should be established to assess the overall systems performance, identify key performance drivers, and guide performance trades and iterations around these drivers, thus decreasing final systems requirements. Unnecessary interfaces should be avoided, and reasonable design and cost margins maintained. Certain aspects of the definition of the Advanced X-ray Astrophysics Facility are used as an example.

Downey, J. A., III↗

NASA NTRS1981

Comparison of sigma(o) obtained from the conventional definition with sigma(o) appearing in the radar equation for randomly rough surfaces

A comparison is made of the radar cross section of rough surface calculated in one case from the conventional definition and obtained in the second case directly from the radar equation. The validity of the conventional definition representing the cross section appearing in the radar equation is determined. The analysis is executed in the special case of perfectly conducting, randomly corrugated surfaces in the physical optics limit. The radar equation is obtained by solving for the radiation scattered from an arbitrary source back to a colocated antenna. The signal out of the receiving antenna is computed from this solution and the result put into a form recognizeable as the radar equation. The conventional definition is obtained by solving a similar problem but for backscatter from an incident planewave. It is shown that these tow forms for sigma are the same if the observer is far enough from the surface.

Levine, D. M.↗

NASA NTRS1981

Semantic definitions of space flight control center languages using the hierarchical graph technique

In this paper a method is described by which the semantic definitions of the Goddard Space Flight Control Center Command Languages can be specified. The semantic modeling facility used is an extension of the hierarchical graph technique, which has a major benefit of supporting a variety of data structures and a variety of control structures. It is particularly suited for the semantic descriptions of such types of languages where the detailed separation between the underlying operating system and the command language system is system dependent. These definitions were used in the definition of the Systems Test and Operation Language (STOL) of the Goddard Space Flight Center which is a command language that provides means for the user to communicate with payloads, application programs, and other ground system elements.

Zaghloul, M. E.↗

NASA NTRS1985

Space Station data system analysis/architecture study. Task 1: Functional requirements definition, DR-5

The initial task in the Space Station Data System (SSDS) Analysis/Architecture Study is the definition of the functional and key performance requirements for the SSDS. The SSDS is the set of hardware and software, both on the ground and in space, that provides the basic data management services for Space Station customers and systems. The primary purpose of the requirements development activity was to provide a coordinated, documented requirements set as a basis for the system definition of the SSDS and for other subsequent study activities. These requirements should also prove useful to other Space Station activities in that they provide an indication of the scope of the information services and systems that will be needed in the Space Station program. The major results of the requirements development task are as follows: (1) identification of a conceptual topology and architecture for the end-to-end Space Station Information Systems (SSIS); (2) development of a complete set of functional requirements and design drivers for the SSIS; (3) development of functional requirements and key performance requirements for the Space Station Data System (SSDS); and (4) definition of an operating concept for the SSIS. The operating concept was developed both from a Space Station payload customer and operator perspective in order to allow a requirements practicality assessment.

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NASA NTRS1984

Space platform expendables resupply concept definition study. Volume 3: Work breakdown structure and work breakdown structure dictionary

The work breakdown structure (WBS) for the Space Platform Expendables Resupply Concept Definition Study is described. The WBS consists of a list of WBS elements, a dictionary of element definitions, and an element logic diagram. The list and logic diagram identify the interrelationships of the elements. The dictionary defines the types of work that may be represented by or be classified under each specific element. The Space Platform Expendable Resupply WBS was selected mainly to support the program planning, scheduling, and costing performed in the programmatics task (task 3). The WBS is neither a statement-of-work nor a work authorization document. Rather, it is a framework around which to define requirements, plan effort, assign responsibilities, allocate and control resources, and report progress, expenditures, technical performance, and schedule performance. The WBS element definitions are independent of make-or-buy decisions, organizational structure, and activity locations unless exceptions are specifically stated.

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NASA NTRS1988

Accuracy study of the Upper Atmosphere Research Satellite (UARS) definitive attitude determination

The Upper Atmosphere Research Satellite (UARS) has two definitive attitude determination requirements: the definitive attitude of the Modular Attitude Control Subsystem (MACS) and the definitive attitude of the gimbaled Solar-Stellar Pointing Platform (SSPP). The onboard computer (OBC) will compute the MACS attitude using a Kalman filter and will transform this attitude solution through the SSPP gimbals to calculate the SSPP attitude. The attitude ground support system (AGSS) will compute the MACS attitude using a batch least-squares differential corrector algorithm and will also transform this solution through the gimbals to obtain the SSPP attitude. This paper reports the results of a prelaunch study to predict the accuracy of the OBC attitude solutions and the accuracy of the AGSS attitude solutions. The OBC and AGSS solution accuracies are then compared to establish the relative quality. The effects of star observability, sensor noise, and sensor misalignment uncertainties on attitude determination accuracy are analyzed for each case.

Snow, Frank↗

NASA NTRS1989

NASA in-house Commercially Developed Space Facility (CDSF) study report. Volume 1: Concept configuration definition

The results of a NASA in-house team effort to develop a concept definition for a Commercially Developed Space Facility (CDSF) are presented. Science mission utilization definition scenarios are documented, the conceptual configuration definition system performance parameters qualified, benchmark operational scenarios developed, space shuttle interface descriptions provided, and development schedule activity was assessed with respect to the establishment of a proposed launch date.

Deryder, L. J.↗

NASA NTRS1991

Resolution of differences between collision number definitions in particle and continuum simulations

The use of the same symbol, Z, representing a 'collision number' for thermal relaxation, has led to confusion regarding its definition in the context of both continuum and particle simulations. Examination of the relaxation mechanics employed in particle simulations demonstrates that these definitions differ by a numerical factor that depends upon the intermolecular potential. Particle and continuum simulations employing appropriate definitions of Z lead to identical results during isothermal and adiabatic stationary relaxation.

Lumpkin, Forrest E., III↗

NASA NTRS1993

NASA assurance terms and definitions

This publication provides a compendium of commonly used safety, reliability, maintainability, and quality assurance (SRM&QA) definitions to ensure standardized assurance communications among NASA Field Installations, Headquarters, and contractors. This list of standard assurance terms and definitions shall be utilized by all NASA organizations and contractors. Program/project tailoring of these definitions may be permitted for specific program applications.

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NASA NTRS1992

Definition of the Spatial Resolution of X-Ray Microanalysis in Thin Foils

The spatial resolution of X-ray microanalysis in thin foils is defined in terms of the incident electron beam diameter and the average beam broadening. The beam diameter is defined as the full width tenth maximum of a Gaussian intensity distribution. The spatial resolution is calculated by a convolution of the beam diameter and the average beam broadening. This definition of the spatial resolution can be related simply to experimental measurements of composition profiles across interphase interfaces. Monte Carlo calculations using a high-speed parallel supercomputer show good agreement with this definition of the spatial resolution and calculations based on this definition. The agreement is good over a range of specimen thicknesses and atomic number, but is poor when excessive beam tailing distorts the assumed Gaussian electron intensity distributions. Beam tailing occurs in low-Z materials because of fast secondary electrons and in high-Z materials because of plural scattering.

Williams, D. B.↗

NASA NTRS1999

An Intercomparison of Ground, Airborne, and Space Instrumentation Definitions of the Lightning Element

For the past century, scientists have made quantitative measurements of lightning discharges. In the process, they refined the definition of a lightning unit, or basic quantum of lightning, in order to base it on observable parameters. In this paper, we will use cluster analysis to derive a basic spatial and temporal definition or scale length for the unit of lightning. We will use data from three different systems that detected pulses from the same storm complex over Central Oklahoma during June, 1998. Since the different instruments detect lightning in different ways with different resolutions, there may not be a single definition of the unit of lightning that can be applied to all three systems. However, common components can be found since all instrumentation are detecting aspects of the same phenomenon.

Mach, Douglas↗

NASA NTRS2003

Inconsistent Definitions of the Pressure-Coupled Response and the Admittance of Solid Propellants

When an acoustic wave is present in a solid propellant combustion environment, the mass flux from the combustion zone oscillates at the same frequency as the acoustics. The acoustic wave is either amplified or attenuated by the response of the combustion to the acoustic disturbance. When the acoustic wave is amplified, this process is called combustion instability. The amplification is quantitatively measured by a response function. The ability to predict combustion stability for a solid propellant formulation is essential to the formulator to prevent or minimize the effects of instabilities, such as an oscillatory thrust. Unfortunately, the prediction of response values for a particular propellant remains a technical challenge. Most predictions of the response of propellants are based on test data, but there are a number of questions about the reliability of the standard test method, the T-burner. Alternate methods have been developed to measure the response of a propellant, including the ultrasound burner, the magnetic flowmeter and the rotating valve burner, but there are still inconsistencies between the results obtained by these different methods. Aside from the experimental differences, the values of the pressure-coupled responses obtained by different researchers are often compared erroneously, for the simple reason that inconsistencies in the definitions of the responses and admittances are not considered. The use of different definitions has led to substantial confusion since the first theoretical treatments of the problem by Hart and McClure in 1959. The definitions and relations derived here seek to alleviate this problem.

Cardiff, Eric H.↗