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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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System and component models for spacecraft thermal control design, considering materials, environmental degradation, measurement errors, manufacturing and quality assurance
Atmospheric transmittance measurement errors in determining temperature, water vapor and ozone distributions from satellite remote sensing
Radio frequency switching technique for single receiver and data processing channel to be used for phase movement measurement is discussed. Components of interferometer radio frequency unit, X-band receiver, and interferometer data processing unit are illustrated. Elimination of major measurement error source is described.
The history of the Apollo very-high-frequency ranging system development program is presented from the program-planning stage through the final-test and flight-evaluation stages. Block diagrams of the equipment are presented, and a description of the theory of operation is outlined. A sample of the distribution of errors measured in the aircraft-flight test program is included. The report is concluded with guidelines or recommendations for the management of development programs having the same general constraints.
Description of a roll angle detector system under development that is designed to measure the relative roll angle of two independent bodies to a high degree of precision. The system involves the imaging of a very small aperture by an optical system on one body onto the surface of the other. A review of the underlying mathematical principle, is followed by an optical-mechanical and electrical description of the system and a listing of several important sources of measurement errors. The ultimate achievement of an accuracy of plus or minus 5 arc seconds is expected.
By using a numerical iterative method, it is demonstrated that the mixing ratio H2/He on the giant planets can be inferred from spectral measurements of the intensity emitted by these planets in the far infrared range. The method is successfully applied to synthetic spectra of Saturn computed from atmospheric thermal models. The effect of random and systematic measurement errors on the determination of the mixing ratio is also studied.
Soundings and imaging measurements from geostationary satellites are presented. The subjects discussed are: (1) meteorological data processing techniques, (2) sun glitter, (3) cloud growth rate study, satellite stability characteristics, and (4) high resolution optics. The use of perturbation technique to obtain the motion of sensors aboard a satellite is described. The most conditions, and measurement errors. Several performance evaluation parameters are proposed.
Parameters for a lumped linear model approximating a distributed elastic structure are determined from dynamic test data comprised of several mode shapes and frequencies. Measurement errors, nonlinear response, and nonmeasurable quantities such as mode slope components are accommodated. Some mass and stiffness parameters may be known accurately, whereas the remainder are to be estimated. The method entails minimizing a quadratic function of the difference between corresponding modes and frequencies of the theoretical model and the test specimen. This technique was applied to some actual vibration test data, and the special techniques that are required to overcome convergence problems are described.
The growth of the field of system identification is discussed along with changes in methodology which have taken place in recent years. The similarity between pattern recognition and system identification is pointed out, involving the modelling in the latter and the feature selection problem in the former. It is stated that once a model is formulated, including the disturbances and measurement errors, the parameter finding can be formulated as a statistical estimation problem. The various techniques and their application are discussed.
The apparent gradual increase of particles in the atmosphere has received considerable attention in recent years due to the possible effect of atmospheric aerosols on the earth's climate. The ERTS-1 satellite offered the opportunity of determining the feasibility of monitoring the atmospheric aerosol content on a global basis, as suggested by theoretical studies, which showed a linear relationship between the upwelling earth atmosphere radiance and the aerosol content. This relationship was investigated at two test sites, San Diego and the Salton Sea, using the MSS radiance data, with ground truth observations of the aerosol content being made with a Volz photometer at the time of the satellite overpasses. Significant results, relating the radiance over water surfaces to the atmospheric aerosol content, have been obtained. The results indicate that the MSS channels, 4, 5 and 6 centered at 0.55, 0.65 and 0.75 micron have comparable sensitivity, and that the aerosol content can be determined within + or - 10% with the assumed measurement errors of the MSS.
The effects of several cable suspension configurations on the first free-free flexural frequency of uniform beams have been determined by experiment and analysis. The results of this study confirm that in general the larger the test vehicle the larger is the flexural frequency measurement error attributable to a given cable suspension configuration. For horizontally oriented beams representing modern aerospace vehicles of average size and flexibility, the restraining effects of all but the shortest support cables were minor. The restraining effects of support cables of moderate length attached near the base of vertically oriented vehicles were overshadowed by the effects of beam compression due to gravity.
Glass plate targets containing multiple contrast three bar patterns and a military standard resolution target were photographed through a light-source collimator-camera system. The glass plate targets and images were then scanned. Through a computer plotting program selected portions of the scanned items were presented. The plots were then measured and analyzed to obtain information of image quality parameters and effects. The measurement errors are discussed together with aspects of resolution determination.
An optimal gain was established by measuring errors at 5 discrete control gain settings in an experimental set-up consisting of a 2-dimensional, first-order pursuit tracking task performed by subjects (S's). No significant experience effect on optimum gain setting was found in the first experiment. During the second experiment, in which control gain was continuously adjustable, high experienced S's tended to reach the previously determined optimum gain quite accurately and quickly. Less experienced S's tended to select a marginally optimum gain either below or above the experimentally determined optimum depending on initial control gain setting, although mean settings of both groups were equal. This quick and simple method is recommended for selecting control gains for different control systems and forcing functions.
A series of experiments was conducted with simple beam and mass launch vehicle and payload models in order to determine the validity of mechanical admittance/impedance techniques applied to development of improved payload vibration tests. Admittances and impedances were measured from tests of the individual components to form matrices which were combined analytically to allow prediction of responses for the complete system. Results were computed for a transmission matrix approach and an admittance matrix approach. Both a rigid body and a flexible payload model were considered. The results clearly demonstrate that the transmission matrix method is too sensitive to measurement error to be practical for this application, while the pure admittance matrix method produces quite satisfactory results. The effects of various errors on the final results are demonstrated.
The ERTS-1 satellite offered the opportunity of determining the feasibility of monitoring the atmospheric aerosol optical thickness on a global basis, as suggested by theoretical studies, which showed relationships between the upwelling earth-atmosphere radiance and the aerosol optical thickness, and between contrast and the aerosol optical thickness. These relationships were investigated at two test sites, using the multispectral scanner (MSS) radiance data, with ground-truth observations of the aerosol optical thickness being made with a Volz photometer at the time of the satellite overpasses. The results indicate that the MSS channels, 4, 5, and 6, centered at 0.55, 0.65, and 0.75 micron have comparable sensitivity, and that the optical thickness can be determined to within plus or minus 10% with the assumed measurement errors of the MSS.
The integration of Doppler frequencies extracted from S-band communication and tracking signals received onboard an orbiting spacecraft provides a means of navigating on-orbit. This paper describes the one way Doppler tracking concept and two mechanizations which are being investigated by the Johnson Space Center to determine a suitable one way Doppler extraction technique for the Space Shuttle Orbiter and other advanced space systems. The designs of two breadboard models are outlined and measurement errors are discussed.
The investigations considered are concerned with a better definition of the achievable accuracy and propagation characteristics of Omega and the provision of data which could be used for an analysis to study the potential application of Omega position determination to support other NASA projects. The data collection program is considered along with the experimental equipment employed. Attention is given to the design of the receiving station, aspects of data processing, position measurement errors, differential errors, problems of lane decision, and the definition of the update rate.
Results are discussed of a study to define a radar and antenna system which best suits the space shuttle rendezvous requirements. Topics considered include antenna characteristics and antenna size tradeoffs, fundamental sources of measurement errors inherent in the target itself, backscattering crosssection models of the target and three basic candidate radar types. Antennas up to 1.5 meters in diameter are within specified installation constraints, however, a 1 meter diameter paraboloid and a folding, four slot backfeed on a two gimbal mount implemented for a spiral acquisition scan is recommended. The candidate radar types discussed are: (1) noncoherent pulse radar (2) coherent pulse radar and (3) pulse Doppler radar with linear FM ranging. The radar type recommended is a pulse Doppler with linear FM ranging. Block diagrams of each radar system are shown.