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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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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

The Optical Corrector for the Dark Energy Spectroscopic Instrument

The Dark Energy Spectroscopic Instrument (DESI) is currently measuring the spectra of 40 million galaxies and quasars, the largest such survey ever made to probe the nature of cosmological dark energy. The 4 m Mayall telescope at Kitt Peak National Observatory has been adapted for DESI, including the construction of a 3$_{.}^{°}$2 diameter prime focus corrector that focuses astronomical light onto a 0.8 m diameter focal surface with excellent image quality over the DESI bandpass of 360–980 nm. The wide-field corrector includes six lenses, as large as 1.1 m in diameter and as heavy as 237 kilograms, including two counterrotating wedged lenses that correct for atmospheric dispersion over zenith angles from 0° to 60°. The lenses, cells, and barrel assembly all meet precise alignment tolerances on the order of tens of microns. The barrel alignment is maintained throughout a range of observing angles and temperature excursions in the Mayall dome by use of a hexapod, which is itself supported by a new cage, ring, and truss structure. In this paper we describe the design, fabrication, and performance of the new corrector and associated structure, focusing on how they meet DESI requirements. In particular, we describe the prescription and specifications of the lenses, design choices and error budgeting of the barrel assembly, stray light mitigations, and integration and test at the Mayall telescope. We conclude with some validation highlights that demonstrate the successful corrector on-sky performance, and we list some lessons learned during the multiyear fabrication phase.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1972

Ground truth data requirements for altimeter performance verification

The amount and type of ground truth required for an altimeter experiment is a function of the uncertainty in the satellite orbit, the altimeter error budget and the type of operation being performed. Ground truth requirements will be discussed with reference to three areas of operation: the global mode, the high intensity mode and calibration.

Walsh, E. J.↗
NASA NTRS1977

Development of a method of alignment between various SOLAR MAXIMUM MISSION experiments

Results of an engineering study of the methods of alignment between various experiments for the solar maximum mission are described. The configuration studied consists of the instruments, mounts and instrument support platform located within the experiment module. Hardware design, fabrication methods and alignment techniques were studied with regard to optimizing the coalignment between the experiments and the fine sun sensor. The proposed hardware design was reviewed with regard to loads, stress, thermal distortion, alignment error budgets, fabrication techniques, alignment techniques and producibility. Methods of achieving comparable alignment accuracies on previous projects were also reviewed.

Source record↗
NASA NTRS1979

Effects of asymmetric passband filtering on the phase of the Costas loop's reconstructed carrier

The reconstructed carrier of a telemetry return signal is used in deriving the Doppler and range information in the radiometric systems. When suppressed carrier BPSK signalling with Costas loop demodulation is used, there are concerns on the amount of shift in the reconstructed carrier phase, when the received signal suffers asymmetric bandpass filtering through the various stages of the receiver. It is concluded that the phase shifts due to asymmetric bandpass filtering on the Costas loop's reconstructed carrier can be slightly worse than those suffered by the residual carrier loop's reconstructed carrier. However, they are well within the error budgets of the radiometric system.

Woo, K. T.↗
NASA NTRS1979

Application of non-attenuating frequency radars for prediction of rain attenuation and space diversity performance

In order to establish transmitter power and receiver sensitivity levels at frequencies above 10 GHz, the designers of earth-satellite telecommunication systems are interested in cumulative rain fade statistics at variable path orientations, elevation angles, climatological regions, and frequencies. They are also interested in establishing optimum space diversity performance parameters. In this work are examined the many elements involved in the employment of single non-attenuating frequency radars for arriving at the desired information. The elements examined include radar techniques and requirements, phenomenological assumptions, path attenation formulations and procedures, as well as error budgeting and calibration analysis. Included are the pertinent results of previous investigators who have used radar for rain attenuation modeling. Suggestions are made for improving present methods.

Goldhirsh, J.↗
NASA NTRS1979

A review of the application of nonattenuating frequency radars for estimating rain attenuation and space-diversity performance

Cumulative rain fade statistics are used by space communications engineers to establish transmitter power and receiver sensitivities for systems operating under various geometries, climates, and radio frequencies. Space-diversity performance criteria are also of interest. This work represents a review, in which are examined the many elements involved in the employment of single nonattenuating frequency radars for arriving at the desired information. The elements examined include radar techniques and requirements, phenomenological assumptions, path attenuation formulations and procedures, as well as error budgeting and calibration analysis. Included are the pertinent results of previous investigators who have used radar for rain-attenuation modeling. Suggestions are made for improving present methods.

Goldhirsh, J.↗
NASA NTRS1979

Microwave power beaming for long range energy transfer

Current studies by NASA have identified space solar power as a potential long term viable candidate for efficient energy transfer at orbital ranges using a microwave beam. This paper will describe some of the power-aperture relationships leading to a potential feasible design of a power beaming system. The topics include a discussion of the system constraints, the transmitter and spaceborne array configuration, and the error budget levied by microwave system requirements.

Nalos, E. J.↗
NASA NTRS1980

The Seasat-A synthetic aperture radar system

The paper discusses the Seasat-A synthetic aperture radar system (SAR). The objective of this system was to detect ocean waves from orbital altitudes. A SAR system operating at 1275 MHz was designed to meet this objective; the choice of wavelength resulted from the imagery obtained by aircraft during 1972 to 1974 and the ease of implementation. The Seasat-A SAR system was turned-on in orbit on July 4, 1978, and gathered imagery until the spacecraft bus failed in orbit in Oct. 1978. The hardware including the antenna, the radar sensor, and data-link subsystem, and the SAR data processing subsystem are described; the radar performance including the SAR system error budget and various SAR imageries are presented, concluding that the performance of the Seasat-A SAR system met all of its parameters on at least some of the imagery.

Jordan, R. L.↗
NASA NTRS1980

Achievable flatness in a large microwave power transmitting antenna

A dual reference SPS system with pseudoisotropic graphite composite as a representative dimensionally stable composite was studied. The loads, accelerations, thermal environments, temperatures and distortions were calculated for a variety of operational SPS conditions along with statistical considerations of material properties, manufacturing tolerances, measurement accuracy and the resulting loss of sight (LOS) and local slope distributions. A LOS error and a subarray rms slope error of two arc minutes can be achieved with a passive system. Results show that existing materials measurement, manufacturing, assembly and alignment techniques can be used to build the microwave power transmission system antenna structure. Manufacturing tolerance can be critical to rms slope error. The slope error budget can be met with a passive system. Structural joints without free play are essential in the assembly of the large truss structure. Variations in material properties, particularly for coefficient of thermal expansion from part to part, is more significant than actual value.

Ried, R. C.↗
NASA NTRS1980

Consideration for high accuracy radiation efficiency measurements for the Solar Power Satellite (SPS) subarrays

The transmit beam and radiation efficiency for 10 metersquare subarray panels were quantified. Measurement performance potential of far field elevated and ground reflection ranges and near field technique were evaluated. The state-of-the-art of critical components and/or unique facilities required was identified. Relative cost, complexity and performance tradeoffs were performed for techniques capable of achieving accuracy objectives. It is considered that because of the large electrical size of the SPS subarray panels and the requirement for high accuracy measurements, specialized measurement facilities are required. Most critical measurement error sources have been identified for both conventional far field and near field techniques. Although the adopted error budget requires advances in state-of-the-art of microwave instrumentation, the requirements appear feasible based on extrapolation from today's technology. Additional performance and cost tradeoffs need to be completed before the choice of the preferred measurement technique is finalized.

Kozakoff, D. J.↗
NASA NTRS1981

Development of a sub-miniature rubidium oscillator for SEEKTALK application

Warm-up and size challenges to oscillator construction are presented as well as the problems involved in these tasks. The performance of M-100 military rubidium oscillator is compared to that of a subminiture rubididum oscillator (M-1000). Methods of achieving 1.5 minute warm-up are discussed as well as improvements in performance under adverse environmental conditions, including temperature, vibration, and magnetics. An attempt is made to construct an oscillator error budget under a set of arbitrary mission conditions.

Fruehauf, H.↗
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 NTRS1982

A rubidium clock for GPS

The design objectives and approach; the more important design features; the signal parameters and error budget; and early test results in the development of a second-source rubidium frequency standard for use in the GPS navigation satellites are discussed. Tests of a breadboard version of the RFS show that the measured time-domain stability is within the goal specification. The results are uncorrected for the conribution of the reference and are probably limited by the reference stability in the medium term region. The Rb reference is bbetter in the medium term region, but the Cs reference is etter at 10,000 seconds and longer, probably because of the barometric sensitivity of the rubidium reference unit.

Riley, W. J.↗
NASA NTRS1982

The Phoretic Motion Experiment (PME) definition phase

The aerosol generator and the charge flow devices (CFD) chamber which were designed for zero-gravity operation was analyzed. Characteristics of the CFD chamber and aerosol generator which would be useful for cloud physics experimentation in a one-g as well as a zero-g environment are documented. The Collision type of aerosol generator is addressed. Relationships among the various input and output parameters are derived and subsequently used to determine the requirements on the controls of the input parameters to assure a given error budget of an output parameter. The CFD chamber operation in a zero-g environment is assessed utilizing a computer simulation program. Low nuclei critical supersaturation and high experiment accuracies are emphasized which lead to droplet growth times extending into hundreds of seconds. The analysis was extended to assess the performance constraints of the CFD chamber in a one-g environment operating in the horizontal mode.

Eaton, L. R.↗
NASA NTRS1982

Spaceborne scanner imaging system errors

The individual sensor system design elements which are the priori components in the registration and rectification process, and the potential impact of error budgets on multitemporal registration and side-lap registration are analyzed. The properties of scanner, MLA, and SAR imaging systems are reviewed. Each sensor displays internal distortion properties which to varying degrees make it difficult to generate on orthophoto projection of the data acceptable for multiple pass registration or meeting national map accuracy standards and is also affected to varying degrees by relief displacements in moderate to hilly terrain. Nonsensor related distortions, associated with the accuracy of ephemeris determination and platform stability, have a major impact on local geometric distortions. Platform stability improvements expected from the new multi mission spacecraft series and improved ephemeris and ground control point determination from the NAVSTAR/global positioning satellite systems are reviewed.

Prakash, A.↗
NASA NTRS1982

Data vs. information: A system paradigm

The data system designer requires data parameters, and is dependent on the user to convert information needs to these data parameters. This conversion will be done with more or less accuracy, beginning a chain of inaccuracies which propagate through the system, and which, in the end, may prevent the user from converting the data received into the information required. The concept to be pursued is that errors occur in various parts of the system, and, having occurred, propagate to the end. Modeling of the system may allow an estimation of the effects at any point and the final accumulated effect, and may prove a method of allocating an error budget among the system components. The selection of the various technical parameters which a data system must meet must be done in relation to the ability of the user to turn the cold, impersonal data into a live, personal decision or piece of information.

Billingsley, F. C.↗
NASA NTRS1981

The solar spectral irradiance 1200-3184 A near solar maximum - July 15, 1980

Results of a sounding rocket program designed to measure the total solar ultraviolet input to the upper atmosphere are presented. Two spectrometers, a far-ultraviolet (FUV) to cover 1160-1850 A, and a middle ultraviolet (MUV) to cover 1600-3184 A, were launched piggy-back on a Black Brant rocket to an altitude of 325 km on 7-15-1980. Tables of the detailed error budgets of the reclaimed instruments are provided. Comparisons are made with results of a 1979 flight, and of 1979 and 1980 flights with solar minimum results of Rottman (1981), and reveal significant solar spectral irradiance variability from solar minimum to maximum. MUV readings below 2100 A were 14% higher in 1980 and 14% lower in 1979 than Rottman's data, and it is concluded that a significant variability occurred at wavelengths less than 1800 A.

Mount, G. H.↗