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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2022

Development of a Deployable Opitcal Aperature

The Deployable Optical Receive Aperture (DORA),a new technology being developed jointly between JetPropulsion Laboratory (JPL) and Arizona State University(ASU), is based on deploying arrays of fast optical detectors tocreate large receive apertures and seeks to achieve gigabitconnectivity at distances of thousands of kilometers. Smallspacecraft forming the LunaNet communications network andequipped with optical communications systems, such as theproposed DORA aperture, should be able to communicate atGigabit per second rates over long distances. This data rateenhancement can allow gigabit per second connectivitybetween lunar assets (astronauts, rovers, instruments) and thelunar gateway. Under sponsorship of NASA's Small SpacecraftTechnology Program (SSTP), JPL is deploying the DORApayload and ASU is developing a 3U CubeSat for a follow-onlow-Earth-orbit (LEO) mission to demonstrate DORA'scapabilities. The basic DORA payload consists of 5 receiverpanels, a transmitting telescope and processing units. Eachreceiver panel contains dozens of power-combined detectors tomimic a large optical aperture. The total receive aperture ofDORA is provided by the sum of the effective detecting area ofthe 5 panels. The transmit telescope includes a 200mW, 850nmlaser and a voice-coil fast steering mirror (FSM). The resultingDORA terminal should be able to provide duplex connectivityat rates up to 1 gigabit per second at the distances of interest.We have designed the entire DORA payload and plan topresent the test results of our DORA engineering model. Theseresults include angle-of-arrival, data rate and bit error ratemeasurements.

Yi, Lin↗
NASA NTRS1981

Field limiter for solar radiometers

Lenses project solar image onto aperature to exclude circumsolar radiation, more precisely measuring energy captured by receiver aperatures of highly-concentrating solar thermal-energy converters. First version uses achromatic objective lens to form image of Sun at aperature ahead of radiometer cavity. Smaller second version with shorter focal length forms image magnified by another lens and thrown onto aperature. Both Versions require calibration against standard radiometer.

Berdahl, C. M.↗
NASA NTRS2003

On the Prospects of Measuring the Cosmic History of Element Synthesis with Future Far-IR/Submillimeter Observatories

To understand the cosmic history of element synthesis it will be important to obtain extinction-free measures of the heavy element contents of high-redshift objects and to chart two monumental events: the collapse of the first metal-free clouds to form stars, and the initial seeding of the universe with dust. The information needed to achieve these objectives is uniquely available in the far-infrared/submillimeter (FIR/SMM) spectral region. Following the Decadal Report and anticipating the development of the Single Aperature Far-IR (SAFIR) telescope capabilities of a large-aperature, background-limited FIR/SMM observatory and an interferometer on a boom, and discuss how such instruments could be used to measure the element synthesis history of the universe.

Leisawitz, David↗
NASA NTRS1969

Energy-storage of a prescribed impedance

Reflector antenna of the parabolic type offers complete control of its aperature illumination function. The antennas beam width can be changed easily by excitation of various amounts of the line-source feed. The conical reflector collimates a beam when the feed complies with certain geometric constraints.

Seaton, A. F.↗
NASA NTRS1971

Digital telemetry system eliminates data redundancy

Floating aperature, zero-order predictor /ZOP/ circuit eliminates telemetered data redundancy by examining data from each sensor before it is multiplexed and transmitted. Digital devices to implement design are off-the-shelf items such as gates, registers and flip-flops, which are readily amenable to large-scale integration techniques.

Hymer, R. L.↗
NASA NTRS1970

Radar monitoring of oil pollution

Radar is currently used for detecting and monitoring oil slicks on the sea surface. The four-frequency radar system is used to acquire synthetic aperature imagery of the sea surface on which the oil slicks appear as a nonreflecting area on the surface surrounded by the usual sea return. The value of this technique was demonstrated, when the four-frequency radar system was used to image the oil spill of tanker which has wrecked. Imagery was acquired on both linear polarization (horizontal, vertical) for frequencies of 428, 1228, and 8910 megahertz. Vertical returns strongly indicated the presence of oil while horizontal returns failed to detect the slicks. Such a result is characteristic of the return from the sea and cannot presently be interpreted as characteristics of oil spills. Because an airborne imaging radar is capable of providing a wide-swath coverage under almost all weather conditions, it offers promise in the development of a pollution-monitoring system that can provide a coastal watch for oil slicks.

Guinard, N. W.↗
NASA NTRS1971

Three-meter telescope study

A means is presented whereby the effect of various changes in the most important parameters of a three meter aperature space astronomy telescope can be evaluated to determine design trends and to optimize the optical design configuration. Methods are defined for evaluating the theoretical optical performance of axisymmetric, centrally obscured telescopes based upon the intended astronomy research usage. A series of design parameter variations is presented to determine the optimum telescope configuration. The design optimum requires very fast primary mirrors, so the study also examines the current state of the art in fabricating large, fast primary mirrors. The conclusion is that a 3-meter primary mirror having a focal ratio as low as f/2 is feasible using currently established techniques.

Wissinger, A.↗
NASA NTRS1977

Molecular beam generator

Vacuum deposition generator has nozzle and aperature designed especially for beams of heavy organic molecules. Deposition rates are from 6 to 15 angstroms per minute.

Richmond, R. G.↗
NASA NTRS1976

Optical data processing study

An onboard coherent optical data processing system was designed to handle large information content of imagery at high speeds, reduce redundancy in picture transmission, and detect specific image features. Theoretically derived Fourier transform characteristics for simple but representative two dimensional images served as a basis for predicting expected features of actual target images. Fourier transformation and spatial filtering of coherent optical images was accomplished theoretically and in the laboratory. The effect of various parameters such as optical aperature, incidence angles, the transparency assumption, the thin lens approximation on resolution, and performance of the system are predicted and tested.

Pinson, L. J.↗
NASA NTRS1977

Solid propellant rocket motor and method of making same

A method is described for making a solid propellant rocket motor having a specific concavity formed within the fuel charge. A mandrel with an aperature wider than that of the casing is inserted within the motor casing and a solidifiable propellant cast above the mandrel. The mandrel is removed after the propellant is cured.

Thibodaux, J. G., Jr.↗
NASA NTRS1978

Search for broad gamma ray lines with the UCR double Compton scatter telescope

The operation of a double scatter telescope and the evaluation of data obtained during a 24 hour balloon flight are discussed. An increase in gamma rays was observed as the galactic anti-center crossed the aperature of the telescope. Searches for lines from p(n,gamma)d at 2.2 MeV, C-12* at 4.4 MeV and on -16* at 6.1 MeV and for other lines broadened or redshifted are being conducted to identify the processes responsible for the production of celestial gamma rays. Two upper limits for lines in the angalactic anti-center direction at 4.4 MeV and 6.1 MeV are 6 and 4 x 10 to the minus 4 power gamma/sq cm-s.

White, R. S.↗
NASA NTRS1979

Eliminating Clutter in Synthetic-Aperture Radar

Diffusion technique reduces clutter noise in coherent SAR (synthetic-aperature radar) image signal without degrading its resolution. Technique makes radar-mapped terrain features more obvious.It also has potential application in holographic microscopy.

Jain, A.↗
NASA NTRS1979

Azimuth Correlator for Synthetic Aperture Radar

Azimuth correlation simulates large antenna aperature. It uses charge-coupled-device (CCD) technology to simplify complex, digital, signal-improvement process. In aircraft or spacecraft, correlator processes images onboard and in real time to simplify transmission to ground stations.

Arens, W. E.↗
NASA NTRS1980

Azimuth correlator design for IC chip

Azimuth correlator circuit synthetic-aperature radar (SAR) is designed for single integrated circuit (IC) chip. Azimuth correlator modules constructed with sets of such chips could make real-time signal processing possible. Primary advantages are realized in areas of weight and power requirement reductions.

Tyree, V. C.↗
NASA NTRS1981

Cavity-backed spiral-slot antenna

Compact, rugged, flush-mounted antenna operates in sum or difference modes with circular polarization. Radiating elements consist of two pairs of centerfed, interleaved spiral slots in conductive aperature plane. At center feedpoint of each slot pair is balanced feed assembly. Center points are fed from split-tube coaxial balun passing through quarter-wave length deep cavity. Circularly polarized patterns represent both rceived and transmitted signals.

Ellis, H., Jr.↗
NASA NTRS1981

Trislot-cavity microstrip antenna

Flush-mountable assembly composed of disk radiator sandwiched between planes of metal-clad dielectric board has greater bandwidths and beamwidths than simple disk antenna. Conducting planes connect so that disk is enclosed in cavity with Y-shaped slot in top plane. Cavity is excited by microwave energy from disk and radiates from trislot aperature.

Ellis, H., Jr.↗