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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

Shuttle and Transfer Orbit Thermal Analysis and Testing of the Chandra X-Ray Observatory Charge-Couple Device Imaging Spectrometer Radiator Shades

Thermal analyses of the Shuttle and Transfer Orbit of the Advanced X-Ray Astrophysics Facility Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS), one of two science instruments on the Chandra X-Ray Observatory, revealed a low-earth orbit (LEO) overheating problem on the goldized Kapton faces of two radiator shades. The shades were coated with the goldized Kapton to provide a low hemispherical emittance to minimize direct and backloaded heating from the sun and the observatory and high specularity to optimize the coupling to space on two passive radiators which cool the focal plane to -120 C +/- 1 C during on-orbit operations. Since the observatory has a highly elliptical final orbit of 10,000 kilometers by 140,000 kilometers and the ACIS radiators and shades are oriented anti-sun, the high solar absorptance to emittance ratio of the goldized Kapton was not an issue. However, during Shuttle bay-to-earth operations, the short duration solar heating occurring near the eclipse entry and exit resulted in shade temperatures in excess of the cure temperature of the adhesive used to bond the goldized Kapton and honeycomb face-sheets. The detailed thermal analysis demonstrating the LEO overheating as well as the redesign options and thermal testing of a redesigned development unit shade are presented.

Sharp, John R.↗
NASA NTRS1981

Single photon X-ray imaging with charge-coupled devices /CCDs/

The paper describes a CCD camera facility designed and built for testing and characterization of CCDs in response to single X-ray photons in the 1-10 keV energy range. Results from the frontside-illuminated Fairchild 211 and 221 area imagers are presented; high quantum efficiency over the 3-6 keV range was verified. In order to avoid the problem of charge spreading at the higher energies, deep-depleted CCDs for soft X-ray imaging have been constructed, and good response was obtained at 6 keV. The present results are a first step toward the demonstration of the CCD as an appropriate device for at least the central part of the focal plane of a large X-ray telescope, e.g., the proposed Advanced X-ray Astrophysics Facility.

Griffiths, R. E.↗
NASA NTRS1973

Image recording using charge-coupled devices

The principle of charge coupling is reviewed and some performance limitations are discussed. The practicality of a two-dimensional charge-coupled area-imaging device is examined. Of several possible design approaches, a frame transfer approach was chosen for detailed consideration because it has a very simple resolution cell. The results obtained in utilizing the proposed approach are given along with some of the problems detected.

Sequin, C.↗
NASA NTRS1987

Flash technology for charge-coupled-device imaging in the ultraviolet

The introduction of the flash gate has made possible the fabrication of backside-illuminated CCDs with high sensitivity and stability throughout a wide range of ultraviolet and visible wavelengths (100 to 5000 A). It had been determined previously that the characteristics of the oxide layer beneath the gate are critical to the ultimate achievable CCD performance. However, by creating an improved oxide layer in conjunction with the flash gate, it is now possible to consistently produce CCDs with near-ideal UV performance. In this paper recent results and related background theory that optimize the flash gate specifically for application in the UV are presented.

Janesick, James R.↗
NASA NTRS1992

Charge-coupled device imaging spectroscopy of Mars. II - Results and implications for Martian ferric mineralogy

Materials similar to nanophase ferric oxides are presently seen to dominate the spectral behavior of the Martian surface in the visible-to-near-IR, in view of imaging spectroscopic observations of Mars. Attention is accordingly given to models for the formation of hematite and other ferric minerals in both current terrestrial environments and in the current and past, possibly wetter Martian climate. It is noted that imaging spectroscopy is an ideal tool for high spatial resolution spacecraft and telescopic studies of the Martian surface.

Bell, James F., III↗
NASA NTRS1992

Charge-coupled device imaging spectroscopy of Mars. I - Instrumentation and data reduction/analysis procedures

This paper describes the collection, reduction, and analysis of 0.4-1.0-micron Mars imaging spectroscopy data obtained during the 1988 and 1990 oppositions from Mauna Kea Observatory and provides a general outline for the acquisition and analysis of similar imaging spectroscopy data sets. The U.H. 2.24-m Wide Field Grism CCD Spectrograph was used to collect 13 3D image cubes covering 90 percent of the planet south of 50 deg N in the 0.4-0.8 micron region and covering 55 percent of the planet south of 50 deg N in the 0.5-1.0 micron region. Spectra extracted from these image cubes reveal the detailed character of the Martian near-UV to visible spectrum. Images at red wavelengths reveal the 'classical' albedo markings at 100-500 km spatial resolution while images at blue wavelengths show little surface feature contrast and are dominated by condensate clouds/hazes and polar ice.

Bell, James F., III↗
NASA NTRS2016

A Synthesis of Star Calibration Techniques for Ground-Based Narrowband Electron-Multiplying Charge-Coupled Device Imagers Used in Auroral Photometry

A technique is presented for the periodic and systematic calibration of ground-based optical imagers. It is important to have a common system of units (Rayleighs or photon flux) for cross comparison as well as self-comparison over time. With the advancement in technology, the sensitivity of these imagers has improved so that stars can be used for more precise calibration. Background subtraction, flat fielding, star mapping, and other common techniques are combined in deriving a calibration technique appropriate for a variety of ground-based imager installations. Spectral (4278, 5577, and 8446 A ) ground-based imager data with multiple fields of view (19, 47, and 180 deg) are processed and calibrated using the techniques developed. The calibration techniques applied result in intensity measurements in agreement between different imagers using identical spectral filtering, and the intensity at each wavelength observed is within the expected range of auroral measurements. The application of these star calibration techniques, which convert raw imager counts into units of photon flux, makes it possible to do quantitative photometry. The computed photon fluxes, in units of Rayleighs, can be used for the absolute photometry between instruments or as input parameters for auroral electron transport models.

Grubbs, Guy II↗
NASA NTRS1991

Altering Interline Transfer In A CCD To Reduce Saturation

In proposed interline-transfer timing scheme for charge-coupled-device (CCD) video imaging array, charges accumulated during some fraction of frame period swept out and dumped to prevent overloading and saturation in intensely illuminated photosites. Excess charges swept out at highest possible rate, while charges used for imaging read out at rate lower but was highest rate that provides complete transfer of charge on array and handled by subsequent signal-processing equipment.

Rentsch, Edward M.↗
NASA NTRS1974

The Ranicon - A resistive anode image converter

A versatile photon and charged particle imaging system is described. The Ranicon employs a microchannel electron multiplier plate to convert each detected event into a charge signal. This charge pulse is proximity-focused onto a large-area resistive anode plate equipped with pickup electrodes on its edges. Each event is located electronically by the ratios of the charges collected at the edges or by the differences of the signals' risetimes. One- or two-dimensional pictures are built up by storing events digitally (e.g., a core memory) or in analog form (e.g., a storage oscilloscope). Compact laboratory models have been constructed and tested. Operating characteristics, applications, limitations, and advantages of the Ranicon are discussed.

Lampton, M.↗
NASA NTRS1981

Soft X-ray and XUV imaging with a charge-coupled device /CCD/-based detector

A soft X-ray/XUV imaging camera which uses a thinned, back-illuminated, all-buried channel RCA CCD for radiation sensing has been built and tested. The camera is a slow-scan device which makes possible frame integration if necessary. The detection characteristics of the device have been tested over the 15-1500 eV range. The response was linear with exposure up to 0.2-0.4 erg/sq cm; saturation occurred at greater exposures. Attention is given to attempts to resolve single photons with energies of 1.5 keV.

Loter, N. G.↗
NASA NTRS1979

Electronic pictures from charged-coupled devices

Imaging system uses charge-coupled devices (CCD's) to generate TV-like pictures with high resolution, sensitivity, and signal-to-noise ratio. It combines detectors for five spectral bands as well as processing and control circuitry all on single silicon chip.

Mccann, D. H.↗
NASA NTRS1981

Preliminary results from a single-photon imaging X-ray charge coupled device /CCD/ camera

A CCD camera is described which has been designed for single-photon X-ray imaging in the 1-10 keV energy range. Preliminary results are presented from the front-side illuminated Fairchild CCD 211, which has been shown to image well at 3 keV. The problem of charge-spreading above 4 keV is discussed by analogy with a similar problem at infrared wavelengths. The total system noise is discussed and compared with values obtained by other CCD users.

Griffiths, R. E.↗
NASA NTRS1981

Subtleties in the flat-fielding of charge-coupled device /CCD/ images

Astronomical photometry with CCDs will often involve relatively low signal levels (less than 1000 charge carriers per pixel), at which nonlinear effects sometimes become significant. These effects will probably play a role in the processing of Space Telescope data. The problem apparently arises because signal charges are not read out equally completely from all columns and all pixels. It is shown that, although a first-order correction can be made by subtracting a low-level flat field from all frames before conventional processing, higher accuracy can be achieved by modeling the response with a nonlinear function.

Baum, W. A.↗
NASA NTRS2000

Charge Detector for the Imaging Calorimeter for ACCESS (ICA)

NASA's Advanced Cosmic Ray Experiment for the Space Station (ACCESS) Mission is planned to consist of a transition radiation detector (TRD) and a thin ionization calorimeter. In order to measure the charge of the primary cosmic ray, it is necessary for the calorimeter to have its own charge detector. Silicon detectors are chosen for the charge detector because of their excellent resolution, small size and nearly square shape. Monte Carlo simulations are performed to find the probability of misidentifying protons as alpha particles due to backscattered radiation from the calorimeter. Simulations were also used to investigate identifying primary cosmic rays that fragmented in the TRD before reaching the calorimeter. For this study algorithms have been developed for determining a direction of the core shower in the calorimeter. These algorithms are used to find the approximate location of the primary particle in the silicon detectors. Results show the probability to misidentify the charge depends upon the energy and direction of the primary particles.

Lee, Jeongin↗
NASA NTRS1981

Texas Instruments /TI/ 800 x 800 charge-coupled device /CCD/ image sensor

Very-large area high-performance CCD image sensors with 800 x 800 pixel format have been successfully fabricated and operated on the basis of a three-level polysilicon gate technology. They are thinned to 8 microns over the entire 12.2 x 12.2 mm active area, and are used in the rear illumination mode. The light transfer characteristic has a gamma value of 1.000 + or - 0.002 over most of the dynamic range. Analysis of the noise behavior shows that the device SNR is shot-noise-limited over most of the dynamic range. Simple on-chip signal processing can be performed using an integration well to noiselessly collect signal charge from multiple pixels prior to reading out the charge. A UV-sensitive phosphor has been applied to the chip, yielding a device capable of imaging at wavelengths from the vacuum UV to the near IR.

Blouke, M. M.↗
NASA NTRS1976

Solid state television camera

The design, fabrication, and tests of a solid state television camera using a new charge-coupled imaging device are reported. An RCA charge-coupled device arranged in a 512 by 320 format and directly compatible with EIA format standards was the sensor selected. This is a three-phase, sealed surface-channel array that has 163,840 sensor elements, which employs a vertical frame transfer system for image readout. Included are test results of the complete camera system, circuit description and changes to such circuits as a result of integration and test, maintenance and operation section, recommendations to improve the camera system, and a complete set of electrical and mechanical drawing sketches.

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