Engineering topics

Chakrabarti, S.

Publications and source records attributed to Chakrabarti, S..

At least 37 records · Page 2

NASA NTRS1990

Use of a personal computer for the real-time reception and analysis of data from a sounding rocket experiment

In September 1988 the Earth and Planetary Atmospheres Group of the Space Sciences Laboratory of the University of California at Berkeley flew an experiment on a high-altitude sounding rocket launched from the NASA Wallops Flight Facility in Virginia. The experiment, BEARS (Berkeley EUV Airglow Rocket Spectrometer), was designed to obtain spectroscopic data on the composition and structure of the earth's upper atmosphere. Consideration is given to the objectives of the BEARS experiment; the computer interface and software; the use of remote data transmission; and calibration, integration, and flight operations.

Herrick, W. D.↗

NASA NTRS1990

Remote sensing of the thermosphere, plasmasphere, and exosphere

An instrument package for remotely measuring thermospheric, exospheric, and plasmaspheric structure and composition is described. This instrument will be flown aboard the second test flight of the Black Brant XII rocket, with an expected apogee of about 1300 km. The experiment package consists of a spectrophotometer to measure He I 584 A, O II 834 A, O I 989 A, hydrogen Lyman beta (1025 A), hydrogen Lyman alpha (1216 A), and O I 1304 A transitions, and a photometer to measure the He II 304 A emission. The He II 304 A photometer consists of a layered synthetic microstructure mirror tuned at 304 A to focus incidence radiation onto a detector. The high altitude to be attained by the rocket is ideally suited to probe the coupling of the various atmospheric regions through the simultaneous measurement of the altitude distributions of several major thermospheric, ionospheric, and exospheric constituents.

Chakrabarti, S.↗

NASA NTRS1990

Magnetospheric and exospheric imaging in the extreme ultraviolet

Extreme ultraviolet line emissions by exospheric oxygen ions and neutrals of ionospheric origin can be used to form images of the dynamic magnetospheric regions with sufficient speed to provide a new global means of observing the dynamics of magnetosphere-ionosphere coupling processes. Computer simulations of such exospheric images based on the latest measurements of ion outflow, on known or estimated solar fluxes, and on known emission and excitation rates are shown. An evaluation of the current and foreseeable EUV imaging technology relevant to magnetospheric imaging is also given.

Chiu, Y. T.↗

NASA NTRS1990

Spatial heterodyne spectroscopy - A novel interferometric technique for the FUV

The optical principles associated with spatial heterodyne spectroscopy (SHS) are described and the results of proof-of-concept tests performed in both the visible and the UV spectral regions are presented. A specific all-reflecting SHS configuration now being developed for high-resolution planetary Lyman-alpha studies is discussed. The expected performance of SHS systems is compared to that of conventional instrumentation in two cases: Venusian Ly-alpha measurements at high resolution from a sounding rocket and the velocity-resolved survey of the diffuse FUV interstellar medium emission from a Small Explorer class satellite.

Harlander, J.↗

NASA NTRS1989

Telescience at the University of California, Berkeley

The University of California at Berkeley (UCB) is a member of a university consortium involved in telescience testbed activities under the sponsorship of NASA. Our Telescience Testbed Project consists of three experiments using flight hardware being developed for the Extreme Ultraviolet Explorer project at UCB's Space Sciences Laboratory. The first one is a teleoperation experiment investigating remote instrument control using a computer network such as the Internet. The second experiment is an effort to develop a system for operation of a network of remote workstations allowing coordinated software development, evaluation, and use by widely dispersed groups. The final experiment concerns simulation as a method to facilitate the concurrent development of instrument hardware and support software. We describe our progress in these areas.

Telemetry/instrumentation/methods↗

NASA NTRS1989

A position sensitive detector for EUV remote sensing

The authors describe a photon-counting extreme ultraviolet (EUV) detector system used in a rocket-borne spectroscopic instrument for remote sensing of upper atmospheric composition and temperature. The detector uses a KBr coated microchannel plate (MCP) Z stack in combination with a wedge-and-strip image readout system. Three separate detector fields of view are used to sense the Earth dayglow spectrum (980 A to 1040 A, and 1300 A to 1360 A) and the solar EUV spectrum (250 A to 1400 A). The authors demonstrate high gain (2 x 107), tight pulse-height distribution (35 percent FWHM), and a spatial resolution of about 35 microns FWHM (full width at half maximum), which is the highest resolution for a wedge-and-strip anode MCP detector flown to date. The background, image linearity, and flat-field performance are discussed. Raw spectra from the rocket flight are also presented.

Siegmund, O. H. W.↗

NASA NTRS1989

An EUV spectrometer for atmospheric remote sensing

This paper describes the Berkeley EUV Airglow Rocket Spectrometer (BEARS) experiment, designed to investigate the interactions between the solar ionizing radiation and the earth's upper atmosphere. The primary objective of this experiment is the verification the feasibility of using EUV observations as a quantitative diagnostic of the terrestrial atmosphere and its plasma environment. The expected information provided by spectroscopic measurements of EUV emission will include data on the excitation mechanisms, excitation rates, and branching ratios. The BEARS experimental package consists of a high-resolution EUV airglow spectrometer, a hydrogen Lyman-alpha photometer to measure both the solar radiations and the geocoronal emissions, and a moderate-resolution solar EUV spectrometer. In a test experiment, the instruments were carried aboard a four-stage sounding rocket to a peak altitude of about 960 km and obtained airglow spectra in the 980-1060 A range and in the 1300-1360 range.

Chakrabarti, S.↗

NASA NTRS1988

A reanalysis of rocket measurements of the ultraviolet dayglow

Rocket measurements of O I 989, 1304, 1356 A and N2 Lyman-Birge-Hopfield band emission in the midlatitude dayglow reported by Gentieu et al. (1979) and Eastes et al. (1985) are reexamined. MSIS-83 atomic oxygen densities, the 1304 and 1356 A excitation cross sections of Zipf and Erdman (1985), and SMM solar 1304 A irradiance measurements are consistent with the observed O I and N2 emission intensities. Atmosphere Explorer E (AE-E) measurements of the solar EUV irradiance near solar maximum are consistent with the 1980 rocket airglow data, but the solar EUV irradiance required to explain the 1978 airglow data is a factor of 1.5 larger than indicated by AE-E. Enhancement of the 1304 A excitation cross section due to radiative entrapment of cascade-feeding photons is much less than the factor of two predicted by the cascade model of Julienne and Davis (1976).

Link, R.↗

NASA NTRS1988

Telescience at the University of California, Berkeley

The University of California at Berkeley (UCB) is a member of a university consortium involved in telescience testbed activities under the sponsorship of NASA. The Telescience Testbed Project consists of three experiments using flight hardware being developed for the Extreme Ultraviolet Explorer project at UCB's Space Sciences Laboratory. The first one is a teleoperation experiment investigating remote instrument control using a computer network such as the Internet. The second experiment is an effort to develop a system for operation of a network of remote workstations allowing coordinated software development, evaluation, and use by widely dispersed groups. The final experiment concerns simulation as a method to facilitate the concurrent development of instrument hardware and support software. Progress in these areas is described.

Chakrabarti, S.↗

NASA NTRS1988

Remote sensing of atmospheric oxygen from a sounding rocket

This paper describes a rocket experiment to investigate mechanisms governing the interactions between two of the fundamental components of the solar-terrestrial system: the solar ionizing radiation and the earth's upper atmosphere. The aim is to characterize the extreme ultraviolet (EUV) emissions resulting from these interactions in terms of physical parameters so that EUV remote sensing can be gainfully employed as a quantitative diagnostic of the terrestrial atmosphere and plasma environment. The payload consists of a high-resolution (about 0.5 A) spectrometer to measure the EUV emissions (980-1360 A) of the earth's dayglow, a moderate resolution (about 15 A) EUV spectrometer (250-1450 A) to measure the solar irradiation responsible for the photoelectron production, and a hydrogen Lyman Alpha photometer to monitor the solar irradiance and geocoronal emissions.

Chakrabarti, S.↗

NASA NTRS1988

An analysis of satellite observations of the O I EUV dayglow

Observations of the latitudinal variation of the 1356-A, 1304-A, and 989-A O I earth dayglow, obtained with the USAF STP78-1 satellite at solar maximum on March 21, 1979, are reported and compared with the predictions of thermospheric models and published laboratory measurements of electron-impact excitation cross sections. The results are presented in extensive tables and graphs and characterized in detail, with particular attention to the 1304-A solar flux and the 989-A branching ratio. The STP78-1 data (as well as simultaneous AE-E satellite measurements ) are shown to indicate exospheric temperatures that were 220-240-K higher, but varied significantly less with latitude, than those predicted by the MSIS-83 model (Hedin, 1983) for the day of the observations.

Link, R.↗

NASA NTRS1988

EUV properties of two diffraction gratings

The efficiency and scattering characteristics of a mechanically ruled grating (MRG) and a holographically ruled grating (HRG) are presented. One of these gratings will be employed in the Extreme Ultraviolet Spectrometer, an instrument of the Remote Atmospheric and Ionospheric Detector System to be flown aboard a TIROS satellite in 1991. The HRG showed much less Lyman alpha scattering, while the MRG had the better efficiency over most of the spectral range covered.

Cotton, D.↗

NASA NTRS1987

Modeling of the O I 989-A to 1173-A ratio in the terrestrial dayglow

The O I 989-A and 1173-A intensities in the midlatitude dayglow are modeled for the conditions of a Jan. 17, 1985, rocket flight. It is found that the branching ratio required to fit the 1173-A data is in agreement with the laboratory measurement of 1.3-1.5 x 10 to the -4th. The results also suggest that the electron impact excitation cross section for the 3s1 3D0 state in current use may be too large by a factor of about 2-3, in agreement with recent laboratory results. If this is indeed the case, then the 1173-A triplet is by far the most important branch for the 989-A multiplet.

Gladstone, G. R.↗

NASA NTRS1986

Wedge and strip image readout systems for photon-counting detectors in space astronomy

EUV and far UV applications of wedge and strip anodes in photon-counting microchannel plate detector systems are discussed in light of performance data obtained as a result of EUV Explorer spacecraft open face detector and FAUST-Spacelab far UV sealed tube sensor calibrations. CsI quantum detection efficiencies of about 80 percent at 114 A and about 40 percent at 600 and 1300 A have been achieved; a position sensitivity of less than 10 microns is demonstrated, and the position resolution, image linearity, background rate, and flat-field characteristics are discussed.

Siegmund, O. H. W.↗

NASA NTRS1986

Application of wedge and strip image readout systems to detectors for astronomy

Microchannel plate (MCP) detector systems that use wedge and strip anodes for imaging radiation in the range 50 A to 8000 A are described. Test data, obtained from the calibration of the Extreme Ultraviolet Explorer Satellite detectors and the ARIA EUV aeronomy sensor is presented. The long-term performance characteristics of Z-stack microchannel plates are investigated and it is shown that stable operation is achieved after an initial settling period. Conventional and new anode designs and their potential for increasing the position resolution are discussed. Position resolution of better than 80 microns FWHM has been attained for 50 mm devices, and this is shown to be essentially independent of event location. Image nonlinearity of less than 0.3 percent has been achieved with stability to better than 0.1 percent. Differential nonlinearity of less than 1 percent and stability to better than 1 percent have been obtained. Measurements of the quantum efficiency of a CsI photocathode on an MCP are presented, demonstrating efficiencies as high as 47 percent.

Siegmund, O. H. W.↗

NASA NTRS1985

Investigation of vehicle glow in the far ultraviolet

To data, all vehicle glow observations have been conducted in the visible and near infrared wavelength regions. As the Space Telescope's wavelength coverage extends to the far ultraviolet range and current plasma theory of the spacecraft glow phenomena predicts bright glow intensities, a study of the ram glow effects in the 800-1400 angstrom region was undertaken. The data were collected between March 21-28, 1979, from 600 km altitude near local midnight by the University of California, Berkeley's extreme ultraviolet spectrometer on board the polar orbiting STP78-1 satellite. Data from several nighttime orbits obtained outside the South Atlantic Anomaly region and within + or - 30 deg magnetic latitude range were separated into forward (south viewing) and backward (north viewing) bins. Each of these binds was subdivided into three directional categories: (1) up (zenith angles 30-80 deg), (2) side (zenith angles 80-100 deg), and (3) down (zenith angles 120-150 deg). The maximum ram glow effects are expected in the side viewing directions. Our data include possible effects of ram glow signatures in the 800-1400 angstrom wavelength region.

Chakrabarti, S.↗

NASA NTRS1984

The OI 989-A tropical nightglow

Attention is given to the morphology and origin of the OI 989 A emission in the tropical nightglow. Dielectronic recombination of O(+) is suggested as the mechanism responsible for populating the 3s' 3D0 state of this 2p4 3P 3s' 3D0 emission. The spectrometer used is that aboard the STP 78-1 satellite, which is in sun-synchronous orbit. The emission morphology is characterized by tropical arcs on each side of the dip equator.

Abreu, V. J.↗

NASA NTRS1983

The 300- to 900-A spectrum of a nightside aurora

Attention is given to the results of a satellite observation of a nightside aurora. The observations had been made with the aid of an instrument which was designed specifically to detect and to measure accurately the intensity of features in a wavelength range from 300 to 900 A. The considered data were acquired by an EUV spectrometer on the USAF STP 78-1 satellite launched on February 24, 1979. A bright, discrete auroral arc was selected for study, taking into account the intense O II, 834 A emission line as the most distinctive auroral diagnostic feature in the wavelength region from 300 to 900 A. There is found to be an excellent correspondence between most of the auroral features and the brightest O II laboratory discharge emission lines.

Paresce, F.↗