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Torr, M. R.

Publications and source records attributed to Torr, M. R..

At least 37 records · Page 2
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NASA NTRS1987

Energetic He(+) precipitation in a mid-latitude aurora

Ground-based spectral observations of a midlatitude aurora on Sept. 22, 1982 indicated that the observed emissions were caused by either O(+) or H(+) energetic ions. In this paper, the model of Ishimoto et al. (1986) is used to simulate the interaction between precipitating energetic He(+) and a neutral atmosphere of He, O, and N2, computing the atmospheric impacts in terms of heating, ionization, and excitation of certain emissions and comparing the results with those obtained earlier with O(+) as the energetic flux. It was found that, of the total energy influx, approximately 50 percent goes into ionization, compared with 2 percent in the case of O(+), and 40 percent is backscattered or escapes, compared with 16 percent in the case of O(+). By contrast, He(+) is much less efficient at heating the atmosphere and does not excite the N2 2P system. It is concluded that the aurora observed on Sept. 22 is well explained by an influx of energetic O(+) together with a 6 percent admixture of He(+).

Ishimoto, M.↗
NASA NTRS1986

Intensified-CCD focal plane detector for space applications A second generation

An intensified-CCD detector system developed for space applications from commercially available components is described. This detector uses components which are readily available and are mechanically, thermally, and optically coupled to produce the final compact system. The CCD is cooled using a Peltier-effect thermoelectric cooler to reduce thermal noise. The image is formed on the photocathode of a proximity-focused image intensifier and is transferred fiber-optically from the intensifier to the CDD. Various photocathode and window materials are used to optimize the system for use within the wavelength range extending from the far UV to the near IR. The basic design, including the image intensifier, intensifier-CCD interface, CCD array, cooling, electronics, and mounting, and the detector performance are described in detail.

Torr, M. R.↗
NASA NTRS1986

The role of energetic O(+) precipitation in a mid-latitude aurora

It is shown that fluxes of precipitating energetic O(+) that have been observed by satellites in the topside ionosphere can explain the magnitude of the N2+(1 N) (first negative) 3914-angstroms and N2(2 P) (second positive) 3371-angstroms emission rate observed during a mid-latitude aurora over Logan, Utah (41 degrees N, 111 degrees W), on 21-22 September 1982. Heavy particle precipitation has previously been invoked to explain the anomalously high populations in the upper vibrational levels of the N2+(1 N) system that are evident in the observed emissions. An improved model is used to investigate the impact of precipitating heavy ions on the atmosphere. The nocturnal thermospheric heating rate and ionization rate during one of these events can be equivalent to the daytime EUV heating and ionization rates. The observed spectrum can be explained by energetic O(+) precipitation to within the uncertainties of the inputs to the model.

Ishimoto, M.↗
NASA NTRS1986

The O2 atmospheric dayglow in the thermosphere

Spectral measurements (Delta lambda = 8A) from Spacelab 1 of the O2 atmospheric bands in the dayglow at thermospheric altitudes are reported for a tangent ray height of 150 km. Vibrational levels up to nu-prime = 4 are found in the data, requiring a source in addition to the energy transfer from O(1D) to O2. It is suggested that this source is the collisional deactivation of N(2D) by O2.

Torr, M. R.↗
NASA NTRS1986

Models of the plasmaspheric thermal plasma distribution

Current understanding of the thermal plasma in the atmosphere and its coupling to the ionosphere is reviewed. Existing models appear adequate to explain the gross behavior of the cold thermal plasma, but there remain some vexing problems. Notably, (1) why does the density in flux tubes appear to saturate at lower values than are predicted theoretically, (2) what causes the sunset peak in measured Te, and (3) why does the equatorial plasmapause signature differ in latitude from the ionosphere signatures. The more difficult problem of what happens during the early stages of refilling after a magnetic storm, when the high altitude plasma is likely to be supersonic and collisionless, has received much attention, but the results are not definite. A number of papers have dealt with the interaction of supersonic counterstreaming fluxes and there are now models that can handle the transition from supersonic to subsonic flows although the transition from a collisionless to a collision-dominated plasma remains difficult to deal with.

Richards, P. G.↗
NASA NTRS1985

The Imaging Spectrometric Observatory

Design and performance features of the Imaging Spectrometric Observatory (ISO) first flown on Spacelab 1 for atmospheric, earth surface and stellar monitoring are outlined. The ISO has five grating spectrometers fitted with CCD arrays for simultaneously gathering spectral and spatial data. The instrument covered the 300-12,700 A range on the Spacelab 1 flight, when it was mounted on a pallet and used for atmospheric scans at high solar zenith angles. A future mission is planned which will include limb-viewing of OH, NO, ClO and NO2 radicals in the middle atmosphere to complement the data collected in the Upper Atmosphere Research Satellite program. Technical details are presented of the instrument components and ground- and balloon-borne test results.

Torr, D. G.↗
NASA NTRS1985

Osmium coated diffraction grating in the Space Shuttle environment - Performance

Samples coated with osmium were flown on the early Shuttle test flights, and on the return of these samples, the osmium coating was found to have disappeared, evidently due to the oxidation of the material in the atomic oxygen atmosphere. An instrument flown on the Spacelab 1 mission comprised an array of five spectrometers covering the extreme ultraviolet (EUV) to near-IR wavelengths. The EUV spectrometer contained an osmium-coated reflective grating located fairly deep within the instruments. Here, results of an assessment of the reflectivity and stability of the osmium surface over the course of the ten-day mission are reported. It is concluded that the osmium reflective coating remained stable relative to the spectrometer coated with MgF2 over the course of the mission. In addition, the ratio of sensitivity of these two spectrometers did not change in any major way from the time of the laboratory calibration until the time of flight two years later. Any changes are within the 50-percent calibration uncertainty.

Torr, M. R.↗
NASA NTRS1985

The O2 atmospheric 0-0 band and related emissions at night from Spacelab 1

A comparison of theoretically determined and measured O2 atmospheric (0-0) band intensities is presented. In view of suggestions that the O2 atmospheric emission and the atomic oxygen O(1S) emission both arise from the same intermediate state of O2, the measured 5577 A emission is also compared with theory; a similar comparison is made for the Herzberg bands of O2. It is concluded that the theories explaining these emissions do not yet provide a consistent picture.

Torr, M. R.↗
NASA NTRS1985

The UV-VIS optical environment of the shuttle

During the Spacelab 1 shuttle mission, spectroscopic measurements were made of the atmospheric emissions over a broad wavelength range extending from the extreme ultraviolet to the near infrared. Those measurements were made under a variety of vehicle attitude and sunlight conditions. Superimposed on such spectra would be any features associated with the induced vehicle environment and its interaction with solar photons and the ambient neutral atmosphere and plasma. Various anomalies and unexpected features in the spectra from the perspective of possible shuttle-induced origins are discussed. The data indicate a dramatic cleanup of the vehicle environment over the course of the 10-day mission, a strong non-atmospheric red continuum underlying the spectra at night and at large angles to the velocity vector, and a variety of molecular band distributions which are not explained by the present understanding of the atmosphere.

Torr, M. R.↗
NASA NTRS1985

Enhanced N(+) Sub 2 in the Shuttle Environment

Observations were made of the N2 first negative and Meinel emission bands with the Imaging Spectrometric Observatory (ISO) on Spacelab 1. These observations have revealed the presence of N2 emissions which exceed those expected on the basis of current ionospheric models by up to a factor of 10. If the emission is of terrestrial origin, large unidentified ionospheric sources of N2 ions must exist. On the other hand, if the source is local to the shuttle environment, a mechanism must be found which is capable of generating emissions of such unexpectedly large intensity. Charge exchange of ambient ionospheric O+ ions with shuttle environmental N2, followed by resonance scattering of sunlight, as a candidate were suggested. However, this model implies that a cloud of N2 gases must surround the vehicle in concentrations in excess of 10 to the 11 c.c. cm with a scale length of tens of meters. In addition, the N2 residence time must be of the order of 10 sec.

Torr, D. G.↗
NASA NTRS1985

A possible glow experiment for the EOM 1-2 mission

A possible opportunity for study of surface glow exists during the Environmental Observation Mission (EOM) 1-2 mission scheduled for launch on September 3, 1986. The EOM 1-2 payload includes spectroscopic and photometric instruments which operate in wavelength regions of great interest to the glow assessment activity. However, as in the case of many remote sensing instruments, these are located in the payload bay in such a way as to avoid viewing any shuttle or payload surfaces. If these instruments are to measure the spectral characteristics of surfaces, it is necessary for such surfaces to be positioned in the field of view of these instruments for the duration of the particular measurement sequence. It is possible that the shuttle of which the EOM 1-2 payload flies will have an Remote Manipulator System (RMS) in place. An assessment has shown that it is indeed feasible to place a four-sided cuff around the end of the RMS. The four sides, each coated with a different material, can then be positioned in turn above the instruments, and in such a way that the surface is alternately pointed into the ram and into the wake.

Torr, M. R.↗
NASA NTRS1985

Ionization frequencies for solar cycle 21 - Revised

Detailed spectra of the extreme ultraviolet solar flux at the earth were provided by instruments on the Atmosphere Explorer satellites. These data have been used for aeronomical purposes in a large number of studies. An important parameter for such studies is the rate of production of various ions through the photoionization process. This parameter, known as an ionization frequency, is the integral over wavelength of the product of the solar flux and the cross section for the ionization of the particular constituent. Thus, the determination of the ionization rate is dependent on a good knowledge of the solar EUV intensities for the solar period in question. Over the past few years the EUV solar spectra that have been developed for use by aeronomers as reference spectra for such photochemical and ionospheric studies have been improved. The results of a redetermination of the most important ionization frequencies using the revised solar fluxes are reported. The impact is found to be more significant at solar maximum, amounting to a reduction of 12-21 percent in the ionization frequencies of the major terrestrial thermospheric constituents for solar-minimum conditions and 21-33 percent for solar-maximum conditions. The corrections are apart from the ongoing debate concerning the absolute intensity of EUV solar-flux measurements for the solar-cycle 21 maximum period.

Torr, M. R.↗
NASA NTRS1985

The N II 2143-A dayglow from Spacelab 1

During the Spacelab 1 Shuttle mission (November 28 to December 7, 1983) spectral measurements were made in the ultraviolet which resolve the N(+)(S-5) doublet at 2143 A from the NO(1-0) gamma band at 2148 A in the upper thermosphere. The measured slant-path surface-brightness profile of the N(+) feature is well explained by photodissociative ionization of N2 with a yield of 0.2. The intensity of the N(+) feature relative to the NO(1-0) gamma band is dependent on the conditions prevailing at the time and location of the measurement. For the near-twilight mid-latitude measurements made in the upper thermosphere the N(+)(S-5) feature would contribute 20 to 75 percent of a low spectral resolution NO measurement.

Torr, M. R.↗
NASA NTRS1985

A spectral search for Lyman-Birge-Hopfield band nightglow from Spacelab 1

Huffman et al. (1980) have reported the observation of significant intensities of the N2 Lyman-Birge-Hopfield (LBH) bands at midlatitudes at night. During the course of the 10-day Spacelab 1 mission, spectral observations were made of the atmosphere on both the dayside and nightside of the earth with the vehicle in various attitudes. The present investigation is concerned with an examination of selected data for evidence of the LBH nightglow. The considered data include far ultraviolet observations which were made on the nocturnal atmosphere at low latitudes and midlatitudes. The investigation confirms that the earlier reported LBH nightglow does appear to be generally present at the time of the Spacelab 1 mission.

Torr, M. R.↗
NASA NTRS1985

Persistence of phosphor glow in microchannel plate image intensifiers

Image intensifier tubes using microchannel plate amplification stages and phosphor output stages are being increasingly used in various detection applications. In this paper, measurements of the decay times of what are attributed to be the P20 phosphors in various image intensifiers are reported. It is found that the long tail on the decay curve of the phosphor following illumination can be a limitation for certain observations. In addition, the background level of phosphor glow (which is seen by the subsequent detection system as a light signal) continues to build with continuing illumination.

Torr, M. R.↗
NASA NTRS1985

A preliminary spectroscopic assessment of the Spacelab 1/Shuttle optical environment

Attention is given to the Space Lab/Space Shuttle-borne Imaging Spectrometric Observatory's 1150-8000 A spectral data, which was gathered while this instrument package was looking tangentially away from the earth and into the velocity vector. The spectrum is noted to contain the expected atmospheric features, together with bright molecular bands between 6400 and 8000 A. These bands appear to be part of the N2 First Positive system. If most of the emission is due to this system, two excitation mechanisms are implied: direct collisional excitation of the local Shuttle atmosphere by the terrestrial atmosphere, or alternatively a surface interaction which generates metastable N2(A); this subsequently radiates via inverse first positive N2 transitions, followed by first positive transitions.

Torr, M. R.↗
NASA NTRS1984

Results of a comprehensive study of the photochemistry of N2(+) in the ionosphere

The improved match that can be obtained between the Atmospheric Explorer (AE) data on the ionospheric F layer N2(+) abundance and theoretical predictions by changing the dissociative recombination rate coefficient is demonstrated. Historically, models have overestimated the N2(+) concentration. It is shown that the calculated enhancement is due to charge exchange between 0(+)(2D) with N2. Increasing alpha by a factor of 2-3, at least in the orbits examined, can augment the destruction of vibrationally excited N2(+) ions. However, the validity of the correction is dependent on the availability of further laboratory data.

Abdou, W. A.↗