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NASA NTRS1985

The new solar magnetograph for the Canary Islands Observatory THEMIS

THEMIS was designed for accurate polarization measurements in order to determine the intensity and direction of the magnetic field without interference with the local variations of the thermodynamical parameters. That goal leads to the following requirements: (1) high spatial resolution in horizontal direction; (2) sufficient resolution in height, which requires observations in several spectral lines with a sufficient spectral resolution; (3) accurate polarization measurements; (4) adequate time coverage to follow the evolution of individual structures; (5) precise tracking and scanning mechanisms; and (6) sufficient field of view for the different observed structures. The design of the instrument is discussed in detail.

Rayrole, J.↗

NASA NTRS1985

The 8.3 and 12.4 micron imaging of the Galactic Center source complex with the Goddard infrared array camera

A 30 x 30 arcsec field at the Galactic Center (1.5 x 1.5 parsec) was mapped at 8.3 microns and 12.41 microns with high spatial resolution and accurate relative astrometry, using the 16 x 16 Si:Bi accumulation mode charge injection device Goddard infrared array camera. The design and performance of the array camera detector electronics system and image data processing techniques are discussed. Color temperature and dust opacity distributions derived from the spatially accurate images indicate that the compact infrared sources and the large scale ridge structure are bounded by warmer, more diffuse material. None of the objects appear to be heated appreciably by internal luminosity sources. These results are consistent with the model proposing that the complex is heated externally by a strong luminosity source at the Galactic Center, which dominates the energetics of the inner few parsecs of the galaxy.

Gezari, D. Y.↗

NASA NTRS1984

Monolithically integrated array of GaAlAs electroabsorption modulators

The operation of an eight-element monolithic array of GaAlAs electroabsorption modulators has been demonstrated. The single-mode waveguide modulators are implemented in a reverse-biased p-pi-n heterojunction configuration, with center-to-center spacing of 9 microns between adjacent channels. This device may be useful for intensity modulation in high (spatial) resolution applications.

Robinson, D. L.↗

NASA NTRS1985

The Shuttle Infrared Leeside Temperature Sensing (SILTS) experiment

The Shuttle Infrared Leeside Temperature Sensing (SILTS) experiment is described. The SILTS experiment will obtain high-spatial-resolution measurements of the temperatures of Shuttle orbiter leeside surfaces during atmospheric entry. The data will be obtained by means of an imaging, infrared radiometer, located atop the orbiter's vertical tail, which will view the orbiter fuselage and left wing. Implementation of the SILTS experiment required a significant change to the configuration of the orbiter's vertical tail fintip. The orbiter Columbia has been modified to carry the SILTS experiment which will be active on Columbia's next flight, currently scheduled for mid-1985.

Throckmorton, D. A.↗

NASA NTRS1984

Recent advances in solar radio physics

High spatial resolution microwave observations of solar active regions, coronal loops and flares are reviewed. Observations of preflare active regions are presented; in particular the interpretations of reversal of polarization at the flare site and the role of newly emerging flux in triggering the onset of flares are considered. The spatial locations of microwave burst emitting regions are discussed; loops or arcades of loops appear to be the sites of flare energy release in microwave bursts. Direct observational evidence of magnetic reconnection as the primary cause of acceleration of electrons in microwave bursts is provided.

Kundu, M. R.↗

NASA NTRS1985

Ellipsometric surface analysis of wear tracks produced by different lubricants

A scanning ellipsometer with high spatial resolution was used to analyze wear tracks generated on M-50 surfaces operated in several lubricant formulations. These formulations included a pure ester base stock of trimethyol propane triheptanoate with additives of either benzotriazole (BTZ), dioctyldiphenylamine (DODPA), or tricresylphosphate (TCP). Results indicated that BTZ and TCP produced patchy oxide surface films consisting mainly of Fe304. DOPDA produced a much more uniform oxide film. These findings may explain the tendency of lubricant formulations containing TCP to scuff more readily than those containing only antioxidants.

Lauer, J. L.↗

NASA NTRS1986

Measurement of heat-transfer coefficients in shock wave-turbulent boundary layer interaction regions with a multi-layered thin film heat transfer gauge

A thin film heat transfer gauge is applied to the measurement of heat transfer coefficients in the interaction regions of incident shock waves and fully developed turbulent boundary layers. It was developed to measure heat flux with high spatial resolution and fast response for wind tunnels with long flow duration. To measure the heat transfer coefficients in the interaction region in detail, experiments were performed under the conditions of Mach number = 4, total pressure = 1.2 MPa, 0.59 to approximately 0.65. Reynolds number = 1.3 to approximately 1.5 x 10 to the 7th power and incident shock angles from 17.8 to 22.8 degrees. The results show that the heat transfer coefficient changes complicatedly in the interaction region. At the beginning the interaction region, the heat transfer coefficient decreases at first, reaches its minimum value at the point where the pressure begins to increase, and then increases sharply. When the boundary layer begins to separate, even a small separation bubble causes significant changes in the heat transfer coefficient, while the pressure does not show any changes which suggests that the boundary layer begins to separate.

Hayashi, M.↗

NASA NTRS1986

Infrared diagnosis using liquid crystal detectors

The possible uses of pulsed carbon dioxide lasers for analysis of plasmas and flows need appropriate infrared image converters. Emphasis was placed on liquid crystal detectors and their operational modes. Performance characterstics and selection criteria, such as high sensitivity, short reaction time, and high spatial resolution are discussed.

Hugenschmidt, M.↗

NASA NTRS1985

The X-ray properties of normal galaxies. What do we know and what can we learn with the next generation of X-ray telescopes?

Einstein Observatory results are used to assess the possibilities of spaceborne X-ray astronomy projects such as XMM (ESA) and AXAF (NASA). Einstein observations show that normal galaxies of all morphological types are spatially extended sources of X-ray emission with 0.5 to 3.0 keV X-ray luminosities of 10 to the 39th to 41st power erg/sec. X-ray telescopes can study the end products of stellar evolution in galaxies of different morphological types. Phenomena linked to starburst nuclear activity can best be detected and studied in X-ray. Hot coronae or a hot phase of the interstellar medium can only be studied through their X-ray emission. It is shown that high spatial resolution is essential for studying normal galaxies and identifying different emission regions. Good spectral sensitivity and spectral imaging capability are essential for gaining a deeper understanding of the phenomena at work.

Fabbiano, G.↗

NASA NTRS1985

Accuracy of geologic maps produced from Landsat data

Remote sensing techniques are now being applied to space-acquired data for use in preparing geologic maps, at least at the reconnaissance level, when maps produced from Landsat multispectral scanner data are compared with those made by conventional ground/aerial techniques, accuracies of the Landsat maps fall in the 40-60 percent range relative to their conventional counterparts. A study of map accuracy achieved with Landsat-4 Thematic Mapper (TM) data indicates a 10-15 percent improvement in this range. Results from TM scenes for Death Valley, California and the Waterpocket Fold, Utah are evaluated in this paper. While accuracy values should improve even more when corrections for topographic effects are made, there appears to be an upper limit to accuracy (not yet determined), owing to a fundamental difference between geologic maps (which show stratigraphic unit distribution below the regolith) and Landsat-derived rock units maps (which identify rock and regolith types at the surface). However, preliminary results from the Utah study indicate a marked improvement and accuracy to better than 80 percent when high spatial resolution TM-equivalent data from an aircraft mission are used.

Short, N. M.↗

NASA NTRS1984

Optical-system design for next-generation pushbroom sensors

Next-generation pushbroom sensors for earth observation require high-performance optics that provide high spatial resolution over wide fields of view. Specifically, blur diameters on the order of 10 to 15 microns are needed over 5 to 15 deg fields. In addition to this fundamental level of optical performance, other characteristics, such as spatial coregistration of spectral bands, flat focal plane, telecentricity, and workable pupil location are significant instrument design considerations. The detector-assembly design, optical line-of-sight pointing method and sensor packaging all hinge on these secondary attributes. Moreover, the need for broad spectral coverage, ranging from 0.4 to 12.5 microns, places an additional constraint on optical design. This paper presents alternative design forms that are candidates for wide-field pushbroom sensors, and discusses the instrument-design tradeoffs that are linked to the selection of these alternate optical approaches.

Mika, A. M.↗

NASA NTRS1986

An infrared reflection nebula surrounding SGS 1 in the NGC 1333 dark cloud

Strom et al. (1974) have conducted a search for infrared sources associated with Herbig-Haro objects. They found an infrared source, SGS 1, near HH 12, embedded in at least 20 visual mag of extinction in the NGC 1333 dark cloud. Various factors suggest the presence of an infrared reflection nebula. In the context of the present investigation, high spatial resolution observations in the infrared have provided the basis for the development of a consistent model for SGS which consists of a low-luminosity, cool star with an accretion disk tilted to the line of sight, and one observed reflection lobe caused by the illumination of material above one of the polar regions of the accretion disk. It is pointed out that this model is similar to that of the infrared reflection nebula GSS 30 in the Ophiuchus dark cloud.

Castelaz, M. W.↗

NASA NTRS1986

A comparison of photospheric electric current and ultraviolet and X-ray emission in a solar active region

This paper presents an extensive set of coordinated observations of a solar active region, taking into account spectroheliograms obtained with the aid of the Solar Maximum Mission (SMM) Ultraviolet Spectrometer Polarimeter (UVSP) instrument, SMM soft X-ray polychromator (XRP) raster maps, and high spatial resolution ultraviolet images of the sun in Lyman-alpha and in the 1600 A continuum. These data span together the upper solar atmosphere from the temperature minimum to the corona. The data are compared to maps of the inferred photospheric electric current derived from the Marshall Space Flight Center (MSFC) vector magnetograph observations. Some empirical correlation is found between regions of inferred electric current density and the brightest features in the ultraviolet continuum and to a lesser extent those seen in Lyman-alpha within an active region.

Haisch, B. M.↗

NASA NTRS1985

8.3 and 12.4 micron imaging of the Galactic Center source complex with the Goddard infrared array camera

Gezari, D. Y.↗

NASA NTRS1985

Ground-based observations of near ecliptic zodiacal light brightness

Ground-based observation of the evening zodiacal light taken by Weinberg and Mann (1967) from Mt. Halaekala, Hawaii, during March 1966 are used to derive a table of zodiacal light brightnesses at high spatial resolution (as little as 0.5 deg in differential ecliptic longitude, DEL and 1.0 deg in ecliptic latitude beta) over the DEL region 29.5-56 deg, beta = -30 to +30 deg. Significant differences are found in the brightness distributions above and below the ecliptic plane.

Misconi, N. Y.↗

NASA NTRS1985

Cumulus cloud venting of mixed layer ozone

Observations are presented which substantiate the hypothesis that significant vertical exchange of ozone and aerosols occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments utilized the airborne Ultra-Violet Differential Absorption Lidar (UV-DIAL) system. This system provides simultaneous range resolved ozone concentration and aerosol backscatter profiles with high spatial resolution. Evening transects were obtained in the downwind area where the air mass had been advected. Space-height analyses for the evening flight show the cloud debris as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approximately the value of the concentration difference between the mixed layer and free troposphere determined from independent vertical soundings made by another aircraft in the afternoon.

Ching, J. K. S.↗

NASA NTRS1985

Improved satellite retrievals and mesoscale moisture variability

The investigations over the past year have led to the finalization of results from the study of mesoscale atmospheric parameters derived from the visible infrared spin scan radiometer (VISSR) atmospheric sounder (VAS). Soundings from several retrieval techniques for the 6 to 7 March 1982 special observation period were evaluated for mesoscale accuracy. Specific results and comparisons between data from a regression and two physical retrieval schemes are forthcoming in the Journal of Atmospheric and Oceanic Technology (JTech) this year. A generalization of these results is outlined. Large temperature and moisture biases existed in the VAS derived profiles, particularly in layers near inversions. Standard errors ranged from 1 to 3 C and 3 to 6 C for temperature and dewpoint, respectively. Parameters derived from VAS soundings (geopotential height, thickness, and precipitable water) often reflected the temperature and moisture profile biases. VAS derived mesoscale gradients were often weaker than those from corresponding rawinsonde data. Little improvement was made in defining the vertical structure of the atmosphere over the first guess information. VAS soundings were able to improve in the horizontal structure due to the high spatial resolution of the radiance data.

Jedlovec, G. J.↗

NASA NTRS1986

CO near the Pleiades: Encounter of a star cluster with a small molecular cloud

Although there is a large amount of interstellar matter near the Pleiades star cluster, the observed dust and gas is not a remnant of the placental molecular cloud from which the star cluster was formed. Carbon monoxide (CO) associated with the visible reflection nebulae was discovered by Cohen (1975). Its radial velocity differs from that of the cluster by many times the cluster escape velocity, which implies that the cloud-cluster association is the result of a chance encounter. This circumstance and the proximity of the Pleiades to the sun creates an unique opportunity for study of interstellar processes at high spatial resolution. To study the molecular component of the gas, a 1.7 square degree field was mapped with the AT&T Bell Laboratories 7-meter antenna (1.7' beam) on a 1' grid in the J=1.0 C(12)O line, obtaining over 6,000 spectra with 50 kHz resolution. The cloud core was mapped in the J=1-0 line of C(13)O. Further observations include an unsuccessful search for CS (J=2-1) at AT&T BL, and some C(12)O J=2-1 spectra obtained at the Millimeter Wave Observatory of the University of Texas.

Bally, J.↗