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NASA NTRS1983

Infrared astronomical imaging using a microcomputer data system

A small, portable data-acquisition and display system with a unique coprocessor was designed and built to collect data from infrared array detectors for astronomical and laboratory use. The system consists of a microcomputer board, two 12-bit analog-to-digital data-acquisition boards, a color-graphics driver board, and two coprocessor boards. The coprocessors are arithmetic logic units designed to achieve the high computation rates necessary for real-time infrared background cancellation. The system can collect data from infrared detectors of 1 to 256 pixel elements with a computation rate of 768 kHz. The software for the system was designed to collect data in the system's background, while performing other tasks in the system's foreground. The data for the detector arrays is stored in block fashion to facilitate variable image size.

Stafford, P. S.↗

NASA NTRS1984

A comparison of surface temperature derived from HCMM infrared measurements with field data

The satellite for the Heat Capacity Mapping Mission (HCMM) was launched on April 26, 1978. The HCMM had the objective to collect data in support of studies concerned with the feasibility of using infrared temperature data to compute the thermal inertia from the earth's surface. The HCMM radiometer had a channel for reflected radiation in the 0.5 to 1.1 micron waveband, and a channel for the infrared radiation in the 10.5 to 12.5 micron band. However, difficulties developed in connection with changes in the characteristics of the radiometer. The present investigation is concerned with a comparison of HCMM infrared temperatures with in situ data from the Mississippi River in the St. Louis, Missouri, area and with sea-surface temperatures collected in the Nantucket Shoals and Gulf of Mexico regions. It was found that, on the average, the difference between satellite in situ data was -4.6 C.

Vukovich, F. M.↗

NASA NTRS1983

Sensitive observations with the Spacelab 2 infrared telescope

The small helium-cooled infrared telescope (Spacelab IRT) is a multiband instrument capable of highly sensitive observations from space. The experiment consists of a cryogenically cooled, very well baffled telescope with a ten channel focal plane array. During the Spacelab 2 flight of the Space Shuttle, this instrument will make observations between 5 and 120 micron wavelength that will be background limited by the expected zodiacal emission. Design considerations necessitated by this level of performance are discussed in this paper. In particular, the operation of a very sensitive focal plane array in the space environment is described. The Spacelab IRT will be used to map the extended, low-surface brightness celestial emission. During the seven day length of the mission better than 70 percent sky coverage is expected. The instrument will also be used to measure the infrared contamination environment of the Space Shuttle. This information will be important in the development of the next generation of infrared astronomical instruments. The performance of the Spacelab IRT, in particular its sensitivity to the contamination environment is detailed.

Young, E. T.↗

NASA NTRS1984

Far-infrared studies of Herbig-Haro objects and their exciting stars

Far-infrared (40-160 micron) observations of Herbig-Haro objects and their probable exciting stars are presented. The importance of these far-infrared observations is epitomized by the fact that, on average, 70 percent of the bolometric luminosity of a typical candidate star is radiated beyond the longest detected ground-based wavelength, even for those objects observed out to 20 micron from the ground. Extended far-infrared emission characterizes some of these regions. Some Herbig-Haro nebulae are themselves conspicuous 100 micron peaks (e.g., HH 1 and HH 25). A bipolar structure is found at 100 micron in the vicinity of the Cohen-Schwartz star. All the exciting stars must be low-mass objects (approximately less than 3 solar mass). It is argued that they might be approximately 1 solar mass protostars still in their accretion phase.

Cohen, M.↗

NASA NTRS1984

Observations of infrared hydrogen recombination line emission from external galaxies

Observations of infrared hydrogen recombination line emission are presented for several positions within the galaxies NGC 1068, NGC 1097, NGC 2903, and NGC 4151. Emission is seen from the arms and nuclei of these spiral galaxies. The luminosity from the most recent burst of star formation is deduced and compared to the infrared luminosity which accounts for the bulk of the total energy. Young stars (primarily O and B stars) provide most of the luminosity in the arms and nuclei of the normal galaxies NGC 1097 and NGC 2903. The infrared luminosities of the nuclei in the Seyfert galaxies NGC 1068 and NGC 4151 exceed those provided by young stars by factors of approximately 10.

Gatley, I.↗

NASA NTRS1984

1-20 micron infrared photometry of 3CR radio galaxies

Seven emission-line radio galaxies in the wavelength range from 1 to 20 microns were observed in February 1983. Three broad emission-line galaxies (BLRGs 3C 109, 3C 234, and 3C 445), and four narrow emission-line radio galaxies (NLRGs 3C 98, 3C 198, 3C 223, and 3C 293) were found. The BLRGs showed strong infrared fluxes beyond 3.5 microns, with steep infrared slopes similar to optical slopes. In a comparison with earlier observational data it was found that two of the BLRGs are variable in the JHK filter range without a change of slope. The NLRGs showed strong excess at 10 microns and normal elliptical galaxy colors at JHK and L. Simple predictions based on type-2 Seyfert galaxies show that strong infrared excesses are absent.

Elvis, M.↗

NASA NTRS1984

Infrared spectroscopy of interstellar shocks

Infrared emission lines from interstellar shocks provide valuable diagnostics for violent events in the interstellar medium, such as supernova remnants and mass outflow from young stellar objects. There are two types of interstellar shocks: in J shocks, gas properties 'jump' from their preshock to their postshock values in a shock front with a thickness equal to or less than one mean free path; radiation is emitted behind the shock front, primarily in the visible and ultraviolet, but with a few strong infrared lines, such as OI(63 microns). Such shocks occur in ionized or neutral atomic gas, or at high velocities (equal to or greater than 50 km/s) in molecular gas. In C shocks, gas is accelerated and heated by collisions between charged particles, which have a low concentration and are coupled to the magnetic field, and neutral particles; radiation is generated throughout the shock and is emitted almost entirely in infrared emission lines. Such shocks occur in weakly ionized molecular gas for shock velocities below about 50 km/s.

Mckee, C. F.↗

NASA NTRS1984

NGC 2024 - Far-infrared and radio molecular observations

New far-infrared continuum and millimeter-wave molecular observations of NGC 2024 are presented. The measurements were obtained at relatively high angular resolution making it possible to describe the source energetics and mass distribution in greater detail than previously reported. The object appears to be dominated by a dense ridge of material, extended in the north-south direction and centered on the dark lane that is seen in visual photographs. The maps of the source using the 'high-density' molecules CS and HCN confirm this picture and makes it possible to describe the core structure and molecular abundances. The radio molecular and infrared observations support the idea that an important exciting star in NGC 2024 has yet to be identified and is centered on the dense ridge about 1 arcmin south of the bright mid-infrared source IRS 2. The data presented here, along with other observations, make it possible to describe a model for the source.

Thronson, H. A., Jr.↗

NASA NTRS1984

An infrared disk at the center of the bipolar planetary nebula NGC 6302

Broad-band infrared photometry and high-resolution infrared maps are presented for NGC 6302, a bipolar planetary nebula in which material is being driven outward by a powerful stellar wind. The infrared morphology is very unlike that seen optically. Maps at 1.25, 2.2, 3.4, and 10 microns show evidence for a disk of material with its short axis oriented parallel to the supersonic flow and located between the optical lobes. This structure is not optically evident partly because of the large extinction along the line of sight to the nebular core. It is suggested that the observed disk is either an expanded fossil toroid that once confined the flow, or else is stellar envelope material that was not in the path of the bipolar flow and that remains in the vicinity of the stellar remnant.

Lester, D. F.↗

NASA NTRS1984

Far-infrared photometry of compact extragalactic sources: OJ 187 and BL Lac

The 50 and 100 micron emissions of OJ 287 were detected and upper limits for BL Lac were obtained. These first measurements of two BL Lac objects in the far-infrared show them to be similar to the few quasars previously observed in the far-infrared. In particular, there is no evidence for significant dust emission, and the lambda approximately 100 micron flux density fits on a smooth line joining the near-infrared and millimeter continuum fluxes. The implications of the results for models of the sources are discussed briefly.

Harvey, P. M.↗

NASA NTRS1984

High Sensitivity, High Angular Resolution Far-infrared Photometry from the KAO

Most of the luminosity of embedded sources is reemitted in the far-infrared continuum. Measurements in the far-infrared are essential to understand the energetics of the interstellar medium, and of star formation regions in particular. Measurements from the KAO, are made in diffraction limited beams that sample a spatial scale considerably smaller than that given by IRAS. The KAO instrument technology has matured to the point that the single scan limiting flux of IRAS at 100 micro can be reached in a diffraction limited beam in a single typical KAO observing leg. The far-infrared photometer system and selections of recent observations are presented.

Lester, D.↗

NASA NTRS1984

Far Infrared Observations of Molecular Clouds in the Outer Galaxy

The existence of molecular clouds in the outer galaxy allows the study of star formation at large galactocentric radii. The study of these clouds has two aims. A systematic survey is underway to study the large scale distribution of the molecular clouds outside the solar circle. To understand the physical conditions in the clouds, fully sampled maps were (and are being) made in CO and other molecules. The continuum emission is also being mapped. The main objective in doing an infrared study was to obtain information on the luminosity of the stars formed in these clouds. Assuming all energy radiated from the star is absorbed by the dust and then re-radiated in the infrared, one can get an estimate of the star's luminosity by integrating the flux over the source and converting it to a luminosity. Until these observations, the only way of judging stellar luminosities was from peak CO temperatures. Accounting for beam dilution, Kutner and Mead inferred from these that the heat sources were late B or later stars. The Kupier Airborne Observatory was used to search 9 sources in 5 clouds for far infrared emission.

Mead, K. N.↗

NASA NTRS1985

Infrared horizon sensor modeling for attitude determination and control: Analysis and mission experience

The work performed by the Attitude Determination and Control Section at the National Aeronautics and Space Administration/Goddard Space Flight Center in analyzing and evaluating the performance of infrared horizon sensors is presented. The results of studies performed during the 1960s are reviewed; several models for generating the Earth's infrared radiance profiles are presented; and the Horizon Radiance Modeling Utility, the software used to model the horizon sensor optics and electronics processing to computer radiance-dependent attitude errors, is briefly discussed. Also provided is mission experience from 12 spaceflight missions spanning the period from 1973 to 1984 and using a variety of horizon sensing hardware. Recommendations are presented for future directions for the infrared horizon sensing technology.

Phenneger, M. C.↗

NASA NTRS1985

Far-infrared line observations of planetary nebulae. 1: The O 3 spectrum

Observations of the far-infrared fine structure lines of O III have been obtained for six planetary nebulae. The infrared measurements are combined with optical O III line fluxes to probe physical conditions in the gas. From the observed line intensity ratios, a simultaneous solution was obtained for electron temperature and density, as well as means of evaluating the importance of inhomogeneities. Densities determined from the far-infrared O III lines agree well density diagnostics from other ions, indicating a fairly homogeneous density in the emitting gas. Temperatures are determined separately from the O III 4363/5007 A and 5007 A/52 micron intensity ratios and compared. Systematically higher values are derived from the former ratio, which is expected from a nebula which is not isothermal. Allowance for the presence of temperature variations within these nebulae raises their derived oxygen abundances, determinations to be reconciled with the solar value.

Dinerstein, H. L.↗

NASA NTRS1985

Search for infrared counterparts of gamma-ray bursters

The result of two searches for infrared counterparts of Gamma-ray Bursters (GRB's) is reported. The first search was made using data from the Infrared Astronomy Satellite and covered 23 positions. The second search was made with the Kitt Peak 1.5 m telescope and covered 3 positions. In neither of these two searches was any infrared candidate detected.

Schaefer, B. E.↗

NASA NTRS1985

Far-infrared emission lines of CO and OH in the Orion-KL molecular shock

Observations of far infrared rotational emission lines which arise in the shocked gas associated with Orion-Kl are presented, including detections of the CO J = 34 yields 33, J = 31 yields 30, J = 26 yields 25, and OH sup 2 PI sub (3/2) J sup P = 7/2(-) yields 5/2(+) emission lines, as well as improved measurements of the CO J = 22 yields 21 and OH sup 2 PI sub (3/2) J = 5/2 yields 3/2 lines. These lines are observed to have velocity widths of Del V approx. 20 to 30 km/sec, somewhat less than either the 2 micro H sub 2 lines or the high velocity plateau component of the millimeter wave CO lines seen in this object. An H sub 2 column density of approx. 3 x 10 to the 21st power, a total mass of approx. 1 solar mass and characteristic temperature and density T approx. 750 K and approx. 2 x 10 to the 6th power per cu cm can be derived from the CO intensities. The density is too low by at least an order of magnitude for the observed infrared H sub 2 and far infrared CO emission to be accounted for by a purely hydrodynamic shock, and support is lent to hydromagnetic shock models. From the present measurements, the relative abundance of CO is estimated to be CO H sub 2 = 1.2 x .0001, corresponding to 20% of the cosmic abundance of C existing in the form of CO. The average relative abundance of OH in the shocked gas is O/H sub 2 or = 5 x 10 to the -7th power. An upper limit to the intensity of the HD J = 1 yields 0 line is used to derive an upper limit of tau or = 3 for the D/H relative abundance in the Orion cloud core.

Watson, D. M.↗

NASA NTRS1983

HgCdTe infrared focal plane arrays for imaging spectrometer applications

It is pointed out that the development of two-dimensional infrared focal plane arrays (FPAs) offers new alternatives in imaging and remote sensing. Attention is given to an imaging spectrometer which represents a new concept exploiting two-dimensional arrays. This instrument is to be used for the remote sensing of the earth on the basis of a utilization of reflected sunlight in both the visible (VIS) and short wavelength infrared (SWIR). The imaging spectrometer concept is to make it possible to obtain contiguous spectral coverage at high resolution without having to use increasingly complex scanners. The concept utilizes a prism spectrometer to disperse the image of the slit across the area arrays in the focal plane. The focal plane consists of silicon CCDs for the VIS and near infrared portions of the spectrum and HgCdTe hybrid arrays for the SWIR.

Rode, J. P.↗

NASA NTRS1984

Granitic terrains viewed remotely by Shuttle infrared radiometry - Some compositional predictions

Ratios of intensities of near-infrared spectral bands, measured in reflectance, quantitatively predict the iron content of granitic rocks. Such data from the 1.60- and 1.05-micron bands of the Shuttle multispectral infrared radiometer have been used to study granitic rocks along orbits crossing Baja California, Mexico, and the Eastern Desert of Egypt. Both regions are arid and relatively to essentially free of vegetation, and there is no indication in the spectra that surface chemical alteration masks the true composition of the unweathered rock. Predicted values of iron are consistent with known compositional types of most of the rocks along the orbital paths. Results demonstrate that the near-infrared method used is a powerful technique to average the variability of these rocks on the scales of meters to kilometers.

Baird, A. K.↗