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Infrared reflectance measurements of igneous rocks, tuffs, and red sandstone from 0.5 to 22 microns to obtain data for use in determining surface composition of planets
A laboratory study of the mid-infrared spectral reflectance properties of typical Apollo lunar rock and soil samples was conducted using a modern interferometric spectrometer. The results show that characteristic spectral features exist in the 4-12 micrometer range that are diagnostic of rock composition and mineralogy, especially for the plagioclase-rich rocks and soils. This is the first phase of a comprehensive infrared reflectance study under way to better understand the use of infrared emission spectroscopy for mapping the surface composition of the moon and other silicate bodies.
A surface brightness map and point-wise photometry at 10 microns of the infrared reflection nebula GSS30 were made with the Wyoming 2.3-m telescope. Extended emission is detected as far as 10 arcsec north of the illuminating star, IRS1. The photometry shows that the nebular surface brightness is a factor of three more than that expected from thermal emission from dust grains. If the 10 micron flux is due to scattering, then grains with a radius of 1.6 microns are required. Alternatively, the 10 micron flux is consistent with the flux expected from the unidentified IR emission features at 7.7, 8.6, and 11.3 microns.
New obervations of Orion Molecular Cloud-2 have been made from 1-100 microns using the NASA Infrared Telescope Facility and the Kuiper Airborne Observatory. An extensive program of polarimetry, photometry and spectrophotometry has shown that the extended emission regions associated with two of the previously known near infrared sources, IRS1 and IRS4, are infrared reflection nebulae, and that the compact sources IRS1 and IRS4 are the main luminosity sources in the cloud. The constraints from the far infrared observations and an analysis of the scattered light from the IRS1 nebula show that OMC-2/IRS1 can be characterized by L less than or equal to 500 Solar luminosities and T approx. 1000 K. The near infrared (1-5) micron albedo of the grains in the IRS1 nebula is greater than 0.08.
Laboratory results show that (1) the Christiansen frequency (CF) feature in mid-infrared reflectance spectra of powders can be used to accurately distinguish plagioclase composition, and (2) the wavelength position of the CF is not affected by vitrification of the plagioclase. Although the CF position does not distinguish glass from crystalline forms of plagioclase, other features (combination-tone, overtone, restrahlen bands) in the mid-IR spectra of plagioclase can be used for that purpose. These results have important implications for application of thermal emission spectroscopy to mapping the surface composition of regolith-covered planetary bodies like the moon, Mars, and asteroids.
New observations of Orion Molecular Cloud 2 have been made from 1 to 100 microns using the NASA Infrared Telescope Facility and the Kuiper Airborne Observatory. An extensive program of polarimetry, photometry, and spectrophotometry has shown that the extended emission regions associated with two of the previously known near-infrared sources, IRS 1 and IRS 4, are infrared reflection nebulae, and that the compact sources IRS 1 and IRS 4 are the main luminosity sources in the cloud. The constraints from the far-infrared observations and an analysis of the scattered light from the IRS 1 nebula show that OMC-2/IRS 1 can be characterized by L of 500 solar luminosities or less and T of roughly 1000 K. The near-infrared albedo of the grains in the IRS 1 nebula is greater than 0.08.
Two micron linear polarimetry of the S 106 and NGC 7538 E regions reveal the presence of infrared reflection nebulae, which may confuse the count of luminosity sources in a region of star formation. S 106 and NGC 7538/IRS 9 are considered the only luminosity sources in their respective regions, and the polarization of S 106/Source 3 is probably due to absorption by aligned grains. Moreover, the reflection nebula model for NGC 7538 E is best supported if the polarization of NGC 7538/IRS 9 itself is due to the absorption by aligned grains.
Far-infrared specular reflectance spectra of six optically black coatings near normal incidence are presented. The spectra were obtained using nine bandpass transmission filters in the wavelength range between 12 and 300 microns. Data on the construction, thickness, and rms surface roughness of the coatings are also presented. The chemical composition of two coatings can be distinguished from that of the others by a strong absorption feature between 20 and 40 microns which is attributed to amorphous silicate material. Inverse relationships between these spectra and coating roughness and thickness are noted and lead to development of a reflecting-layer model for the measured reflectance. The model is applied to the spectra of several coatings whose construction falls within its constraints.
A grazing angle objective on an infrared microspectrometer is studied for quantitative spectroscopy by considering the angular dependence of the incident intensity within the objective's angular aperture. The assumption that there is no angular dependence is tested by comparing the experimental reflectance of Si and KBr surfaces with the reflectance calculated by integrating the Fresnel reflection coefficient over the angular aperture under this assumption. Good agreement was found, indicating that the specular reflectance of surfaces can straight-forwardly be quantitatively integrated over the angular aperture without considering non-uniform incident intensity. This quantitative approach is applied to the thickness determination of dipcoated Krytox on gold. The infrared optical constants of both materials are known, allowing the integration to be carried out. The thickness obtained is in fair agreement with the value determined by ellipsometry in the visible. Therefore, this paper illustrates a method for more quantitative use of a grazing angle objective for infrared reflectance microspectroscopy.
The weathering of Hawaiian basalts is accompanied by chemical and physical changes of the surfaces. These changes have been mapped using remote sensing data from the visible and reflected infrared and thermal infrared wavelength regions. They are related to the physical breakdown of surface chill coats, the development and erosion of silica coatings, the oxidation of mafic minerals, and the development of vegetation cover. These effects show systematic behavior with age and can be mapped using the image data and related to relative ages of pahoehoe and aa flows. The thermal data are sensitive to silica rind development and fine structure of the scene; the reflectance data show the degree of oxidation and differentiate vegetation from aa and cinders. Together, data from the two wavelength regions show more than either separately. The combined data potentially provide a powerful tool for mapping basalt flows in arid to semiarid volcanic environments.
We have studied the protostellar system in S140 at 2.2, 3.1 and 3.45 microns using a 128x128 InSb array at the Lick Observatory 3m telescope. Besides the protostellar sources, the data reveal a bright infrared reflection nebula. We have developed a simple model of this region and derived the physical conditions. IRSI is surrounded by a dense dusty disk viewed almost edge-on. Photons leaking out through the poles illuminate almost directly north and south the inner edge of a surrounding shell of molecular gas, Analysis of the observed colors and intensities of the NIR light, using Mie scattering theory, reveal that the dust grains in the molecular cloud are somewhat larger than in the general diffuse interstellar medium. Moreover, the incident light has a "cool" color temperature, approximately equals 800K, and likely originates from a dust photosphere close to the protostar. Finally, we find little H2O ice associated with the dusty disk around IRSI. Most of the 3.1 micron ice extinction arises instead from cool intervening molecular cloud material. We have compared our infrared dust observations with millimeter and radio observations of molecular gas associated with this region. The large scale structure observable in the molecular gas is indicative of the interaction between the protostellar wind and the surrounding molecular cloud rather than the geometry of the protostellar disk. We conclude that S140 is a young blister formed by this outflow on the side of a molecular cloud and viewed edge-on.
Near-infrared spectral reflectance data were collected at the Infrared Telescope Facility (IRTF) at Mauna Kea Observatories in 1985 and 1986 for the purpose of searching the region near the 3:1 Kirkwood gap for asteroids with the spectral signatures of ordinary chondrite parent bodies. Twelve reflectance spectra are observed. The presence of ordinary chondrite parent bodies among this specific set of observed asteroids is not obvious, though the sample is biased towards the larger asteroids in the region due to limitations imposed by detector sensitivity. The data set, which was acquired with the same instrumentation used for the 52-color asteroid survey (Bell et al., 1987), also presents some additional findings. The range of spectral characteristics that exist among asteroids of the same taxonomic type is noted. Conclusions based on the findings are discussed.
The infrared source R CrA IRS 5 in the R CrA dark cloud has been mapped, and it is found that it is extended at H (1.6 micron) and at K (2.2 micron). The geometry of the data suggest that this object consists of a disk and polar reflection lobe surrounding a star, similar to GSS 30 in the Ophiuchus dark cloud and to SGS 1 in the NGC 1333 dark cloud. The illuminating star has an effective temperature below 8000 K, a luminosity less than 9 solar luminosities, and lies above the main sequence. The luminosity of this star is smaller than the luminosity of any other known star which illuminates an infrared reflection nebula.
The slopes of near-infrared spectra between approximately 1 and 2 microns from quartz-bearing plutonic rocks are strongly correlated with rock chemistry determined by X-ray spectrometry. The empirically derived predictive equations provide compositional data of adequate precision and resolution to discern patterns of regional geochemical variation in granitic batholithic rocks of southern California. As an analytical method, infrared spectrometry is rapid and inexpensive, and the method has potential in applications to direct field measurements and to data from aircraft and spacecraft scanner systems of relatively low spectral and spatial resolution, provided vegetative cover and surface alteration are not prohibitively masking.
IR reflectivity of polyhydrated ferric oxide measured in connection with Martian surface hydration determination from reflection spectra
A useful parameter to estimate terrestrial primary productivity, that can be sensed from space, is the daily averaged fraction of Photosynthetically Available Radiation (PAR) absorbed by plants. To evaluate this parameter, investigators have relied on the fact that the relative amount of radiation reflected by a vegetated surface in the visible and near infrared depends on the fraction of the surface covered by the vegetation and therefore, correlates with absorbed PAR. They have used vegetation indices, namely normalized difference and simple ratio, to derive absorbed PAR. The problem with normalized difference and simple ratio is first, they are non linear functions of radiance or reflectance and therefore, cannot be readily applied to heterogeneous targets, second, they are used in generally nonlinear relationships, which make time integrals of the indices not proportional to primary productivity, and third, the relationships depend strongly on the type of canopy and background. To remove these limitations, linear combinations of visible and near infrared reflectances at optimum (one or two) viewing zenith angles are proposed.
Paint film thickness of spacecraft coatings, effect on spectral directional reflectance and binormal transmittance in far IR
Paint film thickness of spacecraft coatings, effect on spectral directional reflectance and binormal transmittance in far IR