Elsa Abbott

Combined use of visible, reflected infrared, and thermal infrared images for mapping Hawaiian lava flows

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.

Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii

Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10° C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. In general, the emissivity of the flows varied systematically with age but the relationship between age and emissivity was not unique. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows. Such incipient alteration may have been the cause for virtually all of the emissivity variations observed on the flow field, the spectral anomalies representing areas where the acid attack was most intense.

The ASTER Global Emissivity Dataset (ASTER GED): Mapping Earth's emissivity at 100 meter spatial scale

Thermal infrared (TIR) data, acquired by instruments on several NASA satellite platforms, are primarily used to estimate the surface temperature/emissivity of the Earths land surface. One such instrument launched on NASAs Terra satellite in 1999 is the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), which has a spatial resolution of 90 m. Using ASTER data, NASA/Jet Propulsion Laboratory recently released the most detailed emissivity map of the Earth termed the ASTER Global Emissivity Dataset (ASTER GED) that was acquired by processing millions of cloud free ASTER scenes from 2000 to 2008. The ASTER GEDv3 provides an average emissivity at ~100 m and ~1 km, while GEDv4 provides a monthly emissivity from 2000 to 2015 at ~5 km spatial resolution in the wavelength range between 8 and 12 µm. Validation with lab spectra from four desert sites resulted in an average absolute band error of ~1%, compared to current heritage MODIS products that had average absolute errors of 2.4% (Collection 4) and 4.6% (Collection 5).

Structure mapping on enhanced Landsat images of southern Brazil; tectonic control of mineralization and speculations on metallogeny

Computer enhancement, particularly contrast‐stretching, reveals a previously unnoticed east‐west structural zone across a Landsat image of the southern Brazilian Precambrian shield. In this zone occur the only known economic or near‐economic deposits of gold, tin, and copper. Such deposits are typically localized by small east‐west structural elements. Non‐economic copper occurrences elsewhere in the region appear to be related to major northeast‐ and northwest‐trending lineaments mapped on Landsat images. Mineral exploration should be primarily directed at the main east‐west lineament, but two other possible east‐west zones might be worthwhile targets also. The major east‐west lineament projects through a break in the continental shelf, across the Atlantic along a large transoceanic fracture zone and into the African continent along a mapped tectonic trend that goes through an area that produces copper, gold, and tin. Global geophysical data suggest that the mapped east‐west trend in South America is a s...

ASTER/TIR vicarious calibration activities in US and Japan validation sites for 14 years

The ASTER instrument onboard the NASA’s Terra satellite launched in December 1999 has three subsystems divided by the spectral regions. ASTER thermal infrared (TIR) subsystem has five TIR bands with a spatial resolution of 90 m. Since March 2000 after the initial checkout period, many vicarious calibration (VC) experiments have been conducted for ASTER/TIR in lakes such as Lake Tahoe (NV/CA), Salton Sea (CA), and Lake Kasumigaura (Japan), and in dry lakes such as Railroad Valley (NV), Alkali Lake (NV), and Coyote Lake (CA). In the present paper, 307 VC matchup data obtained by three organizations were analyzed. Overall results show that a typical difference between the at-sensor radiance acquired by onboard calibration (OBC) and that predicted by VC is about 0.5 to 1 K in the water sites and about 1 to 2 K in the land sites. The results of the responsivity analysis indicate that VC is well tracking the responsivity changes measured by OBC, though the recent discrepancy at band 10 should be investigated with more VC results. The results of the offset analysis indicate that the short term calibration (STC) which is performed at a blackbody temperature of 270 K before every Earth observation has worked normally. It is therefore concluded that the ASTER/TIR instrument has been keeping the designed accuracy (1 K for the temperature range of 270 to 340 K) since the launch.

Verification of prehistoric campfires by 40Ar39Ar analysis of fire-baked stones

Abstract 40Ar39Ar analysis may be used to test whether or not suspected hearths and cooking pits from archaeological sites of ancient man ever contained fires. Under some circumstances it may even be possible to deduce the intensity of use and to estimate ages for sites too old to be dated by conventional 14C analysis. This is done using the stepwise heating variant of 40Ar39Ar analysis to measure argon loss from rocks caused by heating in the campfire. It appears to be possible to determine if stones containing microcline or other potassium-bearing minerals were ever heated above ∼500°C for 30 min or more.

Thermal-infrared imaging of weathering and alteration changes on the surfaces of basalt flows, Hawai‘i, USA

Basaltic pahoehoe lavas weather on time scales of decades to millennia and are chemically altered by volcanic heat and gases on time scales of days to decades following their eruption. Despite differences in reactions and rates, the end products, viewed spectrally in the thermal infrared (TIR: 8–12 μm), are similar and distinctive: initial rinds of quickly cooled, disordered glass with broad emissivity minima at 9–11 μm devitrify to yield a sharper emissivity band at 9.1 μm; opaline rinds with a similar emissivity feature accrete and gradually transition to cryptocrystalline quartz with an emissivity minimum near 8.1 μm. Ultimately, exposed surfaces are oxidized and hydrated to palagonite, with a loss of spectral contrast and character. We have collected over 600 pahoehoe samples of different ages from seven sites on Mauna Loa and the south coast of Hawai‘i in order to measure hemispheric emissivity spectra and compare them to airborne and spaceborne TIR Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) AST05 emissivity images of Hawai‘i. ASTER, with five 90 m TIR bands, has operated over the 11 year period since launch in late 1999. Images and samples from some of the Hawai‘ian sites were collected repeatedly over a decade or more to study the rate of spectral change there. Continuing eruptions of Pu‘u ‘O‘o since 1983 offered an opportunity to study the effects of a persistent dousing of lavas by acidic rain and air (‘vog’), and older flows from Mauna Loa offered an opportunity to study the effects of weathering away from active vents. Weathering changes and rates quantified spectrally are helpful in mapping and assessing long-term environments on volcanoes.

Aster/TIR vicarious calibration activities in the last 11 years

Since March 2000, the project science team for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard NASAs Terra satellite has conducted vicarious calibration (VC) experiments periodically to verify the onboard calibration (OBC) of ASTER thermal infrared (ASTER/TIR) bands. In the present paper, 287 matchup data obtained from ten experimental sites by three organizations are analyzed. The radiance difference of OBC and VC shows almost no correlation with surface temperature and precipitable water vapor at each experimental site, but shows some dependence on the type of the experimental site. For example, the OBC-VC comparisons at Cold Springs Reservoir (NV) which is a small water body shows some bias due to the straylight effect of ASTER/TIR. The comparisons at Lake Kussharo covered by snow also show some bias maybe because of an extrapolation effect of ASTER radiometric calibration. The comparisons at Mauna Loa lava flows show a large deviation due to non-uniformity of surface temperature caused by the rough surface. Except for these cases, the results show that the latest version of radiometric calibration coefficients (version 3.×) for ASTER/TIR has been keeping the designed accuracy (1 K for the temperature range of 270 to 320 K).

Analysis of Shuttle Multispectral Infrared Radiometer measurements of the western Saudi Arabian shield

During the November 12–14, 1981, mission of the space shuttle Columbia, the Shuttle Multispectral Infrared Radiometer (SMIRR) recorded radiances in ten channels along a 100 m wide groundtrack across the western Saudi Arabian shield. The ten channels are located in the 0.5 to 2.4 μm region, with five positioned between 2.0 and 2.40 μm for measuring absorption features that are diagnostic of OH‐bearing and CO3‐bearing minerals. This exceptionally well exposed area consists of late Proterozoic metamorphic, intermediate to silicic intrusive, and interlayered clastic sedimentary and intermediate silicic volcanic rocks that have not been studied previously using SMIRR data. Plots or traces of unnormalized SMIRR channel ratios were examined before field studies to locate areas with high spectral contrast, especially in the 2.0 μm to 2.40 μm channels. Reflectance spectra were measured in the laboratory for rock and soil samples collected in these areas, and the mineralogic causes of the main absorption features w...

Multiscale thermal-infrared measurements of the Mauna Loa caldera, Hawaii

Until recently, most thermal infrared measurements of natural scenes have been made at disparate scales, typically 10-3-10-2 (spectra) and 102-103m (satellite images), with occasional airborne images (101m) filling the gap. Temperature and emissivity fields are spatially heterogeneous over a similar range of scales, depending on scene composition. A common problem for the land surface, therefore, has been relating field spectral and temperature measurements to satellite data, yet in many cases this is necessary if satellite data are to be interpreted to yield meaningful information about the land surface. Recently, three new satellites with thermal imaging capability at the 101-102m scale have been launched: MTI, TERRA, and Landsat 7. MTI acquires multispectral images in the mid-infrared (3-5micrometers ) and longwave infrared (8-10micrometers ) with 20m resolution. ASTER and MODIS aboard TERRA acquire multispectral longwave images at 90m and 500-1000m, respectively, and MODIS also acquires multispectral mid-infrared images. Landsat 7 acquires broadband longwave images at 60m. As part of an experiment to validate the temperature and thermal emissivity values calculated from MTI and ASTER images, we have targeted the summit region of Mauna Loa for field characterization and near-simultaneous satellite imaging, both on daytime and nighttime overpasses, and compare the results to previously acquired 1--1m airborne images, ground-level multispectral FLIR images, and the field spectra. Mauna Loa was chosen in large part because the 4x6km summit caldera, flooded with fresh basalt in 1984, appears to be spectrally homogeneous at scales with 10-1 and 102m, facilitating the comparison of sensed temperature. The validation results suggest that, with careful atmospheric compensation, it is possible to match ground measurements with measurements from space, and to use the Mauna Loa validation site for cross-comparison of thermal infrared sensors and temperature/emissivity extraction algorithms.