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Development of models for thermal infrared radiation above and within plant canopies
Any significant angular dependence of the emitted longwave radiation could result in errors in remotely estimated energy budgets or evapotranspiration. Empirical data and thermal infrared radiation models are reviewed in reference to anisotropic emissions from the plant canopy. The biometeorological aspects of linking longwave models with plant canopy energy budgets and micrometeorology are discussed. A new soil plant atmosphere model applied to anisotropic longwave emissions from a canopy is presented. Time variation of thermal infrared emission measurements is discussed.
Thermal-infrared spectral observations of geologic materials in emission
The thermal-infrared spectra of geologic materials in emission were studied using the prototype Thermal Emission Spectrometer (TES). A variety of of processes and surface modifications that may influence or alter the spectra of primary rock materials were studied. It was confirmed that thermal emission spectra contain the same absorption features as those observed in transmission and reflection spectra. It was confirmed that the TES instrument can be used to obtain relevant spectra for analysis of rock and mineral composition.
Investigation of forest canopy temperatures recorded by the thermal infrared multispectral scanner at H. J. Andrews Experimental Forest
Thermal Infrared Multispectral Scanner (TIMS) data were collected over the H. J. Andrews Experimental Forest in Western Oregon on July 29, 1983 at approximately 1:30 p.m., Pacific Standard Time. The relation of changes in canopy temperature to green leaf biomass levels in reforested clearcuts and old-growth forest was investigated. A digital data base was generated in order to isolate that portion of the thermal emission that could be attributed to surface properties other than the vegetation biomass component. The TIMS appears to be capable of detecting subtle differences in ERT as related to canopy closure and green lead biomass, however calibration techniques are needed to correct for emissivity and atmospheric effects.
Anisotropy of thermal infrared exitance above and within plant canopies
Any significant angular dependence of the emitted long wave radiation could result in errors in remotely estimated energy budgets or evapotranspiration. Empirical data and thermal infrared radiation models are reviewed in reference to anisotropic emissions from the plant canopy. The biometeorological aspects of linking longwave models with plant canopy energy budgets and micrometeorology are discussed. A new soil plant atmosphere model applied to anisotropic longwave emissions from a canopy is presented. Time variation of thermal infrared emission measurements is discussed.
Determination of water surface temperature based on the use of Thermal Infrared Multispectral Scanner data
A straightforward method for compensating Thermal Infrared Multispectral Scanner (TIMS) digital data for the influence of atmospheric path radiance and the attenuation of target energy by the atmosphere is presented. A band ratioing model useful for estimating water surface temperatures, which requires no ground truth measurements, is included. A study conducted to test the potential of the model and the magnitudes of the corrections for atmosphere encountered is presented. Results of the study, which was based on data collected during an engineering evaluation flight of TIMS, indicate errors in the estimate of the surface temperature of the water fall from +/- 1.0 C for uncorrected data to +/- 0.4 C when data have been corrected according to the model presented. This value approaches the noise-limited thermal resolution of the sensor at the time of the flight.
Landsat 9 Thermal Infrared Sensor 2 Preliminary Stray Light Assessment
Although the Thermal Infrared Sensor 2 (TIRS-2) is a nearidentical copy of the Landsat 8/TIRS-1 instrument, an important design change to the optical system was designed to mitigate the stray light issue that plagued the TIRS-1 instrument [1, 2, 3]. This change involved the addition of several baffles strategically placed within the optical telescope to block the stray light paths that were present in the TIRS- 1 design. The specific optical changes were determined by first characterizing the TIRS-1 stray light paths on-orbit and then deriving a detailed optical model that was used to determine the locations and shapes of the mitigating baffles. The stray light design changes to the TIRS-2 instrument were confirmed through the initial thermal-vacuum characterization tests. Preliminary assessments of TIRS-2 indicate that the total stray light magnitude has been drastically reduced to a total magnitude of approximately 1% or less.
HyspIRI Thermal Infrared (TIR) Band Study Report
One of the many science questions that will be addressed by the Hyperspectral Infrared Imager (HyspIRI) mission will be to help identify natural hazards such as volcanic eruptions and any associated precursor activity, and it will also map the mineralogical composition of the land surface. To answer these questions, the HyspIRI satellite includes a thermal infrared (TIR) multispectral scanner with seven spectral bands in the thermal infrared (TIR) between 7 and 12 µm and one band in the mid-infrared between 3 and 5 µm designed to measure hot targets. The TIR bands have a NEΔT of <0.2 K at 300K and all bands have a spatial scale of 60 m. A critical aspect of HyspIRI being successful at answering these science questions is placement of the 7 TIR bands in the 7-12 µm spectral region. In order to help determine the optimum positions for the TIR bands, a small team was assembled to conduct a study report based on laboratory, spaceborne and airborne data.
Infrared thermal mapping experiment - The Viking Mars Orbiter.
The Mars infrared thermal mapper (IRTM) will be carried on the scan platform of the orbiter of the Viking 1975 mission. The IRTM is a multichannel radiometer with several detectors in each of six spectral regions. The spectral channels are selected to be sensitive to surface emissivity variations and provide good temperature resolution over the entire range of Martian temperatures. These observations will allow determination of the surface kinetic temperature and thermal balance, and by coverage of the dark hemisphere, a search for regions with anomalous cooling can be made. Observations of ground frosts or clouds will help to determine their composition, and in the case of extensive H2O frosts, will allow the local water vapor pressure to be estimated.
The basis for the spectral behaviour of silicates in the thermal infrared and applications to remote sensing
Variations in the thermal infrared (TIR) spectral response of silicate rocks is related to changes in the structures and divalent cation contents of the minerals which form the rocks. These considerations lead to a chemical parameter, SCFM, which reflects mineral structures, rock types, and their spectra. The parameter is the ratio of silica to the abundance of depolymerizing cations, defined as SCFM = SiO2/SiO2 + CaO + MgO + FeO. Parameter SCFM is therefore proposed for use in TIR remote sensing of igneous rocks. It is also demonstrated that two or three broad bands are sufficient for distinguishing among major rock types and the system noise has little effect on the quality of the results. These factors can be traded off against improved spatial resolution in instrument design.
The use of multispectral thermal infrared image data to estimate the sulfur dioxide flux from volcanoes: A case study from Mount Etna, Sicily, July 29, 1986
We have found that image data acquired with NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) can be used to make estimates of the SO2 content of volcanic plumes. TIMS image data are most applicable to the study of partially transparent SO2 plumes, such as those released during quiescent periods or nonexplosive eruptions. The estimation procedure is based on the LOWTRAN 7 radiative transfer code, which we use to model the radiance perceived by TIMS as it views the ground through an SO2 plume. The input to the procedure includes the altitudes of the aircraft and ground, the altitude and thickness of the SO2 plume, the emissivity of the ground, and altitude profiles of the atmospheric pressure, temperature, and relative humidity. We use the TIMS data to estimate both ground temperatures beneath a plume and SO2 concentrations within a plume. Applying our procedure to TIMS data acquired over Mount Etna, Sicily, on July 29, 1986, we estimate that the SO2 flux from the volcano was approximately 6700 t d(exp -1). The use of TIMS to study SO2 plumes represents a bridge between highly localized methods, such as correlation spectroscopy or direct sampling, and small-scale mapping techniques involving satellite instruments such as the Total Ozone Mapping Spectrometer or Microwave Limb Sounder. We require further airborne experiments to refine our estimation procedure. This refinement is a necessary preparation for the schedueled 1998 launch of the Advanced Spaceborne Thermal Emission and Reflectance Radiometer, which will allow large-scale multispectral thermal infrared image data to be collected over virtually any volcano on Earth at least once every 16 days.
In-Flight Wavelength Calibration of Thermal Infrared Multispectral Scanner (TIMS) Data Acquired from the ER-2
In 1991 one flightline of Thermal Infrared Multispectral Scanner (TIMS) data was acquired over Castaic Lake, California and in 1992 four flightlines of TIMS data were acquired over Death Valley, California.
Using Downwelling Far- and Thermal-Infrared Hyperspectral Radiance for Cloud Phase Classification in the Antarctic
The cloud phase is one of the most important parameters of clouds. In this paper, we propose a method for cloud phase classification that synergistically utilizes the far- and thermal-infrared bands based on the Atmospheric Emitted Radiance Interferometer (AERI) at the Atmospheric Radiation Measurement West Antarctic Radiation Experiment (AWARE) observatory in 2016. The possible features in the far- and thermal-infrared bands are analyzed based on the differences in the simulated cloud brightness temperature (BT) spectra with different cloud phases. Using the support vector machine (SVM) algorithm, four features are determined to identify the cloud phase, which include the BT at 900 cm -1 , the slope of the fitted function of BT in the 900–1000 cm -1 interval, the BT difference (BTD) between 512 cm -1 and 726 cm -1 , and the BTD between 550 cm -1 and 726 cm -1 . Here, the performance of the proposed method is evaluated with Shupe’s and Turner’s method. The monthly average accuracy of the proposed method, the method without the two far-infrared features, and Turner’s method are about 76%, 36%, and 49%, respectively, which infer the good performance of the proposed method and also indicate that the far-infrared band features can effectively enhance cloud phase classification. It is notable that, compared to Shupe’s method, the accuracy for the proposed method is only 61% during the Antarctic summer, which results from the definitions of cloud phase and radiative effect. In addition, the accuracy is only 44% for Turner’s method in seasons with a low frequency of mixed clouds due to the significant effect of water vapor.
Capabilities of the Skylab-A spectrometer (S191) for remote sensing of surface targets in the thermal-infrared spectral region
The effects of some of the factors which fundamentally limit the amount of information which can be deduced from spectrometer (S191) measurements, made from the orbital altitude of Skylab-A, of the thermal-infrared power radiated into space from typical surface targets are discussed. The particular significance of this spectral region is that the power radiated at night is comparable in intensity to that in daylight. Calculations were made which simulate the quality of spectrometer data that could be expected from spectral measurements made in space, of the thermal-infrared radiation emitted from typical rocks on the surface. The results indicate that the reststrahlen structure in these spectra is not distinctive enough to permit reliable identification of the rocks. This conclusion is confirmed by relevant data which have already been obtained from aircraft and spacecraft.
2060 Chiron - Visual and thermal infrared observations
Five-color (wavelength = 0.36-0.85 microns) and thermal infrared (wavelength = 22.5 microns) photometric observations of the unusual asteroid 2060 Chiron were made. Between 0.36 and 0.85 microns, Chiron's reflectance spectrum is similar to those of C-class asteroids as well as Saturn's satellite Phoebe. However, the thermal IR measurements imply an albedo greater than 0.05 (i.e., a diameter of less than 250 km at the 2-sigma level) that is probably higher than those of C-class asteroids or Phoebe.
Thermal Infrared Observations of Lava Flows During the 1984 Mauna Loa Eruption
Thermal infrared videotape images of the flowing lava streams and the vent areas at 10.6 microns were made, as well as some broadband images in the 8 to 12 micron range (for gas plume detection). These data were calibrated with on-site hand-held radiometer measurements, in-flow thermocouple measurements, and with later laboratory kiln measurements. Infrared video data are useful in quantitatively assessing the pattern and mode of flow thermal losses, particularly with regard to radiative losses from established/incipient floating crust. The general cooling of the flows downstream was readily apparent. Upper reaches of the active flow exhibited nearly crust-free main channels, radiating at about 700 to 800 degrees C. Below about the 7500 foot level (about 8 km from the vent) the flows formed nearly continuous crust and tended to spread, become less well-defined and founder due to a reduction in slope. Nevertheless, in thermal IR observations, the surface trace of the active subsurface channel was visible, radiating at about 500 to 700 degrees C. At the active flow front, most solid crust radiated at temperatures less than 500 to 600 degrees C, however bright high temperature interiors (approximately 900 to 1000 degrees C) were clearly visible though evolving fissures.
Thermal infrared imagery in urban studies
Techniques and potential role of thermal infrared imagery in urban studies
Thermal-infrared and visual imaging of comet Giacobini-Zinner
Thermal-infrared and visual images obtained simultaneously of comet Giacobini-Zinner on UT 1985 August 4.4 are presented. The 10.8-micron map, which spans several arc minutes with 8-arcsec resolution, is the first ground-based infrared image of a comet. Considerable spatial structure is evident in the map, including a curved dust tail consisting primarily of dust grains larger than 100 microns. The width of this large-grain tail implies that these grains depart the nucleus with velocities less than 3 m/s. The distribution of grain albedo is determined for the central 1 arcmin. It is speculated that an observed increase in the albedo by a factor of 2 with distance from the nucleus and prolonged radius vector results from the confinement to the orbital plane of large fluffy grains previously considered for GZ by others; the lower albedo of this dust could result from multiple internal scattering increasing the probability of absorption of incident light. It is estimated that dust was departing the nucleus at the rate of about 8 x 10 to the 5th g/s, comparable to that derived for many other comets.