Thermal Emission Measurements Research Articles

A method to retrieve blackbody temperature errors in the two points radiometric calibration

Measurements of the atmospheric thermal emission using an infrared Fourier transform spectrometer need to be radiometrically calibrated. As for several existing instruments (IASI-MetOp, IASI-balloon, NAST-I, AERI, etc.), the two points radiometric calibration is generally performed using two well-characterized blackbodies at two different temperatures (or one blackbody and the cold space), which allow to determine the response and the self-emission of the instrument. To perform an accurate radiometric calibration, the emissivity and the temperature of each blackbody should be known accurately. The blackbody temperatures are chosen to fit the characteristics of the instrument. The measurement of these temperatures is essential. This paper proposes a method to perform an accurate radiometric calibration even when one of the two blackbodies temperatures is not perfectly measured, by numerically retrieving this erroneous temperature.

A Laboratory Technique for Thermal Emission Measurement of Hydrated Minerals

Laboratory emission spectra are measured at Arizona State University's Mars Space Flight Facility for comparison to remotely sensed data from Earth and Mars. Such emission spectroscopy using an interferometric spectrometer measures the energy of the sample, including reflected and emitted background sources. The detector is uncooled at ambient temperature, which produces a very low signal when measuring the energy from a sample that has a temperature close to its own. In order to increase the energy difference between the sample and the detector, thereby increasing the signal received by the detector, samples are typically heated to between 60 and 80 degrees C for several hours prior to measurement. While this method is acceptable for most rock and mineral samples, some hydrous minerals dehydrate quickly at low relative humidity and temperatures above room temperature. This change is evident in both the physical appearance of the mineral and in the position and shape of its spectral absorptions. One solution to this problem is to heat samples to lower temperatures (e.g., 40 degrees C) for only a short time period. However, this approach results in a low signal from the sample and does not always avoid dehydration. For this reason, we have developed a technique for measuring and calibrating emission spectra of hydrated minerals that involves cooling samples to well below the temperature of the detector, which avoids dehydration, while creating a large delta temperature and a strong signal from the sample. Our method allows for accurate library spectra, with discrete, pronounced spectral features (high spectral contrast), of hydrated minerals that can be used for comparison to planetary surfaces.

TNOs are Cool: A Survey of the Transneptunian Region

Over one thousand objects have so far been discovered orbiting beyond Neptune. These trans-Neptunian objects (TNOs) represent the primitive remnants of the planetesimal disk from which the planets formed and are perhaps analogous to the unseen dust parent-bodies in debris disks observed around other main-sequence stars. The dynamical and physical properties of these bodies provide unique and important constraints on formation and evolution models of the Solar System. While the dynamical architecture in this region (also known as the Kuiper Belt) is becoming relatively clear, the physical properties of the objects are still largely unexplored. In particular, fundamental parameters such as size, albedo, density and thermal properties are difficult to measure. Measurements of thermal emission, which peaks at far-IR wavelengths, offer the best means available to determine the physical properties. While Spitzer has provided some results, notably revealing a large albedo diversity in this population, the increased sensitivity of Herschel and its superior wavelength coverage should permit profound advances in the field. Within our accepted project we propose to perform radiometric measurements of 139 objects, including 25 known multiple systems. When combined with measurements of the dust population beyond Neptune (e.g. from the New Horizons mission to Pluto), our results will provide a benchmark for understanding the Solar debris disk, and extra-solar ones as well.

Indirect Measurements of Coherent Thermal Emission from a Truncated Photonic Crystal Structure

Indirect Measurements of Coherent Thermal Emission from a Truncated Photonic Crystal Structure

Shocked H2O ice: Thermal emission measurements and the criteria for phase changes during impact events

Impact cratering events on icy planetary bodies may produce transient liquid water and vapor. We present the first thermal emission measurements from shocked H2O ice and derive peak and post‐shock temperatures. Under shock pressures between 8.2 and 13.6 GPa, initially ∼165 K ice is heated to between 673 and 1055 K. In the time frame of the experiment, the shocked H2O releases to the saturation vapor curve and does not achieve full decompression. The temperature results are used to validate the new 5‐Phase H2O model equation of state (EOS). The 5‐Phase EOS is used to predict the critical shock pressures required to induce melting and vaporization of ice for a wide range of ambient pressures and temperatures. Impact events with velocities as low as ∼1 km/s will initiate phase changes on icy surfaces. Thus, shock‐induced melting and vaporization of ice is a widespread process in the solar system.

Celestial body irradiance determination from an underfilled satellite radiometer: application to albedo and thermal emission measurements of the Moon using CERES

The Clouds and the Earth's Radiant Energy System (CERES) is a program that measures the Earth radiation budget (ERB) from two polar orbiting satellite platforms. CERES radiometers are designed to make stable broadband measurements of scattered solar and emitted thermal radiative flux leaving Earth with an accuracy of 1% or better. Using versatile and programmable scan modes, it is also possible for every CERES instrument to view the Moon on each orbit. However, until now, it has not been possible to derive absolute measurements of lunar irradiance using CERES because the Moon's disk fills only 10% of the telescope field of view. This work presents a method of integrating CERES raster-scan data in order to obtain a measurement of the average scattered solar and emitted thermal radiance from the entire lunar disk. The technique results in excellent agreement between CERES instruments on different satellites as to lunar albedo and emitted thermal flux. The average broadband Moon albedo is measured by CERES at a value of 0.1362 (+/-2-3%) when normalized to a static lunar phase angle of 7 degrees using the U.S. Geological Survey lunar irradiance Robotic Lunar Observatory model. The method for the first time also yields very accurate measurements of the thermal irradiance emitted from the Moon. These suggest an average long-wave flux of 977 Wm(-2) (+/-2-3% at 7 degrees phase), implying an approximate mean surface temperature of around 92 degrees C. Statistical analysis on available data suggests that a CERES instrument performing monthly lunar measurements could utilize the Moon as a stability target and reduce calibration drifts to 0.3% per decade or less within an instrument's lifetime. Given the success of the technique, a solar calibration system is proposed that will allow precise tracking of an ERB instrument's optical degradation using the Sun.

Efficient Low-Temperature Thermophotovoltaic Emitters from Metallic Photonic Crystals

We examine the use of metallic photonic crystals as thermophotovoltaic emitters. We coat silica woodpile structures, created using direct laser writing, with tungsten or molybdenum. Optical reflectivity and thermal emission measurements near 650 degrees C demonstrate that the resulting structures should provide efficient emitters at relatively low temperatures. When matched to InGaAsSb photocells, our structures should generate over ten times more power than solid emitters while having an optical-to-electrical conversion efficiency above 32%. At such low temperatures, these emitters have promise not only in solar energy but also in harnessing geothermal and industrial waste heat.

Improving selective thermal emission properties of three-dimensional macroporous silicon through porosity tuning

We present a theoretical and experimental study on the effect of progressive porosity increase, through multiple oxidation/oxide removal steps, upon the optical characteristics in three-dimensional macroporous silicon. It is shown that, by increasing porosity, optical features can be pushed toward higher frequencies. Optimum porosities exist where normal or omnidirectional total reflection bandwidths are maximized, doubling the initial values. Results are confirmed experimentally through angle-resolved reflectance and thermal emission measurements.

Comparison between multiwavelength infrared and visible pyrometry: Application to metals

A device for non-intrusive temperature measurements of metallic materials has been developed. Moreover, as the emissive properties of the metal cannot be known a priori, multiwavelength pyrometry was used to address this issue in the following way:– Simultaneous measurement of thermal emission at N wavelengths.– Use technique of parameter identification including a physical or an empirical model for the emissivity to determine temperature and spectral emissivity.This method was applied to a temperature range between 500K and the melting/solidification point of the metallic materials. The results obtained in visible and infrared spectral range were compared. Various metallic samples were studied (steels, titanium), and for each sample, the relative deviation between identified and experimental (thermocouple) temperatures is lower than 2%, using the more suitable models. For some groups of materials (austenitic stainless steels, and carbon steels), one or several models giving suitable results for similar samples were selected.

In Situ Fast Temperature Measurement of Silicon Thin Films during the Excimer Laser Annealing

The formation and growth mechanism of polysilicon grains in thin films via laser annealing of amorphous silicon thin films are studied. The complete understanding of the mechanism is crucial to improve the thin film transistors used as switches in the active matrix liquid crystal displays. To understand the recrystallization mechanism, the temperature history and liquidsolid interface motion during the excimer laser annealing of 50-nm thick amorphous and polysilicon films on fused quartz substrates are intensively investigated via in-situ time-resolved thermal emission measurements, optical reflectance and transmittance measurements at near infrared wavelengths. The front transmissivity and reflectivity are measured to obtain the emissivity at the 1.52 μm wavelength of the probe IRHeNe laser to improve the accuracy of the temperature measurement. The melting point of amorphous silicon is higher than that of crystalline silicon of 1685 K by 100-150 K. This is the first direct measurement of the melting temperature of amorphous silicon thin films. It is found that melting of polysilicon occurs close to the melting point of crystalline silicon. Also the optical properties such as reflectance and transmittance are used to determine the melt duration by the detecting the difference of the optical properties of liquid silicon and solid silicon.

T e ( R , t ) measurements using electron Bernstein wave thermal emission on NSTX

The National Spherical Torus Experiment (NSTX) routinely studies overdense plasmas with ne of (1–5)×1019m−3 and total magnetic field of <0.6T, so that the first several electron cyclotron harmonics are overdense. The electrostatic electron Bernstein wave (EBW) can propagate in overdense plasmas, exhibits strong absorption, and is thermally emitted at electron cyclotron harmonics. These properties allow thermal EBW emission to be used for local Te measurement. A significant upgrade to the previous NSTX EBW emission diagnostic to measure thermal EBW emission via the oblique B-X-O mode conversion process has been completed. The new EBW diagnostic consists of two remotely steerable, quad-ridged horn antennas, each of which is coupled to a dual channel radiometer. Fundamental (8–18GHz) and second and third harmonic (18–40GHz) thermal EBW emission and polarization measurements can be obtained simultaneously.

Emissivity measurements of analogue materials for the interpretation of data from PFS on Mars Express and MERTIS on Bepi-Colombo

The Planetary Fourier Spectrometer (PFS) onboard the Mars Express Mission provides thermal infrared, hyperspectral images of Mars and in the future the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS), part of the selected payload for the Bepi-Colombo Mission, will collect analogous data for Mercury. To interpret these remote sensing data it is essential to understand the spectral emittance of planetary analogue materials and a spectral library of emissivity measurements is needed. Here we introduce the emissivity device built at DLR (Berlin). The device is coupled to a Fourier transform infrared spectrometer (Bruker IFS 88), purged with dry air and equipped with a cooled MCT-detector. We discuss theoretical background of our thermal emission measurements and describe our standard experimental procedures, which are being used to create the Berlin emissivity database (BED). This study presents and discuss the 6.3–22 μm thermal emission spectra of fine-grained feldspar separates ranging from <25 to 90–125 μm. We discuss diagnostic potential of the features present in the emission spectra of plagioclase and alkali feldspars and the particle size effects.

Detection and monitoring of fatigue damage in SMCR26 specimens using spate, for a constant mean stress – a qualitative approach

The primary aim of the work presented here was to establish the use of thermoelastic measurements in detecting the presence of damage and its subsequent accumulation in sheet moulding compound (SMCR26). To this end, several dog bone shaped specimens of SMCR26 were cycled at a constant mean stress of 38.87 MPa and at varying stress amplitudes, the latter in order to investigate any dependencies on stress amplitude. Surface scans were taken from each specimen at various stages in their load history using the Stress Pattern Analysis by Thermal Emission (SPATE) measurement equipment. The first scan obtained from each specimen was used to determine its initial state of damage, while subsequent scans were used to monitor the accumulation of damage. The thermoelastic signal in the initial and subsequent scans exhibited different magnitudes and distribution for the different specimens, which denoted heterogeneity of the SMCR26 specimens and of the occurrence and accumulation of damage. This was in sharp contrast to the uniform thermoelastic signal that is emitted from the surfaces of cycled, undamaged homogeneous materials. The absence of any apparent relationship between the stress amplitude and the accumulation of damage in the tested specimens was thought to be a result of the in-homogeneity inherent in SMCR26, and of the heterogeneous nature of the accumulation of damage, rather than a limitation of the thermoelastic equipment used. The results obtained in this work demonstrated SPATE to be a fast and useful means of detecting the presence of damage and of monitoring its accumulate Keywords : Sheet Moulding Compound (SMC), fatigue, damage Journal of Agriculture, Science and Technology Vol. 7(1) 2005: 91-121

Linear radiation model for phase of thermal emission spectroscopy

A linear radiation model is developed that overcomes the analytical complexity in phase of thermal emission spectroscopy. It is shown that the linear radiation model can result in a simple algebraic relation between the phase of thermal emission and four coating properties, enabling these properties to be determined by nonlinear regression analysis of experimental measurements. Suitability of the linear radiation model to various measurement conditions is explored, and the model is applied to the phase of thermal emission measurements performed on a thermal barrier coating.

Electron cyclotron emission spectrometry on the Tokamak à Configuration Variable

Electron cyclotron emission (ECE) measurements are an important component of the diagnostic suite on the Tokamak à Configuration Variable (TCV) [F. Hoffman et al., Plasma Phys. Controlled Fusion 36, B277 (1994)]. A recently installed, 24-channel dual-conversion heterodyne radiometer covering the radio frequency range 65–100 GHz and viewing from the low-field side (LFS) of the tokamak greatly enhances the system and, in combination with an existing radiometer viewing from the high-field side (HFS), allows simultaneous measurements of emission from the HFS and LFS. In addition, the new radiometer has multiple lines of sight that can receive the emission perpendicular to the toroidal magnetic field as well as with a finite k‖ (wave vector parallel to magnetic field). Such flexibility allows the LFS radiometer to make standard measurements of thermal emission and nonstandard measurements of nonthermal, anisotropic emission. The toroidal line of sight allows access to overdense plasma via mode converted emission. The enhanced ECE diagnostic is described and examples of measurements made in various configurations are presented.

Physical characteristics of Comet Nucleus C/2001 OG 108 (LONEOS)

A detailed description of the Halley-type Comet C/2001 OG 108 (LONEOS) has been derived from visible, near-infrared, and mid-infrared observations obtained in October and November 2001. These data represent the first high-quality ground-based observations of a bare Halley-type comet nucleus and provide the best characterization of a Halley-type comet other than 1P/Halley itself. Analysis of time series photometry suggests that the nucleus has a rotation period of 57.2 ± 0.5 h with a minimum nuclear axial ratio of 1.3, a phase-darkening slope parameter G of − 0.01 ± 0.10 , and an estimated H = 13.05 ± 0.10 . The rotation period of C/2001 OG 108 is one of the longest observed among comet nuclei. The V- R color index for this object is measured to be 0.46 ± 0.02 , which is virtually identical to that of other cometary nuclei and other possible extinct comet candidates. Measurements of the comet's thermal emission constrain the projected elliptical nuclear radii to be 9.6 ± 1.0 km and 7.4 ± 1.0 km , which makes C/2001 OG 108 one of the larger cometary nuclei known. The derived geometric albedo in V-band of 0.040 ± 0.010 is typical for comet nuclei. Visible-wavelength spectrophotometry and near-infrared spectroscopy were combined to derive the nucleus's reflectance spectrum over a 0.4 to 2.5 μm wavelength range. These measurements represent one of the few nuclear spectra ever observed and the only known spectrum of a Halley-type comet. The spectrum of this comet nucleus is very nearly linear and shows no discernable absorption features at a 5% detection limit. The lack of any features, especially in the 0.8 to 1.0 μm range such as are seen in the spectra of carbonaceous chondrite meteorites and many low-albedo asteroids, is consistent with the presence of anhydrous rather than hydrous silicates on the surface of this comet. None of the currently recognized meteorites in the terrestrial collections have reflectance spectra that match C/2001 OG 108. The near-infrared spectrum, the geometric albedo, and the visible spectrophotometry all indicate that C/2001 OG 108 has spectral properties analogous to the D-type, and possibly P-type asteroids. Comparison of the measured albedo and diameter of C/2001 OG 108 with those of Damocloid asteroids reveals similarities between these asteroids and this comet nucleus, a finding which supports previous dynamical arguments that Damocloid asteroids could be composed of cometary-like materials. These observations are also consistent with findings that two Jupiter-family comets may have spectral signatures indicative of D-type asteroids. C/2001 OG 108 probably represents the transition from a typical active comet to an extinct cometary nucleus, and, as a Halley-type comet, suggests that some comets originating in the Oort cloud can become extinct without disintegrating. As a near-Earth object, C/2001 OG 108 supports the suggestion that some fraction of the near-Earth asteroid population consists of extinct cometary nuclei.

In situ monitoring of bare and K-doped Mo2C catalysts surface depassivation based on emission of electrons and K+ ions

Abstract The method for in situ characterization of surface transformations on heterogeneous catalyst is described. The method is based on the measurements of thermal electron and ion emissions from the catalyst surface. It is demonstrated by investigating the depassivation process of undoped and K-doped Mo 2 C catalysts exposed to air after synthesis and use to identify characteristic steps of reduction-carburization by flowing CH 4 /H 2 gas mixture. The information obtained from thermal emission experiments is consistent with the methane consumption profile, which provided an independent observation of the recarburization step.

Improvements of on-membrane method for thin film thermal conductivity and emissivity measurements

A numerical simulation and various test-structure configurations were developed which enable the measurement of the in-plane thermal conductivity and emissivity of on-membrane thin films in a versatile and accurate manner. The simulation takes into account the two-dimensional heat transfer in the membrane. Consequently, shorter membrane can be used and strained materials can be measured. The numerical simulation along with the new test-structures is used to understand the convective heat transfer at small scales and to quantify it. The measurement method is tested on various materials ranging from ceramics, metals to polycrystalline silicon.

規則的周期構造を付けたSi及びAl_2O_3からの自発的熱放射の測定(OS2 センサおよびセンシングシステム)

規則的周期構造を付けたSi及びAl_2O_3からの自発的熱放射の測定(OS2 センサおよびセンシングシステム)

The Advanced Technology Solar Spectroscopic Imager—a novel experiment employing a transition-edge sensor to probe the soft X-ray solar corona

The Advanced Technology Solar Spectroscopic Imager (ATSSI) is a sounding rocket-borne experiment that will employ a Transition-Edge Sensor (TES) placed at the focus of a Wolter-I mirror to study large active region loops in the solar corona. The TES instrument will operate in the ∼500–1500eV EUV/soft X-ray bandpass, obtaining ∼3eV energy-resolved spectra at ∼6.25arcsec image resolution with a count rate of ∼1000photons/sec/pixel. Over a typical observation period of ∼360sec, we will raster scan over a 0.6×0.6 arcmin field of view to obtain a 6×6 pixel image containing true EUV/soft X-ray spectroheliograms of a solar active region. Using these observations, we can directly determine composition, electron density and thermal differential emission measure of large active region loops in order to constrain models of heating mechanisms and accurately measure the thermal morphology of these structures. In the current analysis, we present an initial instrument concept and discuss some of the mission science goals.