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To realize precise directional spectral emissivity determination of solid materials under the atmosphere, an apparatus what covers the temperature region from 50 °C to 1000 °C and a spectral range of 3 μm–14 μm was developed. The measurement angle can be adjusted from 0° to 60° utilizing a stepper rotary stage. The reliability of the apparatus's reliability was confirmed by measuring the spectral emissivity of a SiC sample at high temperatures. Furthermore, the normal spectral emissivity of SiC was investigated from 50 °C to 1000 °C, and the directional spectral emissivity at 600 °C and 800 °C was shown. The influence of temperature and measurement angle on the spectral emissivity of SiC was analyzed in detail. Additionally, the cause of the silicon dioxide film on the surface of SiC after high temperature heating and its influence on spectral emissivity were explored. Finally, a detailed analysis of the uncertainty components of the emissivity measurement under varying temperatures and wavelengths was performed, and the results showed that the uncertainty of the apparatus was better than 0.05 in its measurement range. [ABSTRACT FROM AUTHOR]

Several new approaches to the measurement of intrinsic noise and dynamic characteristics of superconducting bolometers based on the RFTES technology are demonstrated. The developed methods were tested with an experimental 550–750 GHz sample at reading frequency of ~1.5 GHz at a temperature of 400 mK. The absorption of thin-film resistive coatings on sapphire and quartz substrates was studied, and the emissivity of the experimental heat source was estimated as ~14%. A shot noise source based on Al/AlOx/Al tunnel junction was developed, and the noise temperature of the 1.35–1.6 GHz buffer amplifier referred to the detector output was determined as ~20 K. The response time of RFTES with a hafnium film sized 6 × 2 × 0.08 μm was evaluated as ~3 μs via microwave heat modulation at the second resonance at ~4.2 GHz; the dynamic range at a modulation frequency of 10 kHz was more than 23 dB. The data obtained made it possible to determine the RFTES sensitivity as 1 × 1017 W/ ± 30%, that coincided with the theoretical value up to the measurement error. [ABSTRACT FROM AUTHOR]

The blackbody radiation equation, also known as the Planck equation, has proved to be a challenge for students starting their studies in the field of thermal radiation, and this article aims to overcome this difficulty by presenting it in a simplified way. First, the classical approach to the blackbody derivation performed by the scientist Max Planck will be presented, which uses the concept of entropy, related to the different forms of energy distribution, in a thermodynamic system, complexion, according to Planck. Next, the deduction of the blackbody equation is presented, without resorting to complex calculations, but rather simple ones, from the approach carried out by Richard Feynman. Therefore, the objective of this article is to present the blackbody radiation equation, using basic concepts of average energy, and how the equation can be deduced from simple numerical calculations, without losing sight of the phenomenological character. [ABSTRACT FROM AUTHOR]

Photodetectors operating across the short‐, mid‐, and long‐wave infrared (SWIR–LWIR, λ = 1–14 µm) underpin modern science, technology, and society in profound ways. Narrow bandgap semiconductors that form the basis for these devices require complex manufacturing, high costs, cooling, and lack compatibility with silicon electronics, attributes that remain prohibitive for their widespread usage and the development of emerging technologies. Here, a photoconductive detector, fabricated using a solution‐processed narrow bandgap conjugated polymer is demonstrated that enables charge carrier generation in the infrared and ultrasensitive SWIR–LWIR photodetection at room temperature. Devices demonstrate an ultralow electronic noise that enables outstanding performance from a simple, monolithic device enabling a high detectivity (D*, the figure of merit for detector sensitivity) >2.44 × 109 Jones (cm Hz1/2 W−1) using the ultralow flux of a blackbody that mirrors the background emission of objects. These attributes, ease of fabrication, low dark current characteristics, and highly sensitive operation overcome major limitations inherent within modern narrow–bandgap semiconductors, demonstrate practical utility, and suggest that uncooled detectivities superior to many inorganic devices can be achieved at high operating temperatures. [ABSTRACT FROM AUTHOR]

Abstract Photodetectors operating across the short‐, mid‐, and long‐wave infrared (SWIR–LWIR, λ = 1–14 µm) underpin modern science, technology, and society in profound ways. Narrow bandgap semiconductors that form the basis for these devices require complex manufacturing, high costs, cooling, and lack compatibility with silicon electronics, attributes that remain prohibitive for their widespread usage and the development of emerging technologies. Here, a photoconductive detector, fabricated using a solution‐processed narrow bandgap conjugated polymer is demonstrated that enables charge carrier generation in the infrared and ultrasensitive SWIR–LWIR photodetection at room temperature. Devices demonstrate an ultralow electronic noise that enables outstanding performance from a simple, monolithic device enabling a high detectivity (D*, the figure of merit for detector sensitivity) >2.44 × 109 Jones (cm Hz1/2 W−1) using the ultralow flux of a blackbody that mirrors the background emission of objects. These attributes, ease of fabrication, low dark current characteristics, and highly sensitive operation overcome major limitations inherent within modern narrow–bandgap semiconductors, demonstrate practical utility, and suggest that uncooled detectivities superior to many inorganic devices can be achieved at high operating temperatures.

This study presents an original approach on how to generate a radiator with an emissivity less than one by using a conventional blackbody and a screen with a defined area density of holes. This is needed for the calibration of infrared (IR) radiometry, which is a very useful form of temperature measurement in industrial, scientific, and medical applications. One of the major sources of errors in IR radiometry is the emissivity of the surface being measured. Emissivity is a physically well-defined parameter, but in real experiments, it may be influenced by many factors: surface texture, spectral properties, oxidation, and aging of surfaces. While commercial blackbodies are prevalent, the much-needed grey bodies with a known emissivity are unavailable. This work describes a methodology for how to calibrate radiometers in the lab or in the factory or FAB using the "screen approach" and a novel thermal sensor dubbed Digital TMOS. The fundamental physics required to appreciate the reported methodology is reviewed. The linearity in emissivity of the Digital TMOS is demonstrated. The study describes in detail how to obtain the perforated screen as well as how to do the calibration. [ABSTRACT FROM AUTHOR]

COSMO is a ground-based instrument to measure the spectral distortions (SD) of the Cosmic Microwave Background (CMB). In this paper, we present preliminary results of electromagnetic simulations of its reference blackbody calibrator. HFSS simulations provide a calibrator reflection coefficient of R ∼ 10 - 6 , corresponding to an emissivity ϵ = 1 - R = 0.999999 . We also provide a forecast for the instrument performance by using an ILC-based simulation. We show that COSMO can extract the isotropic Comptonization parameter (modeled as | y | = 1.77 · 10 - 6 ) as | y | = (1.79 ± 0.19) · 10 - 6 , in the presence of the main Galactic foreground (thermal dust) and of CMB anisotropies, and assuming perfect atmospheric emission removal. [ABSTRACT FROM AUTHOR]

We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals using chemical vapor deposition (CVD) assisted by a simple surface treatment of the substrate materials. The main feature of this method is the application of shot blasting with fine alumina shot to create the catalyst support layer that is required for the effective growth of CNTs on the various conductive materials, including the ultrahard metal tungsten. Energy dispersive X-ray spectroscopy shows that the shot blasting forms a noncontinuous layer where alumina nanoparticles are embedded as residue from the blasting media on the treated surfaces. Such a noncontinuous alumina layer can behave as the catalyst support layer, which is normally prepared via sputtering or a vacuum evaporation coating process. The influence of shot size on the characteristics of the nonuniform alumina buffer layer as well as the resultant multiwalled CNT arrays grown via CVD in conjunction with a floating iron catalyst are investigated. The results show that the morphology, crystallinity, and spectral emissivity of CNTs depend on the size of alumina shot used in the shot blasting treatment. The characteristics of the CNTs grown on various metal substrates with a discontinuous and continuous alumina buffer layers are compared with each other. These comparisons indicate that the degrees of hardness and the redox property of the substrates moderately affect the characteristics of CNTs on the discontinuous layer in contrast to the continuous layer.

An experimental procedure for characterizing the size-of-source effect (SSE) is proposed. Such an effect is the cause of one of the main influence variables generating uncertainty in the measurement, both in calibration and use, of direct reading radiation thermometers (RT). The procedure and uncertainty calculation described in the paper are aligned in terms of metrological traceability, with the requirements generally imposed to ensure the accuracy of measurements in industry and science. Results of application and validation of this particular procedure with equipment, including black body (BB) sources normally used in radiation thermometry calibration laboratories in the industrial field, are shown. [ABSTRACT FROM AUTHOR]

The paper considers stages in the development and improvement of high-level measurement standards that provide metrological support to radiance measuring instruments while outlining principles that underlie the realization and transfer of the radiance unit. Increased requirements for the metrological support of radiance measuring instruments led to the creation of GET 48-2018 State Primary Standard of the Unit of Infrared Radiance. The authors describe GET 48-2018 and its constituent emitters, i.e., blackbodies (BB), employing the phase transitions of pure substances (mercury, water, gallium, indium, tin, zinc, aluminum, and copper), as well as radiometer-comparators used to transfer the radiance unit to working standards and measuring instruments. The design of BB emitters and equipment needed to create the required temperature conditions are considered. The conducted studies revealed the long-term stability and high reproducibility of BB emitters developed on the basis of the fixed points of pure substances. In order to increase sensitivity and reduce noise in the radiometer-comparators, the optical design was improved, modern opticalacoustic detectors (Golay cells) were installed, and lock-in amplifiers were used to process the measured output signal of radiation detectors. This factor allowed the error in transferring the radiance unit to be reduced. The conducted studies aimed at maintaining the current scientific and technical level of metrological characteristics of GET 48-2018 and its constituent parts confirm that the reproduced radiance values are as follows: 54.36; 100.39; 151.80; 614.96; 1173.4; 4151.0; 13691; 61282 W/(sr∙m2) with an expanded uncertainty of no greater than 1.5·10−3 relative units. GET 48-2018 is currently at the top of the metrological support system for radiance measuring instruments widely used in the defense industrial sector, life support, space exploration, and environmental protection. [ABSTRACT FROM AUTHOR]

The need for affordable low-power devices has led MEMS-based thermal emitters to become an interesting option for optical gas sensors. Since these emitters have a low thermal mass, they can be easily modulated and combined with a lock-in amplifier for detection. In this paper, we show that the signal measured by a lock-in amplifier from a thermal emitter that varies its temperature periodically can have different spectral profiles, depending on the reference signal used. These virtual emitters appear because the Fourier series expansion of the emitted radiance, as a function of time, has different coefficients for each wavelength, and this spectral signature, which is different for each harmonic, can be retrieved using a reference signal that corresponds to its frequency. In this study, the effect is first proved theoretically and then is measured experimentally. For this purpose, we performed measurements with an IR camera provided with six different spectral filters of a modulated emitter, in combination with lock-in amplification via software. Finally, we show a potential application of this effect using multiple virtual emitters to gain spectral selectivity and distinguish between two gases, CO 2 and CH 4 . [ABSTRACT FROM AUTHOR]

Featured Application: Infrared and millimeter-wave band astronomical superconducting receivers require precise sources for instrument monitoring and calibration inside the cryostat. A cryogenic microwave blackbody radiation source with variable radiation temperature is the main tool for calibrating superconducting detectors and mixers. To avoid 1/f noise, the thermal emitter should have fast electrical modulation speed for lock-in detector mode. An electrically heated blackbody radiation source comprising thin metal film on a dielectric substrate and an integrating cavity was designed, fabricated, and experimentally studied at frequencies from 75 to 500 GHz. Analytical and numerical modeling were performed to optimize the emissivity, spectral uniformity, and modulation frequency of the radiation source with the spherical integrating cavity and thin film absorber. The blackbody emissivity (absorptivity) increased from 0.3 to 0.5 for the bare thin film on dielectric substrate, and up to 0.95 when it was placed inside the integrating cavity. The fabricated source mounted at the 0.5 K stage was used to measure the response time of a few microseconds and for sensitivity measurement down to 10−18 W/Hz1/2 of the superconductor–insulator–normal metal–insulator–superconductor (SINIS) detector at 100 mK. [ABSTRACT FROM AUTHOR]

The far-infrared emission properties of epitaxial graphene on SiC obtained by current injection were investigated using an infrared camera and Fourier-transform infrared spectroscopy. The radiation directivity from the graphene emitter was observed in the directions perpendicular to the surface and edge of the sample. The emission energy density from the graphene edge was larger than that from the graphene surface in all directions. The maximum measured temperature change at 0.4 W for the edge emission was 76.1 K for a tilt angle of 50° and that for the surface emission was 54.1 K for 0°. A blackbody-like emission spectrum with a constant peak wavelength of 10.0 μ m, regardless of the applied electrical power, was observed for both the surface and edge. A far-infrared light emitter was successfully realized using single-crystal graphene on SiC. [ABSTRACT FROM AUTHOR]

This study presents an original approach on how to generate a radiator with an emissivity less than one by using a conventional blackbody and a screen with a defined area density of holes. This is needed for the calibration of infrared (IR) radiometry, which is a very useful form of temperature measurement in industrial, scientific, and medical applications. One of the major sources of errors in IR radiometry is the emissivity of the surface being measured. Emissivity is a physically well-defined parameter, but in real experiments, it may be influenced by many factors: surface texture, spectral properties, oxidation, and aging of surfaces. While commercial blackbodies are prevalent, the much-needed grey bodies with a known emissivity are unavailable. This work describes a methodology for how to calibrate radiometers in the lab or in the factory or FAB using the “screen approach” and a novel thermal sensor dubbed Digital TMOS. The fundamental physics required to appreciate the reported methodology is reviewed. The linearity in emissivity of the Digital TMOS is demonstrated. The study describes in detail how to obtain the perforated screen as well as how to do the calibration.

In this study, we propose a thermal design for an on-board blackbody (BB) for spaceborne infrared (IR) sensor calibration. The main function of the on-board BB is to provide highly uniform and precise radiation temperature reference sources from 0 °C to 40 °C during the calibration of the IR sensor. To meet the functional requirements of BB, a BB thermal design using a heater to heat the BB during sensor calibration and heat pipes to transfer residual heat to the radiator after calibration is proposed and investigated both numerically and experimentally. The main features of the proposed thermal design are a symmetric temperature gradient on the BB surface with less than 1 K temperature uniformity, ease of temperature sensor implementation to estimate the representative surface temperature of the BB, a stable thermal interface between the heat pipes and BB, and a fail-safe function under one heat pipe failure. The thermal control performance of the BB is investigated via in-orbit thermal analysis, and its effectiveness is verified via a heat-up test of the BB under ambient conditions. These results indicate that the temperature gradient on the BB surface was obtained at less than 1 K, and the representative surface temperature could be estimated with an accuracy of 0.005 °C via the temperature sensor. [ABSTRACT FROM AUTHOR]

The effect that the target's temperature has on the characteristics of an ablation plasma as it was cooled from room temperature down to ~ 20 K was investigated. The target was attached to the cold finger of a helium refrigerator, both operating in a vacuum environment for thermal insulation. The plasma was produced by focusing a nanosecond high-power laser onto the sample. A spectrometer and a monochromator were used to monitor both the line and the continuum emissions, with and without time resolution. It was found that, starting at room temperature, the intensity of the lines emitted steadily increased as the target was cooled down to 150–175 K and afterward remained level as the target was further cooled. Using the Boltzmann plot technique the excitation temperature was obtained and it was found that its mean value gradually increased as the target was cooled. The calculated electronic density, on the contrary, decreased with decreasing target temperature. Another effect noted was that the intensity of the continuum also varied with target temperature. We found that the continuum´s distribution does not match a free-free or a recombination source, but it does fit a blackbody one. By fitting Planck's formula to the continuum spectra the blackbody temperature was extracted and it was found to be within the 9400–13,300 K interval. By solving the heat-flow equation before plasma onset we demonstrate that the laser beam heats the sample's surface at a faster rate the cooler it is and that this peculiar behavior is the reason why the excitation temperature increases at cryogenic temperatures. This behavior is a consequence of the fact that the sample's specific heat varies by two orders of magnitude as it is cooled from room temperature to ~ 20 K. [ABSTRACT FROM AUTHOR]

In order to investigate influences of catalyst buffer layers on the spectral emissivity of carbon nanotube (CNT) grown based on a floating catalyst chemical vapor deposition (FCCVD), we have evaluated the characteristics of CNTs grown on catalyst buffer layers made of aluminium oxide covering metal substrates by using shot blasting (SB) and electron beam evaporation (EB) methods, respectively. The comparisons of the microstructures and characteristics of the CNT carpets have indicated the influences of the morphology of the catalyst layer on the metal substrate. The emissivity, crystallinity, and purity of CNTs depends on the size of alumina particles used in the SB treatment.

An experimental procedure for characterizing the size-of-source effect (SSE) is proposed. Such an effect is the cause of one of the main influence variables generating uncertainty in the measurement, both in calibration and use, of direct reading radiation thermometers (RT). The procedure and uncertainty calculation described in the paper are aligned in terms of metrological traceability, with the requirements generally imposed to ensure the accuracy of measurements in industry and science. Results of application and validation of this particular procedure with equipment, including black body (BB) sources normally used in radiation thermometry calibration laboratories in the industrial field, are shown.

Recently Chung and Hassanabadi proposed a higher order general uncertainty principle (GUP∗) that predicts a minimal length as well as possesses a upper bound momentum limit. In this article, we have discussed an ideal gas system and its thermal properties using that deformed canonical algebra introduced by them. Moreover, we examined blackbody radiation spectrum and the cosmological constant in the presence of the GUP∗. After a comparison with the existing literature, we concluded that the given formalism of Chung and Hassanabadi yields more accurate results. [ABSTRACT FROM AUTHOR]

Pouring temperature of molten steel at the outlet of the tundish is the key parameter to control the solidification accurately. However, the stopper occupies the top of the outlet, leading to that the existing sensor cannot measure the molten steel temperature at the outlet. To solve the problem, this work develops a new small sensor installed at the bottom of the stopper, which combines the stopper and the temperature sensor into one. Mo-W-ZrO2 cermet that has excellent corrosion resistance has been used to make a small sensor with a thin-walled structure of 5 mm thickness. To sense the pouring temperature independently, fast and accurately, the length/radius ratio of the small sensor should reach 13 to form a blackbody cavity approximately. According to the industrial test, the pouring temperature of molten steel is measured for the first time in the field of metallurgy. Meanwhile, a deviation (e.g., 8.2 °C or 1.4 °C) between the pouring temperature and the temperature measured by the existing sensor is found. As a result, based on the temperature measured by the existing sensor, the superheat of molten steel and the cooling water flow usually have enough margin for ensuring the safe operation of continuous casting, reducing the control accuracy of the solidification and increasing the risk of quality problems. Therefore, this work will be helpful to control the solidification more accurately, improving the product quality. [ABSTRACT FROM AUTHOR]

Miniature fixed-point blackbody (MFPB) can realize the on-orbit calibration of temperatures by tracing the miniature fixed-point. This ability can effectively improve the precision and life span of earth observation systems. Researchers have verified the feasibility of the MFPB in engineering through experiments. However, the temperature relationship between the miniature fixed-point and the blackbody is unclear at present, which means that the transfer relationship between radiation temperature of space infrared radiation standard source and international temperature scale cannot be established accurately. In this article, a temperature transfer relationship between miniature fixed-point and blackbody in MFPB is established, and the temperature transfer equation (TTE) is proposed to obtain the run-off point temperature of blackbody (RPTB). The effects of heating power and ambient temperature on the temperature transfer relationship between miniature fixed-point and blackbody are investigated numerically. Retrieval results show that a linear relationship exists between the RPTB and the heating power and ambient temperature in a single fixed-point temperature range. The TTE is obtained and explained theoretically. All experimental results of the gallium fixed-point are in good agreement with this equation. Furthermore, the RPTBs are accurately predicted at gallium-stannum and H2O fixed-points by TTE. The average and maximum errors are 0.0044 and 0.0063 K, respectively. The current study is of considerable importance to the development of MFPB technology and improvement of the on-orbit infrared remote sensor calibration. [ABSTRACT FROM AUTHOR]

The ability to assess the performance of a non-contact infrared thermometer (NCIT) may be limited due to the algorithms necessary to predict a reference site temperature (e.g., oral) from a measurement of the forehead skin temperature. The algorithm not only adjusts for the difference between the reference site temperature and forehead temperature, but may also account for hardware corrections, bias adjustments and emissivity settings. These algorithms are proprietary to the manufacturer and can be unique for each device. ASTM E1965-98 (2016) is a standard test method for the evaluation of NCITs. It includes forehead thermometers; however, the algorithm must be known or an unadjusted calibration mode must be accessible. This study evaluates 6 NCIT models (10 units of each) against the ASTM standard error criterion using a blackbody source. Units were tested within the manufacturer's operating and temperature measurement range specification. A method to evaluate measurement outliers and characterize each model's performance when the adjustment algorithm is unknown is proposed. Using this method, 5 of the 6 models had a predicted error > 0.3°C. • 6 models of non-contact infrared thermometers (NCITs) were evaluated using a blackbody reference compliant with ASTM E1965. • 10 samples of each model were tested at 8 blackbody preset temperatures; 8 measurements were taken with each sample at each temperature. • Bench testing may not assess the error introduced by proprietary temperature correction algorithms for a specific mode (e.g. oral temperature display mode) if measurements are taken in unadjusted ("test") mode. • Assuming the algorithm produces an accurate mean reading, results can illustrate that the variance from the mean is greater than the ASTM E1965 allowable error (± 0.3°C). • For a single model, a specific NCIT unit may perform within the allowable error; however, in a sample size of multiple units, some may not. [ABSTRACT FROM AUTHOR]

An electrically heated blackbody radiation source comprising thin metal film on a dielectric substrate and an integrating cavity was designed, fabricated, and experimentally studied at frequencies from 75 to 500 GHz. Analytical and numerical modeling were performed to optimize the emissivity, spectral uniformity, and modulation frequency of the radiation source with the spherical integrating cavity and thin film absorber. The blackbody emissivity (absorptivity) increased from 0.3 to 0.5 for the bare thin film on dielectric substrate, and up to 0.95 when it was placed inside the integrating cavity. The fabricated source mounted at the 0.5 K stage was used to measure the response time of a few microseconds and for sensitivity measurement down to 10−18 W/Hz1/2 of the superconductor–insulator–normal metal–insulator–superconductor (SINIS) detector at 100 mK.

The need for affordable low-power devices has led MEMS-based thermal emitters to become an interesting option for optical gas sensors. Since these emitters have a low thermal mass, they can be easily modulated and combined with a lock-in amplifier for detection. In this paper, we show that the signal measured by a lock-in amplifier from a thermal emitter that varies its temperature periodically can have different spectral profiles, depending on the reference signal used. These virtual emitters appear because the Fourier series expansion of the emitted radiance, as a function of time, has different coefficients for each wavelength, and this spectral signature, which is different for each harmonic, can be retrieved using a reference signal that corresponds to its frequency. In this study, the effect is first proved theoretically and then is measured experimentally. For this purpose, we performed measurements with an IR camera provided with six different spectral filters of a modulated emitter, in combination with lock-in amplification via software. Finally, we show a potential application of this effect using multiple virtual emitters to gain spectral selectivity and distinguish between two gases, CO2 and CH4.

MILD combustion has a wide potential in enhancing thermal efficiency with nearly zero emissions. It has no visible flame since the radiation from the reacting zones is attenuated due to both the intermediate species at reduced temperatures, induced by intensely burned gas recirculation, and the absence of particulate emitters. Beyond these main features, there are other characteristics such as temperature uniformity and distributed ignition that have to be addressed and analyzed looking at the peculiar role of the heat transfer for such reactors. First, the category of combustion systems object of the study is described. Afterwards an analysis on the heat transfer mechanisms under MILD combustion of gaseous fuels is carried out. Therefore, in this Mini-Review, several literature findings highlighting the role of the heat transfer on the combustion peculiarities of MILD reactors (i.e., temperature uniformity, distributed ignition, low pollutant emissions) are reported and discussed. Heat exchange modes, in fact, contribute to providing MILD macroscopic characteristics by means of the strong interplay between wall and gas heat transfer, instead of the reactive structure. In particular, the thermal behavior of these systems is analyzed in order to stress the distinctive role of the heat loss and the relative contributions of the convective and radiative terms. Heat transfer mechanisms between gas and walls and their interactions, in fact, favor the wide temperature distribution within the chamber. In order to better understand the different effects of the heat transfer under MILD regime, the mechanisms regarding walls and recirculating gas are separately investigated.

Dust detection using remotely sensed measurements has been one of the challenging problems encountered by atmospheric scientists. MODerate Resolution Imaging Spectroradiometer (MODIS) on the Terra (T) and Aqua (A) platforms have been a versatile sensor for well over 21 and 18 years respectively, and have been extremely useful in the retrieval of aerosol information over the entire globe. The MODIS radiances from the Level 1B in general are expected to be within 5% accuracy in the reflective wavelengths and within 1% in the thermal emissive wavelengths. In this paper, we evaluate the sensitivity of previously developed dust detection technique based on thermal emissive wavelengths, which correspond to MODIS bands 20, 29, 31, and 32 respectively. The Thermal Emissive Dust Index (TEDI) performed very comparably to the traditional Aerosol Optical Thickness (AOT) retrievals by MODIS reflective channels. Since the MODIS Thermal Emissive Bands (TEB) are well calibrated on-orbit using a BlackBody (BB) source, the calibration of these long wave infrared bands is quite robust. As A-MODIS continues to perform well beyond its designed lifetime of 6 years, the instrument has undergone various levels of degradation during its mission time. As a consequence, it is imperative to check the impacts of calibration on the higher-level retrievals. In this paper, we rigorously analyze the sensitivity of TEDI due to the impact of calibration by the afore-mentioned TEB. The perturbation of the dominant (linear) calibration term demonstrated the following: first, there was a correlation in the sensitivity of the TEDI due to the uncertainty in the linear calibration term. Based on a perturbation in the linear calibration term for all aforementioned bands over a range of ±5% yielded the TEDI sensitivity to vary from approximately −3.2% to about −3.6%. When considering the uncertainty in each individual band significant changes were observed. The least change was observed for the perturbation in the calibration of band 20 with the TEDI sensitivity and the largest sensitivity in TEDI was observed in the perturbation of band 31 calibration. Thus, in the case of TEDI, noticeable sensitivity due to calibration uncertainty was observed in bands 29, 31, and 32, reiterating the importance of the TEB calibration in these bands. Also, the dust detection scheme based on A-MODIS was successfully transferred to the follow-on sensors such as Suomi (SNPP) and NOAA 20 (N20) VIIRS. The results presented in this paper would be extremely helpful in understanding impacts of calibration on the higher-level products for both current and future missions based on the MODIS heritage. Finally, the work also identifies the importance of radiometric fidelity in maintaining the accuracy of the dust detection. Results presented will show drastic improvement of the Saharan dust detection after the reduction of the electronic crosstalk in the 8.5 µm channel of T-MODIS. [ABSTRACT FROM AUTHOR]

Measuring accurate surface temperature using a long-wave infrared camera and a non-contact thermometer, is very difficult due to variables such as atmospheric transmittance, emissivity, and influences from the environment such as atmosphere, sun, and dust. Conventional approaches use geometric correction or atmospheric transmittance modeling for temperature correction. However, these approaches have limitations in finding an accurate temperature because it is difficult to fully model a physical phenomenon. In this paper, a new temperature estimation method using distance information of LiDAR and digital count of long-wave infrared camera is proposed. The proposed method estimates the temperature by redefining the mapping function between radiation and digital count by distance. Using the proposed method, if the digital count is measured at a specific distance, accurate temperature can be estimated through the redefined Radiation-Digital count mapping function at a specific distance. The most important property of proposed method is that complex physical modeling is complemented by mapping function of specific distances. In addition, digital counts that change according to the distance at the same temperature required for the mapping function are obtained through linear interpolation using digital count of specific distances. Experimental results using a blackbody, long-wave infrared camera and LiDAR verify that the proposed method estimates the precise temperature. In addition, through experiments on humans, it shows the possibility of accurate body temperature measurement through fusion of long-wave infrared cameras and LiDAR in the future. However, as a limitation, a new calibration is required when the temperature and humidity of the atmosphere change. [ABSTRACT FROM AUTHOR]

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In this study, we propose a thermal design for an on-board blackbody (BB) for spaceborne infrared (IR) sensor calibration. The main function of the on-board BB is to provide highly uniform and precise radiation temperature reference sources from 0 °C to 40 °C during the calibration of the IR sensor. To meet the functional requirements of BB, a BB thermal design using a heater to heat the BB during sensor calibration and heat pipes to transfer residual heat to the radiator after calibration is proposed and investigated both numerically and experimentally. The main features of the proposed thermal design are a symmetric temperature gradient on the BB surface with less than 1 K temperature uniformity, ease of temperature sensor implementation to estimate the representative surface temperature of the BB, a stable thermal interface between the heat pipes and BB, and a fail-safe function under one heat pipe failure. The thermal control performance of the BB is investigated via in-orbit thermal analysis, and its effectiveness is verified via a heat-up test of the BB under ambient conditions. These results indicate that the temperature gradient on the BB surface was obtained at less than 1 K, and the representative surface temperature could be estimated with an accuracy of 0.005 °C via the temperature sensor.

A series of metal–carbon (M–C) eutectics with robust reproducible melting phase transitions are evolving as the reference high-temperature fixed-points up to 3000 °C for radiation thermometry. The mise-en-pratique prepared for the realization and dissemination of new kelvin allows the use of set of M-C blackbody fixed-points or a combination of M-C fixed-points along with silver (Ag), gold (Au) or copper (Cu) blackbodies for the direct measurement of thermodynamic temperatures at high-temperature range. The iron–carbon (Fe–C) [1153 °C] and cobalt–carbon (Co–C) [1324 °C] fixed-point cells are the doorway to high temperature above a copper fixed-point. This paper describes the in-house development of Fe–C and Co–C eutectic graphite crucible blackbodies and their realizations by linear spectral pyrometer (LP4, 650 nm) at CSIR-NPL, National Metrology Institute (NMI) of India. The novel design and assembly approaches were employed to fabricate the blackbody crucibles with 120o inner-well cone, 100 mm ingot length and 8 mm aperture diameter with 0.9997 emissivity and robust thermo-mechanical stability. The eutectic ingots were prepared by multiple fillings of the homogeneously ground and mixed powders with 4.2 and 2.6 weight percentage of carbon in Fe and Co, respectively. Repeatability of measured melting plateau and uncertainty of the temperature measurement for both Fe–C and Co–C cells are presented. The ITS-90 temperatures (T90) to these M-C fixed-points were assigned by a spectral radiance ratio measurement (Planck's Law) relative to the freezing point of Ag [961.78 °C]. The T90 temperatures thus determined for Fe–C and Co–C blackbody fixed-point cells are 1154.05 °C and 1323.93 °C with the expanded uncertainty of 0.37 °C and 0.50 °C, respectively. [ABSTRACT FROM AUTHOR]

Inspired by nacre that is mechanically strong and versatile in light manipulation, large‐scale black films with a nacre‐like microstructure and carbon nanotube inclusion were prepared using a facile self‐assembly technique. A layered structure promoting blackness and toughness simultaneously was realized, affording robust films with a solar–absorptivity as high as 96.9%. Our design strategy and fabrication process will be beneficial for the facile access to various advanced blackbody coatings. [ABSTRACT FROM AUTHOR]

• A high-efficiency STPV system was designed and fabricated. • Used a multilayer metal-dielectric coated selective emitter for spectral control. • Quantified optical and thermal losses at various stages of energy conversion. • Overall power conversion efficiency of 8.4% was recorded at 1676 K. In this work, we present the design, fabrication, optimization, and experimental results of a high-efficiency planar solar thermophotovoltaic (STPV) system utilizing a micro-textured absorber and a nanostructure multilayer metal-dielectric coated selective emitter fabricated on a tungsten (W) substrate. Light absorptance of more than 90% was achieved at visible and near-infrared wavelengths using the microtextured absorbing surface. The nanostructure selective emitter consists of two thin-film optical coatings of silicon nitride (Si 3 N 4) and a layer of W in between to increase the surface emissivity in spectral regimes matching the quantum efficiency of the thermophotovoltaic (TPV) cells. Gallium antimonide (GaSb)-based TPV cells are used in our STPV design. The experiment was conducted at different operating temperatures using a high-power continuous wave laser diode stack as a simulated source of concentrated incident radiation. Our experimental setup measured a maximum electrical output power density of 1.71 W/cm2 at 1676 K STPV temperature, and the overall power conversion efficiency of 8.4% after normalizing the output power density to the emitter area. This is the highest STPV system efficiency reported so far for any experimental STPV device. The incident optical laser power on the absorber side was 131 W. This is equivalent to a solar concentration factor of ~2100, which is within the practical limit and readily achievable with Fresnel lens setup. [ABSTRACT FROM AUTHOR]

This paper presents a critical analysis of a current typical method to measure sensitivity of solar blind ultraviolet cameras using a high temperature blackbody as a calibrated source of ultraviolet light. It has been shown that measurement of sensitivity of solar-blind ultraviolet (SBUV) cameras defined as minimal detectable blackbody irradiance at optics plane of the tested SBUV camera generates inflated, misleading and prone to measurement errors' results that should not be used for evaluation of SBUV cameras' performance. [ABSTRACT FROM AUTHOR]

Uncooled thermal imaging sensors in the LWIR (7.5 μm to 14 μm) have recently been developed for use with small RPAS. This study derives a new thermal imaging validation methodology via the use of a blackbody source (indoors) and real-world field conditions (outdoors). We have demonstrated this method with three popular LWIR cameras by DJI (Zenmuse XT-R, Zenmuse XT2 and, the M2EA) operated by three different popular DJI RPAS platforms (Matrice 600 Pro, M300 RTK and, the Mavic 2 Enterprise Advanced). Results from the blackbody work show that each camera has a highly linearized response (R2 > 0.99) in the temperature range 5–40 °C as well as a small (

An improved apparatus for measuring the spectral directional emissivity in the wavelength range between 1 µm and 20 µm at temperatures up to 2400 K is presented in this paper. As a heating unit an inductor is used to warm up the specimen, as well as the blackbody reference to the specified temperatures. The heating unit is placed in a double-walled vacuum vessel. A defined temperature, as well as a homogenous temperature distribution of the whole surrounding is ensured by a heat transfer fluid flowing through the gap of the double-walled vessel. Additionally, the surrounding is coated with a high-emitting paint and serves as blackbody-like surrounding to ensure defined boundary conditions. For measuring the spectral directional emissivity at different emission angles, a movable mirror is installed in front of the specimen, which can be adjusted by a rotatable arrangement guiding the emitted radiation into the attached FTIR-spectrometer. The setup of the emissivity measurement apparatus (EMMA) and the measurement procedure are introduced, and the derived measurement results are presented. For evaluating the apparatus, measurements were performed on different materials. The determined emissivities agree well with values published in literature within the derived relative uncertainties below 4% for most wavelengths.

Measuring accurate surface temperature using a long-wave infrared camera and a non-contact thermometer, is very difficult due to variables such as atmospheric transmittance, emissivity, and influences from the environment such as atmosphere, sun, and dust. Conventional approaches use geometric correction or atmospheric transmittance modeling for temperature correction. However, these approaches have limitations in finding an accurate temperature because it is difficult to fully model a physical phenomenon. In this paper, a new temperature estimation method using distance information of LiDAR and digital count of long-wave infrared camera is proposed. The proposed method estimates the temperature by redefining the mapping function between radiation and digital count by distance. Using the proposed method, if the digital count is measured at a specific distance, accurate temperature can be estimated through the redefined Radiation-Digital count mapping function at a specific distance. The most important property of proposed method is that complex physical modeling is complemented by mapping function of specific distances. In addition, digital counts that change according to the distance at the same temperature required for the mapping function are obtained through linear interpolation using digital count of specific distances. Experimental results using a blackbody, long-wave infrared camera and LiDAR verify that the proposed method estimates the precise temperature. In addition, through experiments on humans, it shows the possibility of accurate body temperature measurement through fusion of long-wave infrared cameras and LiDAR in the future. However, as a limitation, a new calibration is required when the temperature and humidity of the atmosphere change.

We discuss the analytical derivation of the absolute brightness temperature uncertainty of a hollow conical blackbody source for radiometer calibration. We introduce a Monte Carlo uncertainty propagation analysis method to quantify uncertainty contributions from nonideal emissivity, physical temperature, and antenna pattern, which are the three major factors contributing to the uncertainty of the brightness temperature radiation from the source. The low reflectance of the hollow conical geometry depends on multiple bounces on the absorber surface. To quantify total brightness temperature over a nonuniform temperature surface, each individual bounce must be considered. We derive a recursive analytical relationship to quantify this multiple-bounce effect as a function of a view angle. The resulting effective blackbody brightness temperature uncertainty is a function of frequency, temperature, antenna pattern, measurement distance, and the measurement environment. We also propagate the uncertainty to the antenna flange of a radiometer viewing the conical blackbody. This includes additional effects, such as spillover, illumination efficiency, and antenna efficiency. We demonstrate the propagation method with an example case. We use fictional input values to investigate the response of the uncertainty to input variables and distance. We find that as the distance between antenna and blackbody increases, the uncertainty due to spillover dominates, but at close distances, the dominant uncertainty contributor is linked to the physical temperature of the absorber. [ABSTRACT FROM AUTHOR]