Search

This article describes a comprehensive testing method for the thermal calibration of the Thermal InfraRed Sensor (TIRS) onboard NASA's Perseverance rover. Ground-based IR detectors operating at the surface of Mars are subjected to inaccuracies caused by the inclusion of thermal gradients in their packages. To reduce such uncertainties, it is necessary to compensate for their effects. Here, details of the TIRS thermo-mechanical design and a simplified thermal mathematical model (TMM) that accounts for the presence of thermal gradients in the detector's package are provided. Then, a set of equations for the estimation and compensation of thermal gradients are proposed based on the results of the TMM. Thermal calibration tests to identify the mathematical estimators are analyzed, providing details of the test setups and highlighting their limitations and restrictions. Finally, experimental results of the calibration tests are presented, along with the uncertainty sources and potential systematic errors associated with the estimation of the gradients. The results presented here show a significant improvement in the accuracy of TIRS versus previous work, thus fulfilling of the radiometer scientific requirements set by the Mars 2020 science team. • A new thermal calibration plan for a ground-based Martian IR radiometer. • Detectors package thermal gradients estimation based on thermal modeling and tests. • Simplified test setups and differences with the Martian environment. • Performance analysis accounting for test setup uncertainties and thermal modeling. • Uncertainties meet the scientific requirements stated by the Mars 2020 science team. [ABSTRACT FROM AUTHOR]

The Mars Environmental Dynamics Analyzer (MEDA) is a suite of environmental sensors onboard NASA’s Mars 2020 mission. The Thermal InfraRed Sensor (TIRS), developed at Centro de Astrobiología of Spain, is one of the six sensors comprising MEDA, and it will measure the net thermal infrared radiation and reflected solar radiation at the surface, as well as the atmospheric and surface skin temperatures using five different channels. In combination with MEDA's other sensors, TIRS will allow the quantification of the surface energy budget and the determination of key geophysical properties of the terrain such as the albedo and thermal inertia. Here we present a general description of the TIRS, its channels scientific requirements, and the mechanical and thermal design. Then, a detailed sensor mathematical model and a sensitivity analysis to model uncertainties are described. Some characterization test results to model parameters identification are included. Finally, accuracy and resolution calculus for each channel versus operational temperature is presented. The calculus is performed based on sensitivity equations, the practical tests results and the estimated values for different uncertainty sources. [ABSTRACT FROM AUTHOR]

Abstract: Limestones used as building material are especially prone to weathering in coastal environments due to interactions between sea mist and the carbonate stone. Subtle variations of the commercial surface finishing may lead to differences in decay patterns and aesthetic properties due to salt crystallization. To explore this potentially contrasting behavior, tablets of rough and polished low-porous limestone were aged in a sea-salt spray corrosion chamber to simulate their exposure in a coastal environment. Different crystallization morphologies and relative proportions of soluble (halite) and less soluble (gypsum) salts were observed in the aged rough and polished surface samples. These morphologies are ascribed to the microtextural characteristics and the surface pore systems of the diverse (rough and polished) substrates that in turn influence fluid (saline solution) transport toward their interior, as well as the different salt solubilities interacting with the substrates. Polished surfaces exhibit little evidence of damage after the ageing test in contrast to the rough samples but do have conspicuous gypsum on the surface together with halite. The scarcity of gypsum on the rough surfaces, in addition to a more severe change in the porosity system, suggests that salts penetrate deeper when the stone surface is not polished. Potential decay induced by salt crystallization pressure is therefore minimized when the stone surface is polished. However, polished surfaces show more significant changes in luminosity and chroma after the ageing test, and so are less attractive from an aesthetic point of view. Surface finishing is thus an important feature that needs to be characterized for a better understanding of the weathering behavior of building stones used in coastal environments. [Copyright &y& Elsevier]

Abstract: This paper analyses the spatial and temporal temperature stabilisation requirements of unchopped thermopile IR pyrometers under different temperature conditions and measurement wavelengths. Each thermopile output signal is affected differently and independently by the appearance of undesired spatial and temporal gradients in a thermopile case structure. Expressions for the ratios of thermopile sensitivity to spatial and temporal gradients versus a change in scene temperature are derived from a simplified static and dynamic thermopile thermal model that takes into account the internal structure and operation of the sensor. The ratios depend on the thermopile and the target absolute temperature, as well as the physical and optical properties of the thermopile. This knowledge may help in selecting the appropriate detector, optimising the design of pyrometer thermal control systems, or in establishing strategies to compensate for the associated uncertainty. [Copyright &y& Elsevier]

Abstract: The technical quality of two compositionally different groups of solid bricks fired between 800 and 1000°C was evaluated. Five weight percentage of fly ash was added to both groups and they were compared with similar bricks with no added fly ash. The textures of the bricks with fly ash were very similar to the textures of those without it, except that the samples with the additive contained spherical fly ash particles with diameters ranging from 0.1 to 10μm. These particles led to a reduction in the density of the bricks and a substantial improvement in their durability, with less decay being caused by salt crystallization in the pores. This is because fly ash causes a reduction in the number of micropores, the pores that make porous materials most vulnerable to salt-induced decay. Use of this additive could have practical implications as a means of recycling and for achieving cost savings in brick production. [Copyright &y& Elsevier]

Abstract: This study shows that the sandstone used in the construction of the Church of San Mateo in Tarifa (Cádiz, Spain) is highly sensitive to processes of decay because of a combination of factors that are intrinsic and extrinsic to the material. The mineralogy, texture and porous system of the sandstone and the proximity of the church to the sea all play a part in these processes. X-ray diffraction reveals that there are interstratified chlorite/smectite clays among the minerals that make up the rock. These mixed layer clays have been shown to undergo hydric expansion. This phenomenon may be accompanied and augmented by the presence of NaCl which acts as an electrolyte in osmotic swelling processes. Two varieties of sandstone were used in the construction of the church, namely grey sandstone and brown sandstone. The latter is more porous and undergoes greater hydric expansion, showing a higher degree of deterioration. Ultrasound analysis has demonstrated that both varieties are anisotropic because they contain bedding planes and are affected by the preferred orientation of the phyllosilicates in the rock. The anisotropic nature of these stones was confirmed by capillary suction tests. The capillary front reaches a relatively low height which means that when water is absorbed, the anisotropic textural properties combined with the presence of chlorite–smectite mixed layers in the sandstone result in mechanical (shear) stress between the first few centimetres of the wet stone and the dry area behind. The latter effect favours the development of flakes, so causing the decay of the ornamental stone and the church façade. [Copyright &y& Elsevier]

The changes in brick porosity upon firing (700 up to 1100 °C) and its relation to the mineralogical composition are examined. Two types of raw clay with a composition representative of that used in brick-making industry were selected to manufacture the bricks: one contains notable amounts of carbonates, with a grain size of under 1 mm, and the other is predominantly quartzitic and lacking in carbonates. We demonstrate that the presence or absence of carbonates strongly influences the porosity development and, therefore, the brick texture and physical-mechanical properties. The carbonates in the raw clay promote the formation of fissures and of pores under 1 μm in size when the bricks are fired between 800 and 1000 °C. The absence of carbonates results in a continuous reduction in porosity and a significant increase in the pore fraction with a radius (r)>1 μm as the firing temperature rises and smaller pores coalesce. Porosity and pore size distribution results obtained from the combined use of hydric tests (HT), mercury intrusion porosimetry (MIP) and digital image analysis (DIA) of scanning electron microscopy photomicrographs are compared. A clear correlation between the water absorption and drying behaviour of the bricks and the porosity plus pore size distribution is observed. DIA discloses the evolution of size, shape and connectivity of macropores (r> 1 μm) and evidences that MIP results underestimate the macropore content. Conversely, MIP gives a good estimate of the open porosity and of the distribution of pores with r<1 μm. It is concluded that the combined use of these complementary techniques helps to fully characterise the pore system of bricks. These results as well as the study of the evolution of the speed of ultrasound waves vs. time yield useful information to evaluate the bricks physical–mechanical behaviour and durability. The relevance of these findings in the conservation of historic buildings is discussed. [Copyright &y& Elsevier]

• A new radiometric and angular calibration plan for a Martian IR radiometer. • Simplified test setups and differences with Martian environmental are described. • Spectral response analysis vs. radiation incidence angle and operational temperature. • Performance analysis accounting for calibration uncertainties and set-up limitations. • Uncertainties meet the scientific requirements stated by the Mars 2020 science team. This article describes a comprehensive testing method for the radiometric and angular calibration of the Thermal InfraRed Sensor (TIRS) onboard NASA's Mars 2020 mission. First, details of the TIRS opto-mechanical design, construction aspects of the IR detectors, and an update of the mathematical model used for the calculation of sensor internal IR fluxes are provided. Then, a set of sequential calibration tests to identify the radiometer model parameters are defined. The test setups are described, highlighting their limitations and restrictions based on differences between simulated and actual Martian environmental conditions. Finally, the uncertainty sources and potential systematic errors associated with the calibration tests are quantified and compared with the radiometer scientific requirements established by the Mars 2020 science team. [ABSTRACT FROM AUTHOR]

This research examines fired clay bricks made with waste pomace from the wine industry as an additive in brick production. To this end, we analyse and discuss the chemical, mineralogical, textural and physical-mechanical behaviour of fired bricks made with three concentrations of wine pomace (2.5, 5 and 10 wt%) and at three different firing temperatures (800, 950 and 1100 °C) and evaluate their durability to salt crystallization. Variations in colour were also examined. The firing process resulted in the decomposition of phyllosilicates and carbonates, the crystallization of Fe oxides and the appearance of high-temperature Ca- (and Mg-) silicates phases such as gehlenite, wollastonite, anorthite and diopside. The bricks made with added wine pomace had very similar mineralogy to the control samples made without it. The bricks made with added wine pomace were lighter than the control samples and underwent less linear shrinkage during the drying process. Particles in the wine pomace were consumed during firing, leading to the appearance of voids. The bricks made with this additive had higher levels of water absorption and poorer mechanical strength. The greatest colour differences were detected after increasing the amount of waste, which generally resulted in yellower bricks. The increase in firing temperature resulted in an improvement in mechanical resistance regardless of the composition of the bricks. However, bricks fired at 1100 °C made without additive are more resistant to damage caused by salts than those made with wine pomace. [Display omitted] • The reuse of wine pomace reduces the quantity of clayey material in the production of bricks. • The addition of wine pomace augments the size and number of pores in the bricks. • Bricks with wine pomace are suitable for use as lightweight materials in the construction industry. • The addition of wine pomace modifies the lightness and chromatism of bricks, not the mineralogy. [ABSTRACT FROM AUTHOR]

Abstract: Bricks proceeding from one of the bastions of the Riga medieval defence wall were studied. Two main type of bricks were identified: one rich in quartz and red coloured and the other with a calcium silicate phase and yellow coloured. The survey of the bastion reveals a partial deterioration of the bricks. It was observed that differences in mineralogy and texture of calcareous and non-calcareous bricks were correlated with their behaviour in hydric and weathering tests. Data from powder X-ray diffraction (presence of high-temperature mineral phase in yellow bricks), optical microscopy (vitrification in yellow bricks), Field Emission Scanning Electron Microscope (development of secondary bubbles due to extensive melting in yellow bricks) and ultrasounds measurements (lower velocity in red bricks) allow to deduce that yellow bricks were fired at a higher temperature than the red ones. The study of the pore system revealed a bad interconnection among pores in yellow bricks (hydric data) since melt isolated the pores and filled the smallest, whereas large pores increased in size (porosimetric data). As a consequence, considering the climatic conditions of the region, yellow bricks are the materials most subjected to environmental alteration. It is in agreement with the freeze–thaw test results. Finally, low contamination of the bricks with water-soluble salts in situ leads to exclude salt-caused decay process. The relevance of these results in the conservation of Cultural Heritage is discussed. [Copyright &y& Elsevier]