Thermal Vacuum Cold Target for the Metop SG MicroWave Imager

Abstract

The assessment of the Metop-SG MicroWave Imager (MWI) radiometric performance is based on a complete set of thermal vacuum tests. Such an extensive experimental campaign requires the development of large calibration targets (black bodies) with controlled systematics and low residual uncertainties. The significant size of such targets, which are based on pyramidal emitting surfaces, does not allow for a complete minimization of the thermal gradients below the required accuracy level. This work presents the modeling approach that has been developed to deal with both such thermal gradients and the proximity of the baffle. Results on the frequency dependence of the cold target brightness temperature (ECCOSORB CR-117) are reported between 18.7 and 183 GHz. The complete uncertainty budget provides 1-sigma errors levels lower than 0.22 K. The systematic effect of thermal coupling with the Earth Target has been found as relevant as the coupling to the chamber. This interdependence requires a look-up-table approach to maintain the low uncertainty levels mentioned above.

Review of Accurate Detection of Human Skin Tissue Temperature Based on Microwave Radiation Method

“…It is impossible to accurately trace the uncertainty of transmitting the brightness temperature actually measured by the radiometer [20,21]. In recent years, scholars, including our team, have been actively studying and constructing quantitative modeling methods, including complex radiation targets and near-field receiving antennas [22][23][24][25]. In 2017, Schöder and colleagues from the University of Bern used far-field reciprocity to calculate the local absorption rate and overall reflectivity of the radiator in an inverse scattering model.…”

“…It also highlights important development trends. In 2021, Virone et al from the Italian Institute of Electronic Information and Telecommunications modelled the radiation brightness temperature of the cone array calibration source and the transmission brightness temperature to the antenna from the perspective of circuit equivalence [23]. This report presents a method for weighting the directional radiation brightness temperature of a calibration source based on the antenna far-field pattern.…”

The THz Catastrophe. Part 1: Discrepancy Between Planck’s Law and Experiments on Silicon Wafers

“…Another important application of eq. ( 2) is the calibration of radiometers for earth observation missions as reported in [11].To our knowledge, the only experimental validation of equation ( 2) has been conducted by Sato et al in 1967, [12] looking at highly doped silicon. In 2001, Ravindra et al, [13], successfully fitted the data from Sato, by using eq.…”

“…12), there are less oscillations since higher doping corresponds to higher attenuation constants. Actually the emissivity for higher doped slabs can be approximated as the one associated to an infinite thickness silicon wafer for which 11) and eq. ( 8) can be safely used to assess the emissivity.…”