Electromagnetic Design of Calibration Targets for MetOp-SG Microwave Instruments

Schröder, Arne; Murk, Axel; Wylde, Richard; Jacob, Karl; Pike, Kevin J.; Winser, Mike; Pujades, Marc Bergada; Kangas, V.

doi:10.1109/tthz.2017.2757442

Cited by 27 publications

(9 citation statements)

References 22 publications

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“…An incidence angle of the beam at the cold load of 3°to the LN2 surface was set to reduce the effect of standing waves between the cold load and the receiver. A temperature insulated epoxybased pyramid target [1] at room temperature serves as the hot reference. The radiometer periodically looks at the cold and the hot reference targets, and the water-based target for 2 s by using a flat flip mirror.…”

Section: B Brightness Temperature Measurementsmentioning

confidence: 99%

“…I N MICROWAVE radiometry, the absolute radiometric calibration of a remote-sensing instrument relies on the availability of accurate calibration sources. The application of blackbody calibration targets is a frequently used method to provide a brightness temperature reference [1]- [6] and the performance of these calibration targets directly influences the accuracy of radiometric measurements [7]- [9]. Hence, a blackbody target should exhibit a microwave emissivity close to unity as well as a homogeneous and well known temperature distribution to provide a distinct brightness temperature reference [8], [9].…”

Section: Introductionmentioning

confidence: 99%

“…However, these absorber materials are not well suited to be applied as calibration targets because their very low thermal conductivity can lead to significant temperature gradients. Therefore, most state-of-the-art calibration targets make use of a thin absorber layer based on iron loaded epoxy resins, which is coated onto a metal structure to ensure a homogeneous temperature distribution [1], [4], [6], [14]. On the one hand this coating needs to be sufficiently thick to absorb the entire radiation, but on the other hand it should be thin enough to be well coupled to the metal backing and keep the temperature gradients in the material small.…”

Section: Introductionmentioning

confidence: 99%

“…Typical target designs are quasi-periodic geometries consisting of absorbing pyramids [1], [2], [15]. This target geometry is often applied in radiometers for space missions due to its compact size.…”

Section: Introductionmentioning

confidence: 99%

“…This target geometry is often applied in radiometers for space missions due to its compact size. In this design, metal kernels are introduced into the pyramids to reduce the thermal gradients at the tips, often with the drawback of an increasing reflectivity [1]. Nevertheless, this target design can exhibit significant temperature gradients along the pyramids and the difference between the brightness temperature as it is measured with a radiometer and the temperature of the metal structure can exceed 100 mK [2], [9].…”

Section: Introductionmentioning

confidence: 99%

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Radiometric Characterization of a Water-Based Conical Blackbody Calibration Target for Millimeter-Wave Remote Sensing

Jacob

Schröder

Murk³

et al. 2019

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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In this paper, we present the design and radiometric characterization of a water-based conical blackbody calibration target to be applied as a precise reference source in laboratories and for the accurate calibration of ground-based microwave instruments. The concept of aqueous blackbody targets circumvents the conflict between the electromagnetic and thermal properties of traditional calibration target designs. The temperature controllable target consists of a conical low loss plastic shell, which has been manufactured using a stereolithography three-dimensional printer to define the water-air interface. An advanced exponential profile of the shell is used to compensate the comparatively high refractive index of water and to obtain a high emissivity. Simulations and active measurements of the coherent backscattering S 11 have been performed verifying its excellent electromagnetic properties. Furthermore, radiometric measurements at 110 GHz demonstrate the outstanding thermal performance at various target temperatures between 10 and 60°C. The differences between the brightness temperature and the water temperature are measured to be less than 40 mK and therefore significantly smaller in comparison to traditional calibration targets. In addition, the measured baseline ripples in the spectra caused by the water-based calibration target are small compared to established blackbody concepts.

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Section: B Brightness Temperature Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Radiometric Characterization of a Water-Based Conical Blackbody Calibration Target for Millimeter-Wave Remote Sensing

Jacob

Schröder

Murk³

et al. 2019

IEEE J. Sel. Top. Appl. Earth Observations Remote Sensing

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Switchable Broadband Terahertz Absorbers Based on Conducting Polymer‐Cellulose Aerogels

Kuang,

Chen,

Luo

et al. 2023

Advanced Science

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Terahertz (THz) technologies provide opportunities ranging from calibration targets for satellites and telescopes to communication devices and biomedical imaging systems. A main component will be broadband THz absorbers with switchability. However, optically switchable materials in THz are scarce and their modulation is mostly available at narrow bandwidths. Realizing materials with large and broadband modulation in absorption or transmission forms a critical challenge. This study demonstrates that conducting polymer‐cellulose aerogels can provide modulation of broadband THz light with large modulation range from ≈ 13% to 91% absolute transmission, while maintaining specular reflection loss < −30 dB. The exceptional THz modulation is associated with the anomalous optical conductivity peak of conducting polymers, which enhances the absorption in its oxidized state. The study also demonstrates the possibility to reduce the surface hydrophilicity by simple chemical modifications, and shows that broadband absorption of the aerogels at optical frequencies enables de‐frosting by solar‐induced heating. These low‐cost, aqueous solution‐processable, sustainable, and bio‐friendly aerogels may find use in next‐generation intelligent THz devices.

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Absorption dominated broadband terahertz electromagnetic shielding properties of ultrathin rGO paper

Sun,

Wu,

Chen

et al. 2024

Carbon

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Electromagnetic Design of Calibration Targets for MetOp-SG Microwave Instruments

Cited by 27 publications

References 22 publications

Radiometric Characterization of a Water-Based Conical Blackbody Calibration Target for Millimeter-Wave Remote Sensing

Radiometric Characterization of a Water-Based Conical Blackbody Calibration Target for Millimeter-Wave Remote Sensing

Switchable Broadband Terahertz Absorbers Based on Conducting Polymer‐Cellulose Aerogels

Absorption dominated broadband terahertz electromagnetic shielding properties of ultrathin rGO paper

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