Thomas Keating Ltd

Free-space polarizing wire grids are often a vital component in quasi-optical circuits. We have long held the belief that they are close to perfect components. An example of this is their ability to create circular polarization (CP) based circulators with extremely good performance (isolation > 50dB) enabling, for example, the W-band cloud profiling radar multiplexing on EarthCARE [1].We are using polarizing wire grids in a number of future space-based projects, for example WIVERN – a candidate for ESA’s 11<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> Earth Explorer mission - is a dual-polarization W-band doppler radar that uses wire grids to combine and separate channels in a novel cross-grid geometry, presented here.However experimental results from a WIVERN breadboard have led us to challenge the assumption that free-standing polarizing wire grids are perfect components. We have seen higher levels of cross-polar generation where a component of the electric field of a gaussian beam on boresight (Ez) – necessary for Div.E to be zero - is allowed to interact with the long axis of the wires. We have matched experimental result and model, and refined our knowledge of how to apply free-standing polarizing grids in low-gain beams, where this effect is most pronounced.

Blackbody on-board calibration targets are key components of spaceborne terahertz radiometers. These must have an emissivity close to 1, uniform temperature, and very low reflectivity. The latter property can be achieved by applying a THz absorbing coating to a surface with a complex reflection geometry. However, the properties of microwave-absorbing media are poorly characterized in the 0.5–5.0 THz. Here, we use a long-path 3.5-THz quantum-cascade laser self-mixing interferometry technique to measure the reflectance of a range of black coatings. Surrey Nanosystems Vantablack S-VIS and N-Science Deep Space Black coatings provide the highest return losses with 28.5 dB and 27.6 dB respectively.

SSOLVE is a heterodyne spectrometer that is under development as a technology demonstration for future lunar lander missions. The system contains a heliostat to target the Sun, optics, and submillimeter-wave, and Terahertz (THz) receivers to measure the column abundance of H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O, OH, and HDO.

Nanoscale magnetic systems play a decisive role in areas ranging from biology to spintronics. Although, in principle, THz electron paramagnetic resonance (EPR) provides high-resolution access to their properties, lack of sensitivity has precluded realizing this potential. To resolve this issue, the principle of plasmonic enhancement of electromagnetic fields that is used in electric dipole spectroscopies with great success is exploited, and a new type of resonators for the enhancement of THz magnetic fields in a microscopic volume is proposed. A resonator composed of an array of diabolo antennas with a back-reflecting mirror is designed and fabricated. Simulations and THz EPR measurements demonstrate a 30-fold signal increase for thin film samples. This enhancement factor increases to a theoretical value of 7500 for samples confined to the active region of the antennas. These findings open the door to the elucidation of fundamental processes in nanoscale samples, including junctions in spintronic devices or biological membranes.

Se analizan comparativamente los efectos del género, el origen social del alumno y el contexto socioeconómico de la escuela sobre los logros en Matemática y Lengua de los alumnos del 6º año de la educación primaria y del último año de la educación secundaria en Argentina. Los datos provienen del Censo Nacional de Finalización del Nivel Secundario y del Operativo Nacional de Evaluación de la Calidad Educativa (Censo primaria), ambos realizados por el Ministerio de Cultura y Educación de la Nación. Para el análisis de los datos se utilizan modelos multinivel con tres niveles (alumno, escuela y Provincia). El análisis se desarrolla a la luz de la teoría de la justicia distributiva en educación y del concepto de igualdad de oportunidad educativa. Se extraen conclusiones comparativas acerca de la magnitud y conformación de la inequidad educativa en ambos niveles del sistema educativo. Se encontró que la distribución del rendimiento está afectada por la extrema segmentación socioeconómica institucional del sistema educativo. La magnitud de la inequidad educativa es similar en primaria y secundaria, pero existen particularidades que diferencian a ambos niveles. Se constató la existencia de una variación importante en los niveles de equidad educativa institucional.Descriptores: Permanencia, educación secundaria, desarrollo positivo, adolescencia. Stay in Secondary Education and its Relationship with Positive Development During adolescenceSchool completion enhances healthy development during adolescence. Findings of a qualitative study in four public high-schools from an area with high dropout rates in San José, Costa Rica, are reported. Participants were students, teachers, other personnel, and parents, who provided their views on personal, familial, and institutional factors that promote school completion. It was found that the identified factors are interrelated among themselves, and related to the conditions that are necessary for positive youth development. Keywords: School completion, high-school education, positive youth development, adolescense.

We demonstrate that very high performance, extremely compact, scalar corrugated feedhorns can be designed and constructed by optimizing the excitation and phasing of the ${\rm HE}_{11}$ , ${\rm HE}_{12}$ , and ${\rm HE}_{13}$ modes near the throat of the horn while limiting excitation of higher order modes. We present the design and measurement of two families of dual-profiled horn, both with a directivity of 20 dBi that couple with very high efficiency to a fundamental Gaussian mode. The first was optimized for sidelobe performance and features sidelobes approaching $-$ 60 dB for a horn length of only 15.6 ${\lambda}$ . The second was designed to minimize horn length and to achieve sidelobe levels below $-35\;\text{dB}$ for a horn that is only 4.8 ${\lambda}$ long. The horns exhibit excellent coupling to the fundamental free-space Gaussian mode, with ${\rm LG}_{00}$ power coupling of 99.92% and 99.75%, respectively. We demonstrate excellent agreement between simulation and experiment at 94 GHz and simulate the performance over a 20% bandwidth. High-performance compact scalar horns are of interest because they reduce manufacturing risk at high frequencies, and reduce size and weight at lower frequencies, which can be important in horn arrays and space applications, where horn arrays often have serious weight and size restrictions.

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