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Advanced shapes for conical blackbody targets, as applied in millimeter wave remote sensing instruments, are designed and analyzed for frequencies between 20 and 600 GHz. We propose exponential shaped targets and show that exponential cones are superior to commonly used linear cones. Design and scattering analyses are carried out using the body of revolution method of moments and the finite-element method. Furthermore, a highly efficient ray-tracing approach is introduced and applied. Numerical studies regarding absorbing materials, beam waists, potential manufacturing artifacts, as well as several types of beam misalignment are performed to study practical challenges. Finally, starting from an exponential profile, the blackbody shape is further improved using numerical optimization techniques. [ABSTRACT FROM PUBLISHER]

The reliability of millimeter and sub-millimeter wave radiometer measurements is dependent on the accuracy of the loads they employ as calibration targets. In the recent past on-board calibration loads have been developed for a variety of satellite remote sensing instruments. Unfortunately some of these have suffered from calibration inaccuracies which had poor thermal performance of the calibration target as the root cause. Stringent performance parameters of the calibration target such as low reflectivity, high temperature uniformity, low mass and low power consumption combined with low volumetric requirements remain a challenge for the space instrument developer. In this paper we present a novel multi-layer absorber concept for a calibration load which offers an excellent compromise between very good radiometric performance and temperature uniformity and the mass and volumetric constraints required by space-borne calibration targets. [ABSTRACT FROM AUTHOR]

We present a conceptual prototype model of a focal plane array unit for the STEAMR instrument, highlighting the challenges presented by the required high relative beam proximity of the instrument and focus on how edge-diffraction effects contribute to the array's performance. The analysis was carried out as a comparative process using both PO & PTD and MoM techniques. We first highlight general differences between these computational techniques, with the discussion focusing on diffractive edge effects for near-field imaging reflectors with high truncation. We then present the results of in-depth modeling analyses of the STEAMR focal plane array followed by near-field antenna measurements of a breadboard model of the array. The results of these near-field measurements agree well with both simulation techniques although MoM shows slightly higher complex beam coupling to the measurements than PO & PTD. [ABSTRACT FROM AUTHOR]

Results are presented for the telescope optics verification of the TELlS instrument which is developed and constructed at the Deutsches Zentrum für Luft- und Raumfahrt (DLR), Germany. TELlS is a balloon-borne limb-sounding radiometer which measures pressure-broadened emission lines of various species of the earth's atmosphere. Due to the strong brightness gradient in the limb-viewing geometry the antenna beam of the instrument needs to be well-defined in order to ensure proper operation. Near-field measurements made at 637 GHz of the TELlS telescope were used to derive the far-field pattern. Error compensation included correction of the phase error of the near-field data due to cable flexing. The phase error due to cable flexing was measured using a technique based on heterodyne reception of the signal reflected at the end of the cable. The results are compared to an optics model based on physical optics. Discrepancies between measurements and the model are resolved by misaligning the mirrors in the optics model while minimizing the deviations from theory and experiment. [ABSTRACT FROM AUTHOR]

In the first half of this paper, an efficient method to calculate transmission and reflection characteristics of wire-grids consisting of periodic arrays of cylindrical conductors for arbitrary directions of incidence is presented by extending exact theory of wire-grids proposed by Yasumoto et al. In the latter half of this paper, an approximate calculation method for wire-grids with slight random irregularity in their spacings between wires is proposed by treating the irregularity as a small perturbation to the theory for regular grids. A comparison with preliminary measurements for actual wire-grids in millimeter- and submillimeter-wave regions demonstrated that this method is effectively applicable to wire-grids whose irregularity is not too much. [ABSTRACT FROM AUTHOR]