Designed to fulfill a critical inspection need for the Space Shuttle Program, the EVA IR Camera System can detect crack and subsurface defects in the Reinforced Carbon-Carbon (RCC) sections of the Space Shuttle's Thermal Protection System (TPS). The EVA IR Camera performs this detection by taking advantage of the natural thermal gradients induced in the RCC by solar flux and thermal emission from the Earth.
This instrument is a compact, low-mass, low-power solution (1.2cm3, 1.5kg, 5.0W) for TPS inspection that exceeds existing requirements for feature detection. Taking advantage of ground-based IR thermography techniques, the EVA IR Camera System provides the Space Shuttle program with a solution that can be accommodated by the existing inspection system. The EVA IR Camera System augments the visible and laser inspection systems and finds cracks and subsurface damage that is not measurable by the other sensors, and thus fills a critical gap in the Space Shuttle's inspection needs. This paper discusses the on-orbit RCC inspection measurement concept and requirements, and then presents a detailed description of the EVA IR Camera System design.
Designed to fulfill a critical inspection need for the Space Shuttle Program, the Infrared On-orbit RCC Inspection System (IORIS) can detect crack and surface defects in the Reinforced Carbon-Carbon (RCC) sections of the Space Shuttle’s Thermal Protection System (TPS). IORIS performs this detection by taking advantage of the natural thermal gradients induced in the RCC by solar flux and thermal emission from the Earth. IORIS is a compact, low-mass, low-power solution (1.2cm3, 1.5kg, 5.0W) for TPS inspection that exceeds existing requirements for feature detection. Taking advantage of ground-based IR thermography techniques, IORIS provides the Space Shuttle program with a solution that can be accommodated by the existing inspection system. IORIS augments the visible and laser inspection systems and finds cracks that are not easily measurable by the other sensors, and thus fills a critical gap in the Space Shuttle’s inspection needs. Based on crack IR signature predictions and on-orbit gradient expectations, IORIS can achieve crack detection over approximately 96% of the wing-leading edge RCC (using multiple inspections in an orbit period). This paper discusses the on-orbit RCC inspection measurement concept and requirements, and then presents a detailed description of the IORIS design.
The environmental and health effects of wildfires are discussed. The monitoring of wildfires from aircraft using remote sensing techniques is reviewed. A future autonomous aerial observing system for fire monitoring is described.
Scientists at NASA's Langley Research Center, in collaboration with researchers at Virginia Tech, are developing the next generation of thermal radiation detectors composed of new space-age materials, including carbon-doped Larc-Si and aerogels. In order to accurately model and design these detectors, it is necessary to determine the in situ thermoelectric properties of these new materials, including thin-film effects and contact resistance. The authors present an approach to determine these properties through the use of simultaneous parameter estimation methods in which experimental results obtained from detector prototypes are compared with results predicted from analytical models. Parametric values are varied using an optimization method to minimize the least-squares error between the experimental and model results. A numerical study is presented to validate the use of this approach. Simulated experimental results were produced using a model based on nominal parameter values. These results were then introduced into a parameter estimation algorithm that was able to recover the parameter values without the benefit of a priori knowledge about the material properties. Genetic algorithms, stochastic hill climbers, and a hybrid of the two methods were investigated for use in parameter estimation.
Described is thermal radiation detector conceived for possible deployment on GERB (Geostationary Earth Radiation Budget). It consists of a linear array of 256 elements, each 60 micrometer square and separated by a 3-micrometer gap. Each element is the active junction of a single-junction-pair zinc- antimonide/platinum thermopile. The reference junction is mounted on an isothermal substrate, and the active junction is thermally isolated from the substrate by a thin layer of parylene. The detector is mounted on one wall of a wedge- shaped, mirrored cavity intended to increase the effective absorptivity and improve the spectral flatness of the detector through multiple reflections. A dynamic opto-electrothermal model of the detector/cavity combination has been formulated in order to facilitate its optimal design. The optical part of the model is based on a Monte-Carlo ray trace that takes into account diffraction at the entrance slit as well as the diffuse and specular components of reflectivity of the cavity surfaces. Heat absorption and diffusion through the thermopile structure has been modeled using the finite element method. The model has been used to validate a method for eliminating optical cross-talk among elements of the array through post- processing of data.
This manuscript outlines a continuing effort to validate and verify the performance of an airborne autonomous wavemeter for tuning solid state lasers to a desired wavelength. The application is measuring the vertical profiles of atmospheric water vapor using a differential absorption lidar (DIAL) technique. Improved wavemeter performance data for varying ambient temperatures are presented. This resulted when the electronic grounding and shielding were improved. The results with short pulse duration lasers are also included. These lasers show that similar performance could be obtained with lasers operating in the continuous and the pulsed domains.
The continuing effort to develop, design, construct, and evaluate the performance of an airborne autonomous wavemeter for tuning solid state lasers is summarized. The wavemeter supports tunable solid state lasers that are used for an atmospheric remote sensing technique. One atmospheric species, water vapor, is measured by tuning one laser to precisely the line center of a water vapor line and by tuning another laser off the line. The two sets of received backscattered radiation are ratioed and corrected to determine the vertical profiles of water vapor. On a spacecraft platform, an advanced system could monitor the vertical water vapor profiles. This would provide a technology improvement for meteorological forecasting.
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