Radiometric infrared focal plane array imaging system for thermographic applications

This document describes research performed under the Radiometric Infrared Focal Plane Array Imaging System for Thermographic Applications contract. This research investigated the feasibility of using platinum silicide (PtSi) Schottky-barrier infrared focal plane arrays (IR FPAs) for NASA Langley's specific radiometric thermal imaging requirements. The initial goal of this design was to develop a high spatial resolution radiometer with an NETD of 1 percent of the temperature reading over the range of 0 to 250 C. The proposed camera design developed during this study and described in this report provides: (1) high spatial resolution (full-TV resolution); (2) high thermal dynamic range (0 to 250 C); (3) the ability to image rapid, large thermal transients utilizing electronic exposure control (commandable dynamic range of 2,500,000:1 with exposure control latency of 33 ms); (4) high uniformity (0.5 percent nonuniformity after correction); and (5) high thermal resolution (0.1 C at 25 C background and 0.5 C at 250 C background)

The OSIRIS-REx Visible and InfraRed Spectrometer (OVIRS): Spectral Maps of the Asteroid Bennu

The OSIRIS-REx Visible and Infrared Spectrometer (OVIRS) is a point spectrometer covering the spectral range of 0.4 to 4.3 microns (25,000-2300 cm-1). Its primary purpose is to map the surface composition of the asteroid Bennu, the target asteroid of the OSIRIS-REx asteroid sample return mission. The information it returns will help guide the selection of the sample site. It will also provide global context for the sample and high spatial resolution spectra that can be related to spatially unresolved terrestrial observations of asteroids. It is a compact, low-mass (17.8 kg), power efficient (8.8 W average), and robust instrument with the sensitivity needed to detect a 5% spectral absorption feature on a very dark surface (3% reflectance) in the inner solar system (0.89-1.35 AU). It, in combination with the other instruments on the OSIRIS-REx Mission, will provide an unprecedented view of an asteroid's surface.Comment: 14 figures, 3 tables, Space Science Reviews, submitte

Multi-wavelength pyrometric systems for emissivity-independent non-contact temperature sensing

A Multi-Wavelength Imaging Pyrometer (M-WIP) for real-time remote sensing of temperature profiles of targets with unknown emissivity was developed and demonstrated. To measure the spectral radiance of a target at several distinct wavelengths an M-WIP system was implemented based on an 320x122-element PtSi IR-CCD imager with an assembly of 7 narrow-band 1k filters in the range from 1790nm to 4536nm. A real-time algorithm for simultaneous estimation of the temperature and model parameters of the target emissivity from the least-squares fit of the theoretical model of 1k camera output signal to the experimental spectral measurements was developed and implemented. This rea1-time least-squares minimization was accomplished by combination of Levenberg-Marquardt and simulated annealing algorithms. The least-squares-based calibration algorithm was developed for evaluation of effective values of peak transmissions and center wavelengths of M-WIP channels based on the detection of radiation from pre-calibrated blackbody source. To achieve high radiometric accuracy, compensation for the dark current charge as function of the detected signal level was implemented. The effect of the response non-linearity of IR imager was minimized by developing an algorithm for imager operation at fixed pre-selected signal level for each M-WIP spectral channel based on adaptive control of the duration of the optical integration time of the imager. Initial testing demonstrated an accuracy of ±l.0°C for real-time temperature measurements of the center of the blackbody aperture in the range from 500°C to 1000°C. Temperature resolution of ±3°C was demonstrated for the blackbody source viewed through a double side polished silicon wafer with unknown spectral transmissivity in the temperature range from 500°C to 900°C

Advanced Atmospheric Sounder and Imaging Radiometer (AASIR)

Design information for the Advanced Atmospheric Sounder and Imaging Radiometer is reported, which was developed to determine the configuration of a sensor for IR and visible imaging. The areas of technology reported include: systems design, optics, mechanics, electronics, detectors, radiative cooler, and radiometric calibration

Silicon based uncooled microbolometer

During the last decade, uncooled microbolometer infrared detectors have attracted the attention of military and civilian infrared detection and imaging industry due to their significant advantages. In actuality, infrared imaging systems play a critical role in sectors such as thermography (predictive maintenance and building inspection), commercial and civilian applications (vision automotive, surveillance, navigation and fire-fighting), and defense industry (thermal weapon sight, soldier vision and vehicle vision enhancer). Compared with the cryogenically cooled infrared photon detectors, uncooled infrared imaging technology offers advantages such as operation at room temperature, light weight and size, reduced power consumption, easy integration with read-out electronics and broadband response capability. The motivation for this study is the consideration of silicon as an alternative candidate to replace the standard infrared detector thermosensing materials, as a result of its low cost and easy integration with the actual silicon planar lithography microfabrication techniques. No prior attempts are known in the literature on the use of low doped p-type silicon (p-Si) as a thermosensing material in thermal infrared detectors. The main aim of this research work is the design, modeling and simulation of low doped p-Si based uncooled microbolometer infrared detector. The theoretical optical modeling, and electronic performance are analyzed and explained. Radiative properties, as function of thin film thickness, of some commonly used thin films of dielectric materials, aluminum oxide (Al2O3), silicon dioxide (SiO2), aluminum nitride (AlN) and silicon nitride (Si3N4) are investigated within the infrared spectral range of 1.5-14.2 μm. A novel thermally isolated, suspended square-shaped multilayer structure microbolometer is proposed. Its radiative properties are simulated and optimized in the long wavelength spectral range of 8-14 µm (transmission window at room temperature). The performance of the proposed microbolometer structure is numerically calculated by the figures of merit that characterize the thermal detector response. The dimensions of the microbolometer structure are optimized in order to achieve the maximum responsivity and low thermal time response required by the imaging systems, while securing the stability and support of the structure

Thermal Modeling and Imaging of As-built Automotive Parts

Simulation is of significant importance in the automotive industry and can be done for various applications ranging from fluid flow analysis to complex thermal management of components. This thesis describes the method and necessary requirements for thermal modeling of automotive parts. Simulation of under hood and under vehicle automotive poses several challenges, the shape and complexity of the geometry used being the first and foremost to be considered. This thesis addresses the simulation of thermal images of as-built automotive parts using the 3D meshes generated from 3D modeling tools, CAD meshes and reverse engineered meshes. Thermal modeling requires complete knowledge about the under hood and under vehicle automotive components. Many factors, both inside and outside the vehicle, affect the heat flow pattern of the vehicle under consideration. Thermal image sequences of under vehicle chassis were acquired to understand the thermal heat pattern and to serve as a basis for simulation. It was inferred that the exhaust system is the system with significant change in temperature and is at temperature close to 450 degree Celsius when the engine is operating at its full capacity. The exhaust system components, namely the catalytic converter, muffler and the exhaust pipes, were considered as the significant components for thermal modeling. The temperature curves of those components were measured with the help of an infrared thermometer to enhance the results of simulation. Application of thermal imaging in the field of threat detection is also addressed in this thesis. Simulation or thermal modeling of the automotive components was done using the software MuSES. The thermal properties and the boundary conditions were assigned to the 3D geometry used and the transient solution was carried out over a period of time. The results for the three types of meshes mentioned earlier are presented and the thermal predictions are analyzed. As-built models can be modeled as they are with the help of reverse engineering, and the temperature predictions of those components provide better simulation results close to reality. The thesis also addresses the idea of comparison between simulation results and real time experimental results

Gaps in Thermal Design Guidelines in the Goddard Space Flight Center GOLD Rules

The GSFC (Goddard Space Flight Center) GOLD Rules (Goddard Open Learning Design; GSFC-STD-1000) provide a reasonably comprehensive list of guidelines for the design and testing of spacecraft and instruments based on the long heritage of successful GSFC missions. In general, all GSFC missions are required to comply with the GOLD Rules across a number of subsystems or to seek waivers to particular GOLD rules where compliance is not practical, either due to the risk posture of a mission or the cost and/or schedule associated with compliance. In thermal subsystems, GOLD Rules are applied to design margins throughout the project life cycle and include temperature margins, heater power margins, and two-phase transport margins. However, no explicit guidance is provided for two thermal design aspects: heater control authority (for stability requirements) and cryogenic design margins (which are often not reasonable to express in terms of temperatures). This can lead to ambiguity and inconsistency among projects when demonstrating GOLD Rules compliance. Two current GSFC projects, TIRS-2 (Thermal InfraRed Sensor 2) and WFIRST (Wide Field InfraRed Survey Telescope), are both missions with cryogenic aspects and active thermal control for stability. This paper seeks to outline the characterization of cryogenic margins during the design process for TIRS-2 and WFIRST as well as the project derived guidelines for heater control authority margin. This effort serves as potential first steps for updating the GOLD Rules to address these two areas in guiding thermal designs at GSFC

Hyperspectral Imaging of a Turbine Engine Exhaust Plume to Determine Radiance, Temperature, and Concentration Spatial Distributions

The usefulness of imaging Fourier transform spectroscopy (IFTS) when looking at a rapidly varying turbine engine exhaust scene was explored by characterizing the scene change artifacts (SCAs) present in the plume and the effect they have on the calibrated spectra using the Telops, Inc.-manufactured Field-portable Imaging Radiometric Spectrometer Technology, Midwave Extended (FIRST-MWE). It was determined that IFTS technology can be applied to the problem of a rapidly varying turbine engine exhaust plume due to the zero mean, stochastic nature of the SCAs, through the use of temporal averaging. The FIRST-MWE produced radiometrically calibrated hyperspectral datacubes, with calibration uncertainty of 35% in the 1800 - 2500 cm-1 (4 - 5.5 µm) spectral region for pixels with signal-to-noise ratio (SNR) greater than 1.5; the large uncertainty was due to the presence of SCAs. Spatial distributions of temperature and chemical species concentration pathlengths for CO2, CO, and H2O were extracted from the radiometrically calibrated hyperspectral datacubes using a simple radiative transfer model for diesel and kerosene fuels, each with fuel flow rates of 300 cm3/min and 225 cm3/min. The temperatures were found to be, on average, within 212 K of in situ measurements, the difference attributed to the simplicity of the model. Although no in situ concentration measurements were made, the concentrations of CO2 and CO were found to be within expected limits set by the ambient atmospheric parameters and the calculated products of the turbine engine, on the order of 1015 and 1017 molecules/cm3, respectively