Structural-Thermal-Optical-Performance (STOP) model development and analysis of a field-widened Michelson interferometer

Scola, Salvatore; Osmundsen, James F.; Murchison, Luke; Davis, W. T.; Fody, Joshua M.; Boyer, C.M.; Cook, Anthony; Hostetler, C. A.; Seaman, Shane T.; Miller, Ian; Welch, Wayne; Kosmer, Adam R.

doi:10.1117/12.2061041

Cited by 5 publications

(3 citation statements)

References 4 publications

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“…Other sources of error that can compromise optimum contrast performance include mirror tilt and wavefront error. Therefore the performance was optimized at the operating temperature by two rounds of corrective polishing [11,13]. In flight, the instrument is enclosed in an environmentally controlled box, and the temperature of the interferometer housing is carefully controlled.…”

Section: Nm Density-tuned Field-widened Michelson Interferometermentioning

confidence: 99%

Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES

et al. 2018

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The NASA Langley airborne second-generation High Spectral Resolution Lidar (HSRL-2) uses a density-tuned field-widened Michelson interferometer to implement the HSRL technique at 355 nm. The Michelson interferometer optically separates the received backscattered light between two channels, one of which is dominated by molecular backscattering, while the other contains most of the light backscattered by particles. This interferometer achieves high and stable contrast ratio, defined as the ratio of particulate backscatter signal received by the two channels. We show that a high and stable contrast ratio is critical for precise and accurate backscatter and extinction retrievals. Here, we present retrieval equations that take into account the incomplete separation of particulate and molecular backscatter in the measurement channels. We also show how the accuracy of the contrast ratio assessment propagates to error in the optical properties. For both backscattering and extinction, larger errors are produced by underestimates of the contrast ratio (compared to overestimates), more extreme aerosol loading, and-most critically-smaller true contrast ratios. We show example results from HSRL-2 aboard the NASA ER-2 aircraft from the 2016 ORACLES field campaign in the southeast Atlantic, off the coast of Africa, during the biomass burning season. We include a case study where smoke aerosol in two adjacent altitude layers showed opposite differences in extinction- and backscatter-related Ångström exponents and a reversal of the lidar ratio spectral dependence, signatures which are shown to be consistent with a relatively modest difference in smoke particle size.

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Section: Nm Density-tuned Field-widened Michelson Interferometermentioning

confidence: 99%

Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES

et al. 2018

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“…Briefly, the performance of the HSRL hinges on the separation of molecular returns from particulate returns. 3,4 The implementation of a unique Michelson Interferometer is a very efficient way of separating the returns (i.e., via an interferometric spectral filter). The unique interferometer utilizes an air spacer in one arm and a solid glass spacer in the other arm.…”

Section: Introductionmentioning

confidence: 99%

Cryogenic refractive index of Heraeus homosil glass

Miller

Quijada

Leviton

2017

Current Developments in Lens Design and Optical Engineering XVIII

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This paper reports measurements of the refractive index of Homosil (Heraeus) over the wavelength range of 0.34-3.16 µm and temperature range of 120-335 K. These measurements were performed by using the Cryogenic High Accuracy Refraction Measuring System (CHARMS) facility at the NASA's Goddard Space Flight Center. These measurements were in support of an integrated Structural-Thermal-Optical-Performance (STOP) model that was developed for a fieldwidened Michelson interferometer that is being built and tested for the High Spectral Resolution Lidar (HSRL) project at the NASA Langley Research Center (LaRC). The cryogenic refractive index measurements were required in order to account for the highly sensitive performance of the HSRL instrument to changes in refractive index with temperature, temperature gradients, thermal expansion, and deformation due to mounting stresses. A dense coverage of the absolute refractive index over the aforementioned wavelength and temperature ranges was used to determine the thermo-optic coefficient (dn/dT) and dispersion relation (dn/dλ) as a function of wavelength and temperature. Our measurements of Homosil will be compared with measurements of other glasses from the fused silica family studied in CHARMS as well as measurements reported elsewhere in the literature.

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“…The ability to re-use the same template across different projects is also a significant advantage, and a key difference between similar analyses performed using Comet, where a project specific template was used (Geiss 3 , Scola 4 ). As long as the same, standardized naming conventions are used across projects, STOP analysis for most optical systems can be completed with the same template.…”

Section: Introductionmentioning

confidence: 99%

Development and implementation of a generic analysis template for structural-thermal-optical-performance modeling

et al. 2016

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Performance-related effects of system level temperature changes can be a key consideration in the design of many types of optical instruments. This is especially true for space-based imagers, which may require complex thermal control systems to maintain alignment of the optical components. Structural-Thermal-Optical-Performance (STOP) analysis is a multi-disciplinary process that can be used to assess the performance of these optical systems when subjected to the expected design environment. This type of analysis can be very time consuming, which makes it difficult to use as a trade study tool early in the project life cycle. In many cases, only one or two iterations can be performed over the course of a project. This limits the design space to best practices since it may be too difficult, or take too long, to test new concepts analytically. In order to overcome this challenge, automation, and a standard procedure for performing these studies is essential. A methodology was developed within the framework of the Comet software tool that captures the basic inputs, outputs, and processes used in most STOP analyses. This resulted in a generic, reusable analysis template that can be used for design trades for a variety of optical systems. The template captures much of the upfront setup such as meshing, boundary conditions, data transfer, naming conventions, and post-processing, and therefore saves time for each subsequent project. A description of the methodology and the analysis template is presented, and results are described for a simple telescope optical system.

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Structural-Thermal-Optical-Performance (STOP) model development and analysis of a field-widened Michelson interferometer

Cited by 5 publications

References 4 publications

Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES

Calibration of a high spectral resolution lidar using a Michelson interferometer, with data examples from ORACLES

Cryogenic refractive index of Heraeus homosil glass

Development and implementation of a generic analysis template for structural-thermal-optical-performance modeling

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