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  • 1
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    Design of Fiber Optic Sensors for Measuring Hydrodynamic Parameters (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The science of optical hydrodynamics involves relating the optical properties to the fluid dynamic properties of a hydrodynamic system. Fiber-optic sensors are being designed for measuring the hydrodynamic parameters of various systems. As a flowing fluid makes an encounter with a flat surface, it forms a boundary layer near this surface. The region between the boundary layer and the flat plate contains information about parameters such as viscosity, compressibility, pressure, density, and velocity. An analytical model has been developed for examining the hydrodynamic parameters near the surface of a fiber-optic sensor. An analysis of the conservation of momentum, the continuity equation and the Navier-Stokes equation for compressible flow were used to develop expressions for the velocity and the density as a function of the distance along the flow and above the surface. When examining the flow near the surface, these expressions are used to estimate the sensitivity required to perform direct optical measurements and to derive the shear force for indirect optical measurements. The derivation of this result permits the incorporation of better design parameters for other fiber-based sensors. Future work includes analyzing the optical parametric designs of fiber-optic sensors, modeling sensors to utilize the parameters for hydrodynamics and applying different mixtures of hydrodynamic flow. Finally, the fabrication of fiber-optic sensors for hydrodynamic flow applications of the type described in this presentation could enhance aerospace, submarine, and medical technology.
    Keywords: Optics
    Type: P16 , HBCUs/OMUs Research Conference Agenda and Abstracts; 24; NASA/TM-2001-211289
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  • 2
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    Optical Electronic Bragg Reflection Sensor System with Hydrodynamic Flow Applications (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This project, as described in the following report, involved design and fabrication of fiber optic sensors for the detection and measurement of dynamic fluid density variations. These devices are created using UV (ultraviolet) ablation and generally modified transverse holographic fiber grating techniques. The resulting phase gratings created on or immediately underneath the flat portion of D-shaped optical waveguides are characterized as evanescent field sensing devices. The primary applications include the sensor portion of a real-time localized or distributed measurement system for hydrodynamic flow, fluid density measurements, and phase change phenomena. Several design modifications were implemented in an attempt to accomplish the tasks specified in our original proposal. In addition, we have established key collaborative relationships with numerous people and institutions.
    Keywords: Optics
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  • 3
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    Cryogenic Optical Performance of the Cassini Composite InfraRed Spectrometer (CIRS) Flight Telescope (1998)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The CIRS half-meter diameter beryllium flight telescope's optical performance was tested at the instrument operating temperature of 170 Kelvin. The telescope components were designed at Goddard Space Flight Center (GSFC) but fabricated out of house and then assembled, aligned and tested upon receipt at GSFC. A 24 inch aperture cryogenic test facility utilizing a 1024 x 1024 CCD array was developed at GSFC specifically for this test. The telescope,s image quality (measured as encircled energy), boresight stability and focus stability were measured. The gold coated beryllium design exceeded the cold image performance requirement of 80% encircled energy within a 460 micron diameter circle.
    Keywords: Optics
    Type: Cryogenic Optical Systems and Instruments; Jul 01, 1998; San Diego, CA; United States
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  • 4
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    Lightweight Aluminum Mirrors Using Foam Core Sandwich Construction (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The possible use of all aluminum mirrors made from thin faceplates supported by aluminum foam is explored from an optomechanical design and fabrication perspective. Foam mirrors can be relatively cheaply and easily made using conventional foam fabrication and diamond turning; such a mirror recently flew for the first time on the Stardust mission. The proposed structural concept is highly weight efficient and should not be prone to quilting. The weight and structural stability of such mirrors is presented, along with plans underway at GSFC for developing this concept.
    Keywords: Optics
    Type: Ultra Lightweight Space Optics Challenge; Mar 23, 1999 - Mar 24, 1999; Napa, CA; United States
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  • 5
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    Cryogenic Optical Performance of the Cassini Composite Infrared Spectrometer (CIRS) Flight Telescope (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The CIRS half-meter diameter beryllium flight telescope's optical performance was tested at the instrument operating temperature of 170 Kelvin. The telescope components were designed at Goddard Space Flight Center (GSFC) but fabricated out of house and then assembled, aligned and tested upon receipt at GSFC. A 24 inch aperture cryogenic test facility utilizing a 1024 x 1024 CCD array was developed at GSFC specifically for this test. The telescope's image quality (measured as encircled energy), boresight stability and focus stability were measured. The gold coated beryllium design exceeded the image performance requirement of 80% encircled energy within a 432 microns diameter circle.
    Keywords: Optics
    Type: Cryogenic Optical Systems and Instruments VIII; Jul 19, 1998 - Jul 24, 1998; San Diego, CA; United States
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  • 6
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    Maintaining Flatness of a Large Aperture Potassium Bromide Beamsplitter through Mounting and Vibration (1998)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: The Composite Infrared Spectrometer (CIRS) instrument on the Cassini Mission launched in October of 1997. The CIRS instrument contains a mid-infrared and a far-infrared interferometer and operates at 170 Kelvin. The mid-infrared interferometer is a Michelson- type Fourier transform spectrometer utilizing a 3 inch diameter potassium bromide beamsplitter/compensator pair. The potassium bromide elements were tested to verify effects of cooldown and vibration prior to integration into the instrument. The instrument was then aligned at ambient temperatures, tested cryogenically and re-verified after vibration. The stringent design optical figure requirements for the beamsplitter and compensator included fabrication errors, mounting stresses and vibration load effects. This paper describes the challenges encountered in mounting the elements to minimize distortion and to survive vibration.
    Keywords: Optics
    Type: Cryogenic Optical Systems and Instruments VIII; Jul 19, 1998 - Jul 24, 1998; San Diego, CA; United States
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  • 7
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    Fiber Bragg Grating Filter High Temperature Sensors (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.
    Keywords: Optics
    Type: P20 , HBCUs/OMUs Research Conference Agenda and Abstracts; 28; NASA/TM-2001-211289
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  • 8
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    Radiation Losses Due to Tapering of a Double-Core Optical Waveguide (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The theoretical model we designed parameterizes the power losses as a function of .the profile shape for a tapered, single mode, optical dielectric coupler. The focus of this project is to produce a working model that determines the power losses experienced by the fibers when light crosses a taper region. This phenomenon can be examined using coupled mode theory. The optical directional coupler consists of a parallel, dual-channel, waveguide with minimal spacing between the channels to permit energy exchange. Thus, power transfer is essentially a function of the taper profile. To find the fields in the fibers, the approach used was that of solving the Helmholtz equation in cylindrical coordinates involving Bessel and modified Bessel functions depending on the location.
    Keywords: Optics
    Type: P18 , HBCUs/OMUs Research Conference Agenda and Abstracts; 26; NASA/TM-2001-211289
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  • 9
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    The Fabrication of an Evanescent Field Sensor (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We present current results concerning novel sensor-based applications for tilted angle fiber Bragg gratings summarized in a recently filed patent. In addition, concepts involving the coupling of light out of the core region of an optical fiber using ablated corrugations to induce interactions with the surrounding media will also be discussed. The interactions between the media and the coupled light formulate the sensing mechanism for both of these devices. The research illustrated here is an extension of previous work that investigated the affects of intense UV radiation fields on both SiO2 and Ge-doped SiO2-based structures (specifically optical fibers and preforms). Finally, these sensors were devised in order to satisfy an experimental task set forth by NASA Glenn involving the production of a prototype evanescent field sensor capable of real-time, dynamic index of refraction measurements as well as early (ultra-high sensitivity) detection of icing on airplane wings.
    Keywords: Optics
    Type: P17 , HBCUs/OMUs Research Conference Agenda and Abstracts; 25; NASA/TM-2001-211289
    Format: text
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  • 10
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    High quality optically polished aluminum mirror and process for producing (2005)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: A new technical advancement in the field of precision aluminum optics permits high quality optical polishing of aluminum monolith, which, in the field of optics, offers numerous benefits because of its machinability, lightweight, and low cost. This invention combines diamond turning and conventional polishing along with india ink, a newly adopted material, for the polishing to accomplish a significant improvement in surface precision of aluminum monolith for optical purposes. This invention guarantees the precise optical polishing of typical bare aluminum monolith to surface roughness of less than about 30 angstroms rms and preferably about 5 angstroms rms while maintaining a surface figure accuracy in terms of surface figure error of not more than one-fifteenth of wave peak-to-valley.
    Keywords: Optics
    Format: application/pdf
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