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NASA NTRS2020

Characterization of Nancy Grace Roman Space Telescope Slitless Spectrometer (grism)

We have published the optical design and early test results of the Roman Space Telescope grism spectrometer in previous SPIE proceedings. We report the follow-on activity of the spectral and radiometric calibrations, including the calibration methods, experiment designs, and test equipment calibration, such as the light source and detectors used in the test. The grism calibration includes the throughput versus wavelength, which is largely determined by the diffraction efficiency of the two diffractive surfaces. It also includes spectral resolution, point spread function, and relative radiometric measurements. The measured results are presented. The comparisons between the test data and the theoretical simulations are also presented. The tests and results presented are from the engineering test unit in ambient room temperature environment. The thermal/vacuum tests are planned to verify the results when the flight unit is ready.

Qian Gong↗
NASA NTRS1993

Unsteady fluid and optical simulation of transonic aero-windows

The time-varying fluid and optical fields of several cavity configurations have been computed on overset mesh systems using the Reynolds-averaged Navier-Stokes equations and geometric optics. Comparisons between numerical results and Airborne Optical Adjunct (AOA) flight data are made in two-dimensions for a quieted cavity geometry with two lip-blowing rates. In three-dimensions, two proposed aero-window locations for the Stratospheric Observatory For Infrared Astronomy (SOFIA) are discussed. The simulations indicate that convection of large shear layer structures across the aperture cause the blur circle diameter to be three times the diffraction-limited diameter in the near-infrared band.

Atwood, Christopher A.↗
NASA NTRS2012

RIMAS - Optical Design Development of the Imager/Spectrometer for the Discovery Channel Telescope

The Rapid IMAger - Spectrometer (RIMAS) is a collaborative effort between the University of Maryland at College Park, NASA-GSFC and Lowell Observatory designed for use on the 4.3 meter Discovery Channel Telescope at Lowell. The primary science goal of the instrument is the study of gamma-ray burst (ORB) afterglow appearing in the near-infrared. Continuous operation will allow measurements beginning minutes after the prompt emission. We present the results of the RIMAS optical design development. The instrument consists of two arms separated by a dichroic: the first for the Y and J bands (0.9 - 1.35 microns) and the second for the Hand K-bands (1.5 - 1.8 and 2.0 - 2.4 microns). Each arm will be equipped with two broad band filters for imaging, as well as low resolution and echelle grisms. The imaging modes are designed to be diffraction limited, with one pixel corresponding to approx.0.35 arcseconds, while the diffractive modes have resolving powers of approximately 20 and 4,000. With photometric and spectroscopic capabilities, RIMAS will be well positioned to quickly determine redshifts, followed by high resolution spectroscopic studies of ORB afterglow.

Capone, John↗
NASA NTRS1994

The application of spaceborne GPS to atmospheric limb sounding and global change monitoring

This monograph is intended for readers with minimal background in radio science who seek a relatively comprehensive treatment of the mission and technical aspects of an Earth-orbiting radio occultation satellite. Part 1 (chapters 1-6) describes mission concepts and programmatic information; Part 2 (chapters 7-12) deals with the theoretical aspects of analyzing and interpreting radio occultation measurements. In this mission concept the navigation signals from a Global Positioning System (GPS) satellite that is being occulted by the Earth's limb are observed by a GPS flight receiver on board a low Earth orbiter (LEO) satellite. This technique can be used to recover profiles of the Earth's atmospheric refractivity, pressure, and temperature using small, dedicated, and relatively low-cost space systems. Chapter 2 summarizes the basic space system concepts of the limb-sounding technique and describes a low-cost strawman demonstration mission. Chapter 3 discusses some of the scientific benefits of using radio occultation on a suite of small satellites. Chapter 4 provides a more detailed discussion of several system elements in a radio occultation mission, including the launch system for small payloads, the LEO microsat, the GPS constellation, the GPS flight receiver payload, the mission operations ground control and data receiving system, the ground-based GPS global tracking network for precision orbit determination, and the central data processing and archive system. Chapter 5 addresses the various technology readiness questions that invariably arise. Chapter 6 discusses the overall costs of a demonstration mission such as GPS/MET (meteorological) proposed by the University Navstar Consortium (UNAVCO). Chapter 7 describes a geometrical optics approach to coplanar atmospheric occultation. Chapter 8 addresses major questions regarding accuracy of the occultation techniques. Chapter 9 describes some simulations that have been performed to evaluate the sensitivity of the recovered profiles of atmospheric parameters to different error sources, such as departure from spherical symmetry, water vapor, etc. Chapter 10 discusses horizontal and vertical resolution associated with limb sounders in general. Chapter 11 treats selected Fresnel diffraction techniques that can be used in radio occultation measurements to sharpen resolution. Chapter 12 provides brief discussions on selected special topics, such as strategies for handling interference and multipath processes that may arise for rays traveling in the lower troposphere.

Melbourne, W. G.↗
NASA NTRS2012

The Shock State of Itokawa Sample

One of the fundamental aspects of any astromaterial is its shock history, since this factor elucidates critical historical events, and also because shock metamorphism can alter primary mineralogical and petrographic features, and reset chronologies [1]. Failure to take shock history into proper account during characterization can result in seriously incorrect conclusions being drawn. Thus the Hayabusa Preliminary Examination Team (HASPET) made shock stage determination of the Itokawa samples a primary goal [2]. However, we faced several difficulties in this particular research. The shock state of ordinary chondrite materials is generally determined by simple optical petrographic observation of standard thin sections. The Itokawa samples available to the analysis team were mounted into plastic blocks, were polished on only one side, and were of non-standard and greatly varying thickness, all of which significantly complicated petrographic analysis but did not prevent it. We made an additional estimation of the sample shock state by a new technique for this analysis - electron back-scattered diffraction (EBSD) in addition to standard petrographic techniques. We are also investigating the crystallinity of Itokawa olivine by Synchrotron X-ray diffraction (SXRD).

Zolensky, Michael↗
NASA NTRS1990

Imaging other planetary systems from the moon

This paper studies the problem of using a telescope like the HST, only larger and sensitive to a wider range of wavelengths, to image systems of planets like the solar system around other stars. Both reflected starlight and thermal radiation from the planets are treated. The instrumental effects of aperture diffraction, scattering due to the power spectral density of telescope mirror surface errors, and telescope thermal emission are included. The integration time required to achieve a signal-to-noise ratio is computed at 5 for photon-statistical random errors only, which is a necessary but not sufficient criterion for detection at a confidence level of five standard deviations. A cold telescope on the moon with 16m aperture and the optical quality of HST could detect and characterize planets around nearby stars.

Brown, Robert A.↗
NASA NTRS2010

NASA Tech Briefs, April 2010

Topics covered include: Active and Passive Hybrid Sensor; Quick-Response Thermal Actuator for Use as a Heat Switch; System for Hydrogen Sensing; Method for Detecting Perlite Compaction in Large Cryogenic Tanks; Using Thin-Film Thermometers as Heaters in Thermal Control Applications; Directional Spherical Cherenkov Detector; AlGaN Ultraviolet Detectors for Dual-Band UV Detection; K-Band Traveling-Wave Tube Amplifier; Simplified Load-Following Control for a Fuel Cell System; Modified Phase-meter for a Heterodyne Laser Interferometer; Loosely Coupled GPS-Aided Inertial Navigation System for Range Safety; Sideband-Separating, Millimeter-Wave Heterodyne Receiver; Coaxial Propellant Injectors With Faceplate Annulus Control; Adaptable Diffraction Gratings With Wavefront Transformation; Optimizing a Laser Process for Making Carbon Nanotubes; Thermogravimetric Analysis of Single-Wall Carbon Nanotubes; Robotic Arm Comprising Two Bending Segments; Magnetostrictive Brake; Low-Friction, Low-Profile, High-Moment Two-Axis Joint; Foil Gas Thrust Bearings for High-Speed Turbomachinery; Miniature Multi-Axis Mechanism for Hand Controllers; Digitally Enhanced Heterodyne Interferometry; Focusing Light Beams To Improve Atomic-Vapor Optical Buffers; Landmark Detection in Orbital Images Using Salience Histograms; Efficient Bit-to-Symbol Likelihood Mappings; Capacity Maximizing Constellations; Natural-Language Parser for PBEM; Policy Process Editor for P(sup 3)BM Software; A Quality System Database; Trajectory Optimization: OTIS 4; and Computer Software Configuration Item-Specific Flight Software Image Transfer Script Generator.

Source record↗
NASA NTRS1995

Integrated optical components in thin films of polymers

The results will be reported on the study of integrated optical components based on nonlinear optical polymeric films. Polymers poly(methyl methacrylate) (PMMA) and polyimide (PI) doped with organic laser dyes 4-dicyanomethylene-2-methyl-6-p dimethylaminostyryl-4H pyran (DCM) and 1, 3, 5, 7, 8 - pentamethyl-2,6 -diethyl-pyrromethene -BF2-complex (Pyrommethene 567, PM-567) were selected as materials for light guiding films. Additionally, UV polymerized polydiacetylene (PDA) on glass substrate was used as a waveguide material. Optical waveguides were fabricated using spin coating of preoxidized silicon wafers (1.5 micrometer silicon oxide layer) with organic dye/polymer solution followed by soft baking. the modes in slab waveguides were studied using prism coupling techniques. Measured values of mode coupling angles in multimode waveguides were used to calculate film thickness and refractive index for different polarizations. Refractive index anisotropy was found in PDA waveguide. The optimal conditions of spin coating for single mode waveguide fabrication were estimated. Propagation losses were measured by collecting the light scattered from the trace of a propagating mode either by scanning photo detector or by CCD camera. Different types of light coupling techniques were used including end-dire coupling, prism and grating coupling. Mechanical printing technique was developed for coupling grating fabrication resulting in gratings with 4% diffraction efficiency. The gratings demonstrated good stability with diffraction efficiency relaxation rate 2.4 dB/hour at a temperature approximately 15-20 C below glass transition point. Dye doped waveguides were transversally pumped with frequency doubled Nd:YAG Q-switched laser producing intensive light emission with apparent 6 kW/sq cm pump threshold and spectrum narrowing near 617 nm peak in the case of DCM doped waveguide. PM-567 doped waveguide pumped with CW Ar(+) laser (514 nm wavelength) far below threshold (0.1 W/sq.cm pump power) demonstrated emission spectrum narrowing near 616 nm peak with 18% power conversion slope efficiency. In this case emission spectrum modification was caused by the enhanced light absorption along the direction of propagating waveguide modes. Changing length, thickness, and other morphlogical waveguide parameters one can modify emission spectrum in predictable direction. The results show that polymeric waveguides, especially based on high temperature polymers such as Pl, can be used to produce a varietiy of active and passive silicon compatible integrated optical components for aerospace applications.

Sarkisov, Sergey↗
NASA NTRS1976

Study report on laser storage and retrieval of image data

The theoretical foundation is presented for a system of real-time nonphotographic and nonmagnetic digital laser storage and retrieval of image data. The system utilizes diffraction-limited laser focusing upon thin metal films, melting elementary holes in the metal films in laser focus. The metal films are encapsulated in rotating flexible mylar discs which act as the permanent storage carries. Equal sized holes encompass two dimensional digital ensembles of information bits which are time-sequentially (bit by bit) stored and retrieved. The bits possess the smallest possible size, defined by the Rayleigh criterion of coherent physical optics. Space and time invariant reflective read-out of laser discs with a small laser, provides access to the stored digital information. By eliminating photographic and magnetic data processing, which characterize the previous state of the art, photographic grain, diffusion, and gamma-distortion do not exist. Similarly, magnetic domain structures, magnetic gaps, and magnetic read-out are absent with a digital laser disc system.

Becker, C. H.↗
NASA NTRS2008

The Selection of Q-Switch for a 350mJ Air-borne 2-micron Wind Lidar

In the process of designing a coherent, high energy 2micron, Doppler wind Lidar, various types of Q-Switch materials and configurations have been investigated for the oscillator. Designing an oscillator with a relatively low gain laser material, presents challenges related to the management high internal circulating fluence due to high reflective output coupler. This problem is compounded by the loss of hold-off. In addition, the selection has to take into account the round trip optical loss in the resonator and the loss of hold-off. For this application, a Brewster cut 5mm aperture, fused silica AO Q-switch is selected. Once the Q-switch is selected various rf frequencies were evaluated. Since the Lidar has to perform in single longitudinal and transverse mode with transform limited line width, in this paper, various seeding configurations are presented in the context of Q-Switch diffraction efficiency. The master oscillator power amplifier has demonstrated over 350mJ output when the amplifier is operated in double pass mode and higher than 250mJ when operated in single pass configuration. The repetition rate of the system is 10Hz and the pulse length 200ns.

Petros, Mulugeta↗
NASA NTRS1991

Diffraction limited infrared images of the binary star T Tauri

High-resolution images of T Tau and its infrared companion have been reconstructed from near- and midinfrared data collected at the Hale 5-m telescope. The near-infrared (1-5 microns) results were obtained by 2D speckle imaging and the midinfrared (10-20 microns) results were derived from shift-and-add procedures applied to slit scans. The spectral energy distributions of the separated components were constructed from 1- to 20-micron data collected in less than half a year (September 1990 to January 1991). The spectral energy distribution of the optical component (T Tau N) is interpreted as containing two distinct constituents, a photosphere and a surrounding disk of circumstellar material. Measurements at a number of infrared wavelengths over the period December 1985 to January 1991 show a 2-mag color-independent change in the brightness of the infrared component (T Tau S). It is proposed that this may have been caused by an increase in accretion onto T Tau S and model the spectral energy distribution of T Tau S as being dominated by an accretion disk.

Ghez, A. M.↗
NASA NTRS1989

Catadioptric optics for laser Doppler velocimeter applications

This paper examines the adaptation of low-cost Schmidt-Cassegrain astronomical telescopes to perform the laser-beam-focusing and scattered-light collection tasks associated with dual-beam laser Doppler velocimetry. A generic telescope design is analyzed using ray-tracing methods and Gaussian beam-propagation theory. A straightforward modification procedure to convert from infinite to near unity conjugate-ratio operation with very low residual aberration is identified and tested with a 200-mm-aperture telescope modified for f/10 operation. Performance data for this modified telescope configuration are near the diffraction limit and agree well with predictions.

Dunagan, Stephen E.↗
NASA NTRS1991

Optical correlator method and apparatus for particle image velocimetry processing

Young's fringes are produced from a double exposure image of particles in a flowing fluid by passing laser light through the film and projecting the light onto a screen. A video camera receives the image from the screen and controls a spatial light modulator. The spatial modulator has a two dimensional array of cells the transmissiveness of which are controlled in relation to the brightness of the corresponding pixel of the video camera image of the screen. A collimated beam of laser light is passed through the spatial light modulator to produce a diffraction pattern which is focused onto another video camera, with the output of the camera being digitized and provided to a microcomputer. The diffraction pattern formed when the laser light is passed through the spatial light modulator and is focused to a point corresponds to the two dimensional Fourier transform of the Young's fringe pattern projected onto the screen. The data obtained fro This invention was made with U.S. Government support awarded by the Department of the Army (DOD) and NASA grand number(s): DOD #DAAL03-86-K0174 and NASA #NAG3-718. The U.S. Government has certain rights in this invention.

Farrell, Patrick V.↗
NASA NTRS1984

Ion beam deposited silicon carbide on glass optics and replica gratings

The results of an attempt to coat optical flats and replace echelle gratings with ion-deposited SiC are reported. Deposition was performed by bombarding a SiC target with an ion beam angled 45 deg relative to the target. Half the target was covered with stainless steel to furnish a comparison opportunity. After precleaning SiC coatings of 300-2200 A thickness were deposited. The specimens had previously been coated with either Au or Al or were left blank. Reflectance and diffraction data were taken of the finished flats and gratings. The SiC-coated flats performed as well as uncoated flats while the echelles exhibited deteriorating performance with increasing coating thickness. Further studies are indicated on the effect of coating thickness on surface roughness.

Windt, D. L.↗
NASA NTRS2021

ORCAS – Orbiting Configurable Artificial Star Mission Architecture

In this paper, we establish the mission operation concept for the Orbiting Configurable Artificial Star mission, a hybrid space-ground observatory, which aims to enable ground observations of near-diffraction limited resolution and exquisite sensitivity. We present the mission requirements, introduce a potential orbit solution that can meet them, detail the concrete operational steps to be taken to enable such observations, and develop a mission planning tool which generates a mission schedule that meets all mission requirements and can be altered in real time in the case of disruptions to the mission. Finally, we show the the mission could enable 300 adaptive optics and 1500 flux calibration observations throughout its lifetime.

Eliad Peretz↗
NASA NTRS1979

Applications of high power lasers

The use of computer generated, reflection holograms in conjunction with high power lasers for precision machining of metals and ceramics was investigated. The Reflection holograms which were developed and made to work at both optical wavelength (He-Ne, 6328 A) and infrared (CO2, 10.6) meet the primary practical requirement of ruggedness and are relatively economical and simple to fabricate. The technology is sufficiently advanced now so that reflection holography could indeed be used as a practical manufacturing device in certain applications requiring low power densities. However, the present holograms are energy inefficient and much of the laser power is lost in the zero order spot and higher diffraction orders. Improvements of laser machining over conventional methods are discussed and addition applications are listed. Possible uses in the electronics industry include drilling holes in printed circuit boards making soldered connections, and resistor trimming.

Angus, J. C.↗
NASA NTRS2004

Wide Angle Liquid Crystal Optical Phased Array

Accurate modeling of a high resolution, liquid crystal (LC) based, optical phased array (OPA) is shown. The simulation shows excellent agreement with a test 2-D LC OPA. The modeling method is extendable to cases where the array element size is close to the wavelength of light. The fringing fields of such a device are first studied, and subsequently reduced. This results in a device that demonstrates plus or minus 7.4 degrees of continuous beam steering at a wavelength of 1550 nm, and a diffraction efficiency (DE) higher than 72%.

Wang, Xing-Hua↗
NASA NTRS2002

Residual wave front phase estimation in the reimaged lyot plane for the eclipse coronographic telescope

Coronagraphs for extra-solar planet detection remove diffracted stellar light through the combination of a coronagraphic mask and a Lyot stop. When the entrance pupil contains a nearly perfect wave fiont, most of the stellar light is absorbed at the mask. Light scattered around the spot due to mid- and high-spatial frequency phase errors in the pupil appears at the Lyot plane as speckles whose amplitudes are proportional to the local wave front phase residuals. The speckles scale with optical wavelength but are not radially smeared. The Eclipse deformable mirror (DM) can be used to modify the Lyot amplitude distribution, providing a simple means of estimating the residual phase content and controlling the wave front. To reduce the detrimental noise carried by uncontrollable high-spatial frequency wave front components, theLyot plane signal is filtered at the science plane to pass only the controllable spatial frequencies that contribute to the dark hole. The Lyot stop is then reimaged onto a detector. We demonstrate through simulations that this approach signiscantly improves the signal-to-noise ratio of the planet measurement.

coronagraph wave front sensing wave front control↗