Search NASA⌕ Search

SEARCH · Search NASA

Results for “MICHELSON INTERFEROMETERS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

322 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Demonstration of the Wide-Field Imaging Interferometer Testbed Using a Calibrated Hyperspectral Image Projector

The Wide-field Imaging Interferometer testbed (WIIT) at NASA's Goddard Space Flight Center uses a dual-Michelson interferometric technique. The WIIT combines stellar interferometry with Fourier-transform interferometry to produce high-resolution spatial-spectral data over a large field-of-view. This combined technique could be employed on future NASA missions such as the Space Infrared Interferometric Telescope (SPIRIT) and the Sub-millimeter Probe of the Evolution of Cosmic Structure (SPECS). While both SPIRIT and SPECS would operate at far-infrared wavelengths, the WIIT demonstrates the dual-interferometry technique at visible wavelengths. The WIIT will produce hyperspectral image data, so a true hyperspectral object is necessary. A calibrated hyperspectral image projector (CHIP) has been constructed to provide such an object. The CHIP uses Digital Light Processing (DLP) technology to produce customized, spectrally-diverse scenes. CHIP scenes will have approximately 1.6-micron spatial resolution and the capability of . producing arbitrary spectra in the band between 380 nm and 1.6 microns, with approximately 5-nm spectral resolution. Each pixel in the scene can take on a unique spectrum. Spectral calibration is achieved with an onboard fiber-coupled spectrometer. In this paper we describe the operation of the CHIP. Results from the WIIT observations of CHIP scenes will also be presented.

Bolcar, Matthew R.↗
NASA NTRS2000

Phase Shift Interferometer and Growth Set Up to Step Pattern Formation During Growth From Solutions. Influence of the Oscillatory solution Flow on Stability

We have assembled an experimental setup based on Michelson interferometry with the growing crystal surface as one of the reflective surfaces. The crystallization part of the device allows optical monitoring of a face of a crystal growing at temperature stable within 0.05 C in a flow of solution of controlled direction and speed. The reference arm of the interferometer contains a liquid crystal element that allows controlled shifts of the phase of the interferograms. We employ an image-processing algorithm, which combines five images with a pi/2 phase difference between each pair of images. The images are transferred to a computer by a camera capable of capturing 60 frames per second. The device allows data collection on surface morphology and kinetics during the face layers growth over a relatively large area (approximately 4 sq. mm) in situ and in real time during growth. The estimated depth resolution of the phase shifting interferometry is approximately 50 Angstroms. The data will be analyzed in order to reveal and monitor step bunching during the growth process. The crystal chosen as a model for study in this work is KH2PO4 (KDP). This optically non-linear material is widely used in frequency doubling applications. There have been a number of studies of the kinetics of KDP crystallization that can serve as a benchmark for our investigations. However, so far, systematic quantitative characteristics of step interaction and bunching are missing. We intend to present our first quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, flow rate, and flow direction. Behavior of a vicinal face growing from solution flowing normal to the steps and periodically changing its direction in time was considered theoretically. It was found that this oscillating flow reduces both stabilization and destabilization effects resulted from the unidirectional solution flow directed up the step stream and down the step stream. This reduction of stabilization and destabilization comes from effective mixing which entangles the phase shifts between the spatially periodic interface perturbation and the concentration wave induced by this perturbation. Numerical results and simplified mixing criterion will be discussed.

Chernov, Alex A.↗
NASA NTRS2011

Miniature, Low-Power, Waveguide Based Infrared Fourier Transform Spectrometer for Spacecraft Remote Sensing

Fourier transform spectrometers have a venerable heritage as flight instruments. However, obtaining an accurate spectrum exacts a penalty in instrument mass and power requirements. Recent advances in a broad class of non-scanning Fourier transform spectrometer (FTS) devices, generally called spatial heterodyne spectrometers, offer distinct advantages as flight optimized systems. We are developing a miniaturized system that employs photonics lightwave circuit principles and functions as an FTS operating in the 7-14 micrometer spectral region. The inteferogram is constructed from an ensemble of Mach-Zehnder interferometers with path length differences calibrated to mimic scan mirror sample positions of a classic Michelson type FTS. One potential long-term application of this technology in low cost planetary missions is the concept of a self-contained sensor system. We are developing a systems architecture concept for wide area in situ and remote monitoring of characteristic properties that are of scientific interest. The system will be based on wavelength- and resolution-independent spectroscopic sensors for studying atmospheric and surface chemistry, physics, and mineralogy. The self-contained sensor network is based on our concept of an Addressable Photonics Cube (APC) which has real-time flexibility and broad science applications. It is envisaged that a spatially distributed autonomous sensor web concept that integrates multiple APCs will be reactive and dynamically driven. The network is designed to respond in an event- or model-driven manner or reconfigured as needed.

Hewagama, TIlak↗
NASA NTRS2009

From Michelson and Fizeau to a Space-borne Infrared Instrument Capable of Detecting an Earth Twin: Development and Recent Accomplishments of Stellar Interferometry

In recent years, the evolution of technology has led to significant advances in high angular resolution astronomy and the precision of new observations. In particular, the interferometric combination of light from physically separated telescopes has shown both great promise and great challenge. We describe the first scientific results from the Keck Interferometer Nuller an instrument that combines the light of the two largest optical telescopes in the world in the context of the historic development of interferometry from its beginning in the work of Fizeau, Stephan and Michelson. We also describe our efforts to build a space-borne mid-infrared interferometer the Fourier Kelvin Stellar Interferometer (FKSI) - for the characterization of exoplanets. We report results of a recent engineering study on an enhanced version of FKSI that includes 1-meter primary mirrors, 20-meter boom length, and an advanced sun shield that will provide a 45-degree FOR and 40K operating temperature for all optics, including siderostats, enabling the characterization of exozodiacal debris disks, extrasolar planets and other phenomena requiring extremely high spatial resolution. We are further investigating the possibility of characterizing the atmospheres of several super-Earths and a few Earth twins by a combination of spatial modulation and spectral analysis.

Barry, Richard K.↗
NASA NTRS1991

Sapphire fiber interferometer for microdisplacement measurements at high temperatures

We report the use of a short-length, multimode sapphire rod as an extension to a Michelson configuration, but operated as a low-finesse Fabry-Perot cavity. We demonstrate the performance of such a device as an interferometric sensor, where the interference between the reflections from the sapphire-air interface and an air-metallic surface is observed for microdisplacement of the metallic surface which is placed close to the sapphire endface. We describe in detail the fabrication procedure and present results obtained from the detection of temperature changes, applied strain, and surface acoustic waves.

Murphy, Kent A.↗
NASA NTRS1992

Sapphire fiber interferometer for microdisplacement measurements at high temperature

Attention is given to the use of a short-length multimode sapphire rod as an extension to a conventional Michelson interferometric configuration, but with operation of Fabry-Perot cavity-based sensor element type. The performance of such a device as an interferometric sensor is demonstrated for a case where the interference between the reflections from the sapphire-air interface and an air-metallic surface is inspected for microdisplacements of the metallic surface. A detailed account is given of the sensor's fabrication procedure; results are presented for the detection of surface-acoustic waves.

Murphy, Kent A.↗
NASA NTRS1994

Mesospheric and lower thermospheric winds, temperatures densities, and volume emission rates

This memo has been written to report on the progress made under grant NAG1-1315 and to request a continuation of funding for this work. Our proposal involved a plan to utilize an existing ground-based chain of optical and radar facilities to assemble a comprehensive, long-term, multi-station base of upper-mesospheric and lower thermospheric measurements of neutral winds, temperatures, and volume emission rates that can be used to make comparisons with data from the HRDI and WINDII instruments that are flying aboard the UARS spacecraft. The ground-based, optical data were to be obtained on a routine basis from five geographically separated observatories at: Thule, Greenland; Sondrestrom, Greenland; Watson Lake, Yukon (replacing Calgary, Alberta); Ann Arbor, Michigan; and Maynooth, Eire. Several different optical instruments are present at these sites: the total array of instruments is comprised of five Fabry-Perot interferometers, two half meter Ebert-Fastie spectrometers, one all-sky CCD imager, and a near infra-red Michelson Fourier transform spectrometer. In addition to these optical instruments, data were to be obtained from the incoherent scatter radar at Sondrestrom, Greenland. These radar measurements are comprised of neutral winds, temperatures, and densities from altitudes between approximately 70 - 120 km. The optical measurements are obtained locally from specific altitudes depending on the emission line studied. For example, red line optical data come from about 220 km. In this report we summarize the progress made in obtaining these data and relate it to the specific tasks outlined in the original grant application. These tasks are discussed in the next section. Progress towards their completion is discussed in section three, while future plans and summary are described in section four.

Killeen, Timothy L.↗
NASA NTRS1986

Balloon-borne cryogenic spectrometer for measurement of lower stratospheric trace constituents

A liquid-nitrogen cooled, multidetector Fourier transform spectrometer has been constructed to measure minor stratospheric constituents via high resolution, earth-limb emission spectroscopy from a balloon-borne platform. Cryogenic cooling, combined with the use of extrinsic silicon photoconductor detectors cooled to liquid-helium temperature, allows the detection of weak emission features of gaseous species. The spectrometer has two basic scan modes: the first mode records the continuous spectrum from 650-2100/cm with 0.2/cm resolution; the second simultaneously records four preselected narrow intervals (about 175/cm bandpass each) with 0.02/cm resolution, unapodized. Filtering of the interferogram signal is done by real-time, digital signal processing. The most important feature of this flat mirror Michelson system, with respect to remote balloon-borne operation, is the dynamic alignment system which maintains the relative parallelism of the two flat reflectors of the interferometer. Species identified to date in data obtained during a Nov. 6, 1984, flight include: CO2, O3, H2O, CH4, HNO3, N2O, NO2, NO, CCl3F (Freon-11) and CF2Cl2 (Freon-12).

Brasunas, J. C.↗
NASA NTRS2002

Stellar Interferometry from the Ground and Space

Stellar Interferometry began more than 80 years ago with the pioneering measurement of the diameter of Betelqueuse by Michelson and Pease using a 20 foot beam mounted at the top of the 10011 Hooker telescope at Mt. Wilson. Essentially no other work was done in this field until the 1960's when Hanbury-Brown and his colleagues developed and used the Intensity Interferometer at Narrabri, Australia to measure the diameters of a number of important hot stars. The modern period of Stellar Interferometry really began in the 1970's with the successes of 3 or 4 small research groups in the US and Europe, and scientific and technical progress in the field has been outstanding, particularly in the last decade. This has lead to the development of two major ground based facilities: NASA's own Keck Interferometer and ESO's Very Large Telescope Interferometer, and a number of space interferometers such as the Space Interferometer Mission (SIM), and the Terrestrial Planet Finder (TPF), among others. I will review the principles, history, and scientific progress in the field both on the ground and in space, and I will discuss a mission concept under development here at NASA Goddard, the Fourier-Kelvin Stellar Interferometer, a near-term mid-infrared imaging interferometer, which can serve as a scientific and technical pre-cursor for some of the more ambitious concepts being discussed within the Astronomical and NASA communities.

Danchi, William C.↗
NASA NTRS1979

Fourier emission infrared microspectrophotometer for surface analysis. I - Application to lubrication problems

A far-infrared interferometer was converted into an emission microspectrophotometer for surface analysis. To cover the mid-infrared as well as the far-infrared the Mylar beamsplitter was made replaceable by a germanium-coated salt plate, and the Moire fringe counting system used to locate the moveable Michelson mirror was improved to read 0.5 micron of mirror displacement. Digital electronics and a dedicated minicomputer were installed for data collection and processing. The most critical element for the recording of weak emission spectra from small areas was, however, a reflecting microscope objective and phase-locked signal detection with simultaneous referencing to a blackbody source. An application of the technique to lubrication problems is shown.

Lauer, J. L.↗
NASA NTRS1971

Development and testing of the infrared interferometer spectrometer for the Mariner Mars 1971 spacecraft

The design, development and testing of the infrared interferometer spectrometer is reported with emphasis on the unique features of the Mariner instrument as compared to previous IRIS instruments flown on the Nimbus meteorological research satellites. The interferometer functions in the spectral range from 50 microns to 6.3 microns. A noise equivalent radiance of 0.5 X 10 to the -7th power W/sq cm/ster/cm has been achieved. Major improvements that were implemented included the cesium iodide beamsplitter and electronic features to suppress the effect of vibration on the Michelson mirror motion and digital filtering through the summation of increased sampling of the infrared signal. A bit error detection and correction scheme was also implemented in order to recover the science data with a higher level of confidence over the telecommunication link.

Hanel, R. H.↗
NASA NTRS2001

Effects of Convective Transport of Solute and Impurities on Defect-Causing Kinetics Instabilities

For in-situ studies of the formation and evolution of step patterns during the growth of protein crystals, we have designed and assembled an experimental setup based on Michelson interferometry with the surface of the growing protein crystal as one of the reflective surfaces. The crystallization part of the device allows optical monitoring of a face of a crystal growing at temperature stable within 0.05 C in a developed solution flow of controlled direction and speed. The reference arm of the interferometer contains a liquid-crystal element that allows controlled shifts of the phase of the interferograms. We employ an image processing algorithm which combines five images with a pi/2 phase difference between each pair of images. The images are transferred to a computer by a camera capable of capturing 6-8 frames per second. The device allows data collection data regarding growth over a relatively large area (approximately .3 sq. mm) in-situ and in real time during growth. The estimated dept resolution of the phase shifting interferometry is about 100 A. The lateral resolution, depending on the zoom ratio, varies between 0.3 and 0.6 micrometers. We have now collected quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, position on the facet, crystal size and temperature with the proteins ferritin, apoferritin and thaumatin. Comparisons with theory, especially with the AFM results on the molecular level processes, see below, allow tests of the rational for the effects of convective flows and, as a particular case, the lack thereof, on step bunching.

Vekilov, Peter G.↗
NASA NTRS1991

Holographic interferometry at the NASA-Ames Hypervelocity Free-Flight Aerodynamic Facility

A laser holographic interferometer has been designed and developed to improve flow visualization for models in free-flight at high velocities and low freestream static pressures. Of special interest is the flow structure due to high-temperature effects in the post-shock region of models traveling at hypervelocity. A dual-plate technique with a double-pass, Michelson-type configuration has been incorporated in an existing hypervelocity ballistic range. Holograms of 5-deg blunt conical models traveling at 5 km/sec in air at a freestream static pressure of 0.08 atm have been made. Finite- and infinite-fringe interferograms were reconstructed from the holograms and provided qualitative flowfield results. In addition, a digital scanning technique was also used to produce a 'synthetic' infinite-fringe interferogram from the analysis of an experimental finite-fringe interferogram. A 'synthetic' infinite-fringe interferogram shows detail in the wake region not found in the experimental interferograms.

Tam, Tim C.↗
NASA NTRS2004

Keck Interferometer status and plans

Keck Interferometer is a NASA-funded project to combine the two 10 m Keck telescopes for high sensitivity near-infrared fringe visibility measurements, nulling interferometry at 10 µm to measure the quantity of exozodiacal emission around nearby stars, and differential-phase measurements to detect "hot-Jupiters" by their direct emission. Recent activity has included formal visibility mode commissioning, as well as science observations, and we briefly review some of the significant technical aspects and updates to the system. We have also completed laboratory development of the nuller. The nuller uses two modified Mach-Zehnder input nullers, a Michelson cross combiner, and a 10 µm array camera to produce background-limited null measurements. To provide required temporal stability for the nuller, the system incorporates end-to-end laser metrology with phase referencing from two 2.2 µm fringe trackers. The nuller recently completed its pre-ship review and is being installed on the summit. After nuller integration and test, the differential phase mode will be deployed, which uses a 2-5 µm fringe detector in combination with a precision path length modulator and a vacuum delay line for dispersion control.

Akeson, Rachel L.↗
DOE OSTI2025

Experimental study of high-energy single-pulse nanosecond discharges in pin-to-pin configuration

Single-pulse pin-to-pin nanosecond pulsed discharges in ambient air (gap distances of 3–7 mm) were investigated at high pulse energies (∼20–30 mJ deposited energy per 11 ns full width at half maximum pulse). A Michelson interferometry setup (532 nm continuous-wave laser) was employed to record time-resolved interferograms of the discharge, enabling spatially resolved calculation of the electron number density. An intensified charge-coupled device camera was used to capture the spatiotemporal evolution of the discharge (streamer formation and spark channel development), and Coherent Anti-Stokes Raman Spectroscopy (CARS) was used to measure post-discharge N 2 vibrational temperatures. Discharge current and voltage were monitored with a back-current shunt. The discharge was initiated with simultaneous cathode-directed and anode-directed streamers that bridge the gap within ∼1 ns and form a luminous, filamentary plasma channel immediately after breakdown. Laser interferometry measurements showed peak electron number densities of the order of 10 1 7–10 18 cm −3 , occurring about 15–20 ns after pulse arrival at the discharge gap. Shorter gap discharges yielded higher peak electron densities, consistent with the higher energy density in the smaller gaps. Spatially, the electron density was highest near the electrodes and decreased toward the midgap region, with 5 and 7 mm gaps exhibiting a pronounced drop in the central channel. CARS indicated initial vibrational temperatures of approximately 4000–6000 K in the spark core of ∼50 ns after the discharge onset, decaying on a ∼500 ns timescale as the plasma cooled and recombined.

Coherent anti-Stokes Raman spectroscopy↗