SEARCH · Engineering Papers

Results for “optical interferometry”

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.

SourceResearch connectionFrom yearThrough year

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

At least 1,189 records · Page 66

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Arcsecond Positions for Milliarcsecond VLBI Nuclei of Extragalactic Radio Sources, Part 2: 207 Sources

Very long base interferometry measurements of time delay and fringe frequency at 2.29 GHz on baselines of 10,000 km between Deep Space Network stations were used to determine the positions of the milliarcsecond nuclei in 207 extragalactic radio sources. Estimated accuracies generally range from approximately 0.1 to approximately 1.0, in both right ascension and declination, with all sources having uncertainties 4" in both coordinates. The observed sources are part of an all-sky VLBI catalog of milliarcsecond radio sources. Arcsecond positions are now determined for 752 of these sources. Arcsecond positions serve as a useful starting point in the construction of high-precision VLBI reference frames and are also important for unambiguous determination of optical counterparts to compact radio sources.

Morabito, D. D.↗

NASA NTRS2008

Brassboard Astrometric Beam Combiner (ABC) Development for the Space Interferometry Mission (SIM)

The Astrometric Beam Combiner (ABC) is a critical element of the Space Interferometry Mission (SIM) that performs three key functions: coherently combine starlight from two siderostats; individually detect starlight for angle tracking; and disperse and detect the interferometric fringes. In addition, the ABC contains: a stimulus, cornercubes and shutters for in-orbit calibration; several tip/tilt mirror mechanisms for in-orbit alignment; and internal metrology beam launcher for pathlength monitoring. The detailed design of the brassboard ABC (which has the form, fit and function of the flight unit) is complete, procurement of long-lead items is underway, and assembly and testing is expected to be completed in Spring 2009. In this paper, we present the key requirements for the ABC, details of the completed optical and mechanical design as well as plans for assembly and alignment.

PlanetQuest↗

NASA NTRS1979

Self-synchronizing Schlieren photography and interferometry for the visualization of unsteady transonic flows

The use of self synchronizing stroboscopic Schlieren and laser interferometer systems to obtain quantitative space time measurements of distinguished flow surfaces, steakline patterns, and the density field of two dimensional flows that exhibit a periodic content was investigated. A large field single path stroboscopic Schlieren system was designed, constructed and successfully applied to visualize four periodic flows: near wake behind an oscillating airfoil; edge tone sound generation; 2-D planar wall jet; and axisymmetric pulsed sonic jet. This visualization technique provides an effective means of studying quasi-periodic flows in real time. The image on the viewing screen is a spatial signal average of the coherent periodic motion rather than a single realization, the high speed motion of a quasi-periodic flow can be reconstructed by recording photographs of the flow at different fixed time delays in one cycle. The preliminary design and construction of a self synchronizing stroboscopic laser interferometer with a modified Mach-Zehnder optical system is also reported.

Kadlec, R.↗

DOE OSTI2022

In Situ Ion Counting for Improved Implanted Ion Error Rate and Silicon Vacancy Yield Uncertainty

An in situ counted ion implantation experiment improving the error on the number of ions required to form a single optically active silicon vacancy (SiV) defect in diamond 7-fold compared to timed implantation is presented. Here, traditional timed implantation relies on a beam current measurement followed by implantation with a preset pulse duration. It is dominated by Poisson statistics, resulting in large errors for low ion numbers. Instead, our in situ detection, measuring the ion number arriving at the substrate, results in a 2-fold improvement of the error on the ion number required to generate a single SiV compared to timed implantation. Through postimplantation analysis, the error is improved 7-fold compared to timed implantation. SiVs are detected by photoluminescence spectroscopy, and the yield of 2.98% is calculated through the photoluminescence count rate. Hanbury–Brown–Twiss interferometry is performed on locations potentially hosting single-photon emitters, confirming that 82% of the locations exhibit single photon emission statistics.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2023

Enhancing strontium clock atom interferometry using quantum optimal control

Strontium clock atom interferometry is a promising new technology, with multiple experiments under development around the world to explore its potential for dark matter and gravitational wave detection. In these detectors, large momentum transfer using sequences of many laser pulses is necessary, and thus high-fidelity pulses are important since small errors become magnified. Quantum optimal control (QOC) is a framework for developing control pulse waveforms that achieve high fidelity and are robust against experimental imperfections. Resonant single-photon transitions using the narrow clock transition of strontium involve significantly different quantum dynamics than more established atom interferometry methods based on far-detuned two-photon Raman or Bragg transitions, which leads to new opportunities and challenges when applying QOC. Here, we study in simulation QOC pulses for strontium clock interferometry and demonstrate their advantage over basic square pulses (primitive pulses) and composite pulses in terms of robustness against multiple noise channels. In conclusion, this could improve the scale of large momentum transfer in Sr clock interferometers, paving the way to achieving these scientific goals.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRS1998

The HST T tauri star SNAPshot survey

In the nearest star-forming regions, protoplanetary disks have angular sizes of only 3-4". Millimeter interferometry has generally been limited to a resolution of 1". Groundbased coronagraphic imaging of YSOs has been restricted to radii exterior to an occulting mask (r >2"), and detect nebulosity only in the most extreme dusty systems. The Hubble Space Telescope (HST) is the only observatory which can provide a spatial resolution of approx. 10 AU in combination with a stable point-spread function for high dynamic range imaging at visual wavelengths. Since the December 1993 servicing mission, only 12 nearby young stars have been observed by HST with the sensitivity needed to detect circumstellar reflection nebulosity. All six of the classical T Tauri stars observed so far have shown nebulosity; three objects are compact bipolar nebulae without an optically visible star; and the three weak-line T Tauri stars observed show no evidence for circumstellar nebulosity. Disks have been directly observed in 3 of the 12 systems studied so far: HH 30, GM Aurigae, and Haro 6-5B. A larger survey offers the prospect of many more detections, and thereby can address such fundamental questions as: What is the frequency for direct detection of disks around premain sequence stars? What is the range of disk masses and sizes? How are disks different in binary systems? Our proposal for an HST T Tauri Star SNAPshot survey was approved for 75 targets in Cycle 7. A SNAPshot survey consists of short-duration (25 minutes or less) sequences of observations which can be used to fill gaps in the HST observing schedule. This is well-matched to the needs of disk imaging, where typical T Tauri stars (11 < V < 14) saturate the WFPC2 detectors in a minute or less. Only wide-band R and I images will be taken.

Stapelfeldt, Karl↗

DOE OSTI2015

Integrating and Live-time Radiation Dosimetry by Optical Crystal Damage, Initial Results with Neutrons

Radiation damage can be assessed through many techniques, though the assessment is usually offline and shows only integrated dose. Transparent crystals can be optically monitored for radiation damage nondestructively, to serve as a detector for both immediate dose and integrated dose for signatures of radiation exposure history. There is also some difference in gamma-ray and neutron interactions which can be observed. Gamma ray interactions primarily produce electron displacements, which are preserved as color centers in ionic crystals and produce specific spectral absorption lines. Neutron interactions strongly produce lattice displacements that affect the index of refraction. The differences may allow us to use inexpensive crystals for long time neutron monitoring. Spectroscopic absorption lines can be quantified using prior technology, but due to prior limits in phase sensitivity there was no previous use of index of refraction measurements. Using novel techniques based on intracavity phase interferometry to assess lattice displacements, we are able to examine neutron irradiation in CaF2 crystals. Initial results with neutrons will be presented.

99 GENERAL AND MISCELLANEOUS↗

NASA NTRS2001

Comparison of full-aperture interferometry to sub-aperture stitched interferometry for a large diameter fast mirror

The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope. Stitching sub aperture interferograms may offer considerable cost savings during testing of the flight telescope as compared to other techniques. A comparative demonstration is presented of interferogram stitching techniques that enable a composite map of a 3-D surface to be assembled from a sequence of sub-aperture measurements. This paper describes the fundamental procedures for stitching together component data sets and demonstrates such techniques with real data sets.

carbon fiber composite cryogenic optics high slope↗

NASA NTRS1996

Exploration an the Search for Origins: A Vision for Ultraviolet-Optical-Infrared Space Astronomy

Public support and enthusiasm for astronomy have been strong in the final decades of the twentieth century. Nowhere is this better demonstrated than with the Hubble Space Telescope (HCT), a grand endeavor, which is enabling astronomers to make giant strides in understanding our universe, our place in it, and our relation to it. The NASAs first infrared observatory, the Space Infrared Telescope Facility (SIRTF), promises to take the crucial next steps towards understanding the formation of stars and galaxies. Toward their completion, the HST and Beyond Committee identifies major goals, whose accomplishment will justify a commitment well into the next century: (1) the detailed study of the birth and evolution of normal galaxies such as the Milky Way; (2) the detection of Earth-like planets around other stars and the search for evidence of life on them; (3) NASA should develop a space observatory of aperture 4m or larger, optimized for imaging and spectroscopy over the wavelength range 1-5 microns; and (4) NASA should develop the capability for space interferometry.

Dressler, Alan↗

DOE OSTI2023

The co-located arrangement of ECEI and MIR microwave imaging diagnostics on EAST tokamak

The co-located configuration of Passive Electron Cyclotron Emission Imaging (ECEI) and active Microwave Imaging Reflectometry (MIR) diagnostics systems has been successfully implemented on the EAST fusion reactor. These advanced 2D microwave diagnostic tools offer 10–20 mm poloidal spatial resolution through large aperture quasi optics. This arrangement not only optimizes the utilization of limited observation windows but also facilitates concurrent measurements of plasma density and electron temperature at specific toroidal positions. Furthermore, this co-located setup holds great promise for enhancing research into electron heat transport and other pivotal plasma phenomena.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS2006

Digital Front End for Wide-Band VLBI Science Receiver

An upgrade to the very-long-baseline-interferometry (VLBI) science receiver (VSR) a radio receiver used in NASA's Deep Space Network (DSN) is currently being implemented. The current VSR samples standard DSN intermediate- frequency (IF) signals at 256 MHz and after digital down-conversion records data from up to four 16-MHz baseband channels. Currently, IF signals are limited to the 265-to-375-MHz range, and recording rates are limited to less than 80 Mbps. The new digital front end, denoted the Wideband VSR, provides improvements to enable the receiver to process wider bandwidth signals and accommodate more data channels for recording. The Wideband VSR utilizes state-of-the-art commercial analog-to-digital converter and field-programmable gate array (FPGA) integrated circuits, and fiber-optic connections in a custom architecture. It accepts IF signals from 100 to 600 MHz, sampling the signal at 1.28 GHz. The sample data are sent to a digital processing module, using a fiber-optic link for isolation. The digital processing module includes boards designed around an Advanced Telecom Computing Architecture (ATCA) industry-standard backplane. Digital signal processing implemented in FPGAs down-convert the data signals in up to 16 baseband channels with programmable bandwidths from 1 kHz to 16 MHz. Baseband samples are transmitted to a computer via multiple Ethernet connections allowing recording to disk at rates of up to 1 Gbps.

Jongeling, Andre↗

DOE OSTI2024

Technology and times scales in Photonic Doppler Velocimetry (PDV)

Photonic Doppler Velocimetry (PDV) is a fiber-based measurement amenable to a wide range of experimental conditions. Interference between two optical signals—one Doppler shifted and the other not—is the essential principle in these measurements. A confluence of commercial technologies, largely driven by the telecommunication industry, makes PDV particularly convenient at near-infrared wavelengths. This discussion considers how measurement time scales of interest relate to the design, operation, and analysis of a PDV measurement, starting from the steady state through nanosecond resolution. Benefits and outstanding challenges of PDV are summarized, with comparisons to related diagnostics.

47 OTHER INSTRUMENTATION↗

NASA NTRS2002

Projection Moire Interferometry for Rotorcraft Applications: Deformation Measurements of Active Twist Rotor Blades

Projection Moire Interferometry (PMI) has been used during wind tunnel tests to obtain azimuthally dependent blade bending and twist measurements for a 4-bladed Active Twist Rotor (ATR) system in simulated forward flight. The ATR concept offers a means to reduce rotor vibratory loads and noise by using piezoelectric active fiber composite actuators embedded in the blade structure to twist each blade as they rotate throughout the rotor azimuth. The twist imparted on the blades for blade control causes significant changes in blade loading, resulting in complex blade deformation consisting of coupled bending and twist. Measurement of this blade deformation is critical in understanding the overall behavior of the ATR system and the physical mechanisms causing the reduction in rotor loads and noise. PMI is a non-contacting, video-based optical measurement technique capable of obtaining spatially continuous structural deformation measurements over the entire object surface within the PMI system field-of-view. When applied to rotorcraft testing, PMI can be used to measure the azimuth-dependent blade bending and twist along the full span of the rotor blade. This paper presents the PMI technique as applied to rotorcraft testing, and provides results obtained during the ATR tests demonstrating the PMI system performance. PMI measurements acquired at select blade actuation conditions generating minimum and maximum rotor loads are provided to explore the interrelationship between rotor loads, blade bending, and twist.

Fleming, Gary A.↗

DOE OSTI2017

Pressure-induced complexity in dynamically compressed calcium

In this project we studied the series of structural phase transitions that occurs in the alkali earth metal Ca as it transforms to increasingly complex arrangements with pressure. The experiments were designed specifically for the ultra-bright X-ray source of the LCLS and the optical capabilities of the MEC nanosecond drive laser. We studied in detail the unusual structural behavior near the minimum of Ca’s melt curve along the Hugoniot and investigated possible metastable phase formation as an explanation for large discrepancies in pressure-volume data from previous shock and static experiments. In total 200 data shots were taken. Using the laser pulse shaping capabilities for the MEC nanosecond laser permitted two thermodynamic compression paths to be explored: (i) Along the principal Hugoniot within the solid and liquid phases, (ii) along a double-shock path to access a cooler P-T compression path within the solid state. Probing the compressed Ca sample with the LCLS XFEL permitted structural determination of the Ca through x-ray diffraction. Pressure was determined with Doppler Interferometry (MEC VISAR diagnostic) and the known equation-of-state of Ca. These data represent the first direct measurements of lattice level rearrangement in Ca under shock compression. We observe the onset of melt, structure within the liquid and an evolution of crystal structure along off-Hugoniot paths up to 100 GPa. These experiments yield important insights into non-equilibrium phase formation under dynamic loading and the deviation away from nearly free electron like behavior, which has been found to be ubiquitous among the elements.

36 MATERIALS SCIENCE↗

NASA NTRS2004

Mid-IR interferometric nulling for TPF

By the middle of 2006, the Interferometry Technology development program for NASA’s Terrestrial Planet Finder (TPF) Mission has the goal of demonstrating deep and stable interferometric nulling of broadband Mid-IR thermal radiation under conditions that are traceable to the expected on-orbit conditions. Specifically, the task is to demonstrate null levels of 10 to the negative 6 power, with a 50% BW centered at 10 um, with null stabilities of 10 to the negative 7 power all at cryogenic temperatures for observational periods of a couple of hours. The Achromatic Nulling activity at JPL addresses this concern in two testbeds: the warm nulling testbed and the cryonulling testbed. The warm nulling testbed will demonstrate the physics of nulling broadband thermal sources in an environment that is conducive to efficient research. We’ll explore nulling techniques, optical-mechanical alignment methods, motion control, and path-length metrology for a single beam interferometer, as well as preliminary planet detection techniques. Ultimate nulling capabilities under conditions that are more flight-like will be demonstrated in cryogenic nulling testbed. Knowledge gained from operation at room temperature will be applied to the cryongenic experiment where we face the additional challenges of extreme temperatures, cryongenic actuators, component survivability and fluxes that are within an order of magnitude of expected flux levels on orbit. Concurrently, we will develop a low flux mid-IR camera that will allow us to measure the nulls at these faint photon fluxes. This talk will review this development activity and will include recent nulling experimental results and plans for future work.

Vasisht, Gautam↗

NASA NTRS2018

A Dispersive Backend Design for the 'Double-Fourier' Interferometer BETTII

BETTII (Balloon Experimental Twin Telescope for Infra-red Interferometry) is designed to provide high angular resolution spectroscopic data in the far-infrared (FIR) wavelengths. The most significant limitation for BETTII is its sensitivity; obtaining spectral signal-to-noise ratio greater than 5 in less than 10 minutes requires sources greater than 13 Janskys (Jy). One possible way to improve the signal-to-noise ratio (SNR) for future BETTII flights is by reducing the spectral bandwidth post beam-combination. This involves using a dispersive element to spread out a polychromatic point source PSF (Point Spread Function) on the detector array, such that each pixel corresponds to a small fraction of the bandwidth. This results in a broader envelope of the interferometric fringe pattern allowing more fringes to be detected, and thereby improving the spectral SNR. Here we present the analysis and optical design of the dispersive backend, discussing the tradeoffs and how it can be combined with the existing design.

Dhabal, Arnab↗

NASA NTRS2007

Interferometry from Space

Space-based interferometric observatories will be challenging projects, equal at least to that of building the Great Observatories (the Hubble Space Telescope (HST), Spitzer Space Telescope (SST), Chandra X-ray Observatory, and the Gamma Ray Observatory), if not the Pyramids of Eygpt - but they represent the next logical step in examining our Universe at substantially higher angular resolution. Increasing our resolving power by factors of 100 or more (as is needed to make meaningful improvements in this observational arena) over existing facilities such as HST and SST requires mirror diameters (100's to 1000's of meters) much larger than can be supported by single or segmented mirrors - and thus the design and construction of sparse aperture, inteferometric arrays such as those described herein will be required. But just imagine the rewards of being able to see, for the first time, the surfaces of other stars, the location and type of extrasolar planets and even pictures of those same planets, the inner workings of Active Galactic Nuclei, the close-in details of supernovae explosions, black hole event horizons, and the infrared universe at the same resolution of the UV-optical Hubble Deep Fields. As a slight variation on the "Star Trek: Enterprise" theme song might say, it'll be a "long road, getting from here to there", but it will one well-worth taking.

Carpenter, Kenneth↗

NASA NTRS2016

Multilayer Active Shell Mirrors for Space Telescopes

A novel active mirror technology based on carbon fiber reinforced polymer (CFRP) substrates and replication techniques has been developed. Multiple additional layers are implemented into the design serving various functions. Nanolaminate metal films are used to provide a high quality reflective front surface. A backing layer of thin active material is implemented to provide the surface-parallel actuation scheme. Printed electronics are used to create a custom electrode pattern and flexible routing layer. Mirrors of this design are thin (< 1.0 mm), lightweight (2.7 kg/m2 ), and have large actuation capabilities. These capabilities, along with the associated manufacturing processes, represent a significant change in design compared to traditional optics. Such mirrors could be used as lightweight primaries for small CubeSat-based telescopes or as meter-class segments for future large aperture observatories. Multiple mirrors can be produced under identical conditions enabling a substantial reduction in manufacturing cost and complexity. An overview of the mirror design and manufacturing processes is presented. Predictions on the actuation performance have been made through finite element simulations demonstrating correct abilities on the order of 250−300× for astigmatic modes with only 41 independent actuators. A description of the custom metrology system used to characterize the active mirrors is also presented. The system is based on a Reverse Hartmann test and can accommodate extremely large deviations in mirror figure (> 100 µm PV) down to sub-micron precision. The system has been validated against several traditional techniques including photogrammetry and interferometry. The mirror performance has been characterized using this system, as well as closed-loop figure correction experiments on 150 mm dia. prototypes. The mirrors have demonstrated post-correction figure accuracies of 200 nm RMS (two dead actuators limiting performance).

Reverse Hartmann↗