Optimal Passive Damper Placement Methodology for Interferometers Using Integrated Structures/Optics Modeling
This paper focuses specifically on passive structural damping with the goal to lower the control demand on active optics.
passive↗
SEARCH · Engineering Papers
Results for “optical Interferometer”
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.
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The Terrestrial Planet Finder Coronagraph Optical Surface Requirements
Coronagraph telescope and instrument optics for spatial frequencies within and beyond the spatial control bandwidth of the wave front control system. Three different wave front control systems are considered: a zero-path difference Michelson interferometer with two deformable mirrors at a pupil image; a sequential pair of deformable mirrors with one placed at a pupil image; and the Visible Nuller spatially-filtered controller. We show that the optical bandwidth limits the useful outer working angle.
telescope requirements↗
Facility for interferometric testing of 1.25-m mirrors at liquid helium temperatures
A concept is presented for a national cryogenic optics test facility capable of optical characterization of 1.25 m diameter optics having focal lengths up to 6.2 m at temperatures from 300 K to near 4 K. The facility will be comprised of a large Dewar with a phase shift interferometer, a two stage vacuum system employing a turbomolecular pump, and an integral vibration isolation system. The entire facility will be housed in a concrete site with a massive floor to assist in reducing vibration during optical tests. By providing interchangeable sections, the overall height of the Dewar can be adjusted to provide for testing of shorter focal length optics. The background for the facility is discussed along with the facility location, and the requirements and the performance considerations which drive the Dewar design with respect to the vibration isolation system, vacuum system, and optical interferometry.
Salerno, Louis J.↗
An Integrated Model Validation Study of the Wave Front Tip/Tilt System Using the Micro-Precision Interferometer Testbed
This paper presents a validation study of a specific integrated modeling methodology which is a candidate tool for modeling complex opto-mechanical systems such as spaceborne interferometers.
interferometry↗
Facility for interferometric testing of 1.25-m mirrors at liquid helium temperatures
A concept is presented for a national cryogenic optics test facility capable of optical characterization of 1.25 m diameter optics having focal lengths up to 6.2 m at temperatures from 300 K to near 4 K. The facility will be comprised of a large Dewar with a phase shift interferometer, a two-stage vacuum system employing a turbomolecular pump, and an integral vibration isolation system. The entire facility will be housed in a concrete site with a massive floor to assist in reducing vibration during optical tests. By providing interchangeable sections, the overall height of the Dewar can be adjusted to provide for testing of shorter focal length optics. The background for the facility is discussed along with the facility location, and the requirements and the performance considerations which drive the Dewar design with respect to the vibration isolation system, vacuum system, and optical interferometry.
Salerno, Louis J.↗
Common-Path Interferometric Wavefront Sensing for Space Telescopes
This paper presents an optical configuration for a common-path phase-shifting interferometric wavefront sensor.1 2 This sensor has a host of attractive features which make it well suited for space-based adaptive optics. First, it is strictly reflective and therefore operates broadband, second it is common mode and therefore does not suffer from systematic errors (like vibration) that are typical in other interferometers, third it is a phase-shifting interferometer and therefore benefits from both the sensitivity of interferometric sensors as well as the noise rejection afforded by synchronous detection. Unlike the Shack-Hartman wavefront sensor, it has nearly uniform sensitivity to all pupil modes. Optical configuration, theory and simulations for such a system will be discussed along with predicted performance.
wavefront sensors↗
Optical observations of thermospheric dynamics at Arecibo
A description is given of wind and temperature data obtained with a 15-cm Fabry-Perot interferometer. The observations were made between February and August 1980 and confirm the details of the conceptual model of Herrero and Meriwether (1980). Attention is given to the method used to analyze the neutral wind field, the zonal winds, the meridional wind, the horizontal wind gradient, the vertical wind velocity, the full wind field, and the neutral temperature. The most regular feature of the neutral wind at Arecibo is the zonal component, which has a peak velocity in the eastward direction near sunset, and decreases in velocity as the night progresses. Both the wind and temperature measurements reported provide ample confirmation of the importance of the equatorial midnight pressure bulge in modifying the dynamic behavior of the nighttime thermosphere at Arecibo.
Burnside, R. G.↗
A Polarimetric Extension of the van Cittert-Zernike Theorem for Use with Microwave Interferometers
The van Cittert-Zernike theorem describes the Fourier-transform relationship between an extended source and its visibility function. Developments in classical optics texts use scalar field formulations for the theorem. Here, we develop a polarimetric extension to the van Cittert-Zernike theorem with applications to passive microwave Earth remote sensing. The development provides insight into the mechanics of two-dimensional interferometric imaging, particularly the effects of polarization basis differences between the scene and the observer.
Piepmeier, J. R.↗
System converts optical phase changes to RF phase changes
System converts phase changes at optical frequencies to equal phase changes at RF. This system operates in conjunction with either a Michelson interferometer or conventional interferometers.
Logue, S. S.↗
Precise Measurement of Effective Focal Length
Computerized instrument measures effective focal lengths to 0.01 percent accuracy. Laser interferometers measure mirror angle and stage coordinate y in instrument for accurate measurment of focal properties of optical systems. Operates under computer control to measure effective focal length, focal surface shape, modulation transfer function, and astigmatism.
Wise, T. D.↗
Study of optical techniques for the Ames unitary wind tunnels. Part 1: Schlieren
Alignment procedures and conceptual designs for the rapid alignment of the Ames Unitary Wind Tunnel schlieren systems were devised. The schlieren systems can be aligned by translating the light source, the mirrors, and the knife edge equal distances. One design for rapid alignment consists of a manual pin locking scheme. The other is a motorized electronic position scheme. A study of two optical concepts which can be used with the schlieren system was made. These are the 'point diffraction interferometers' and the 'focus schlieren'. Effects of vibrations were studied.
Lee, George↗
High-resolution imaging of the galactic cloud Monoceros R2
We present high-resolution images (9.8 arcsec x 8.5 arcsec beam size) of HCO(+) J = 1-0 emission from the Galactic cloud Mon R2 obtained using the Hat Creek millimeter interferometer and the Five College Radio Astronomy Observatory 14 m antenna. The HCO(+) emission comes from small optically thick clumps as well as from an extended component. We discuss the relationship between the H II region, as traced by the continuum emission, molecular outflows, as traced by CO emission, and the dense molecular cloud, as traced by the HCO(+) emission. The abundance of HCO(+) in the most massive part of the cloud is consistent with values derived from recent molecular line surveys, but it is relatively enhanced in the less massive regions.
Gonatas, Constantine P.↗
Investigation of Fiber Optics Based Phased Locked Diode Lasers
Optical power beaming requires a high intensity source and a system to address beam phase and location. A synthetic aperture array of phased locked sources can provide the necessary power levels as well as a means to correct for phase errors. A fiber optic phase modulator with a master oscillator and power amplifier (MOPA) using an injection-locking semiconductor optical amplifier has proven to be effective in correcting phase errors as large as 4pi in an interferometer system. Phase corrections with the piezoelectric fiber stretcher were made from 0 - 10 kHz, with most application oriented corrections requiring only 1 kHz. The amplifier did not lose locked power output while the phase was changed, however its performance was below expectation. Results of this investigation indicate fiber stretchers and amplifiers can be incorporated into a MOPA system to achieve successful earth based power beaming.
Burke, Paul D.↗
Optical Diagnostics of Solution Crystal Growth
Non-contact optical techniques such as, optical heterodyne, ellipsometry and interferometry, for real time in-situ monitoring of solution crystal growth are demonstrated. Optical heterodyne technique has the capability of measuring the growth rate as small as 1A/sec. In a typical Michelson interferometer set up, the crystal is illuminated by a Zeeman laser with frequency omega(sub 1) and the reference beam with frequency omega(sub 2). As the crystal grows, the phase of the rf signal changes with respect to the reference beam and this phase change is related to the crystal growth rate. This technique is demonstrated with two examples: (1) by measuring the copper tip expansion/shrinkage rate and (2) by measuring the crystal growth rate of L-Arginine Phosphate (LAP). The first test shows that the expansion/shrinkage rate of copper tip was fast in the beginning, and gets slower as the expansion begins to stabilize with time. In crystal growth, the phase change due the crystal growth is measured using a phase meter and a strip chart recorder. Our experimental results indicate a varied growth rate from 69.4 to 92.6A per sec. The ellipsometer is used to study the crystal growth interface. From these measurements and a theoretical modeling of the interface, the various optical parameters can be deduced. Interferometry can also be used to measure the growth rate and concentration gradient in the vicinity of the crystal.
Kim, Yongkee↗
CubeSat Array for Detection of RF Emissions from Exoplanets using Inter-Satellite Optical Communicators
We are presenting a CubeSat mission concept wherein a large number of small spacecraft furnished with Ultra-Long Wavelength (ULW) observation antennas is to be implemented to synthesize a large aperture for detecting ULW emissions from selected exoplanets. The CubeSat Array for the Detection of RF Emissions from Exoplanets (CADRE) concept involves the placement of a swarm arrangement of CubeSats into small amplitude Lissajous orbits around the Earth-Moon L2 point. In addition to the ULW receivers, each CADRE CubeSat will be furnished with a novel omnidirectional optical communicator which should allow data sharing at gigabit per second data rates. In this paper we discuss the science goals, potential architecture and key technical challenges of an eventual CADRE implementation. We present the estimated interferometer specifications needed to detect Exoplanet RF emissions, CubeSat orbits and formations as well as CubeSat design considerations. Special focus is placed on the design of the mission-enabling inter-CubeSat optical cross link which allows for fast sharing of the detected RF signals for subsequent correlation.
Bentum, Mark↗
Sky input horn for a far-infrared interferometer
A unique design has been developed whereby a compound parabolic concentrator (CPC) and a compound elliptical concentrator (CEC) are joined at their throats. The CPC serves as the field-defining optics, in that it accepts up to a certain maximum acceptance angle and then concentrates this accepted energy at its throat. Energy incident from angles greater than the acceptance angle is rejected. The CEC takes the energy concentrated at the CPC throat and then redirects this energy into a finite-sized pupil a given distance away. The considered design will be used as the sky input horn for a cryogenic far-infrared polarizing interferometer to be flown on NASA's Cosmic Background Explorer satellite. The interferometer will operate at 2 K and measure the 3-K cosmic background radiation of the universe in the 100-micrometer-1-cm spectral range.
Miller, M. S.↗
Design considerations and validation of the MSTAR absolute metrology system
Absolute metrology measures the actual distance between two optical fiducials. A number of methods have been employed, including pulsed time-of-flight, intensity-modulated optical beam, and two-color interferometry. The rms accuracy is currently limited to -5 microns. Resolving the integer number of wavelengths requires a 1-sigma range accuracy of -0.1 microns. Closing this gap has a large pay-off the range (length measurement) accuracy can be increased substantially using the unambiguous optical phase. The MSTAR sensor (Modulation Sideband Technology for Absolute Ranging) is a new system for measuring absolute distance, capable of resolving the integer cycle ambiguity of standard interferometers, and making it possible to measure distance with sub-nanometer accuracy. In this paper, we present recent experiments that use dispersed white light interferometry to independently validate the zero-point of the system. We also describe progress towards reducing the size of optics, and stabilizing the laser wavelength for operation over larger target ranges. MSTAR is a general-purpose tool for conveniently measuring length with much greater accuracy than was previously possible, and has a wide range of possible applications.
Jeganathan, Muthu↗
Spectroscopic photoelectric imaging Fabry-Perot interferometer - Its development and preliminary observational results
In order to observe extended astronomical objects at high spatial and spectral resolution, we have constructed a spectroscopic photoelectric imaging Fabry-Perot interferometer (SPIFI). Among the properties chosen for the instrument are an air-spaced, piezoelectrically scanned design allowing an accurately settable free spectral range and employing a single etalon of high finesse. Careful design of the etalon mountings and optical train preserves high light throughput. We either obtain spectra of single spatial elements with a photomultiplier or use an SEC vidicon detector to record a series of images through the interferometer while scanning the wavelength in discrete steps. The latter procedure yields sufficient information to reconstruct spectral features over the entire object. For the conditions assumed, either series of observations requires only a small fraction of a rotational period for Jupiter or Saturn, for example.
Smith, W. H.↗