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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Estimation of cyclic error due to scattering in the internal OPD metrology of the Space Interferometry Mission

A common-path laser heterodyne interferometer capable of measuring the internal OPD with accuracy of the order of 10 picometers was demonstrated at JPL. To achieve this accuracy, the relative power received by the detector that is contributed by the scattering of light at the optical surfaces should be less than -97 dB. A method has been developed to estimate the cyclic error caused by the scattering of the optical surfaces. The result of the analysis is presented.

Zhao, Feng↗
NASA NTRS2001

Adjustable Focus Optical Correction Lens (AFOCL)

This report describes a metrology plan that was developed for the characterization of PLZT-based devices, such as the Adjustable Focus Optical Correction Lens (AFOCL) in support of and as part of the deliverables for NASA contract NAS8-00118. The areas to be investigated include intensiometric effects (those that limit or alter the intensity of the light transmitted through the optic); interferometric effects (the phase change induced through the optic); and polarimetric effects (evaluating the differential lag between two polarization states propagating through the optic). These distinct phenomena are often coupled together in real applications consequently, there is a need to develop different standardized testing apparatus to: (1) isolate one effect from another; (2) gather information for understanding the physical effects; (3) anchor wavefront corrector modeling efforts; (4) develop the ability to decouple different effects; (5) demonstrate the suitability of PLZT technology to perform wavefront correction. The Center for Applied Optics (CAO) at the University of Alabama in Huntsville (UAH) is skilled in the characterization of transmission wavefront shaping devices using traditional interferometers available within the CAO Optical Metrology Laboratory and their Advanced Polarization Test Facility. Besides the imaging and interferometers available, the polarimetry facility has at its disposal, a Mueller Matrix Imaging Polarimeter (MMIP) which is well suited to the characterization of SLMs, polarizers, and thin film coatings within the visible and near-IR spectrums. In addition, the phase-shifting interferometry facilities at NASA-MSFC and the unique interferometers they processes are some of the most advanced available and may be of value especially for performing real-time optical performance evaluation of AFOCL test components.

Peters, Bruce R.↗
NASA NTRS2002

Wavefront tilt feedforward for the formation interferometer testbad (FIT)

Separated spacecraft interferometry is a candidate architecture for several future NASA missions. The Formation Interferometer Testbed (FIT) is a ground based testbed dedicated to the validation of this key technology for a formation of two spacecraft. In separated spacecraft interferometry, the residual relative motion of the component spacecraft must be compensated for by articulation of the optical components. In this paper, the design of the FIT interferometer pointing control system is described. This control system is composed of a metrology pointing loop that maintains an optical link between the two spacecraft and two stellar pointing loops for stabilizing the stellar wavefront at both the right and left apertures of the instrument. A novel feedforward algorithm is used to decouple the metrology loop from the left side stellar loop. Experimental results from the testbed are presented that verify this approach and that fully demonstrate the performance of the algorithm.

formation flying↗
NASA NTRS2010

LISA Pathfinder Instrument Data Analysis

LISA Pathfinder (LPF) is an ESA-launched demonstration mission of key technologies required for the joint NASA-ESA gravitational wave observatory in space, LISA. As part of the LPF interferometry investigations, analytic models of noise sources and corresponding noise subtraction techniques have been developed to correct for effects like the coupling of test mass jitter into displacement readout, and fluctuations of the laser frequency or optical pathlength difference. Ground testing of pre-flight hardware of the Optical Metrology subsystem is currently ongoing at the Albert Einstein Institute Hannover. In collaboration with NASA Goddard Space Flight Center, the LPF mission data analysis tool LTPDA is being used to analyze the data product of these tests. Furthermore, the noise subtraction techniques and in-flight experiment runs for noise characterization are being defined as part of the mission experiment master plan. We will present the data analysis outcome of preflight hardware ground tests and possible noise subtraction strategies for in-flight instrument operations.

Guzman, Felipe↗
NASA NTRSDate not supplied

Metrological and Spectral Characterization of the Aspera Flight Optics

Aspera is a NASA's Astrophysics Pioneers mission, led by the University of Arizona. The aim of this mission is to study the presence of hot gasses (T=10^5-10^6 K) in the circumgalactic medium (CGM) and how the flow of these gasses affects galactic formation. One key enabling technology in the Aspera optical system is the use of more efficient UV-reflective optical coatings particularly at around 103.2 nm where the O VI emission line is located . In order to meet radiometric effective area requirements, the Goddard Space Flight Center (GSFC) code 551 Optics Branch applied Al (aluminum) + eLiF (enhanced lithium fluoride) on these optics, where the Al+LiF is annealed at elevated temperature (~250˚C) after the deposition and thus providing an improved version of the Al+LiF used in FUSE . Furthermore, these optics are encapsulated with a thin film of atomic layer deposited MgF2 at the Jet Propulsion Laboratory for enhanced durability . The efficiency and durability of these coatings depends on the quality of the optical surface in terms of cleanliness and roughness. Roughness increases the scatter off the coating and reduces the specular reflectance, and surface contaminants can accommodate moisture and other contaminants, increase scattering, and are weak points in the coating that may affect adhesion and subsequently the longevity of these coatings. Extensive optical metrology is necessary to minimize and quantify the impact of surface roughness and contaminants on optical surfaces. In this proceeding we report the inspection procedure implemented for Aspera optics at GSFC, from initial receiving of the optics to post-coating. Inspection includes Atomic Force Microscopy (AFM), Scanning White Light Interferometry (SWILI), Dark Field Microscopy (DFM), Phase Shifting Interferometry (PSI), and Vacuum ultraviolet (VUV) spectroscopy. Combinations of these techniques are used to inspect flight optics at each of the following steps: i) as-received, pre-cleaning inspection, ii) pre-coating, post-cleaning inspection, and iii) post-coating inspection. The evolution of roughness and other surface inspections such as contaminants are compared between each step to quantify the effect each step has on the flight optics. The final far ultraviolet (FUV) spectral performance of witness samples coated with the flight optics are presented.

Far Ultraviolet (FUV)↗
NASA NTRS2004

Kite: Status of the External Metrology Testbed for SIM

Kite is a system level testbed for the External Metrology system of the Space Interferometry Mission (SIM). The External Metrology System is used to track the fiducial that are located at the centers of the interferometer's siderostats. The relative changes in their positions needs to be tracked to tens of picometers in order to correct for thermal measurements, the Kite testbed was build to test both the metrology gauges and out ability to optically model the system at these levels. The Kite testbed is an over-constraint system where 6 lengths are measured, but only 5 are needed to determine the system. The agreement in the over-constrained length needs to be on the order of 140 pm for the SIM Wide-Angle observing scenario and 8 pm for the Narrow-Angle observing scenario. We demonstrate that we have met the Wide-Angle goal with our current setup. For the Narrow-Angle case, we have only reached the goal for on-axis observations. We describe the testbed improvements that have been made since our initial results, and outline the future Kite changes that will add further effects that SIM faces in order to make the testbed more SIM like.

metrology↗
NASA NTRS2001

Optical metrology for testing an all-composite 2-meter diameter mirror

The Herschel Space Observatory (formerly known as FIRST) consists of a 3.5 m space telescope designed for use in the long IR and sub-milimeter wavebands. To demonstrate the viability of a carbon fiber composite telescope for this application, Composite Optics Incorporated (COI) manufactured a fast (f/1), large (2 m), lightweight (10.1 kg/m squared) demonstration mirror. A key challenge in demonstrating the performance of this novel mirror was to characterize the surface accuracy at cryogenic (70 K) temperatures. A wide variety of optical metrology techniques were investigated and a brief survey of empirical test results and limitations of the various techniques will be presented in this paper. Two complementary infrared (IR)techniques operating at a wavelength of 10.6 microns were chosen for further development: (1) IR Twyman-Green Phase Shifting Interferometry (IR PSI) and (2) IR Shack-Hartmann (IR SH) Wavefront Sensing. Innovative design modifications made to an existing IR PSI to achieve high-resolution, scannable, infrared measurements of the composite mirror are described. The modified interferometer was capable of measuring surface gradients larger than 350 microradians. The design and results of measurements made with a custom-built IR SH Wavefrong Sensor operating at 10.6 microns are also presented. A compact experimental setup permitting simultaneous operation of both the IR PSI and IR SH tools is shown. The advantages and the limitations of the two key IR metrology tools are discussed.

IR metrology phase shifting interferometry Shack-H↗
NASA NTRS1991

A fiber-coupled heterodyne interferometric displacement sensor

Space-based interferometers and large segmented reflectors will require precision metrology with nanometer accuracy for active control systems. This paper summarizes an experimental study of an optical heterodyne interferometer with resolution of about 3 nm. Optical signals are carried to and from the interferometer by optical fibers to avoid thermally loading the reflector panels. Heterodyne detection provides far greater precision than does traditional interferometry.

Nerheim, Noble↗
NASA NTRS2019

Spectrally Resolved Synthetic Aperture Imaging Interferometer: Final Report of NASA Innovative Advanced Concepts - Phase 1 Study

The Spectrally Resolved Synthetic-Aperture Imaging Interferometer (SRSAII) is a system proposed to provide high-resolution and high-sensitivity measurements of astronomical objects. SRSAII uses long baseline interferometric methods to achieve the resolution and low-noise, high time-precision detection to achieve the sensitivity. The primary goal of the SRSAII study was to lay out a framework for using new optical physics technologies to directly resolve, both spatially and spectrally, the disk of an exoplanet. In addition to the ambitious goal of directly resolving an exoplanet, the SRSAII team also sought to identify science opportunities achievable with intermediate system configurations which may offer resolution significantly higher than the current state of the art, but insufficient for direct resolution of an exoplanetary disk. An operational SRSAII system can function with essentially arbitrarily large baselines, achieving correspondingly high angular resolution. The primary limitation occurs in the system sensitivity, which became the major technical focus for study. In this report, we compare the predicted performance (sensitivity in SNR (Signal-to-Noise Ratio) along with angular resolution) of three interferometric techniques: direct detection (also known as homodyne interferometry), multi-channel intensity interferometry (using the Hanbury Brown and Twiss effect), and multi-channel heterodyne interferometry (using an optical frequency comb as a local oscillator). Additionally, quantum-assisted interferometry is also explored as a prospective enhancement of established methods. This report presents a survey of the technologies that enable the SRSAII techniques - optical frequency combs, single photon detectors, and photonic integrated circuits. These technologies are the basis of methods critical to SRSAII's success: precision timing, length and frequency metrology, sensitive photodetection, fine-scale wavelength filtering, and dense multi-channel operation. Lastly, we give some notional performance metrics and propose some possible experimental observations.

High Resolultion↗
NASA NTRS1995

Orbiting Stellar Interferometer: An Overview

The Orbiting Stellar Interferometer (OSI) is a concept for a first-generation space interferometer with astrometric and imaging capabilities and is responsive to the recommendations of the Astronomy and Astrophysics Survey Committee for an astrometric interferometry mission. OSI is a triple Michelson interferometer with articulating siderostats and optical delay lines. The design uses a 7m maximum baseline and aperture diameters of 33 cm; the targeted astrometric performance is a wide-field accuracy of 5µas for 20-mag objects. The instrument would also be capable of synthesis imaging with a resolution of 10mas. Laser metrology is used to relax structural requirements thereby reducing cost. The currently envisaged flight system fits into an Atlas II shroud, for insertion into a 900 km sun-synchronous orbit.

['OSI↗
NASA NTRS1989

Surface characterization and testing II; Proceedings of the Meeting, San Diego, CA, Aug. 10, 11, 1989

Various papers on surface characterization and testing are presented. Individual topics addressed include: simple Hartmann test data interpretation, optimum configuration of the Offner null corrector, system for phase-shifting interferometry in the presence of vibration, fringe variation and visibility in speckle-shearing interferometry, functional integral representation of rough surfaces, calibration of surface heights in an interferometric optical profiler, image formation in common path differential profilometers, SEM of optical surfaces, measuring surface profiles with scanning tunneling microscopes, surface profile measurements of curved parts, high-resolution optical profiler, scanning heterodyne interferometer with immunity from microphonics, real-time crystal axis measurements of semiconductor materials, radial metrology with a panoramic annular lens, surface analysis for the characterization of defects in thin-film processes, Spacelab Optical Viewport glass assembly optical test program for the Starlab mission, scanning differential intensity and phase system for optical metrology.

Greivenkamp, John E.↗