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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Optics Alignment of a Balloon-Borne Far-Infrared Interferometer BETTII

The Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) is an 8-m baseline far-infrared (FIR: 30 90 micrometer) interferometer providing spatially resolved spectroscopy. The initial scientific focus of BETTII is on clustered star formation, but this capability likely has a much broader scientific application.One critical step in developing an interferometer, such as BETTII, is the optical alignment of the system. We discuss how we determine alignment sensitivities of different optical elements on the interferogram outputs. Accordingly, an alignment plan is executed that makes use of a laser tracker and theodolites for precise optical metrology of both the large external optics and the small optics inside the cryostat. We test our alignment on the ground by pointing BETTII to bright near-infrared sources and obtaining their images in the tracking detectors.

Dhabal, Arnab↗
NASA NTRS2018

Securing and Auto-Synchronizing Communication over Free-Space Optics Using Quantum Key Distribution and Chaotic Systems

Free-Space Optical (FSO) communication provides very large bandwidth, relatively low cost, low power, low mass of implementation, and improved security when compared to conventional Free-Space Radio-Frequency (FSRF) systems. In this paper, we demonstrate a communication protocol that demonstrates improved security and longer-range FSO communication, compared to existing FSO security techniques, such as N-slit interferometers. The protocol integrates chaotic communications with Quantum Key Distribution (QKD) techniques. A Lorenz chaotic system, which is inherently secure and auto-synchronized, is utilized for secure data communications over a classical channel, while QKD is used to exchange crucial chaotic system parameters over a secure quantum channel. We also provide a concept of operations for a NASA mission combining chaotic communications and QKD operating synergistically in an end-to-end space communications link. The experimental simulation results and analysis are favorable towards our approach.

Chaotic Communication↗
NASA NTRS2018

Impact of Assimilating Cloud-Cleared and Adaptively Thinned Infrared Hyperspectral Data on Tropical Cyclones in a Global Data Assimilation and Forecast Framework

A simple adaptive thinning methodology for Atmospheric Infrared Sounder (AIRS), Cross-track Infrared Sounder (CrIS) and Infrared Atmospheric Sounding Interferometer (IASI) radiances is evaluated through a combination of Observing System Experiments (OSEs) and adjoint methodologies. In addition, the impact of cloud-cleared radiances for AIRS is also evaluated. The OSEs are performed with the NASA Goddard Earth Observing System (GEOS, version 5) data assimilation and forecast model. The adaptive strategy uses a denser coverage in a moving domain centered around tropical cyclones (TCs), sparser everywhere else.The OSEs consist of three sets of data assimilation runs that cover the period from September 1st to 10 November 2014, with the first 20 days discarded for spin-up. All sets assimilate conventional and satellite observations used operationally. In addition, one ingests clear-sky AIRS, CrIS, and IASI radiances at different densities, another AIRS cloud-cleared radiances, and CrIS and IASI clear-sky radiances, and the third adaptively thinned AIRS, CrIS and IASI radiances. Daily 10-day forecasts are initialized from all these analyses and evaluated with focus on TCs over the Atlantic and the Pacific.Evidence is provided that this simple TC-centered adaptive radiance thinning strategy, in full agreement with previous theoretical studies, increases the global forecast skill and improves tropical cyclone representation and intensity forecast. In addition, the impact of AIRS cloud-cleared radiances is demonstrated to be particularly strong on TCs. The implications are that cloud-cleared radiances, if thinned more aggressively than the currently used clear-sky radiances, could be operationally used with large gain in TC forecasting and no loss of global skill.

Reale, Oreste↗
NASA NTRS2004

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↗
NASA NTRS2018

ST7 Disturbance Reduction System (DRS) Colloid Micronewton Thruster Performance and Control Algorithm Model Simulation Validation in Flight

Colloid Micronewton Thrusters (CMNT) were flight demonstrated for the first time on the ST7Disturbance Reduction System (DRS) payload on the European Space Agency (ESA) Laser Interferometer Space Antenna (LISA) Pathfinder spacecraft for attitude and drag-free spacecraft control. LISA Pathfinder was a technology demonstration mission for ESA’s LISA gravitational wave observatory, currently in Phase A with a launch date of 2034. The DRS included the Integrated Avionics Unit (IAU), eight Colloid Micronewton Thrusters (CMNT), Dynamic Control Software (DCS) and Flight Software (FSW). The CMNT technology met performance requirements operating at 5-30 µN of thrust with ≤0.1 µN resolution and ≤0.1 µN/Hz thrust noise to deliver the required nanometer-level precision spacecraft control measured by the gravitational reference sensor (GRS) in the ESA LISA Technology Package (LTP). The performance of seven of the CMNT in flight was consistent with ground test results. The colloid thruster performance model of thrust and thrust noise as a function of operational parameters (i.e. beam current, voltage, temperature, etc.) was validated in flight over a wide range of conditions. A model and simulation of the thruster control algorithm was developed and validated with flight data to predict thrust noise. This capability is important because it is considered to be a significant source of position noise on the spacecraft and, therefore, the acceleration noise on the test masses, which provide the gravity wave measurements. The CMNT thruster model data and validation with LISA Pathfinder/ST7-DRS flight experiments are discussed in this paper.

Hruby, Vlad↗
NASA NTRS1991

Fiber-optic push-pull sensor systems

Fiber-optic push-pull sensors are those which exploit the intrinsically differential nature of an interferometer with concommitant benefits in common-mode rejection of undesired effects. Several fiber-optic accelerometer and hydrophone designs are described. Additionally, the recent development at the Naval Postgraduate School of a passive low-cost interferometric signal demodulator permits the development of economical fiber-optic sensor systems.

Gardner, David L.↗
NASA NTRS1995

Optical diagnostics of solution crystal growth

Solution crystal growth monitoring of LAP/TGS crystals by various optical diagnostics systems, such as conventional and Mach-Zehnder (M-Z) interferometers, optical heterodyne technique, and ellipsometry, is under development. The study of the dynamics of the crystal growth process requires a detailed knowledge of crystal growth rate and the concentration gradient near growing crystals in aqueous solution. Crystal growth rate can be measured using conventional interferometry. Laser beam reflections from the crystal front as well as the back surface interfere with each other, and the fringe shift due to the growing crystal yields information about the growth rate. Our preliminary results indicate a growth rate of 6 A/sec for LAP crystals grown from solution. Single wavelength M-Z interferometry is in use to calculate the concentration gradient near the crystal. Preliminary investigation is in progress using an M-Z interferometer with 2 cm beam diameter to cover the front region of the growing crystal. In the optical heterodyne technique, phase difference between two rf signals (250 KHZ) is measured of which one is a reference signal, and the other growth signal, whose phase changes due to a change in path length as the material grows. From the phase difference the growth rate can also be calculated. Our preliminary results indicate a growth rate of 1.5 A/sec. the seed and solution temperatures were 26.46 C and 27.92 C respectively, and the solution was saturated at 29.0 C. an ellipsometer to measure the growth rate and interface layer is on order from JOBIN YVON, France. All these systems are arranged in such a manner that measurements can be made either sequentially or simultaneously. These techniques will be adapted for flight experiment.

Kim, Yongkee↗
NASA NTRS2009

Data Processing for Atmospheric Phase Interferometers

This paper presents a detailed discussion of calibration procedures used to analyze data recorded from a two-element atmospheric phase interferometer (API) deployed at Goldstone, California. In addition, we describe the data products derived from those measurements that can be used for site intercomparison and atmospheric modeling. Simulated data is used to demonstrate the effectiveness of the proposed algorithm and as a means for validating our procedure. A study of the effect of block size filtering is presented to justify our process for isolating atmospheric fluctuation phenomena from other system-induced effects (e.g., satellite motion, thermal drift). A simulated 24 hr interferometer phase data time series is analyzed to illustrate the step-by-step calibration procedure and desired data products.

Acosta, Roberto J.↗
NASA NTRS1975

Analytical evaluation of ILM sensors, volume 1

The functional requirements and operating environment constraints are defined for an independent landing monitor ILM which provides the flight crew with an independent assessment of the operation of the primary automatic landing system. The capabilities of radars, TV, forward looking infrared radiometers, multilateration, microwave radiometers, interferometers, and nuclear sensing concepts to meet the ILM conditions are analyzed. The most critical need for the ILM appears in the landing sequence from 1000 to 2000 meters from threshold through rollout. Of the sensing concepts analyzed, the following show potential of becoming feasible ILM's: redundant microwave landings systems, precision approach radar, airborne triangulation radar, multilateration with radar altimetry, and nuclear sensing.

Kirk, R. J.↗
DOE OSTI2026

Development of a magnetic field monitoring system for the MAGIS-100 experiment

The MAGIS-100 collaboration is building a long-baseline atom interferometer designed to investigate dark matter, novel forces, gravitational waves, and quantum science. A major design challenge is external, time-varying magnetic fields, the effect of which can mimic gravitational waves or expected dark matter signals; static magnetic fields must also be tightly controlled to manage measurement resolution. Several tools are being applied to the problem, including mu-metal shielding, field biasing, and a suite of magnetometers. This report details the development of a magnetic field monitoring system to be built from commercially available parts and installed at seventeen locations, one for each of the modular sections making up the length of the MAGIS-100 apparatus.

Arce, Edwin [Unlisted, US, CA]↗
NASA NTRS2018

Progress and Plans for a US Laser System for the LISA Mission

NASA Goddard Space Flight Center is developing a master oscillator power amplifier (MOPA) laser transmitter for the ESA-led Laser Interferometer Space Antenna (LISA) mission. Taking advantage of our space laser experience and the emerging telecom laser technology, we are developing a full laser system for the LISA mission. Our research effort has included both master oscillator (MO) and power amplifier (PA) developments, and their environmental testing and reliability for space flight. Our current baseline for the MO is a low-mass, compact micro NPRO (m-NPRO) laser. The amplifier uses a robust mechanical design based on fiber components. We have performed laser system noise tests by amplitude- and frequency-stabilizing the PA output. We will describe our progress and plans to demonstrate a TRL 6 laser system, which is an essential step toward qualifying lasers for space applications, by 2021.

lasers↗
NASA NTRS2018

Progress and Plans for a US Laser System for the LISA Mission

NASA Goddard Space Flight Center is developing a master oscillator power amplifier (MOPA) laser transmitter for the ESA-led Laser Interferometer Space Antenna (LISA) mission. Taking advantage of our space laser experience and the emerging telecom laser technology, we are developing a full laser system for the LISA mission. Our research effort has included both master oscillator (MO) and power amplifier (PA) developments, and their environmental testing and reliability for space flight. Our current baseline for the MO is a low-mass, compact micro non-planar ring oscillator (m- NPRO) laser. The amplifier uses a robust mechanical design based on fiber components. We have performed laser system noise tests by amplitude- and frequency-stabilizing the PA output. We will describe our progress and plans to demonstrate a TRL 6 laser system, which is an essential step toward qualifying lasers for space applications, by 2021.

Numata, Kenji↗
NASA NTRS1985

Advanced Optical Measurement Techniques

This research analyzes four areas: (1) Improved Techniques for Optical Measurement; (2) KC-135 Low Gravity Simulation Flight Preparation; (3) In-Line Holographic Microscopy; and (4) Holographic Optical Schlieren System (HOSS). The first task provides for laboratory breadboarding of advanced optical measurement techniques which appear promising for use in Material Processing System (MPS) flight experiments. A laboratory schlieren system has been constructed which simulates a similar optical system on the Fluids Experiment System (FES) which is to be flown on Spacelab 3. The second task allows improved optical systems and breadboards to be built for experiments and hardware tests on the KC-135 aircraft. A new, more stable Mach-Zehnder interferometer has been developed and components have been ordered. The third task is concerned with improvements on the optical system being used to study immiscible fluids. Experiments studying the dynamics of nucleation and the separation of immiscible fluids have been conducted. The four task involves building breadboard reconstruction systems for holograms taken in the HOSS. The HOSS is an early prototype of the Fluids Experiments System (FES) which is scheduled to fly on Spacelab 3.

Owen, R. B.↗
NASA NTRS2008

Direct-View Multi-Point Two-Component Interferometric Rayleigh Scattering Velocimeter

This paper describes an instantaneous velocity measurement system based on the Doppler shift of elastically scattered laser light from gas molecules (Rayleigh scattering) relative to an incident laser. The system uses a pulsed laser as the light source, direct-viewing optics to collect the scattered light, an interferometer to analyze spectrally the scattered light mixed with the incident laser light, and a CCD camera to capture the resulting interferogram. The system is capable of simultaneous, spatially (approximately 0.2 mm(exp 3)) and temporally (approximately 40 ns) resolved, multiple point measurements of two orthogonal components of flow velocity in the presence of background scattered light, acoustic noise and vibrations, and flow particulates. Measurements in a large-scale axi-symmetric Mach 1.6 H2-air combustion-heated jet running at a flow sensible enthalpy specific to Mach 5.5 hypersonic flight are performed to demonstrate the technique. The measurements are compared with CFD calculations using a finite-volume discretization of the Favre-averaged Navier-Stokes equations (VULCAN code).

Bivolaru, Daniel↗
NASA NTRS1998

Shear/Defocus Sensitivity of the Mid Infrared Channel (MIR) of the Composite Infrared Spectrometer (CIRS) for the Cassini Mission to Saturn

The Composite Infrared Spectrometer (CIRS) of the Cassini mission to Saturn has two interferometers covering the far infrared and mid infrared wavelength region. The mid infrared wavelength interferometer has a focal plane consisting of a germanium focus lens and HgCdTe array. System level calibration of the CIRS Flight Unit indicated a discrepancy between the expected and actual signal levels. Testing on the CIRS breadboard and Engineering Unit indicated that defocus of the germanium lens could significantly reduce the modulation efficiency of the interferometer in the presence of a moderate degree of wavefront shear. Defocus of the lens in the focal plane was of concern because of the temperature dependence of the index of refraction of germanium and our nominal operation temperature of 170 K. The shear/defocus interaction was extensively investigated and correlated to a newly developed analytical model, It was eventually determined that the CIRS instrument was in focus, had no appreciable wavefront shear and was operating near theoretical limits. The shear/defocus effect is however, of considerable interest, since it has not been described in previous literature on interferometers.

Martino, Anthony J.↗
NASA NTRS1989

Hubble Space Telescope fine guidance sensor control system

The fine pointing information required for the extraordinary pointing stability of the Hubble Space Telescope (HST) is provided by the fine guidance sensor (FGS), which is capable of measuring extremely small pointing errors, of the order of 3 milliarcseconds. The FGS provides this fine pointing information over a relatively large, continuous range of angles of guide stars relative to the optical axis of the telescope. The FGS accomplishes this task by a judicious design involving the following: a two-axis high precision star selector servo system; an optical deflection system that provides high reduction from shaft angle to optical angle; a unique interferometer using Koester prisms and extremely sensitive photomultiplier tubes that enable the FGS to lock onto guide stars whose magnitude may be any value over a wide range of brightness (including 14.5 Mv and fainter); and the use the large aperture of the telescope itself to advantage. This paper describes the FGS control systems involved in achieving this performance, supported by test data.

Nurre, Gerald S.↗
DOE OSTI2024

X-ray Irradiance Distribution for an Interferometer with a Curved Biprism Array

The development of interferometry-based X-ray phase contrast imaging systems that provide highly resolved X-rays with spatially-modulated intensity is enabling the full potential of X-ray optics to image phase, attenuation, and small angle scatter properties of soft tissue. In this work we present analytical formulations of a new hardware concept for X-ray phase contrast imaging wherein the phase grating is replaced with an array of Fresnel biprisms. We derive expressions for the irradiance distribution pattern of a biprism interferometer composed of a curved biprism array with multiple biprisms and multiple point sources. These expressions are used to plot fringe patterns for X-ray design parameters, including 1) size, number, and period of X-ray point sources; 2) biprism parameters of material composition, angle, number, and period; and 3) biprism array to X-ray source and detector distances. Analytical results show that the biprism interferometer provides a longitudinally-nonperiodic pattern of spatially modulated intensity different from the Talbot longitudinally-periodic pattern common in grating interferometry. The curvature of the biprism array brings a sharper longitudinal fringe pattern. Experiments are being performed to verify the analytical calculations for a biprism plastic material of SU-8 using a synchrotron source. X-ray biprism material has widely varied indexes of refraction relative to wavelength and thus the separation of the virtual sources and resulting interference fringe period also varies with X-ray wavelength. Our aim is to develop biprism interferometry imaging systems with excellent polychromatic performance that produce high-contrast fringes with spatially incoherent X-ray illumination. Biprism interferometry will potentially provide higher fringe visibility with better image quality to that of diffraction grating interferometry.

62 RADIOLOGY AND NUCLEAR MEDICINE↗