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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Large‐Area, High‐Numerical‐Aperture, Freeform Metasurfaces

Abstract Nanophotonic devices are optical platforms capable of unprecedented wavefront control. To push the limits of experimental device performance, scalable design methodologies that combine the simplicity and fabricability of conventional design paradigms with the extended capabilities of freeform optimization are required. A novel gradient‐based design framework for large‐area freeform metasurfaces is introduced in which nonlocal interactions between simply shaped nanostructures, placed on an irregular lattice, are tailored to produce high‐order hybridized modes that support customizable large‐angle scattering profiles. Utilizing this approach, multifunctional super‐dispersive metalenses are designed and experimentally demonstrated. The approach to high‐numerical‐aperture radial metalenses capable of diffraction limited focusing and the generation of donut‐shaped point spread functions is also extended. It is anticipated that these concepts will have utility in super‐resolution microscopy, particle trapping, additive manufacturing, and metrology applications that require ultra‐high numerical apertures.

Optics↗
NASA NTRS2014

Performance of an Achromatic Focal Plane Mask for Exoplanet Imaging Coronagraphy

Coronagraph technology combined with wavefront control is close to achieving the contrast and inner working angle requirements in the lab necessary to observe the faint signal of an Earth-like exoplanet in monochromatic light. An important remaining technological challenge is to achieve high contrast in broadband light. Coronagraph bandwidth is largely limited by chromaticity of the focal plane mask, which is responsible for blocking the stellar PSF. The size of a stellar PSF scales linearly with wavelength; ideally, the size of the focal plane mask would also scale with wavelength. A conventional hard-edge focal plane mask has a fixed size, normally sized for the longest wavelength in the observational band to avoid starlight leakage. The conventional mask is oversized for shorter wavelengths and blocks useful discovery space. Recently we presented a solution to the size chromaticity challenge with a focal plane mask designed to scale its effective size with wavelength. In this paper, we analyze performance of the achromatic size-scaling focal plane mask within a Phase Induced Amplitude Apodization (PIAA) coronagraph. We present results from wavefront control around the achromatic focal plane mask, and demonstrate the size-scaling effect of the mask with wavelength. The edge of the dark zone, and therefore the inner working angle of the coronagraph, scale with wavelength. The achromatic mask enables operation in a wider band of wavelengths compared with a conventional hard-edge occulter.

Focal Plane Mask↗
DOE OSTI2024

Controlling cantilevered adaptive X-ray mirrors

Modeling the behavior of a prototype cantilevered X-ray adaptive mirror (held from one end) demonstrates its potential for use on high-performance X-ray beamlines. Similar adaptive mirrors are used on X-ray beamlines to compensate optical aberrations, control wavefronts and tune mirror focal distances at will. Controlled by 1D arrays of piezoceramic actuators, these glancing-incidence mirrors can provide nanometre-scale surface shape adjustment capabilities. However, significant engineering challenges remain for mounting them with low distortion and low environmental sensitivity. Finite-element analysis is used to predict the micron-scale full actuation surface shape from each channel and then linear modeling is applied to investigate the mirrors' ability to reach target profiles. Using either uniform or arbitrary spatial weighting, actuator voltages are optimized using a Moore–Penrose matrix inverse, or pseudoinverse, revealing a spatial dependence on the shape fitting with increasing fidelity farther from the mount.

47 OTHER INSTRUMENTATION↗
NASA NTRS2003

Control in Unmanned NASA Missions

This viewgraph presentation reviews several general aspects of control for NASA space missions. Included in the review are the Entry, Descent and Landing (EDL) for both Mars Exploration Rover (MER), and Mars Science Laboratory (MSL); and the control of the MER Rover. Also included is discussion about control issues in relation to formation flying, adaptive optics and precision wavefront control, sensors for environmental control- ENose. Essential developments in the areas of control are important for increase in Autonomy/Automation is essential for deep space manned missions. Other areas of concern are robustness and the need to address life support system control issues.

wavefront control↗
NASA NTRS2010

Advanced Wavefront Sensing and Control Testbed (AWCT)

The Advanced Wavefront Sensing and Control Testbed (AWCT) is built as a versatile facility for developing and demonstrating, in hardware, the future technologies of wave front sensing and control algorithms for active optical systems. The testbed includes a source projector for a broadband point-source and a suite of extended scene targets, a dispersed fringe sensor, a Shack-Hartmann camera, and an imaging camera capable of phase retrieval wavefront sensing. The testbed also provides two easily accessible conjugated pupil planes which can accommodate the active optical devices such as fast steering mirror, deformable mirror, and segmented mirrors. In this paper, we describe the testbed optical design, testbed configurations and capabilities, as well as the initial results from the testbed hardware integrations and tests.

active optics↗
NASA NTRS2018

LUVOIR Primary Mirror Segment Alignment Control With Joint Laser Metrology and Segment Edge Sensing

An approach is developed for the alignment and stability maintenance of the LUVOIR segmented primary mirror using a segment state estimation and wavefront control method based on a hybrid segment motion sensing architecture of laser truss metrology and segment edge sensors. Our current computer model was generated for LUVOIR Architecture Option A with a 15-meter aperture, 120segment primary mirror. The methodology and simulation results will be presented and analyzed. JPL has a long history of technology development in laser metrology and edge sensors, including work in SIM [7], Keck and TMT [8], CCAT [3] and LUVOIR [1]. We will discuss our current efforts of LUVOIR laser metrology and edge-sensor models development, showing sensitivities of sensor measurements to various mirror eigenmodes, removing global modes and strengthening weak modes by performing joint (hybrid) laser-metrology and edge sensing. We will define and derive an important performance metric called wavefront error multiplier (WEM), and show that WEM provides a simple link between sensor errors and the closed-loop (controlled) system wavefront error. We will show WEM values for several hybrid sensor configuration options studied. We will discuss an algorithm for mirror shape control and maintenance through segment state and wavefront estimations using joint edge-metrology sensing. We will compare simulated performance of mirror state estimation, wavefront estimation and wavefront control based on joint edge-metrology sensing among several sensor configurations, and show the impact of sensor error distributions on the segmented mirror alignment performance. Mirror shape control performance will be also be evaluated in terms of imaging contrast between inner working angles (IWA) and outer working angles (OWA) of a LUVOIR coronagraph. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. LUVOIR is a mission concept under study for the next astronomy Decadal Survey—the information presented in this paper is pre-decisional and is provided for planning and discussion purposes only.

Shelton, Chris↗
NASA NTRS2021

Flight mask designs of the Roman Space Telescope Coronagraph Instrument

Over the past two decades, thousands of con?rmed exoplanets have been detected; the next major challenge is to characterize these other worlds and their stellar systems. Much information on the composition and formation of exoplanets and circumstellar debris disks can only be achieved via direct imaging. Direct imaging is challenging because of the small angular separations (< 1 arcsec) and high star-to-planet ux ratios (?109 for a Jupiter analog or ?1010 for an Earth analog in the visible). Atmospheric turbulence prohibits reaching such high ux ratios on the ground, so observations must be made above the Earth's atmosphere. The Nancy Grace Roman Space Telescope (Roman), set to launch in the mid-2020s, will be the ?rst space-based observatory to demonstrate high-contrast imaging with active wavefront control using its Coronagraph Instrument. The instrument's main purpose is to mature the various technologies needed for a future agship mission to image and characterize Earth-like exoplanets. These technologies include two high-actuator-count deformable mirrors, photon-counting detectors, two complementary wavefront sensing and control loops, and two di?erent coronagraph types. In this paper, we describe the complete set of ight coronagraph mask designs and their intended combinations in the Roman Coronagraph Instrument. There are three types of mask con?gurations included: a primary one designed to meet the instrument's top-level requirement, three that are supported on a best-e?ort basis, and several unsupported ones contributed by the NASA Exoplanet Exploration Program. The unsupported mask con?gurations could be commissioned and used if the instrument is approved for operations after its initial technology demonstration phase.

Zimmerman, Neil T.↗
DOE OSTI2017

Wavefront modulation and controlling for Lamb waves using surface bonded slice lenses

We present that there is a growing interest in controlling the propagation of Lamb waves to achieve better performance for structural health monitoring and nondestructive evaluation. In this study, we present new methods of controlling Lamb waves using simple slice lenses through wavefront modulation. The lenses are made of metal slices with designed shapes. Once bonded on plates, the lenses modify the effective plate thickness, and therefore change the Lamb wave characteristics such as the wavenumber and phase velocity, providing convenient ways of modulating wavefront and controlling Lamb waves in plates. Numerically and experimentally, we demonstrated that a straight wavefront A 0 mode can be focused on the desired focal point using a plano-concave aspherical lens. We also demonstrated that the A 0 mode can be steered with different frequency components steered to different directions using a simple prism made of metal slices. The work shows that such simple slice lenses provide easy ways for controlling Lamb waves, and have a great potential for Lamb wave based applications.

42 ENGINEERING↗
NASA NTRS2018

WFIRST Low Order Wavefront Sensing and Control Testbed Performance under Flight Like Photon Flux

To maintain the required performance for the WFIRST Coronagraph Instrument (CGI) in a realistic space environment, a Low Order Wavefront Sensing and Control (LOWFS/C) subsystem is necessary. The WFIRST CGI LOWFS/C subsystem would use the Zernike wavefront sensor, which has the phase-shifting disk combined with the coronagraph’s focal plane mask, to sense the low-order wavefront drift and line-of-sight (LoS) error using the rejected starlight. The dynamic tests on JPL’s on the Occulting Mask Coronagraph (OMC) Testbed have demonstrated that LOWFS/C can maintain coronagraph contrast to better than 10-8 in presence of WFIRST-like line of sight and low order wavefront disturbances in both Shaped Pupil Coronagraph (SPC) and Hybrid Lyot Coronagraph (HLC) modes. However, the previous dynamic tests have been done using a bright source with photon flux equivalent to stellar magnitude of Mv = -3.5. The LOWFS/C technology development continues on the OMC testbed especially in evaluating and improving the LOWFS/C performance under the realistic photon flux that is equivalent to WFIRST Coronagraph target stars. Our recent testbed tests have demonstrated that the LOWFS/C can work cohesively with the stellar light suppression wavefront control, which brings broad band coronagraph contrast from 1x10-6 to 6x10-9, while LOWF/C is simultaneously suppressing the WFIRST like LoS and low order wavefront drift disturbances on a source that photon flux is equivalent to a Mv = 2 star. This demonstration mimics the CGI initial dark hole establish process on a bright reference star. We also demonstrated on the testbed that LOWFS/C can maintain the coronagraph contrast by suppressing the WFIRST like line-of-sight disturbances on a fainter Mv = 5 star. This mimics scenario of CGI science target observations. In this paper we will present the recent testbed results on LOWFS/C LoS loops and low order wavefront error correction loop performance on the flight like photon flux.

Truong, Tuan↗
NASA NTRS2022

Laser-Guided Space Interferometer

The mirrors of astronomical interferometers need to be aligned within a fraction of a wavelength relative to one another. This would be especially challenging for optical instruments with mirrors separated by hundreds of meters flying in Earth’s orbit. However, in this work, we show that this alignment can be achieved by means of: (i) flying the mirror cluster in a particular orbital configuration; (ii) closing a coarse positioning loop using GNSS (Global Navigation Satellite System); and (iii) closing a fine wavefront-control loop using light from a laser guide star. The orbital configuration is designed to keep the mirrors passively pointing at the target star (up to a small orbital perturbation) while the interferometer cluster is orbiting and changing its baseline. The laser guide star would be flying in the same orbit but in the opposite direction. In medium- or high-Earth orbit, the interferometer would be able to observe a star for several hours per orbit. In this work, we analyzed the performance of an optical space interferometer consisting of nine 20 cm mirrors mounted on CubeSats and flying 3 km apart (together with a combiner and a laser guide star small satellite). This configuration supports a resolution of 0.04 milliarcseconds - an order of magnitude better than current ground-based interferometers. We estimate the performance of this system imaging stellar surfaces assuming perfect wavefront estimation and control.

Leonid Pogorelyuk↗
NASA NTRS2003

Wavefront sensing and control for large space optics

Large space optical systems will require on-orbit wavefront sensing and control systems to correct misalignments and figure errors incurred during manufacture, launch and deployment.

NGST wavefront sensing wavefront control segmented↗
NASA NTRS2001

Preliminary Investigation of an Active PLZT Lens

The design, analysis and preliminary testing of a prototype Adjustable Focus Optical Correction Lens (AFOCL) is described. The AFOCL is an active optical component composed of solid state lead lanthanum-modified zirconate titanate (PLZT) ferroelectric ceramic with patterned indium tin oxide (ITO) transparent surface electrodes that modulate the refractive index of the PLZT to function as an electro-optic lens. The AFOCL was developed to perform optical re-alignment and wavefront correction to enhance the performance of Ultra-Lightweight Structures and Space Observatories (ULSSO). The AFOCL has potential application as an active optical component within a larger optical system. As such, information from a wavefront sensor would be processed to provide input to the AFOCL to drive the sensed wavefront to the desired shape and location. While offering variable and rapid focussing capability (controlled wavefront manipulation) similar to liquid crystal based spatial light modulators (SLM), the AFOCL offers some potential advantages because it is a solid-state, stationary, low-mass, rugged, and thin optical element that can produce wavefront quality comparable to the solid refractive lens it replaces. The AFOCL acts as a positive or negative lens by producing a parabolic phase-shift in the PLZT material through the application of a controlled voltage potential across the ITO electrodes. To demonstrate the technology, a 4 mm diameter lens was fabricated to produce 5-waves of optical power operating at 2.051 micrometer wavelength. Optical metrology was performed on the device to measure focal length, optical quality, and efficiency for a variety of test configurations. The data was analyzed and compared to theoretical data available from computer-based models of the AFOCL.

Lightsey, W. D.↗
NASA NTRS2013

SCExAO: First Results and On-Sky Performance

We present new on-sky results for the Subaru Coronagraphic Extreme Adaptive Optics imager (SCExAO) verifying and quantifying the contrast gain enabled by key components: the closed-loop coronagraphic low-order wavefront sensor (CLOWFS) and focal plane wavefront control ("speckle nulling"). SCExAO will soon be coupled with a high-order, Pyramid wavefront sensor which will yield greater than 90% Strehl ratio and enable 10(exp 6) -10(exp 7) contrast at small angular separations allowing us to image gas giant planets at solar system scales. Upcoming instruments like VAMPIRES, FIRST, and CHARIS will expand SCExAO's science capabilities.

Subaru Coronagraphic Extreme Adaptive Optics image↗
NASA NTRS2011

Phase-Controlled Magnetic Mirror for Wavefront Correction

Typically, light interacts with matter via the electric field and interaction with weakly bound electrons. In a magnetic mirror, a patterned nanowire is fabricated over a metallic layer with a dielectric layer in between. Oscillation of the electrons in the nanowires in response to the magnetic field of incident photons causes a re-emission of photons and operation as a "magnetic mirror." By controlling the index of refraction in the dielectric layer using a local applied voltage, the phase of the emitted radiation can be controlled. This allows electrical modification of the reflected wavefront, resulting in a deformable mirror that can be used for wavefront control. Certain applications require wavefront quality in the few-nanometer regime, which is a major challenge for optical fabrication and alignment of mirrors or lenses. The use of a deformable magnetic mirror allows for a device with no moving parts that can modify the phase of incident light over many spatial scales, potentially with higher resolution than current approaches. Current deformable mirrors modify the incident wavefront by using nano-actuation of a substrate to physically bend the mirror to a desired shape. The purpose of the innovation is to modify the incident wavefront for the purpose of correction of fabrication and alignment-induced wavefront errors at the system level. The advanced degree of precision required for some applications such as gravity wave detection (LISA - Laser Interferometer Space Antenna) or planet finding (FKSI - Fourier-Kelvin Stellar Interferometer) requires wavefront control at the limits of the current state of the art. All the steps required to fabricate a magnetic mirror have been demonstrated. The modification is to apply a bias voltage to the dielectric layer so as to change the index of refraction and modify the phase of the reflected radiation. Light is reflected off the device and collected by a phase-sensing interferometer. The interferometer determines the initial wavefront of the device and fore optics. A wavefront correction is calculated, and voltage profile for each nanowire strip is determined. The voltage is applied, modifying the local index of refraction of the dielectric under the nanowire strip. This modifies the phase of the reflected light to allow wavefront correction.

Hagopian, John↗
NASA NTRS1990

Adaptive optics and optical structures; Proceedings of the Meeting, European Congress on Optics, 3rd, The Hague, Netherlands, Mar. 12-14, 1990

The present conference on adaptive optics (AO) and optical structures addresses AO systems and controls, AO components, nonlinear optics applications to AO, astronomical applications of AO, large telescopes and optical alignment, as well as the wavefront control experiment for the use of AO in beam propagation. Specific references are made to applications of electromagnetic theory in optics, theoretical studies of system performance and design parameters, Hartmann-Shack wavefront sensing, the use of ray-based techniques in cophasing segmented mirrors, the use of a phase-conjugating mirror for real-time phase visualization, and the absolute instability of oppositely directed waves with respect to a high-reflectivity phase-conjugate mirror. Also addressed are automatic control systems, precision segmented reflectors, AO system creation, the VLT's 8.2-m primary mirrors, an optical 12-m telescope, alignment optimization via the Talbot effect, and a combination of interferometry and ray-tracing analysis.

Tyson, Robert K.↗
NASA NTRS2010

Hybrid Architecture Active Wavefront Sensing and Control

A method was developed for performing relatively high-speed wavefront sensing and control to overcome thermal instabilities in a segmented primary mirror telescope [e.g., James Webb Space Telescope (JWST) at L2], by using the onboard fine guidance sensor (FGS) to minimize expense and complexity. This FGS performs centroiding on a bright star to feed the information to the pointing and control system. The proposed concept is to beam split the image of the guide star (or use a single defocused guide star image) to perform wavefront sensing using phase retrieval techniques. Using the fine guidance sensor star image for guiding and fine phasing eliminates the need for other, more complex ways of achieving very accurate sensing and control that is needed for UV-optical applications. The phase retrieval occurs nearly constantly, so passive thermal stability over fourteen days is not required. Using the FGS as the sensor, one can feed segment update information to actuators on the primary mirror that can update the primary mirror segment fine phasing with this frequency. Because the thermal time constants of the primary mirror are very slow compared to this duration, the mirror will appear extremely stable during observations (to the level of accuracy of the sensing and control). The sensing can use the same phase retrieval techniques as the JWST by employing an additional beam splitter, and having each channel go through a weak lens (one positive and one negative). The channels can use common or separate detectors. Phase retrieval can be performed onboard. The actuation scheme would include a coarse stage able to achieve initial alignment of several millimeters of range (similar to JWST and can use a JWST heritage sensing approach in the science camera) and a fine stage capable of continual updates.

Feinberg, Lee↗
NASA NTRS2021

Characterizing Deformable Mirrors for the MagAO-X Instrument

The MagAO-X instrument is a new extreme adaptive optics system for high-contrast imaging at visibleand near-infrared wavelengths on the Magellan Clay Telescope. A central component of this system is a 2040-actuatormicroelectromechanical deformable mirror (DM) from Boston Micromachines Corp. that operates at 3.63 kHz forhigh-order wavefront control (the tweeter). Two additional DMs from ALPAO perform the low-order (the woofer)and non-common-path science-arm wavefront correction (the NCPC DM). Prior to integration with the instrument, wecharacterized these devices using a Zygo Verifire Interferometer to measure each DM surface. We present the resultsof the characterization effort here, demonstrating the ability to drive tweeter to a flat of 6.9 nm RMS surface (and 0.56nm RMS surface within its control bandwidth), the woofer to 2.2 nm root mean square (RMS) surface, and the NCPCDM to 2.1 nm RMS surface over the MagAO-X beam footprint on each device. Using focus-diversity phase retrievalon the MagAO-X science cameras to estimate the internal instrument wavefront error (WFE), we further show that theintegrated DMs correct the instrument WFE to 18.7 nm RMS, which, combined with a 11.7% pupil amplitude RMS,produces a Strehl ratio of 0.94 at H↵

Kyle Van Gorkom↗
NASA NTRS2015

Low Order Wavefront Sensing and Control for WFIRST-AFTA Coronagraph

To maintain the required WFIRST Coronagraph performance in a realistic space environment, a low order wavefront sensing and control (LOWFS/C) subsystem is necessary. The LOWFS/C use s the rejected stellar light from coronagraph to sense and suppress the telescope pointing drift and jitter as well as the low order wavefront errors due to changes in thermal loading of the telescope and the rest of the observatory. In this paper we will present an overview of the low order wavefront sensing and control subsystem for the WFIRST -AFTA Coronagraph. We will describe LOWFS/C's Zernike wavefront sensor concept and WFIRST LOWFS/C control design. We will present an overview of our analysis and modeling results on the Zernike wavefront sensor, the line -of-sight jitter suppression loop performance, as well as the low order wavefront error correction with the coronagraph's deformable mirror. In this paper we will also report the LOWFS/C testbed design and the preliminary in-air test results, which show a very promising performance of the Zernike wavefront sensor and FSM feedback loop.

exoplanets↗