Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Adaptive optics”

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.

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

At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
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 NTRS1990

Amplitude and intensity spatial interferometry; Proceedings of the Meeting, Tucson, AZ, Feb. 14-16, 1990

Attention is given to such topics as ground interferometers, space interferometers, speckle-based and interferometry-based astronomical observations, adaptive and atmospheric optics, speckle techniques, and instrumentation. Particular papers are presented concerning recent progress on the IR Michelson array; the IOTA interferometer project; a space interferometer concept for the detection of extrasolar earth-like planets; IR speckle imaging at Palomar; optical diameters of stars measured with the Mt. Wilson Mark III interferometer; the IR array camera for interferometry with the cophased Multiple Mirror Telescope; optimization techniques appliesd to the bispectrum of one-dimensional IR astronomical speckle data; and adaptive optical iamging for extended objects.

Breckinridge, Jim B.↗
NASA NTRS2013

The Architecture of the Laser Communications Relay Demonstration Ground Stations: An Overview

NASA's Laser Communication Relay Demonstration (LCRD) will be NASA's first long-duration demonstration of laser communications (lasercom) in space, providing geosynchronous-satellite-hosted bidirectional relay services between two Earth ground stations. LCRD will leverage and enhance existing ground stations. Ground Station 1 (GS-1) will leverage the Optical Communications Telescope Laboratory (OCTL) built by JPL, while Ground Station 2 (GS-2) will leverage the Lunar Laser Communications Demonstration (LLCD) Ground Terminal (LLGT) built by MIT Lincoln Laboratory. While each ground system has unique telescopes and integrated optics, many of the backend subsystems (e.g., communications, environmental monitoring, control, user simulators) will be common to both terminals. Here we provide an overview of the architecture of the LCRD ground stations, and the planned enhancements to the existing facilities.

deformable mirror↗
NASA NTRSDate not supplied

NASA's Laser Communications Relay Demonstration (LCRD) Experiment Program: Characterization and Initial Operations

The National Aeronautics and Space Administration’s (NASA) Laser Communications Relay Demonstration (LCRD) completed the first 18 months of its Experiment Program in December 2023. Geosynchronous-ground experiments to date have included demonstrations of optimetrics and of Delay/Disruption Tolerant Networking (DTN), and measurements of the effects of the atmosphere on lasercom performance and availability. Future operational scenarios have been emulated. This paper provides an overview and highlights of the first 18 months of LCRD experiments, and a preview of the upcoming experiments, including relaying data to and from the International Space Station.

optical communications↗
NASA NTRS1995

A three-dimensional orthogonal laser velocimeter for the NASA Ames 7- by 10-foot wind tunnel

A three-component dual-beam laser-velocimeter system has been designed, fabricated, and implemented in the 7-by 10-Foot Wind Tunnel at NASA Ames Research Center. The instrument utilizes optical access from both sides and the top of the test section, and is configured for uncoupled orthogonal measurements of the three Cartesian coordinates of velocity. Bragg cell optics are used to provide fringe velocity bias. Modular system design provides great flexibility in the location of sending and receiving optics to adapt to specific experimental requirements. Near-focus Schmidt-Cassegrain optic modules may be positioned for collection of forward or backward scattered light over a large solid angle, and may be clustered to further increase collection solid angle. Multimode fiber optics transmit collected light to the photomultiplier tubes for processing. Counters are used to process the photomultiplier signals and transfer the processed data digitally via buffered interface controller to the host MS-DOS computer. Considerable data reduction and graphical display programming permit on-line control of data acquisition and evaluation of the incoming data. This paper describes this system in detail and presents sample data illustrating the system's capability.

Dunagan, Stephen E.↗
NASA NTRS2015

High-Contrast Coronagraph Performance in the Presence of DM Actuator Defects

Deformable Mirrors (DMs) are critical elements in high contrast coronagraphs, requiring precision and stability measured in picometers to enable detection of Earth-like exoplanets. Occasionally DM actuators or their associated cables or electronics fail, requiring a wavefront control algorithm to compensate for actuators that may be displaced from their neighbors by hundreds of nanometers. We have carried out experiments on our High-Contrast Imaging Testbed (HCIT) to study the impact of failed actuators in partial fulfillment of the Terrestrial Planet Finder Coronagraph optical model validation milestone. We show that the wavefront control algorithm adapts to several broken actuators and maintains dark-hole contrast in broadband light.

adaptive optics↗
DOE OSTI2022

Calibration of Distributed Temperature Sensors Using Commercially Available SMF-28 Optical Fiber From 22 °C to 1000 °C

Optical frequency domain reflectometry (OFDR) is a family of optical techniques which can be used to produce distributed temperature measurements from the spectral shift of an interference pattern based on the Rayleigh backscatter signature of an optical fiber. Adaptive signal processing techniques have recently been used with OFDR to record meaningful spectral shift data from commercially available SMF-28 optical fibers heated beyond 950 °C. Furthermore, a correlation between the measured spectral shift and temperature has not yet been developed at these high temperatures. To extend the measurable temperature range of OFDR in SMF-28, this work describes the development of such a correlation from room temperature (22 °C) to 1000 °C. The relationship between spectral shift and temperature change over this range was found to be best characterized by the fourth-order polynomial ΔT=(-4.241 * 10 -11 )S 4 + (-2.017 * 10 -7 )S 3 + (-3.677 * 10 -4 )S 2 + (-0.8057)S, where ΔT represents the temperature difference compared to the reference temperature, and S represents the spectral shift measured by the fibers. The calibration developed in this work assumes that the fiber has been fully annealed by heating the fiber to 1000 °C for a few hours. This paper is the first to demonstrate the calibration and use of SMF-28 distributed optical fiber sensors up to 1000 °C, enabled using adaptive OFDR-based signal processing.

47 OTHER INSTRUMENTATION↗
NASA NTRS1977

DKDP /potassium dideuterium phosphate/ light valves

The use of potassium dideuterium phosphate (DKDP) light valves for optical data processing is discussed. The operating principles and structure of optically and electron beam addressed DKDPs are compared, and specifications for both devices given. Optically addressed DKDPs are capable of higher resolution and contrast, but both systems represent viable real time spatial light modulators adaptable to optical processing. Examples of real time data processing performed by the DKDPs include: image addition and subtraction; reduction of noise introduced by scattered light in recording media; reconstruction of computer generated and acoustic holograms; reconstruction of synthetic aperture radar data; retrieval of three-dimensional information in X-ray diagnoses; radar signal processing and display; and optical pattern recognition and correlation of images, which has applications for missile guidance systems.

Casasent, D.↗
NASA NTRS2003

Optical ground station site diversity for Deep Space Optical Communications the Mars Telecom Orbiter optical link

Future NASA deep space missions will fly advanced high resolution imaging instruments that will require high bandwidth links to return the huge data volumes generated by these instruments. Optical communications is a key technology for returning these large data volumes from deep space probes. Yet to cost effectively realize the high bandwidth potential of the optical link will require deployment of ground receivers in diverse locations to provide high link availability. A recent analysis of GOES weather satellite data showed that a network of ground stations located in Hawaii and the Southwest continental US can provide an average of 90% availability for the deep space optical link. JPL and AFRL are exploring the use of large telescopes in Hawaii, California, and Albuquerque to support the Mars Telesat laser communications demonstration. Designed to demonstrate multi-Mbps communications from Mars, the mission will investigate key operational strategies of future deep space optical communications network.

laser communications↗
NASA NTRS2009

Phased-array optical whispering gallery mode modulation and method

A whispering gallery mode (WGM) resonator device and method capable of filtering sidebands of optical modulators are provided. The method includes providing an optical resonator adapted to support whispering gallery modes and forming a first field and a second field from a first location and a second location, respectively, at the circumference of the optical resonator and being separated by an arc angle, .alpha.. The method includes adjusting relative phase between the first field and the second field in accordance to a differential phase, .beta., and combining the first and the second fields into an output. Particular selection of the arc angle, .alpha., and the differential phase, .beta., can determine the function of the output.

Strekalov, Dmitry V.↗