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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Lyman-Alpha Imaging Polarimetry with the CLASP2 Sounding Rocket Mission

Ultraviolet polarimetry offers a unique opportunity to explore the upper solar chromosphere and the transition region (TR) to the million-degree corona. These outer atmospheric regions play a key role in the transfer of mass and energy from the solar photosphere to the corona. With a sounding rocket experiment called the Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP), in September 2015 we succeeded in obtaining the first measurement of the linear polarization produced by scattering processes in the hydrogen Lyman-alpha line of the solar disk radiation. The analysis and interpretation of such spectro-polarimetric observation allowed us to obtain information on the geometrical complexity of the corrugated surface that delineates the TR, as well as on the magnetic field strength via the Hanle effect. At the same time, the CLASP slit-jaw (SJ) optics system, which is a Lyman-alpha filter imager characterized by a FWHM (Full Width Half Maximum) equals 7 nanometers, allowed us to obtain broad-band Stokes-I and Q/I images over a large field of view. The obtained broad-band Q/I images are dominated by the scattering polarization signals of the Lyman-alpha wings, and not by the much weaker line-center signals where the Hanle effect operates. On April 11, 2019, we performed another sounding rocket experiment, called the Chromospheric LAyer Spectro-Polarimeter (CLASP2). We used the same instrument after significant modifications in order to obtain spectro-polarimetric observations of a plage and a quiet region in the Mg II h & k lines. At the same time, the CLASP2 SJ optics system allowed us to obtain broad-band Q/I and U/I images around the Lyman-alpha wavelength, in addition to the well- known SJ intensity images.

Kano, Ryouhei↗
NASA NTRS1999

NGST Optical Testing

An Integrated Product Team (IPT) was formed to develop a detailed optical test methodology for testing of the Next Generation Space Telescope (NGST) mirrors and the optical system on the ground. Optical testing is a significant cost driver therefore the testing has to be planned in detailed fashion early. This paper will discuss the preliminary metrology test plan at the mirror component and telescope system level. Instrumentation, facilities and schedule will also be addressed.

Keski-Kuha, Ritva↗
NASA NTRS2010

Wavefront Control and Image Restoration with Less Computing

PseudoDiversity is a method of recovering the wavefront in a sparse- or segmented- aperture optical system typified by an interferometer or a telescope equipped with an adaptive primary mirror consisting of controllably slightly moveable segments. (PseudoDiversity should not be confused with a radio-antenna-arraying method called pseudodiversity.) As in the cases of other wavefront- recovery methods, the streams of wavefront data generated by means of PseudoDiversity are used as feedback signals for controlling electromechanical actuators of the various segments so as to correct wavefront errors and thereby, for example, obtain a clearer, steadier image of a distant object in the presence of atmospheric turbulence. There are numerous potential applications in astronomy, remote sensing from aircraft and spacecraft, targeting missiles, sighting military targets, and medical imaging (including microscopy) through such intervening media as cells or water. In comparison with prior wavefront-recovery methods used in adaptive optics, PseudoDiversity involves considerably simpler equipment and procedures and less computation. For PseudoDiversity, there is no need to install separate metrological equipment or to use any optomechanical components beyond those that are already parts of the optical system to which the method is applied. In Pseudo- Diversity, the actuators of a subset of the segments or subapertures are driven to make the segments dither in the piston, tilt, and tip degrees of freedom. Each aperture is dithered at a unique frequency at an amplitude of a half wavelength of light. During the dithering, images on the focal plane are detected and digitized at a rate of at least four samples per dither period. In the processing of the image samples, the use of different dither frequencies makes it possible to determine the separate effects of the various dithered segments or apertures. The digitized image-detector outputs are processed in the spatial-frequency (Fourier-transform) domain to obtain measures of the piston, tip, and tilt errors over each segment or subaperture. Once these measures are known, they are fed back to the actuators to correct the errors. In addition, measures of errors that remain after correction by use of the actuators are further utilized in an algorithm in which the image is phase-corrected in the spatial-frequency domain and then transformed back to the spatial domain at each time step and summed with the images from all previous time steps to obtain a final image having a greater signal-to-noise ratio (and, hence, a visual quality) higher than would otherwise be attainable.

Lyon, Richard G.↗
DOE OSTI2022

To what extent can space be compressed? Bandwidth limits of spaceplates

Spaceplates are novel flat-optic devices that implement the optical response of a free-space volume over a smaller length, effectively “compressing space” for light propagation. Together with flat lenses such as metalenses or diffractive lenses, spaceplates have the potential to enable the miniaturization of any free-space optical system. While the fundamental and practical bounds on the performance metrics of flat lenses have been well studied in recent years, a similar understanding of the ultimate limits of spaceplates is lacking, especially regarding the issue of bandwidth, which remains as a crucial roadblock for the adoption of this platform. In this work, we derive fundamental bounds on the bandwidth of spaceplates as a function of their numerical aperture and compression ratio (ratio by which the free-space pathway is compressed). The general form of these bounds is universal and can be applied and specialized for different broad classes of space-compression devices, regardless of their particular implementation. Our findings also offer relevant insights into the physical mechanism at the origin of generic space-compression effects and may guide the design of higher performance spaceplates, opening new opportunities for ultra-compact, monolithic, planar optical systems for a variety of applications.

Shastri, Kunal (ORCID:0000000169282753)↗
NASA NTRS2015

Solar Lyman-Alpha Polarization Observation of the Chromosphere and Transition Region by the Sounding Rocket Experiment CLASP

We are planning an international rocket experiment Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is (2015 planned) that Lyman α line (Ly(alpha) line) polarization spectroscopic observations from the sun. The purpose of this experiment, detected with high accuracy of the linear polarization of the Ly(alpha) lines to 0.1% by using a Hanle effect is to measure the magnetic field of the chromosphere-transition layer directly. For polarization photometric accuracy achieved that approx. 0.1% required for CLASP, it is necessary to realize the monitoring device with a high throughput. On the other hand, Ly(alpha) line (vacuum ultraviolet rays) have a sensitive characteristics that is absorbed by the material. We therefore set the optical system of the reflection system (transmission only the wavelength plate), each of the mirrors, subjected to high efficiency of the multilayer coating in accordance with the role. Primary mirror diameter of CLASP is about 30 cm, the amount of heat about 30,000 J is about 5 minutes of observation time is coming mainly in the visible light to the telescope. In addition, total flux of the sun visible light overwhelmingly large and about 200 000 times the Ly(alpha) line wavelength region. Therefore, in terms of thermal management and 0.1% of the photometric measurement accuracy achieved telescope, elimination of the visible light is essential. We therefore, has a high reflectivity (> 50%) in Lyα line, visible light is a multilayer coating be kept to a low reflectance (<5%) (cold mirror coating) was applied to the primary mirror. On the other hand, the efficiency of the polarization analyzer required chromospheric magnetic field measurement (the amount of light) Conventional (magnesium fluoride has long been known as a material for vacuum ultraviolet (MgF2) manufactured ellipsometer; Rs = 22%) about increased to 2.5 times were high efficiency reflective polarizing element analysis. This device, Bridou et al. (2011) is proposed "that is coated with a thin film of the substrate MgF2 and SiO2 fused silica." As a result of the measurement, Rs = 54.5%, to achieve a Rp = 0.3%, high efficiency, of course, capable of taking out only about s-polarized light. Other reflective optical elements (the secondary mirror, the diffraction gratingcollector mirror), subjected to high-reflection coating of Al + MgF2 (reflectance of about 80%), less than 5% in the entire optical system by these (CCD Science was achieved a high throughput as a device for a vacuum ultraviolet ray of the entire system less than 5% (CCD of QE is not included).

Narukage, Noriyuki↗
NASA NTRS2015

High-Reflectivity Multi-Layer Coatings for the CLASP Sounding Rocket Project

We are planning an international rocket experiment Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) is (2015 planned) that Lyman alpha line (Ly alpha line) polarization spectroscopic observations from the sun. The purpose of this experiment, detected with high accuracy of the linear polarization of the Ly alpha lines to 0.1% by using a Hanle effect is to measure the magnetic field of the chromosphere-transition layer directly. For polarization photometric accuracy achieved that approximately 0.1% required for CLASP, it is necessary to realize the monitoring device with a high throughput. On the other hand, Ly alpha line (vacuum ultraviolet rays) have a sensitive characteristics that is absorbed by the material. We therefore set the optical system of the reflection system (transmission only the wavelength plate), each of the mirrors, subjected to high efficiency of the multilayer coating in accordance with the role. Primary mirror diameter of CLASP is about 30 cm, the amount of heat about 30,000 J is about 5 minutes of observation time is coming mainly in the visible light to the telescope. In addition, total flux of the sun visible light overwhelmingly large and about 200 000 times the Ly alpha line wavelength region. Therefore, in terms of thermal management and 0.1% of the photometric measurement accuracy achieved telescope, elimination of the visible light is essential. We therefore, has a high reflectivity (greater than 50%) in Ly alpha line, visible light is a multilayer coating be kept to a low reflectance (less than 5%) (cold mirror coating) was applied to the primary mirror. On the other hand, the efficiency of the polarization analyzer required chromospheric magnetic field measurement (the amount of light) Conventional (magnesium fluoride has long been known as a material for vacuum ultraviolet (MgF2) manufactured ellipsometer; Rs = 22%) about increased to 2.5 times were high efficiency reflective polarizing element analysis. This device, Bridou et al. (2011) is proposed "that is coated with a thin film of the substrate MgF2 and SiO2 fused silica." As a result of the measurement, Rs = 54.5%, to achieve a Rp = 0.3%, high efficiency, of course, capable of taking out only about spolarized light. Other reflective optical elements (the secondary mirror, the diffraction grating-collector mirror), subjected to high-reflection coating of Al + MgF2 (reflectance of about 80%), less than 5% in the entire optical system by these (CCD Science was achieved a high throughput as a device for a vacuum ultraviolet ray of the entire system less than 5% (CCD of QE is not included).

sounding rocket↗
NASA NTRS1991

Intelligent vision system for autonomous vehicle operations

A complex optical system consisting of a 4f optical correlator with programmatic filters under the control of a digital on-board computer that operates at video rates for filter generation, storage, and management is described.

Scholl, Marija S.↗
NASA NTRS1988

Phase Length Optical Phase-Locked-Loop Sensor

The invention is a device that provides a high resolution measurement of the change in optical phase length from the device optical system source to an optical reflector. The invention consists of a optical phase locked loop that uses a laser beam as a carrier of an intensity modulated energy source. The novelty of the invention appears to lie in the overall combination of elements which provide high resolution without loss of wide dynamic range. The invention does not depend on coherent reflection from a target, and thus can measure targets that do not have special preparation or corner reflectors. The use of carrier modulation achieves high resolution without the problems of high speed pulse duration systems. Thus the invention has the advantages of simplicity, low cost, and small size without sacrificing resolution.

Heyman, Joseph S.↗
NASA NTRS2007

Zernike-like Orthogonal Basis Functions for Wavefront Characterization over Sampled, Irregular Apertures

For optical systems with circular apertures, wavefronts are often analyzed using Zernike polynomials, and individual Zernike functions are associated with familiar optical aberrations. For systems with noncircular apertures, or in practical situations in which wavefronts are measured at a limited number of points in the aperture, the Zernike polynomials are no longer an orthogonal basis for the measured data. Although there are an endless number of ways to create a basis for such measured data, a "Zernike-like" basis is useful to connect with our experience with the usual optical aberrations. In this paper, the steps required to identify a Zernike-like basis for wavefronts over sampled, irregular apertures are presented, based on the Gram-Schmidt orthogonalization technique. The benefits of analyzing optical wavefronts using an orthogonal basis specific to an optical system's aperture shape and wavefront sampling, instead of using the traditional Zernike polynomials, are detailed in two examples, from image-based wavefront sensing on a segmented-aperture telescope (the James Webb Space Telescope Testbed Telescope at Ball Aerospace) and from interferometer characterization for surface metrology of a hexagonal mirror segment.

Aronstein, David L.↗
DOE OSTI2022

A SiPM-based optical readout system for the EIC dual-radiator RICH

Silicon photomultipliers (SiPM) are candidates selected as the potential photodetector technology for the dual-radiator Ring-Imaging Cherenkov (dRICH) detector at the future Electron-Ion Collider (EIC). SiPM are cheap devices, highly efficient and insensitive to the high magnetic field at the expected location of the sensors in the experiment. Here, on the other hand, SiPM are not radiation tolerant. Despite the integrated radiation level is expected to be moderate it should be tested whether single photon-counting capabilities and the increase in dark count rate can be kept under control to maintain the optimal dRICH detector performance across the years. The current status of the research for the EIC dRICH application and the first results on studies performed on a sample of commercial and prototype SiPM sensors are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Germanium Telluride Chalcogenide Switches for RF Applications

This project developed prototype germanium telluride switches, which can be used in RF applications to improve SWAP (size, weight, and power) and signal quality in RF systems. These switches can allow for highly reconfigurable systems, including antennas, communications, optical systems, phased arrays, and synthetic aperture radar, which all have high impact on current National Security goals for improved communication systems and communication technology supremacy. The final result of the project was the demonstration of germanium telluride RF switches, which could act as critical elements necessary for a single chip RF communication system that will demonstrate low SWAP and high reconfigurability

42 ENGINEERING↗
NASA NTRS1966

United States weather satellites

Performance characteristics, attitude stabilization systems, power sources and optical systems of Tiros, TOS and Nimbus weather satellites

TIROS SATELLITE↗