Search NASA⌕ Search

SEARCH · Search NASA

Results for “MIRROR POINT”

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 307 records · Page 17

Design and testing of a free floating dual flap wave energy converter

With a wide variety of wave energy device archetypes currently under consideration, it is a major challenge to ensure that research findings and methods are broadly applicable. In particular, the design and testing of wave energy control systems, a process which includes experimental design, empirical modeling, control design, and performance evaluation, is of interest. This goal motivated the redesign and testing of a floating dual flap wave energy converter. As summarized in this paper, the steps taken in the design, testing, and analysis of the device mirrored those previously demonstrated on a three-degree of freedom point absorber device. The method proposed does not require locking WEC degrees of freedom to develop an excitation model, and presents a more attainable system identification procedure for at-sea deployments. The results show that the methods employed work well for this dual flap device, lending additional support for the broad applicability of the design and testing methods applied here. The aim of this paper is to demonstrate that these models are particularly useful for deducing areas of device design or controller implementation that can be reasonably improved to increase device power capture.

16 TIDAL AND WAVE POWER↗

Rigidity of MHD equilibria to smooth incompressible ideal motion near resonant surfaces

In ideal MHD, the magnetic flux is advected by the plasma motion, freezing flux-surfaces into the flow. An MHD equilibrium is reached when the flow relaxes and force balance is achieved. We ask what classes of MHD equilibria can be accessed from a given initial state via smooth incompressible ideal motion. It is found that certain boundary displacements are formally not supported. This follows from yet another investigation of the Hahm–Kulsrud–Taylor (HKT) problem, which highlights the resonant behaviour near a rational layer formed by a set of degenerate critical points in the flux-function. When trying to retain the mirror symmetry of the flux-function with respect to the resonant layer, the vector field that generates the volume-preserving diffeomorphism vanishes at the identity to all order in the time-like path parameter.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

HEAO project - Revisited

A stellar inertial attitude reference with strapdown rate integrating gyros, together with star trackers and a general purpose computer, constitute the attitude control subsystem shared by NASA's HEAO observatories. HEAO-2, which is equipped with the largest and most precise grazing incidence X-ray mirror deployed aboard a satellite to date, has achieved accurate telescope pointing in autonomous maneuvering to selected targets, the acquisition of guide stars for attitude updating, and the positioning of unique experiments at the telescope focal point. Performance data have confirmed maneuvering accuracies of 1 arcmin, and pointing accuracies of 2-5 arcsec. Additional performance results presented support the extrapolation of the present HEAO attitude reference design to future applications.

Wojtalik, F. S.↗

Cosmology with liquid mirror telescopes

Liquid mirrors provide an exciting means to obtain large optical telescopes for substantially lower costs than conventional technologies. The liquid mirror concept has been demonstrated in the lab with the construction of a diffraction limited 1.5 m mirror. The mirror surface, using liquid mercury, forms a perfect parabolic shape when the mirror cell is rotated at a uniform velocity. A liquid mirror must be able to support a heavy mercury load with minimal flexure and have a fundamental resonant frequency that is as high as possible, to suppress the amplitude of surface waves caused by small vibrations transmitted to the mirror. To minimize the transmission of vibrations to the liquid surface, the entire mirror rests on an air bearing. This necessitates the mirror cell being lightweight, due to the limited load capabilities of the air bearing. The mirror components must also have physical characteristics which minimize the effects of thermal expansion with ambient temperature fluctuations in the observatory. In addition, the 2.7 m mirror construction is designed so that the techniques used may be readily extended to the construction of large mirrors. To attain the goals of a lightweight, rigid mirror, a composite laminant construction was used. The mirror consists of a foam core cut to the desired parabolic shape, with an accuracy of a few mm. An aluminum hub serves as an anchor for the foam and skin, and allows precise centering of the mirror on the air bearing and drive system. Several plys of Kevlar, covered in an epoxy matrix, are then applied to the foam. A final layer of pure epoxy is formed by spin casting. This final layer is parabolic to within a fraction of a mm. An aluminum ring bonded to the circumference of the mirror retains the mercury, and incorporates stainless-steel hard-points for the attachment of balance weights.

Hogg, David W.↗

Rocket and Laboratory Studies in Astronomy

This report covers the period from March 1, 2001 to August 31, 2004. This grant was the continuation of NASA grant NAG5-5122 and supported the Johns Hopkins sounding rocket program that had its roots in the 1960s. The emphasis of this program has been the development of instrumentation for far-ultraviolet astronomy, the training of graduate students in all aspects of a space mission, and the application of these techniques to timely scientific problems. During this period we completed the fabrication of our new long-slit dual-order spectrograph (LIDOS), and successfully flew it on a Black Brant sounding rocket on December 16, 2003 (36.208 UG). The targets were the bright star gamma-Cassiopeiae and its surrounding reflection nebulae, IC 59 and IC 63. We also continued the analysis of the data from our previous flight to study the reflection nebula IC 405 (36.198 UG), which revealed a far-ultraviolet nebular scatter to stellar flux ratio that, contrary to expectations, rises steeply toward the blue. Verifying this result required extensive post-flight analysis and calibration of the Faint Object Telescope FOT) payload, which entailed measuring the telescope mirror reflectivities, the absolute efficiency of the spectrograph, and the telescope point spread function, using a new vacuum collimator developed as part of former graduate student Eric Burgh's Ph.D. dissertation. This work, being done with graduate student Kevin France, has been completed and a paper describing the results has been accepted for publication by the Astrophysical Journal. We have also continued a number of laboratory calibration studies and design efforts.

Feldman, Paul D.↗

The Astro-E2 Mission

The Astro-E2 observatory is a rebuild of the original Astro-E observatory that was lost during launch in February 2000. It is scheduled for launch into low earth orbit on a Japanese M-V rocket in early 2005. The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, is developing the observatory with major contributions from the US. The three instruments on the observatory are the high-resolution x-ray spectrometer (the XRS) featuring a 30-pixel x-ray microcalorimeter array, a set of four CCD cameras (the XIS) and a combination photo-diode/scintillator detector system (the HXD) that will extend the band pass up to nearly 700 keV. A significant feature of Astro-E2 is that all of the instruments are coaligned and operated simultaneously. With its high spectral resolution and collecting area for spectroscopy above 1 keV, Astro-E2 should enable major discovery space and pioneer new technology for use in space. Prime areas for investigation are supernova remnants, active galaxies and the measurement of black hole properties via relativistically-broadened Fe-K emission galaxies. A number of enhancements have been made for the Astro-E2/XRS, including a higher resolution microcalorimeter array, ii mechanical cooler for longer cryogen life, and an improved in-flight calibration system. The Astro-E2/XIS has also been improved to include two back-side-illuminated CCDs to enhance the low energy response. Improvements have also been made to the x-ray mirrors used for both the XRS and XIS to sharpen the point spread function and reduce the effects of stray light. In this talk we will present the essential features of Astro-E2, paying particular attention to the enhancements, and describe the major scientific strengths of the observatory.

Kelley, Richard L.↗

JWST Near-Infrared Detector Degradation: Finding the Problem, Fixing the Problem, and Moving Forward

The James Webb Space Telescope (JWST) is the successor to the Hubble Space Telescope. JWST will be an infrared optimized telescope, with an approximately 6.5 m diameter primary mirror, that is located at the Sun-Earth L2 Lagrange point. Three of JWST's four science instruments use Teledyne HgCdTe HAWAII-2RG (H2RG) near infrared detector arrays. During 2010, the JWST Project noticed that a few of its 5 micron cutoff H2RG detectors were degrading during room temperature storage, and NASA chartered a "Detector Degradation Failure Review Board" (DD-FRB) to investigate. The DD-FRB determined that the root cause was a design flaw that allowed indium to interdiffuse with the gold contacts and migrate into the HgCdTe detector layer. Fortunately, Teledyne already had an improved design that eliminated this degradation mechanism. During early 2012, the improved H2RG design was qualified for flight and JWST began making additional H2RGs. In this article we present the two public DD-FRB "Executiye Summaries" that: (1) determined the root cause of the detector degradation and (2) defined tests to determine whether the existing detectors are qualified for flight. We supplement these with a brief introduction to H2RG detector arrays, and a discussion of how the JWST Project is using cryogenic storage to retard the degradation rate of the existing flight spare H2RGs.

Rauscher, Bernard J.↗

The Design & Development of the Ocean Color Instrument Precision Superduplex Hybrid Bearing Cartridge

A high precision, high-resolution Ocean Color Imaging (OCI) instrument is under development for the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission which requires a pair of medium speed mechanisms to scan the ocean surface continuously. The design of the rotating telescope (RT) mechanism operating at 360 RPM and the half-angle mirror (HAM) mechanism synchronized at 180 RPM was concern for maintaining pointing precision over the required life and continuous operations. An effort was undertaken with the manufacturer to design and analyze a special bearing configuration to minimize axial and radial runout, minimize torque, and maintain nominal contact stresses and stiffness over the operating temperature range and to maximize life. The bearing design, development effort, analysis and testing will be discussed as will the technical challenges that this specific design imposed upon the mechanism engineers. Bearing performance, runout as achieved and verified during encoder installation and operating torque will be described.

mechanism↗

Pointing control for LDR

One important aspect of the LDR control problem is the possible excitations of structural modes due to random disturbances, mirror chopping, and slewing maneuvers. An analysis was performed to yield a first order estimate of the effects of such dynamic excitations. The analysis involved a study of slewing jitters, chopping jitters, disturbance responses, and pointing errors, making use of a simplified planar LDR model which describes the LDR dynamics on a plane perpendicular to the primary reflector. Briefly, the results indicate that the command slewing profile plays an important role in minimizing the resultant jitter, even to a level acceptable without any control action. An optimal profile should therefore be studied.

Yam, Y.↗

ASTRO-H Soft X-Ray Telescope (SXT)

ASTRO-H is an astrophysics satellite dedicated for X-ray spectroscopic study non-dispersively and to carry out survey complementally, which will be borne out of US-Japanese collaborative effort. Among the onboard instruments there are four conically approximated Wolter-I X-ray mirrors, among which two of them are soft X-ray mirrors\ of which the energy range is from a few hundred eV to 15 keY, currently being fabricated in the X-ray Optics Lab at Goddard Space Flight Center. The focal point instruments will be a calorimeter (SXS) and a CCD camera (SXI), respectively. The reflectors of the mirror are made of heat-formed aluminum substrate of the thickness gauged of 152 micron, 229 micron, and 305 micron of the alloy 5052 H-19, followed by epoxy replication on gold-sputtered smooth Pyrex cylindrical mandrels to acquire the X-ray reflective surface. The epoxy layer is 10 micron nominal and surface gold layer of 0.2 micron. Improvements on angular response over the Astro-El/Suzaku mirrors come from error reduction on the figure, the roundness, and the grazing angle/radius mismatching of the reflecting surface, and tighter specs and mechanical strength on supporting structure to reduce the reflector positioning and the assembly errors. In this paper, we report the results of calibration of the engineering model of SXT (EM), and project the quality of the flight mirrors.

Soong, Yang↗

Design Study of 8 Meter Monolithic Mirror UV/Optical Space Telescope

The planned Ares V launch vehicle with its 10 meter fairing shroud and 55,000 kg capacity to the Sun Earth L2 point enables entirely new classes of space telescopes. NASA MSFC has conducted a preliminary study that demonstrates the feasibility of launching a 6 to 8 meter class monolithic primary mirror telescope to Sun-Earth L2 using an Ares V. Specific technical areas studied included optical design; structural design/analysis including primary mirror support structure, sun shade and secondary mirror support structure; thermal analysis; launch vehicle performance and trajectory; spacecraft including structure, propulsion, GN&C, avionics, power systems and reaction wheels; operations and servicing; mass and power budgets; and system cost.

Stahl, H. Philip↗

Mirror symmetry breaking in a model insulating cuprate

Among the most actively studied issues in the cuprates are the natures of the pseudogap and strange metal states and their relationship to superconductivity. There is general agreement that the low-energy physics of the Mott-insulating parent state is well captured by a two-dimensional spin S = 1/2 antiferromagnetic Heisenberg model. However, recent observations of a large thermal Hall conductivity in several parent cuprates appear to defy this simple model and suggest proximity to a magneto-chiral state that breaks all mirror planes that are perpendicular to the CuO 2 layers. Here we use optical second harmonic generation to directly resolve the point group symmetries of the model parent cuprate Sr 2 CuO 2 Cl 2 . We report evidence of an order parameter that breaks all perpendicular mirror planes and is consistent with a magneto-chiral state in zero magnetic field. Although this order is clearly coupled to the antiferromagnetism, we are unable to realize its time-reversed partner by thermal cycling through the antiferromagnetic transition temperature or by sampling different spatial locations. Finally, this suggests that the order onsets above the Neel temperature and may be relevant to the mechanism of pseudogap formation.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

High-power non-perturbative laser delivery diagnostics at the final focus of 100-TW-class laser pulses

Controlling the delivery of multi-terawatt and petawatt laser pulses to final focus, both in position and angle, is critical to many laser applications such as optical guiding, laser–plasma acceleration, and laser-produced secondary radiation. We present an online, non-destructive laser diagnostic, capable of measuring the transverse position and pointing angle at focus. The diagnostic is based on a unique double-surface-coated wedged-mirror design for the final steering optic in the laser line, producing a witness beam highly correlated with the main beam. By propagating low-power kilohertz pulses to focus, we observed spectra of focus position and pointing angle fluctuations dominated by frequencies below 70 Hz. The setup was also used to characterize the excellent position and pointing angle correlation of the 1 Hz high-power laser pulses to this low-power kilohertz pulse train, opening a promising path to fast non-perturbative feedback concepts even on few-hertz-class high-power laser systems.

47 OTHER INSTRUMENTATION↗

Optical Design of the Origins Space Telescope

The optical design is presented for the Origins Space Telescope, one of four large missions under study in preparation for the 2020 Decadal Survey in Astronomy and Astrophysics is presented. Sensitive to the mid- and far-infrared spectrum (between 2.8 and 588 µm) and set to launch in approximately 2035, Origins sets out to answer a number of important scientific questions by addressing NASA's three key science goals in astrophysics: How does the universe work?, How did we get here, and Are we alone? To do so, Origins seeks to answer three main questions: 1) How do galaxies form stars, build up metals, and grow their central supermassive black holes from reionization to today? 2) How do the conditions for habitability develop during the process of planet formation? 3) Do planets orbiting M-dwarf stars support life?The Origins telescope has a 5.9 m diameter primary mirror and operates at f/14. The large on-axis primary consists of 18 'keystone' segments of two different prescriptions arranged in two annuli (six inner and twelve outer segments) that together form a circular aperture in the goal of achieving a symmetric point spread function. To simplify the design, the telescope will be launched with both the primary mirror segments and the secondary mirror already deployed. To accommodate the 46 x 15 arcminute full field of view of the telescope at the design wavelength of = 30 µm, a three-mirror anastigmat configuration is used. The design is diffraction-limited across its instruments' fields of view. A brief discussion of each of the three baselined instruments within the Instrument Accommodation Module (IAM) is presented: 1) Origins Survey Spectrometer (OSS), 2) Mid-infrared Spectrometer, Camera (MISC) transit spectrometer channel, and 3) Far-Infrared Polarimeter/Imager (FIP). In addition, the upscope options for the observatory are laid out as well, including a fourth instrument: the Heterodyne Receiver for Origins (HERO).

Howard, Joseph↗

Science Enabled by the Ares V: A Large Monolithic Telescope Placed at the Second Sun-Earth Lagrange Point

The payload mass and volume capabilities of the planned Ares V launch vehicle provide the science community with unprecedented opportunities to place large science payloads into low earth orbit and beyond. One example, the outcome of a recent study conducted at the NASA Marshall Space Flight Center, is a large, monolithic telescope with a primary mirror diameter of 6.2 meters placed into a halo orbit about the second Sun-Earth Lagrange point, or L2, approximately 1.5 million kin beyond Earth's orbit. Operating in the visible and ultraviolet regions of the electromagnetic spectrum, such a large telescope would allow astronomers to detect bio-signatures and characterize the atmospheres of transiting exoplanets, provide high resolution imaging three or more times better than the Hubble Space Telescope and the James Webb Space Telescope, and observe the ultraviolet light from warm baryonic matter.

Hopkins, Randall C.↗

The Alignment Test System for AXAF-I's High Resolution Mirror Assembly

The AXAF-1 High Resolution Mirror Assembly (HRMA) consists of four nested mirror pairs of Wolter Type-1 grazing incidence optics. The HRMA assembly and alignment will take place in a vibration-isolated, cleanliness class 100, 18 meter high tower at an Eastman Kodak Company facility in Rochester, NY. Each mirror pair must be aligned such that its image is coma-free, and the four pairs must be aligned such that their images are coincident. In addition, both the HRMA optical axis and focal point must be precisely known with respect to physical references on the HRMA. The alignment of the HRMA mirrors is measured by the HRMA Alignment Test System (HATS), which is an integral part of the tower facility. The HATS is configured as a double-pass, autocollimating Hartmann test where each mirror aperture is scanned to determine the state of alignment. This paper will describe the design and operation of the HATS.

Waldman, Mark↗

Surface finish quality of the outer AXAF mirror pair based on X-ray measurements of the VETA-I

We employ the X-ray measurements of the VETA-I taken at the X-Ray Calibration Facility (XRCF) of the Marshall Space Flight Center (MSFC) to extract information about the surface finish quality of the outermost pair of AXAF mirrors. The particular measurements we consider are 1D scans of the core of the point response function (PRF) (FWHM scans), the encircled energy as a function of radius, and 1D scans of the wings of the PRF. We discuss briefly our raytrace model which incorporates the numerous effects present in the VETA-I test, such as the finite source distance, the size and shape of the X-ray source, the residual gravitational distortions of the optic, the despace of the VETA-I, and particulate contamination. We show how the data constrain the amplitude of mirror surface deviations for spatial frequencies greater than about 0.1/mm. Constraints on the average amplitude of circumferential slope errors are derived as well.

Hughes, John P.↗

Rapid Test Bed Concentrator (TBC) Alignment Techniques

A new, labor and cost saving method was developed to eliminate the procedure of covering all (220) mirrors and uncovering then one-by-one in sequence to adjust each to the focal plane. This latest method being used to align mirrors of a parabolic solar concentrator utilizes a computer-derived target of discreet images made up of individual mirror reflections on a plane in front of the intended, nominal, focal point. Incorporating this computer technique increases accuracy and gives potential to develop flux distributions required by different receiver designs.

Argoud, M. J.↗