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Results for “REFLECTING TELESCOPE”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Bragg crystal polarimeter for the Spectrum-X-Gamma mission

A Bragg crystal polarimeter for the focal plane of the SODART telescope on the Spectrum-X-Gamma mission is being designed. A mosaic graphite crystal will be oriented at 45 deg to the optic axis of the telescope, thereby preferentially reflecting those X-rays which satisfy the Bragg condition and have electric vectors that are perpendicular to the plane defined by the incident and reflected photons. The reflected X-rays will be detected by an imaging proportional counter with the image providing direct X-ray aspect information. The crystal will be about 50 microns thick to allow X-rays with energies of 4 keV or greater to be transmitted to a lithium block mounted below the graphite. The lithium is used to measure the polarization of these high energy X-rays by exploiting the polarization dependence of Thomson scattering. The development of thin mosaic graphite crystals is discussed and recent reflectivity, transmission, and uniformity measurements are presented.

Holley, J.↗
NASA NTRS2004

Final Report for the Advanced Camera for Surveys (ACS)

ACS was launched aboard the Space Shuttle Columbia just before dawn on March 1, 2002. At the time of liftoff, the Hubble Space Telescope (HST) was reflecting the early morning sun as it moved across the sky. After successfully docking with HST, several components were replaced. One of the components was the Advanced Camera for Surveys built by Ball Aerospace & Technologies Corp. (BATC) in Boulder, Colorado. Over the life of the HST contract at BATC, hundreds of employees had the pleasure of working on the concept, design, fabrication, assembly, and test of ACS. Those employees thank NASA - Goddard Space Flight Center and the science team at Johns Hopkins University (JHU) for the opportunity to participate in building a great science instrument for HST.

Source record↗
NASA NTRS2017

Highly accurate positions of asteroids using astrometry

Astrometry is the precise measurement of positions in the sky of stars and other celestial bodies. In this paper, measurements of asteroids and outer planet natural satellites are discussed. We used the Astro Mechanics, Ritchey-Chrétien reflecting, 0.6m telescope at Table Mountain Observatory (TMO) located in Wrightwood, CA. Equipped with a 4k CCD camera (the ProLine4096x4096 imaging array with 9μm pixels), using 180 second exposures, we imaged the asteroids and outer satellites. We calculated two to three different positions of the asteroids, with different star fields, to best obtain positions. We obtained many different accurate positions of asteroids and the observing conditions, which were noted, inputted, then reduced with other data. We submit our data to the Minor Planet Center, and by the Solar System Dynamics (SSD) group at JPL. The data are also used for predicting occulting events. Through the execution of several Linux reduction programs and scripts, we reduce the data for the most accurate orbital positions.

Carr, Alexander G.↗
NASA NTRS2016

Characterizing Cool Giant Planets in Reflected Light

While the James Webb Space Telescope will detect and characterize extrasolar planets by transit and direct imaging, a new generation of telescopes will be required to detect and characterize extrasolar planets by reflected light imaging. NASA's WFIRST space telescope, now in development, will image dozens of cool giant planets at optical wavelengths and will obtain spectra for several of the best and brightest targets. This mission will pave the way for the detection and characterization of terrestrial planets by the planned LUVOIR or HabEx space telescopes. In my presentation I will discuss the challenges that arise in the interpretation of direct imaging data and present the results of our group's effort to develop methods for maximizing the science yield from these planned missions.

James Webb Space Telescope↗
NASA NTRS2021

The Science Case for Spacecraft Exploration of the Uranian Satellites: Candidate Ocean Worlds in an Ice Giant System

The 27 satellites of Uranus are enigmatic, with dark surfaces coated by material that could be rich in organics. Voyager 2 imaged the southern hemispheres of Uranus’s five largest “classical” moons—Miranda, Ariel, Umbriel, Titania, and Oberon, as well as the largest ring moon, Puck—but their northern hemispheres were largely unobservable at the time of the flyby and were not imaged. Additionally, no spatially resolved data sets exist for the other 21 known moons, and their surface properties are essentially unknown. Because Voyager 2 was not equipped with a near-infrared mapping spectrometer, our knowledge of the Uranian moons’ surface compositions, and the processes that modify them, is limited to disk-integrated data sets collected by ground- and space-based telescopes. Nevertheless, images collected by the Imaging Science System on Voyager 2 and reflectance spectra collected by telescope facilities indicate that the five classical moons are candidate ocean worlds that might currently have, or had, liquid subsurface layers beneath their icy surfaces. To determine whether these moons are ocean worlds, and to investigate Uranus’s ring moons and irregular satellites, close-up observations and measurements made by instruments on board a Uranus orbiter are needed.

Richard J. Cartwright↗
NASA NTRS1973

Measurement of X-ray scattering by optical surfaces

Optical surfaces built for X-ray telescopes are made to reflect very short wavelengths that range in magnitude from 2 to 100 angstroms. Minor irregularities or contamination on sufrace of any telescope mirror can affect quality of optical image. Apparatus checks reflection of optical surfaces; scattering of X-rays is measured with angular accuracy of one arc-second.

Wriston, R. S.↗
NASA NTRS2016

Recent Variability Observations of Solar System Giant Planets: Fresh Context for Understanding Exoplanet and Brown Dwarf Weather

Over the past several years a number of high cadence photometric observations of solar system giant planets have been acquired by various platforms. Such observations are of interest as they provide points of comparison to the already expansive set of brown dwarf variability observations and the small, but growing, set of exoplanet variability observations. By measuring how rapidly the integrated light from solar system giant planets can evolve, variability observations of substellar objects that are unlikely to ever be resolved can be placed in a fuller context. Examples of brown dwarf variability observations include extensive work from the ground (e.g., Radigen et al. 2014), Spitzer (e.g., Metchev et al. 2015), Kepler (Gizis et al. 2015), and HST (Yang et al. 2015).Variability has been measured on the planetary mass companion to the brown dwarf 2MASS 1207b (Zhou et al. 2016) and further searches are planned in thermal emission for the known directly imaged planets with ground based telescopes (Apai et al. 2016) and in reflected light with future space based telescopes. Recent solar system variability observations include Kepler monitoring of Neptune (Simon et al. 2016) and Uranus, Spitzer observations of Neptune (Stauffer et al. 2016), and Cassini observations of Jupiter (West et al. in prep). The Cassini observations are of particular interest as they measured the variability of Jupiter at a phase angle of approximately 60 deg, comparable to the viewing geometry expected for space based direct imaging of cool extrasolar Jupiters in reflected light. These solar system analog observations capture many of the characteristics seen in brown dwarf variability, including large amplitudes and rapid light curve evolution on timescales as short as a few rotation periods. Simon et al. (2016) attribute such variations at Neptune to a combination of large scale, stable cloud structures along with smaller, more rapidly varying, cloud patches. The observed brown dwarf and exoplanet variability may well arise from comparable cloud structures. In my presentation I will compare and contrast the nature of the variability observed for the various solar system and other substelar objects and present a wish list for future observations.

giant planets↗
NASA NTRS2010

Adaptive Nulling for Interferometric Detection of Planets

An adaptive-nulling method has been proposed to augment the nulling-optical- interferometry method of detection of Earth-like planets around distant stars. The method is intended to reduce the cost of building and aligning the highly precise optical components and assemblies needed for nulling. Typically, at the mid-infrared wavelengths used for detecting planets orbiting distant stars, a star is millions of times brighter than an Earth-sized planet. In order to directly detect the light from the planet, it is necessary to remove most of the light coming from the star. Nulling interferometry is one way to suppress the light from the star without appreciably suppressing the light from the planet. In nulling interferometry in its simplest form, one uses two nominally identical telescopes aimed in the same direction and separated laterally by a suitable distance. The light collected by the two telescopes is processed through optical trains and combined on a detector. The optical trains are designed such that the electric fields produced by an on-axis source (the star) are in anti-phase at the detector while the electric fields from the planet, which is slightly off-axis, combine in phase, so that the contrast ratio between the star and the planet is greatly decreased. If the electric fields from the star are exactly equal in amplitude and opposite in phase, then the star is effectively nulled out. Nulling is effective only if it is complete in the sense that it occurs simultaneously in both polarization states and at all wavelengths of interest. The need to ensure complete nulling translates to extremely tight demands upon the design and fabrication of the complex optical trains: The two telescopes must be highly symmetric, the reflectivities of the many mirrors in the telescopes and other optics must be carefully tailored, the optical coatings must be extremely uniform, sources of contamination must be minimized, optical surfaces must be nearly ideal, and alignments must be extremely precise. Satisfaction of all of these requirements entails substantial cost.

Lay, Oliver P.↗
NASA NTRS1990

Survey Of Infrared-Absorbing Coatings

Carbon black and silicon carbide grit low reflectance additives. Report presents results of survey of candidate materials for use as attenuators of stray radiation in far-infrared telescopes. More than 40 reflectance spectra at 17 degrees incidence, in wave-length range from 20 to 500 micrometer, obtained from variety of coatings, binders, and additives.

Smith, Sheldon M.↗
NASA NTRS2010

Monolithic afocal telescope

An afocal monolithic optical element formed of a shallow cylinder of optical material (glass, polymer, etc.) with fast aspheric surfaces, nominally confocal paraboloids, configured on the front and back surfaces. The front surface is substantially planar, and this lends itself to deposition of multi-layer stacks of thin dielectric and metal films to create a filter for rejecting out-of-band light. However, an aspheric section (for example, a paraboloid) can either be ground into a small area of this surface (for a Cassegrain-type telescope) or attached to the planar surface (for a Gregorian-type telescope). This aspheric section of the surface is then silvered to create the telescope's secondary mirror. The rear surface of the cylinder is figured into a steep, convex asphere (again, a paraboloid in the examples), and also made reflective to form the telescope's primary mirror. A small section of the rear surface (approximately the size of the secondary obscuration, depending on the required field of the telescope) is ground flat to provide an unpowered surface through which the collimated light beam can exit the optical element. This portion of the rear surface is made to transmit the light concentrated by the reflective surfaces, and can support the deposition of a spectral filter.

Roberts, William T.↗
NASA NTRS1976

Focused laser Doppler velocimeter

A system for remotely measuring velocities present in discrete volumes of air is described. A CO2 laser beam is focused by a telescope at such a volume, a focal volume, and within the focusable range, near field, of the telescope. The back scatter, or reflected light, principally from the focal volume, passes back through the telescope and is frequency compared with the original frequency of the laser, and the difference frequency or frequencies represent particle velocities in that focal volume.

Bilbro, J. W.↗
NASA NTRS1985

Nearly Anastigmatic X-Ray Telescope

Proposed X-ray telescope made of many concentric reflecting rings, each of which consists of two portions of cone. Proposed design is variation on conventional grazing incidence X-ray telescope, which has just one twosegment reflecting element but suffers from excessive astigmatism and field curvature. Using many short elements instead of single long element, new design gives nearly anastigmatic image.

Korsch, D.↗
NASA NTRSDate not supplied

An Overview of MaGIXS-2: The second flight of the Marshall Grazing Incidence X-ray Spectrometer

The Marshall Grazing Incidence X-ray Spectrometer (MaGIXS) is a sounding rocket mission that completed a successful flight from the White Sands Missile Range on July 30, 2021. MaGIXS captured spatially resolved soft X-ray spectra from portions of two solar active regions during its roughly 5-minute flight. The instrument was originally designed as a grazing incidence slit spectrograph but flew in a slit-less configuration that produced overlapping spectroheliograms. For the second flight, MaGIXS-2, the instrument has been reconfigured to a more simplified optical layout that reuses the Wolter-I telescope and blazed varied-line space reflective grating. The field stop at the telescope focal plane and the finite conjugate spectrometer mirror pair have been removed – the telescope now directly feeds the grating. Additionally, an identical but new 2k x 1k CCD camera has been built for this flight. The MaGIXS-2 data product will again be overlapping spectroheliograms of at least one solar active region, but with improved resolution, a larger field of view and increased effective area. Here we present the updated instrument layout, the expected performance, the integration and calibration approach, and proposed future improvements, including the implementation of additional complimentary spectral diagnostics.

Imaging Spectrometer↗
NASA NTRS1976

Starsat: A space astronomy facility

Preliminary design and analyses of a versatile telescope for Spacelab missions are presented. The system is an all-reflective Korsch three-mirror telescope with excellent performance characteristics over a wide field and a broad spectral range, making it particularly suited for ultraviolet observations. The system concept is evolved around the utilization of existing hardware and designs which were developed for other astronomy space projects.

Hamilton, E. C.↗
NASA NTRS1993

Compositional diversity of the lunar North Pole: Preliminary analyses of Galileo SSI data

In December 1992, the Galileo spacecraft passed through the Earth-Moon system for its final gravity assist to Jupiter. The SSI camera obtained several 6-color mosaics of the lunar north polar region and the sunlit nearside and eastern limb at approximately 1.3 km/pixel. Initial analyses have concentrated on the north polar areas to assess the composition of the crust in that region. Representative 6-color calibration SSI spectra (typically 5 x 5 pixels) are shown. Photometric corrections have not yet been applied, and all spectra are scaled to unity at 0.56 microns. The data were first calibrated relative to MS2, a standard are in Mare Serenitatis (18.7 deg N, 21.5 deg E), and the top four plots of highlands, highland craters, maria, and mare craters are displayed relative to MS2. SSI spectra of areas measured with telescopic data (mare MT1/MS2 and mare crater MSA/MS2) agree well with previous data, confirming that the calibration procedures and SSI data are spectrally accurate. The bottom three plots of craters/sun have been calibrated to reflectance using previously obtained telescopic spectra of Apollo 16/MS2 (shown with Highlands/MS2) and laboratory spectra of mature Apollo 16 soil (shown for reference with the Highland Craters/Sun). Although some variations in these spectra mimic previously observed spectra of lunar terrains, several characteristics are unusual. Familiar and unfamiliar properties are observed in these northern latitudes and both types merit further investigation in their geologic context.

Pieters, C. M.↗
NASA NTRS1990

Reflected Sunlight Reduction and Characterization for a Deep-Space Optical Receiver Antenna (DSORA)

A baffle system for the elimination of first-order specular and diffuse reflection of sunlight from the sunshade of a deep-space optical receiver telescope is presented. This baffle system consists of rings of 0.5cm blades spaced 2.5 cm apart on the walls of GO hexagonal sunshade tubes that combine to form the telescope sunshade. The shadow cast by the blades, walls, and rims of the tubes prevent all first-order reflections of direct sunlight from reaching the primary mirror of the telescope. A reflection model of the sunshade without baffles is also presented for comparison. Since manufacturers of absorbing surfaces do not measure data near grazing incidence, the reflection properties at anticipated angles of incidence must be characterized. A description of reflection from matte surfaces in term of bidirectional reflection distribution function (BRDF) is presented along with a discussion of measuring BRDF near grazing incidence.

Clymer, B. D.↗