SEARCH · Engineering Papers

Results for “TELESCOPES”

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.

SourceResearch connectionFrom yearThrough year

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

At least 1,207 records · Page 67

All sources NASA NTRS DOE OSTI

NASA NTRS1986

Transverse ray aberrations of Wolter type 1 telescopes

Transverse ray aberration expansions are derived for Wolter type 1 telescopes. The analysis gives third order aberration terms, most of the fifth order terms and two seventh order terms as functions of system parameters and entrance aperture coordinates. The third order distortion is negligible and, therefore, this term is omitted in the expansions. The spot diagrams derived from exact ray tracing and aberration expansions agree well. The importance of fifth and seventh order terms is discussed. The derived aberration expansions are also valid for Wolter type 2 telescopes.

Saha, Timo T.↗

NASA NTRS1986

Optical arrays for future astronomical telescopes in space

NASA's Marshall Space Flight Center is currently evaluating several advanced optical space telescope concepts for the achievement of both higher sensitivity and greater angular resolution than the Hubble Space Telescope; their designs encompass one- and two-dimensional coherent arrays of mirrors in both focal and afocal configurations. Attention is given to those arrays that appear capable of fabrication and orbital deployment by the year 2005, and to the tradeoff involved between synthetic aperture concepts that furnish high angular resolution and those that yield sensitivity for faint, extended source imaging.

Bunner, Alan N.↗

NASA NTRS1987

Fiber-linked telescope arrays on the ground and in space

The use of single-mode optical fibers in telescope arrays, first proposed for a set of free-flying spacecraft, is developed and applied to more modest, shorter range projects. The basic advantage remains a considerable simplification in the control system; the main limitation is spectral range. Two proposals are described: a ground-based array of small optical telescopes supported on a radio dish, and a similar space array. The control system is almost the same in both cases, hence the ground-based array can be considered a test-bench for the space device.

Connes, P.↗

NASA NTRS1987

Preliminary analysis of recent 2.2-4.2 micrometers telescopic observations of Elysium, Mars: Implications for crystallinity and hydration state of surface materials

Comparisons of the telescopic reflectance spectrum of a Martian bright region, in the 2.2 to 4.2 micrometers region, with recent laboratory studies of materials in this same wavelength range are consistent with: terrestrial materials which are dehydrated relative to the terrestrial environment, and terrestrial materials which exhibit spectral behavior indicative of some degree of sample crystallinity which is greater than that of amorphous palagonites. This second conclusion is in agreement with recent suggestions concerning the Martian bright regions. However, additional laboratory research is required in order to constrain: the degree of crystallinity required to result in the 2.8 to 2.9 micrometers spectral behavior seen in the terrestrial samples, and the limit of crystalline material which can be accommodated in a mixture with measured telescopic data of Mars (0.3 to 4.2 micrometers).

Roush, T. L.↗

NASA NTRS1987

STRAY - An interactive program for the computation of stray radiation in infrared telescopes

The STRAY program to model the amount of stray radiation reaching the focal plane of a well-baffled telescope is described. The STRAY telescope model is addressed, including the aperture shade, barrel baffle, optics, mirror sectioning and chopping, and off-axis points in focal plane. The possible illumination paths are shown, and calculation options using STRAY are discussed. The stored data and computational aspects of STRAY are addressed. STRAY is compared to the MINI-APART model, and applications of STRAY are described.

St. Clair Dinger, Ann↗

NASA NTRS1987

An advanced imaging space telescope concept

This paper describes the results of a recent study of possible configurations for a next-generation optical space telescope with order-of-magnitude improvements over the Hubble Space Telescope. Overall configuration characteristics including optical performance, weights, and dimensions are given. Launch vehicle packaging concepts are described, and a scenario for orbital assembly developed. Finally, an assessment of technology readiness is provided.

Krim, Michael H.↗

NASA NTRS1986

Performance characterization of the Hubble Space Telescope Rate Gyro Assembly

An account is given of the design features and performance characteristics of the Rate Gyro Assembly employed by the Hubble Space Telescope's Pointing Control System to effect accurate spacecraft maneuvers and support fine pointing telescope operation, in conjunction with the fine guidance sensors. The rate sensor attitude quantization is 0.00025 arcsec. Fine-pointing stability is the driver for gyro noise performance, while spacecraft-pointing accuracy requirements at the end of maneuvers has driven the gyro scale factor and mechanical alignment stability performance.

Dougherty, H.↗

NASA NTRS1987

Baffle design for telescopes with tiltable secondary mirrors

A procedure is presented for the design of primary and secondary baffles (light shields) for telescopes with tiltable secondary mirrors (typically for use in the infrared). The procedure is applied to the Space Infrared Telescope Facility (SIRTF) for which results are presented.

Davis, Paul K.↗

NASA NTRS1988

Direct imaging of extra-solar planetary systems with the Circumstellar Imaging Telescope (CIT)

In a joint study conducted by the Jet Propulsion Laboratory and the Perkin-Elmer Corporation it was found that an earth orbital, 1.5 meter diameter low scattered light coronagraphic telescope can achieve a broad range of scientific objectives including the direct detection of Jupiter-sized planets around the nearby stars. Recent major advances in the understanding of coronagraphic performance and in the field of super smooth mirror fabrication allow such an instrument to be designed and built within current technology. Such a project, called the Circumstellar Imaging Telescope (CIT), is currently being proposed.

Terrile, Richard J.↗

NASA NTRS1987

Experimental study of damping of graphite epoxy composite material of the Space Telescope truss system

The truss system of the Hubble Space Telescope is made of graphite epoxy tubes and beams that have very low material damping. This paper describes a systematic experimental evaluation of the damping capacity of the graphite epoxy material used in the telescope truss system. The damping capacity of the composite material was measured both under normal and elevated temperatures in atmospheric conditions and in vacuum. Both free decay and steady state methods were used to measure the damping ratio of different specimens under different boundary conditions. A method that involves an iterative least-squares curve-fitting technique for the measured frequency response data has been developed to improve the accuracy of the damping ratio estimation. A unique experimental setup was developed to measure the damping of the material in a vacuum chamber. It was found that outgassing (moisture desorption) has little effect on the damping of the specimen. On the other hand, it was observed that temperature has a significant effect on both the damping and resonance frequencies of the specimen.

Rao, M. D.↗

NASA NTRS1988

Aberrations for grazing incidence telescopes

The wavefront aberration polynomial and transverse ray aberration expansions will be derived for grazing incidence two-mirror Wolter telescopes including all paraboloid-hyperboloid and paraboloid-ellipsoid combinations. The reference sphere is determined with the help of the principal surface of the telescope, and the aberration polynomials will be given as functions of the coordinates of the ray intersection with the reference sphere. Third -and some of the fifth-order and seventh-order aberration terms will be analyzed. Also, the well-known relationship between wavefront aberration polynomials and transverse ray aberration polynomials will be verified.

Saha, Timo T.↗

NASA NTRS1987

Hubble Space Telescope particulate optical test

The Particulate Optical Test was designed to record and measure particulate contaminants on the Hubble Space Telescope primary mirror. The objective of the test was to quantify the primary mirror particulate contamination prior to launch. The test consists of taking dark-field photographs of the primary mirror from in front of the telescope's aperture door. These photographs are subsequently digitized and analyzed to produce the areal coverage estimates. The estimated particulate areal obscuration is approximately 1.0 percent of the primary mirror surface in the usable region. This level of contamination is within the budget value of 2.5 percent and indicates that there was little increase in particulate contamination during the HST assembly process or the acoustic test period.

Metheny, Wayne↗

NASA NTRS1988

Space and lunar-based optical telescopes

The growth of space observatories, especially at optical wavelengths, during the next several decades is considered. It is concluded that large aperture optical telescopes on the Moon, possibly constructed of lunar glasses, will be very competitive with and in some instances superior to Earth orbiting telescopes.

Stockman, H. S.↗

NASA NTRS1988

Far Ultraviolot Space Telescope (FAUST)

The Far Ultraviolet Space Telescope is a compact, wide field-of-view, far ultraviolet instrument designed for observations of extended and point sources of astronomical interest. It was originally used in sounding rocket work by both French and American investigators. The instrument was modified for flight on the space shuttle and flew on the Spacelab 1 mission as a joint effort between the Laboratoire d'Astronomie Spatiale and the University of California, Berkeley. The prime experiment objective of this telescope on the Atmospheric Laboratory Applications and Science (ATLAS 1) NASA mission is to observe faint astronomical sources in the far ultraviolet with sensitivities far higher than previously available. The experiment will cover the 1300 to 1800 A band, which is inaccessible to observers on earth. The observing program during the mission consists of obtaining deep sky images during spacecraft nighttime. The targets will include hot stars and nebulae in our own galaxy, faint diffuse galactic features similar to the cirrus clouds seen by the Infrared Astronomical Satellite (IRAS), large nearby galaxies, nearby clusters of galaxies, and objects of cosmological interest such as quasars and the diffuse far ultraviolet background.

Bowyer, S.↗

NASA NTRS1987

Matching a curved focal plane with CCD's - Wide field imaging of glancing incidence X-ray telescopes

The design of a wide field imaging camera suitable for use with a glancing incidence X-ray telescope is complicated by the sharply concave nature of the optimum focal surface of such a telescope. Such a camera made up of a mosaic of CCDs is being designed which is intended for flight aboard the Advanced X-ray Astrophysics Facility (AXAF). The design rationale and tradeoffs are discussed, and the layout for the imaging CCD array is presented. The related issue of optimizing performance of transmission objective gratings is also discussed, and the array of CCD orientations suitable for this problem is presented.

Nousek, J. A.↗

NASA NTRS1988

Soft X-ray images of the solar corona with a normal-incidence Cassegrain multilayer telescope

High-resolution images of the sun in the soft X-ray to EUV regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 A. The bandpass centered at 173 A is dominated by emission from the ions Fe IX and Fe X. This emission is from coronal plasma in the temperature range (8-14) x 10 to the 6th K. The images have angular resolution of about 1.0-1.5 arcsec and show no degradation because of X-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to everlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.

Walker, Arthur B. C., Jr.↗

NASA NTRS1988

Wide field of view three-mirror telescopes having a common optical axis

Two coincident-optical-axis, three-mirror telescopes have been designed that feature relatively low focal ratios (f/2.3 and f/3), unobscured optical aperture, large circular fields of view (6 and 8 deg), good resolution, flat field, reimaging with accessible field stop, Lyot or glare stop, effective stray light suppression, and ease of spectral filter integration. The design for the f/3 telescope with 8 deg field of view has been fabricated and validated using single-point diamond-turned optics.

Johnson, R. Barry↗

NASA NTRS1988

Flight software operation of the Hubble Space Telescope fine guidance sensor

The Hubble Space Telescope (HST) is to carry five major scientific instruments to collect imagery, spectrographic, and photometric astronomical data. The Pointing Control System is designed to achieve pointing accuracies and line of sight jitter levels an order of magnitude less than can be achieved with ground mounted telescopes. This paper describes the operation of the pointing control system flight software in targeting a celestial object in a science instrument aperture and in performing the coordinate transformations necessary for commanding the fine guidance sensor and determining the attitude-error corrections.

Rodden, J. J.↗