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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 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Thermo/structural design considerations to achieve the Large Space Telescope line-of-sight requirements

The Large Space Telescope (LST) which is scheduled for launch in 1982, is a long-life, precision-pointing, earth-orbiting satellite requiring a structural system that provides high dimensional stability, minimum thermal distortion, and minimum response to onboard dynamic environments (e.g., reaction wheels). The results of a detailed thermostructural finite element computer analysis show that the telescope structure, even though fabricated from a material with a zero coefficient of thermal expansion, must be isolated from the external structure by a three-point support (flex joints or spherical bearings will accomplish this). Other thermo/structural analysis of the metering structure showed that second-order deformations have a significant effect on the alignment of the primary and secondary mirrors.

Tenerelli, D. J.↗
NASA NTRS1976

Ultrahigh-accuracy body-pointing system for the Large Space Telescope

The Large Space Telescope (LST) is a 3-m diffraction-limited telescope. Pointing stability requirements necessary to assure diffraction-limited images are plus or minus 0.005 arc-sec, over possible experiment observation times of several hours. In order to determine whether these stringent pointing requirements could be met, a complex simulation model was defined which consisted of detailed dynamic representations of control moment gyros (CMGs) and reaction wheels (RWs), including their noise characteristics, dynamic sensor representations with sensor noise, shock mounts for the CMG actuators, a detailed representation of an image motion compensation (IMC) system, and a detailed flexible body structural model with all significant vehicle and solar panel bending modes. On the basis of both stability and performance studies utilizing this model, it was determined that a body-pointing system will meet LST requirements in the presence of CMG vibrational disturbances and sensor noise. The recommended system consists of three orthogonally mounted RWs for primary short-term control, and a cluster of CMG actuators for continuous RW desaturation and vehicle maneuvering.

Rybak, S. C.↗
NASA NTRS1976

Space Telescope science program

The advantages of an orbiting astronomical observatory are discussed. The principal consequence of having the telescope in space is that more light will be concentrated in the images, which has two effects: (1) the ability to view more accurately complex sources, and (2) the ability to detect and measure extremely faint point sources. The fact that higher resolution will reveal complex and unexpected detail is demonstrated by comparing a well-known astronomical scene with an image artifically degraded. Five scientific functions are envisaged for the Space Telescope. The first flight will feature performance of four of these functions with these four pieces of equipment: the f24 field camera, the faint object spectrograph, the infrared photometer, and the faint object camera. Astrometry will be done not by any specialized scientific instrument but with the fine guidance and pointing system.

Odell, C. R.↗
NASA NTRS1977

Anastigmatic three-mirror telescope

Proposed three-mirror telescope provides high resolution over flat image field of 1.5 degrees. Telescope also suppresses stray-light without elaborate baffling system, making it well suited for space astronomy and other high performance and low-light level applications.

Korsch, D.↗
NASA NTRS1976

Vignetting characteristics of the S-056 X-ray telescope

A ray trace analysis of the vignetting characteristics of the S-056 X ray telescope is presented. The relative energy is calculated in the spot formed in the focal plane of the S-056 X ray telescope by an off axis point source at infinity for off axis angles of 0, 1, 2, ..., 35 arc minutes. At each off axis angle, the relative energies are evaluated using theoretical X ray reflectivity curves for wavelengths of 8.34 A, 17.57 A, and 27.39 A, and also using an experimental X ray reflectivity curve for 8.34 A. The effects of vignetting due purely to the geometry of the S-056 optical system are evaluated separately, as well as jointly with the effects of mirror reflectivity.

Foreman, J. W., Jr.↗
NASA NTRS1977

An infrared foreoptics adaptor for the Learjet Telescope

A foreoptics adapter has been built for the Learjet telescope which permits simultaneous viewing of the visible star field in the image plane and acquisition of astronomical data at infrared wavelengths (less than 1 micrometer). The device uses an adjustable dichroic beamsplitter to transmit visible wavelengths to an eyepiece (or television camera), and to reflect infrared wavelengths to a port where an infrared detector system can be mounted. The instrument is intended as a multiple user facility for the Learjet telescope. This report describes the adapter and its use.

Erickson, E. F.↗
NASA NTRS1976

TV system considerations for the Space Telescope

The Space Telescope, designed as a permanent observatory in space, will be launched into orbit, maintained, and refurbished by the Space Shuttle. One of the primary instruments to fly with the telescope is the f/24 Camera. The camera's mission requirements and their impact on the choice and design of a television system are discussed, along with the system engineering aspects of the TV system design and spacecraft design. An SEC type television camera tube was selected as the primary data acquisition sensor, because of its ability to accommodate exposure times of several hours with only modest cooling.

Lowrance, J. L.↗
NASA NTRS1977

Correction of atmospheric distortion with an image-sharpening telescope

A 30 x 5 cm aperture telescope employing six movable mirrors to compensate for atmospherically induced phase distortion is built and tested. A feedback system adjusts the mirrors in real time to maximize the intensity of light passing through a narrow slit in the image plane. Essentially diffraction-limited performance is achieved when imaging both laser and white-light objects through 250 m of turbulent atmosphere. The behavior of the telescope is accurately predicted by computer simulations. The system has yet to achieve its full potential, but has already operated successfully for objects as dim as 5th magnitude.

Buffington, A.↗
NASA NTRS1977

Variation of energy throughput with off-axis angle for the S056 X-ray telescope

The S056 solar X-ray telescope, a paraboloidal-hyperboloidal Wolter type I instrument, was used in the Skylab solar observatory to photograph the sun in various soft X-ray wavelength bands. It is necessary to know how the energy throughput of the telescope varies as a function of off-axis angle at various wavelengths in order to compare the relative intensities of solar X-ray emission from various areas of the sun captured on the same photographic frame.

Foreman, J. W., Jr.↗
NASA NTRS1977

Effect of the Shuttle contaminant environment on a sensitive infrared telescope

A sensitive IR telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the IR radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter's contaminant atmosphere were used to predict its spectral radiance from 3 to 300 microns. At 350 km, statistical fluctuations in the radiation from a water vapor column, and a noise equivalent power were measured. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 to 30 microns. The column density of all IR emitting molecules can be kept low only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicate that sightings of particles 2 microns and larger in radius will not seriously hamper telescope performance provided that liquid vents and rocket firings are properly restricted.

Simpson, J. P.↗
NASA NTRS1977

Anastigmatic three-mirror telescope

A three-mirror telescope arrangement that can be corrected for four aberrations (coma, spherical aberration, field curvature, and astigmatism) is described. Geometric spot size is less than 0.1 sec of arc, in an easily accessible flat field of 1.5 deg. The primary-secondary configuration is Cassegrain-like, with the real image formed closely behind the primary. This secondary image is re-imaged by a tertiary mirror at roughly unit magnification. A small, flat mirror at the exit pupil, located between primary and tertiary, folds the light rectangularly away from the telescope axis. The shape of the large image area is helpful in space applications where several instruments may share the focal plane.

Korsch, D.↗
NASA NTRS1977

The S-054 X-ray telescope experiment on Skylab

A description of the S-054 X-ray telescope on Skylab is presented with a discussion of the experimental objectives, observing program, data reduction and analysis. Some results from the Skylab mission are given. The telescope photographically records high-resolution images of the solar corona in several broadband regions of the soft X-ray spectrum. It includes an objective grating used to study the line spectrum. The spatial resolution, sensitivity, dynamic range and time resolution of the instrument were chosen to survey a wide variety of solar phenomena. It embodies improvements in design, fabrication, and calibration techniques which were developed over a ten-year period. The observing program was devised to optimize the use of the instrument and to provide studies on a wide range of time scales. The data analysis program includes morphological studies and quantitative analysis using digitized images. A small sample of the data obtained in the mission is presented to demonstrate the type of information that is available and the kinds of results that can be obtained from it.

Vaiana, G. S.↗
NASA NTRS1977

Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit.

Smith, S. M.↗
NASA NTRS1978

Search for broad gamma ray lines with the UCR double Compton scatter telescope

The operation of a double scatter telescope and the evaluation of data obtained during a 24 hour balloon flight are discussed. An increase in gamma rays was observed as the galactic anti-center crossed the aperature of the telescope. Searches for lines from p(n,gamma)d at 2.2 MeV, C-12* at 4.4 MeV and on -16* at 6.1 MeV and for other lines broadened or redshifted are being conducted to identify the processes responsible for the production of celestial gamma rays. Two upper limits for lines in the angalactic anti-center direction at 4.4 MeV and 6.1 MeV are 6 and 4 x 10 to the minus 4 power gamma/sq cm-s.

White, R. S.↗
NASA NTRS1978

Alignment displacements of the solar optical telescope primary mirror

Solar optical telescope is a space shuttle payload which is at the present time (1978) being planned. The selected alignment method for the telescope's primary mirror is such that the six inclined legs supporting the mirror are at the same time motorized alignment actuators, changing their own length according to the alignment requirement and command. The alignment displacements were described, including circumvention of some apparent NASTRAN limitations.

Medenica, W. V.↗