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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Low energy gamma ray observations with the MPI-Compton telescope

Although the evaluation of data from the first balloon-flight of a large area Compton telescope is incomplete, two preliminary results are discussed. From the measured background spectrum at float altitude, the sensitivity of the telescope for the detection of cosmic gamma ray lines is estimated. The energy spectra is determined for an enhanced gamma ray flux observed from the direction of the Seyfert galaxy NGC 4151. A schematic drawing of the telescope is presented and discussed.

Graml, F.↗
NASA NTRS1978

Direct imaging of extra-solar planets with stationary occultations viewed by a space telescope

The use of a telescope in space to detect planets outside the solar system by means of imaging at optical wavelengths is discussed. If the 'black' limb of the moon is utilized as an occulting edge, a hypothetical Jupiter-Sun system could be detected at a distance as great as 10 pc, and a signal-to-noise ratio of 9 could be achieved in less than 20 min with a 2.4 m telescope in space. An orbit for the telescope is proposed; this orbit could achieve a stationary lunar occultation of any star for a period of nearly two hours.

Elliot, J. L.↗
NASA NTRS1979

World atlas of large optical telescopes

By 1980 there will be approximately 100 large optical telescopes in the world with mirror or lens diameters of one meter (39 inches) and larger. This atlas gives information on these telescopes and shows their locations on continent-sized maps. Observatory locations considered suitable for the construction of future large telescopes are also shown.

Meszaros, S. P.↗
NASA NTRS1978

Experimental investigation of contamination prevention techniques for a cryogenically cooled telescope in earth-orbit

A one-tenth scale model of the Shuttle Infrared Telescope Facility (SIRTF) was constructed to experimentally investigate the feasibility of a helium purge system to reduce contamination on cryogenic surfaces. The on-orbit ambient contaminant environment was simulated with ion beams of N2(+), O(+) and H2O(+). Helium was injected into the model telescope at the simulated plane of the primary optics using two techniques: a) porous plug, b) nozzle. Helium flow rates and telescope pressures were varied to determine the purge effectiveness against potential contaminants. Based on the subscale results, a 90% reduction in O, N2, and H2O at the primary optics of the SIRTF can be obtained using 20 K helium with a pressure of .00001 torr and a flow rate of less than 0.1 g/s.

Hetrick, M. A.↗
NASA NTRS1978

Large multi-lensed telescope - A receiver for point sources in the sky

A large 80-in. (2-meter) multilensed computer-controlled and encoder-pointed telescope is described. It is being used as the receiver in the high-performance lunar laser ranging station on Mt. Haleakala on the island of Maui, Hawaii; however, it could also be used for other astronomical applications when the moon is not up. This telescope, which was designed for applications requiring aperture but not field, could affect the design of future very large astronomical instruments intended mainly for point-source spectroscopy and similar applications. The telescope and its performance to date are discussed.

Faller, J. E.↗
NASA NTRS1979

A CCD star sensor for fine pointing control of spaceborne telescopes

A star sensor for measuring small pointing errors in astronomical telescopes is described. By using solid state imaging arrays (CCDs) to track guide star images, this design realizes a number of performance advantages relative to more conventional approaches. Specific topics include star image position measurement, CCD sensitivity including color effects, and performance simulation results. Experimental results for CCDs operating at temperatures below 100 K are also summarized. Two telescope configurations are considered to illustrate the range of possible applications of this technology: (1) a large orbiting telescope for general astronomy requiring a multi-CCD sensor, and (2) a Space Shuttle-based infrared observatory operating at 20 K. Although the requirements and configurations of these applications are widely different, the CCD approach offers substantial advantages to both systems.

Stanton, R. H.↗
NASA NTRS1979

A 1.2 meter balloon-borne telescope for a submillimeter wave sky survey

A balloon-borne, 1.2 meter Cassegrain telescope designed for diffraction-limited imagery at 100 microns is being developed for a survey of the Galactic plane at submillimeter wavelengths. The telescope pointing system is servocontrolled using a gyroscope for the primary stabilization reference. Extensive use is made of microprocessors for flight sequencing, pointing control and stabilization, and telemetry formatting. A description of the telescope, helium-cooled detectors, and the orientation subsystems are presented together with a brief discussion of the proposed astronomical observations.

Silverberg, R. F.↗
NASA NTRS1979

A cryogenically-cooled, balloon-borne far infrared survey telescope

The design and performance of the Arizona cryogenically-cooled, balloon-borne, multiband far infrared survey telescope are described. The 40 cm Cassegrain telescope is completely contained in a liquid helium dewar. The focal plane array consists of Fabry optics and four detectors which each have a 12 arc minute field of view. Both photoconductive and bolometer detectors are utilized at effective wavelengths of 20, 80, 100 and 150 microns. In 1977 the telescope was used to make multicolor large scale maps of 70 square degrees in the Cygnus X region and the W3 region.

Campbell, M. F.↗
NASA NTRS1980

High resolution imaging at large telescopes

Image recovery at a resolution limited only by diffraction is now possible at large telescopes. The theory of speckle image reconstruction is explained and the current status of a video recording and digitization system for the reconstruction procedure is described. Potential applications of the process when used with very large telescopes are discussed. The constraints on telescope design imposed by these techniques are listed.

Nisenson, P.↗
NASA NTRS1979

Space telescope, a long-life free flyer

The paper describes NASA's Space Telescope (ST) adapted to Shuttle capabilities for launch and retrieval which utilizes the full Shuttle cargo bay space available for payloads and can be returned to the ground for refurbishment. Its objective is to maximize ST's productive lifetime, to probe the universe, and to analyze light from energy sources which cannot be studied by ground-based telescopes. The Shuttle orbiting lifetime will be extended to at least five years, and scientific instruments or failed spacecraft components will be replaced on-orbit. The ST will be returned to earth for major overhauls, refurbished, and relaunched. In summary, the Shuttle will allow space astronomy to be accomplished in the usual manner - by observing, adjusting, changing detectors, and reobserving. The support systems module, the optical telescope assembly, scientific instruments, including the wide field/planetary camera, the faint object spectrograph and the high speed photometer are described.

Field, E. L.↗
NASA NTRS1979

Infrared telescope on Spacelab 2

The infrared telescope (IRT) on Spacelab 2 which will be the first cryogenically cooled telescope operated from the Orbiter is discussed. Its objectives are to measure the induced environment about the Orbiter and to demonstrate the ability to manage a large volume of superfluid helium in space. The prime astrophysical objectives are to map extended sources of low surface brightness infrared emission, including the zodiacal light, the galactic plane, and extragalactic regions. The IRT design is described, including the f/4 15.2 cm highly baffled Herschelian telescope cooled to 8 K which may scan to within 35 deg of the sun. The focal plane cooled to 3 K consists of nine discrete photoconductors covering the wavelength of 4.5-120 microns in five bands, with a single stellar detector used for aspect determination. Overlapping scans, contiguous orbits, and a six degree per second scan rate permit rapid redundant coverage of 60 % of the sky.

Koch, D.↗
NASA NTRS1979

Spacelab 2 infrared telescope cryogenic system

The paper discusses the development of a cryogenic helium system to provide cooling to a scanning infrared telescope for the Spacelab 2 mission. The infrared optical/detector system and related electronics are being developed by the Smithsonian Astrophysical Observatory and the University of Arizona. A superfluid helium dewar and porous plug phase separator permit gas cooling of the infrared focal plane assembly to about 2.5 K, and of the two telescope sections to 8 K and 60 K. The design of the cryogenic system,including a commandable vacuum cover, and the prelaunch liquid helium servicing and maintenance approach were discussed. It is concluded that the system will satisfy the Infrared Telescope requirements, and the superfluid helium system shall be capable of satisfying cryogenic helium cooled requirements for the next several years.

Urban, E. W.↗
NASA NTRS1980

Lensless scanning telescope

A lensless scanning telescope composed of two circular apertures and having good response with minimum aliasing is described. By analogy with an arrangement of two slits, the modulation transfer function (MTF) of this telescope is derived. The MTF of a lensless telescope scanning the earth's surface from 500-km orbit is developed for both the scan and cross-scan directions. Response of 48% or better at 100-km wavelength in both directions is shown with aliasing errors due to sampling of 1% or less.

Edwards, H. B.↗
NASA NTRS1978

Simulation of the Infrared Astronomical Satellite /IRAS/ telescope system

The Infrared Astronomical Satellite (IRAS), a joint Dutch-British-U.S. project scheduled for launch in February 1981, will conduct the first all-sky infrared survey between 8 and 120 microns using a 60-cm aperture, cryogenically-cooled telescope. A computer simulation program has been developed at Ames Research Center to aid in the design of this complex telescope. The development and implementation of the IRAS Telescope Simulator (IRTS), its input data sources, and its output data products are described.

Henderson, E.↗
NASA NTRS1980

Payload maintenance cost model for the space telescope

An optimum maintenance cost model for the space telescope for a fifteen year mission cycle was developed. Various documents and subsequent updates of failure rates and configurations were made. The reliability of the space telescope for one year, two and one half years, and five years were determined using the failure rates and configurations. The failure rates and configurations were also used in the maintenance simulation computer model which simulate the failure patterns for the fifteen year mission life of the space telescope. Cost algorithms associated with the maintenance options as indicated by the failure patterns were developed and integrated into the model.

White, W. L.↗
NASA NTRS1980

Cerenkov x total energy telescopes for the study of the mass composition of cosmic rays

The mass resolution attainable with cosmic ray telescopes employing Cerenkov counters for velocity measurement was examined. It is shown that in most cases, the limiting mass resolution is determined by the resolution of the Cerenkov counter. The resolution achieved in the UNH telescope flown on a balloon in 1977 is studied as a function of charge and energy. This telescope determines the mass using the Cerenkov x total energy technique. It is shown that the mass resolution for heavier nuclei can be accurately predicted using the response of the Cerenkov counter to sea level mu-mesons. The actual in flight resolution for heavier nuclei, including broadening effects, may be predicted using the beta = 1 Cerenkov distributions, and independently by studying the distribution function of the differences of the two banks of photomultipliers employed on each Cerenkov counter.

Webber, W. R.↗
NASA NTRS1981

Scientific management of Space Telescope

A historical summay is given on the science management of the Space Telescope, the inception of which began in 1962, when scientists and engineers first recommended the development of a nearly diffraction limited substantial-size optical telescope. Phase A, the feasibility requirements generation phase, began in 1971 and consisted largely of NASA scientists and a NASA design. Phase B, the preliminary design phase, established a tiered structure of scientists, led by the Large Space Telescope operations and Management Work Group. A Mission Operations Working Group headed six instrument definition teams to develop the essential instrument definitions. Many changes took place during Phase B, before design and development, which began in 1978 and still continues today.

Odell, C. R.↗
NASA NTRS1979

Testing of the Kuiper Airborne Observatory 91-CM telescope

The 91 cm telescope of the Kuiper Airborne Observatory was tested for optical figure errors in the surface of the mirrors and misalignment of the optical components. When the present set of optical components are installed in the telescope in proper alignment, the telescope produces an image with 80% of the energy in a circle of 1.50 arc seconds in diameter; that is, a 0.11 mm spot diameter in the focal plane. The primary mirror, an f/2 parabola, was tested against a flat and has a quality that puts 80% of the energy in a 0.51 arc second diameter spot. Two principal sources account for the residual error: the tertiary folding flat and the chopping secondary. It appears that the method of mounting the folding flat causes some distortion and that the secondary mirror has some residual spherical aberration in its figure.

Parks, R. E.↗