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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 217 records · Page 12
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NASA NTRS1978

Infrared Astronomical Satellite /IRAS/ and Shuttle Infrared Telescope Facility /SIRTF/ - Implications of scientific objectives on focal plane sensitivity requirements

The full potential of infrared astronomy can be realized only through observations made with space-based telescopes cooled to cryogenic temperatures. The paper outlines the scientific mission, system description, and focal plane requirements for two cryogenic telescopes: the Infrared Astronomical Satellite (IRAS) and the Shuttle Infrared Telescope Facility (SIRTF). IRAS, a 60-cm superfluid-helium-cooled telescope system, will perform a one-year 8-120-micron IR sky survey; it will provide results of high reliability and sensitivity, produce the first complete survey data for the 30-120-micron region, and fill in missing portions (spectrally and spatially) of previous surveys short of 30 microns; its focal plane assembly is being designed to approach background-limited performance with an array of 62 discrete detectors. The SIRTF design will allow detailed follow-up studies in the 1-1000-micron range with a 116-160-cm observatory-class instrument. The Shuttle sortie capability introduces the unique SIRTF concept of an easily refurbishable or replaceable focal plane instrument complement in an orbiting cryogenic telescope.

Mccreight, C. R.↗
NASA NTRS1979

The Spacelab Wide Angle Telescope (SWAT)

A fast wide angle telescope that will be capable of imaging to the darker sky limit and in the ultraviolet wavelength region available above the atmosphere is described. The telescope (SWAT) has a resolution comparable to that of the large ground-based Schmidt telescope and a field of at least five degrees. A number of astrophysically important investigations can only be accomplished with such a telescope, e.g., detection of hidden, hot objects like hot white dwarfs and subwarfs in stellar binary systems, and energetic regions in globular clusters and galaxy nuclei. It permits unique studies of the UV-morphology of extended objects and allows discovery of very faint extensions, halos, jets, and filaments in galaxies. It can contribute to the investigation of dust in the Milky Way and in other galaxies and, with an objective prism, spectra of very faint objects can be obtained. The SWAT will localize objects for further study with the narrow-field Space Telescope.

West, R. M.↗
NASA NTRS1979

Design alternatives for the Shuttle Infrared Telescope Facility

The paper discusses the Shuttle Infrared Telescope Facility (SIRTF), a versatile astronomical telescope that can accomodate photometric, spectroscopic, and polarimetric measurements. It is expected to be 100 to 1000 times more sensitive than any existing infrared telescope; detailed designs of cooled IR telescopes were made for the Infrared Astronomical Satellite and the Small Helium Cooled Infrared Telescope for Spacelab 2. Rocket tests verified the capability of using superfluid helium as a cryogen in zero gravity. Constraints on funds for Shuttle payloads require an evolutionary approach to the development of the full potential of SIRTF, necessitating consideration of design alternatives involving the optical configuration, the cryogen, the mechanical structure, and size of SIRTF.

Witteborn, F. C.↗
NASA NTRS1981

A 102 cm balloon-borne telescope for far-infrared astronomical observations

In early 1971, a program was initiated to develop a balloon-borne 102-cm telescope, capable of carrying out far-infrared observations of astronomical interest above the earth's atmosphere in the wavelength range from 40 to 250 micrometers. Since 1972 the telescope has been flown and successfully recovered a total of sixteen times. Ten of the flights have produced high quality astronomical data, resulting in more than 80 hours of photometric and spectroscopic observations of numerous objects, such as H II regions, dark clouds, molecular clouds, X-ray sources, galaxies, the galactic center, planets, the Moon, and an asteroid. Attention is given to the telescope optics, the gondola, altitude control, the auxiliary attitude control system, the determination of telescope pointing position, telemetry, power requirements, the flight record, and the four instruments which are available for use on the balloon-borne telescope.

Fazio, G. G.↗
NASA NTRS1981

The Space Telescope

The Space Telescope, still under construction, is discussed in light of the constraints imposed on ground-based telescopes. The history of the Space Telescope is traced from its conceptual origin to its actual construction, and design considerations used to determine the Space Telescope construction are described. The optical system of the telescope will have an aperture of 2.4 m, a focal ratio of 24, and a front of primary to focus of 1.5 m. The fine guidance system will use astigmatic images at the edge of the field of view to provide the guidance signal for maintaining stability to 0.007 arcseconds. The guidestars are required for 85% of random fields located at the galactic poles, and the system sensitivity must meet performance specifications for stars brighter than 13.5 magnitude. The scientific instruments - the wide field camera, the faint object camera, the faint object spectrograph, the high resolution spectrograph, the high speed photometer, and the fine guidance sensors - are discussed in detail. Finally, the operations system, including schedule contraints and the Science Institute, is presented.

Odell, C. R.↗
NASA NTRS1982

A preliminary assessment of the self-induced environment and contamination of the Space Telescope

Preliminary estimates for the internal pressures and surface contamination of the Space Telescope were made. The calculations for the transient pressures in the aft-shroud and telescope compartments considered two large communicating volumes that contain gaseous sources and sinks. The outgassing sources in the aft shroud consist of several scientific instruments, paints, insulations, and graphite-epoxy structures. With the exception of the instruments, these sources also exist in the telescope compartment. the outgassing functions were generated from ample test results at various temperatures and from internal pressure measurements in a vacuum test of one of the instruments. The venting occurs through combinations of series and parallel passages in both compartments. The calculated time constant of the two volumes and their respective passages, with the telescope protective door closed, is a few seconds, which is slightly less than that of the shuttle bay volume with the bay doors closed. With the telescope door closed, the pressures in the two compartments should decay to about 1OE-5 torr in about 200 hours. The contaminant deposits were assessed on the basis of expected partial pressures of the contaminant fraction of the outgassing. These pressures and the activation energies of the source materials were used to calculate the adsorbed and condensed deposits on the surfaces as a function of time.

Scialdone, J. J.↗
NASA NTRS1983

Image motion compensation for the OSS-3/7 telescopes

The three telescope for the NASA Office of Space Science (OSS) Missions 3/7 will be clustered on the Instrument Point System (IPS). The IPS is to be mounted on a Spacelab pallet in the space shuttle orbiter. The three telescopes include the Ultraviolet Imaging Telescope (UIT), the Hopkins Ultraviolet Telescope (HUT), and the Wisconsin Ultraviolet Photopolarimetry Experiment (WUPPE). All three instruments have the ability to view from earth orbit stellar objects which are fainter than those which can be seen with ground-based telescopes. An Image Motion Compensation (IMC) system will be required for the appropriate conduct of the observations. The OSS-3/7 pointing problem is discussed, and a cost effective IMC system is proposed.

Shelton, H.L.↗
NASA NTRS1986

World Atlas of large optical telescopes (second edition)

By early 1986 there will be over 120 large optical telescopes in the world engaged in astronomical research with mirror or lens diameters of one meter (39-inches) and larger. This atlas gives information on these telescopes and shows their observatory sites on continent sized maps. Also shown are observatory locations considered suitable for the construction of future large telescopes. Of the 126 major telescopes listed in this atlas, 101 are situated in the Northern Hemisphere and 25 are located in the Southern Hemisphere. The totals by regions are as follows: Europe (excluding the USSR), 30; Soviet Union, 9; Asia (excluding the USSR), 5; Africa, 9; Australia, 6; The Pacific, 4 (all on Hawaii); South America, 17; North America, 46 (the continental US has 38 of these). In all, the United States has 42 of the world's major telescopes on its territory (continental US plus Hawaii) making it by far the leading nation in astronomical instrumentation.

Meszaros, S. P.↗
NASA NTRS1985

Optical performance of synthetic aperture telescope configurations

The diffraction-limited performances of synthetic aperture configuration arrays of four telescopes, used for coherent imaging or beam transmission, are calculated and compared. The optical performance of phased telescope arrays was found to be more sensitive to rms piston errors than to rms tilt errors. Image degradation due to pupil mapping errors imposes tight tolerances upon the structural integrity of the telescope. One part in 10,000 pupil mapping error limits the field-of-view to approximately 30 arcsec. Field curvature of the independent telescopes provides a fundamental limit to the field-of-view for phased arrays made up of two-mirror telescopes. These field-of-view limitations may profoundly affect target acquisition, tracking, or imaging applications.

Harvey, J. E.↗
NASA NTRS1986

Theoretical analysis of segmented Wolter/LSM X-ray telescope systems

The Segmented Wolter I/LSM X-ray Telescope, which consists of a Wolter I Telescope with a tilted, off-axis convex spherical Layered Synthetic Microstructure (LSM) optics placed near the primary focus to accommodate multiple off-axis detectors, has been analyzed. The Skylab ATM Experiment S056 Wolter I telescope and the Stanford/MSFC nested Wolter-Schwarzschild x-ray telescope have been considered as the primary optics. A ray trace analysis has been performed to calculate the RMS blur circle radius, point spread function (PSF), the meridional and sagittal line functions (LST), and the full width half maximum (PWHM) of the PSF to study the spatial resolution of the system. The effects on resolution of defocussing the image plane, tilting and decentrating of the multilayer (LSM) optics have also been investigated to give the mounting and alignment tolerances of the LSM optic. Comparison has been made between the performance of the segmented Wolter/LSM optical system and that of the Spectral Slicing X-ray Telescope (SSXRT) systems.

Shealy, D. L.↗
NASA NTRS1986

Cryogenic star-tracking telescope for Gravity Probe B

This paper describes the design, development and preliminary testing of the cryogenic star-tracking telescope used as an optical reference for the gyroscopes in the Gravity Probe B Relativity Gyroscope experiment. The telescope is operated at 1.8 K; it is fabricated entirely from fused quartz components held together by optical contacting; it has a physical length of 14 in., a focal length of 150 in. and an aperture of 5.6 in. Readout is by two photomultiplier chopper-detector assemblies at ambient satellite temperature. When fully operational, the telescope may be expected to have a precision approaching 0.1 milliarcsec over a linear range of 70 + or 70 milliarcsec. Its projected noise performance corresponds to an angular resolution of 1 milliarcsec in 1 Hz bandwidth. The paper includes a theoretical analysis, a description of the design and fabrication of a laboratory version of the telescope, a discussion of techniques of optical contacting, an account of vibration tests on a separate mass model of the telescope, a description of the artificial star developed for optical tests, and an account of preliminary experimental results.

Everitt, C. W. F.↗
NASA NTRS1989

Digital control of the Kuiper Airborne Observatory telescope

The feasibility of using a digital controller to stabilize a telescope mounted in an airplane is investigated. The telescope is a 30 in. infrared telescope mounted aboard a NASA C-141 aircraft known as the Kuiper Airborne Observatory. Current efforts to refurbish the 14-year-old compensation system have led to considering a digital controller. A typical digital controller is modeled and added into the telescope system model. This model is simulated on a computer to generate the Bode plots and time responses which determine system stability and performance parameters. Important aspects of digital control system hardware are discussed. A summary of the findings shows that a digital control system would result in satisfactory telescope performance.

Mccormack, Ann C.↗
NASA NTRS1990

Calibration and performance of the UCR double Compton gamma ray telescope

Results of the field calibration and performance of the UCR double Compton gamma-ray telescope are presented. The telescope is a balloon-borne instrument with an upper array of 16 plastic scintillator bars and a lower one of 16 NaI(Tl) bars. The telescope is sensitive to celestial gamma rays from 1 to 30 MeV. The data were collected on February 14, 1988 prior to launch in Alice Springs, Australia to observe SN 1987A. Radioactive sources were used to calibrate the energy deposits in the scintillators. Each bar was analyzed laterally using pulse height or timing to obtain the positions of the gamma ray interactions. Double scatter events from an Na-24 source simulating a celestial source were studied to obtain the general performance of the telescope and to develop imaging techniques, later used with the flight data. An angular resolution of 11 deg FWHM and energy resolutions of 13 and 10 percent FWHM at 1.37 and 2.75 MeV, respectively, were found. The efficiency of the telescope is 0.0035 at 1.37 MeV and zenith angle 31 deg.

Ait-Ouamer, Farid↗
NASA NTRS1990

The Hubble Space Telescope optical systems failure report

The findings of the Hubble Space Telescope Optical Systems Board of Investigation are reported. The Board was formed to determine the cause of the flaw in the telescope, how it occurred, and why it was not detected before launch. The Board conducted its investigation to include interviews with personnel involved in the fabrication and test of the telescope, review of documentation, and analysis and test of the equipment used in the fabrication of the telescope's mirrors. The investigation proved that the primary mirror was made in the wrong shape (a 0.4-wave rms wavefront error at 632.8 nm). The primary mirror was manufactured by the Perkin-Elmer Corporation (Hughes Danbury Optical Systems, Inc.). The critical optics used as a template in shaping the mirror, the reflective null corrector (RNC), consisted of two small mirrors and a lens. This unit had been preserved by the manufacturer exactly as it was during the manufacture of the mirror. When the Board measured the RNC, the lens was incorrectly spaced from the mirrors. Calculations of the effect of such displacement on the primary mirror show that the measured amount, 1.3 mm, accounts in detail for the amount and character of the observed image blurring. No verification of the reflective null corrector's dimensions was carried out by Perkin-Elmer after the original assembly. There were, however, clear indications of the problem from auxiliary optical tests made at the time. A special optical unit called an inverse null corrector, designed to mimic the reflection from a perfect primary mirror, was built and used to align the apparatus; when so used, it clearly showed the error in the reflective null corrector. A second null corrector was used to measure the vertex radius of the finished primary mirror. It, too, clearly showed the error in the primary mirror. Both indicators of error were discounted at the time as being themselves flawed. The Perkin-Elmer plan for fabricating the primary mirror placed complete reliance on the reflective null corrector as the only test to be used in both manufacturing and verifying the mirror's surface with the required precision. This methodology should have alerted NASA management to the fragility of the process and the possibility of gross error. Such errors had been seen in other telescope programs, yet no independent tests were planned, although some simple tests to protect against major error were considered and rejected. During the critical time period, there was great concern about cost and schedule, which further inhibited consideration of independent tests.

Source record↗
NASA NTRS1990

Performance of compact multilayer coated telescopes at soft X-ray/EUV and far ultraviolet wavelengths

Compact soft X-ray/EUV (XUV) and far-ultraviolet (FUV) multilayer coated telescopes have been developed for the study of the solar chromosphere corona and corona/solar wind interface. Because they operate at short wavelengths (between about 40 and 1550 A), the modest apertures of 40 to 127 mm allow observations at very high angular resolution (0.1 to 0.7 arcsec). In addition to permitting traditional normal incidence optical configurations such as Cassegrain, Ritchey-Chretien, and Herschelian to be used at XUV wavelengths, multilayer coatings also allow a narrow wavelength band to be selected for imaging. The resulting telescopes provide a very powerful and flexible diagnostic instrument for the study of both the fine scale structure of the chromosphere/corona interface and the large scale structure of the corona and corona/solar wind interface. A new solar rocket payload, the Multi-Spectral Solar Telescope Array (MSSTA), composed of 17 of these compact telescopes, was developed. This paper reports on the performance of seven MSSTA Ritchey-Chretien telescopes.

Hoover, Richard B.↗
NASA NTRS1989

Digital control of the Kuiper Atmospheric Observatory telescope

The feasibility of using a digital controller to stabilize a telescope mounted in an airplane is investigated. The telescope is a 30-in. infrared telescope mounted aboard a NASA C-141 aircraft known as the Kuiper Airborne Observatory. Current efforts to refurbish the 14-year-old compensation system have led to considering a digital controller. A typical digital controller is modeled and added into the telescope system model. This model is simulated on a computer to generate the Bode plots and time responses which determine system stability and performance parameters. Important aspects of digital control system hardware are discussed. A summary of the findings shows that a digital control system would result in satisfactory telescope performance.

Mccormack, Ann C.↗
NASA NTRS1991

Hubble Space Telescope overview

A general overview of the performance and current status of the Hubble Space Telescope is presented. Most key spacecraft subsystems are operating well, equaling or exceeding specifications. Spacecraft thermal properties, power, and communications, are superb. The only spacecraft subsystem to have failed, a gyro, is briefly discussed. All science instruments are functioning extremely well and are returning valuable scientific data. The two significant problems effecting the Hubble Space Telescope science return, the pointing jitter produced by thermally induced bending of the solar array wings and the optical telescope assembly spherical aberration, are discussed and plans to repair both problems are mentioned. The possible restoration of full optical performance of the axial scientific instruments through the use of the Corrective Optics Space Telescope Axial Replacement, currently under study for the 1993 servicing mission, is discussed. In addition, an overview of the scientific performance of the Hubble Space Telescope is presented.

Polidan, Ronald S.↗
NASA NTRS1990

Advanced technology optical telescopes IV; Proceedings of the Meeting, Tucson, AZ, Feb. 12-16, 1990. Parts 1 & 2

The present conference on the current status of large, advanced-technology optical telescope development and construction projects discusses topics on such factors as their novel optical system designs, the use of phased arrays, seeing and site performance factors, mirror fabrication and testing, pointing and tracking techniques, mirror thermal control, structural design strategies, mirror supports and coatings, and the control of segmented mirrors. Attention is given to the proposed implementation of the VLT Interferometer, the first diffraction-limited astronomical images with adaptive optics, a fiber-optic telescope using a large cross-section image-transmitting bundle, the design of wide-field arrays, Hartmann test data reductions, liquid mirrors, inertial drives for telescope pointing, temperature control of large honeycomb mirrors, evaporative coatings for very large telescope mirrors, and the W. M. Keck telescope's primary mirror active control system software.

Barr, Lawrence D.↗