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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Large deployable reflector: An infrared and submillimeter orbiting observatory

The Large Deployable Reflector (LDR) is to be a dedicated astronomical observatory in space. It will operate in the 1 mm to 30 micron wavelength region where the Earth's atmospheric opacity makes ground-based observations nearly impossible. The primary mirror will be 20 m in diameter, made up of 37 individual segments. The reflector will be actively controlled to provide an overall surface accuracy of less than or approximately 2 microns. The LDR will be placed in orbit by the Space Shuttle and revisited at approximately 2 year intervals during its 10 year lifetime.

Swanson, P. N.↗
NASA NTRS1982

Plans for a large deployable reflector for submillimeter and infrared astronomy from space

Continuing plans for a large deployable reflector (LDR), conceived as a 10- to 30-m-diameter clear-aperture telescope, operating at wavelengths from 1000 microns to a diffraction-limited 30 microns, and to be placed in orbit for a life of 10 years by the Space Shuttle, are discussed. The primary reflector will be composed of a number of closely packed hexagonal segments of glass or lightweight composite material and attached to a truss integrating structure through position actuators providing three degrees of freedom for each segment. Technical aspects of optical design, surface measurement systems, deployment, and detectors are discussed, as are practical and fiscal limitations.

Swanson, P. N.↗
NASA NTRS1983

First detection of the ground-state J(K) = 1(0)-0(0) submillimeter transition of interstellar ammonia

The JK = 1 sub 0 approaching 0 sub 0 transition of ammonia at 572.5 GHz was detected in OMC-1 from NASA's Kuiper Airborne Observatory. The central velocity of the line (VLSR approximately = 9 km/s) indicates that it originates in the molecular cloud material, not the hot core. The derived filling factor of approximately 0.09 in a 2' beam implies a source diameter of approximately 35' if it is a single clump. This clump area is much larger than that derived from observations of the sub 1 inversion transition. The larger optical depth in the 1 sub 0 approaching 0 sub 0 transition (75-350) can account for the increased source area and linewidth as compared with those seen in the 1 sub 0 inversion transition. Previously announced in STAR as N83-25630

Keene, J.↗
NASA NTRS1984

Dielectric based submillimeter backward wave oscillator circuit

A ladder circuit especially useful in backward wave oscillators operating in the 500 GHz to 2000 GHz range has a waveguide with transversely orientated slabs which contact an upper wall of the waveguide. The edges of the slabs adjacent to the physical center of waveguide are curved segments and stubs of electrically conductive, nonmagnetic material. The ends of slabs include metal layers at opposite ends to provide a conductive leakage path. A ridge bar is attached to the inside of the bottom wall of the waveguide and includes a concave upper surface which partially straddles the electron beam. The novelty of the invention lies in the ladder structure compared of thin, vapor deposited rungs supported on the edge of diamond slabs; each rung having a curved segment which straddles the electron beam together with a ridge bar which also straddles the electron beam.

Kosmahl, H. G.↗
NASA NTRS1984

Submillimeter wavelength survey of the galactic plane from l = -5 deg to l = +62 deg: Structure and energetics of the inner disk

Results from a large scale survey of the first quadrant of the Milky Way galactic plane at wavelengths of 150, 250, and 300 microns with a 10x10 arcmin beam are presented. The emission detected in the survey arises from compact sources, most of which are identified with known peaks of 5 GHz and/or CO emission, and from an underlying diffuse background with a typical angular width of approximately 0.9 deg (FWHM) which accounts for most of the emission. A total of 80 prominent discrete sources were identified and characterized, of which about half were not previously reported at far infrared wavelengths. The total infrared luminosity within the solar circle is approximately 1 to 2x10 to the 10th power L sub 0, and is probably emitted by dust that resides in molecular clouds.

Hauser, M. G.↗
NASA NTRS1983

Large Deployable Reflector (LDR) - A concept for an orbiting submillimeter-infrared telescope for the 1990s

The history and background of the Large Deployable Reflector (LDR) are reviewed. The results of the June 1982 Asilomar (CA) workshop are incorporated into the LDR science objectives and telescope concept. The areas where the LDR may have the greatest scientific impact are in the study of star formation and planetary systems in the own and nearby galaxies and in cosmological studies of the structure and evolution of the early universe. The observational requirements for these and other scientific studies give rise to a set of telescope functional requirements. These, in turn, are satisfied by an LDR configuration which is a Cassegrain design with a 20 m diameter, actively controlled, segmented, primary reflector, diffraction limited at a wavelength of 30 to 50 microns. Technical challenges in the LDR development include construction of high tolerance mirror segments, surface figure measurement, figure control, vibration control, pointing, cryogenics, and coherent detectors. Project status and future plans for the LDR are discussed.

Swanson, P. N.↗
NASA NTRS1983

Submillimeter-wave receivers - A status report

A development status assessment is presented for the work of U.S. and Western European research groups on heterodyne sub-mm receivers in the 300-1000 GHz frequency range. The applications driving sub-mm receiver and local oscillator source technologies are radio astronomy, atmospheric measurements, plasma diagnostics, and laboratory spectroscopy. Progress is concentrated in two areas, cooled Schottky diode mixers and solid state local oscillators employing frequency multipliers.

Wilson, W. J.↗
NASA NTRS1984

Far-infrared and submillimeter observations of the low-luminosity protostars L1455 FIR and L1551 IRS 5 - The confinement of bipolar outflows

Far-IR observations of L1455 FIR and L1551 IRS 5 obtained in December, 1981, and in September, 1982, and January, 1983, respectively, using the H-1 and G-2 bolometer systems on the 91-cm telescope of the NASA Kuiper Aiborne Observatory are reported. Additional observations at 400 microns were obtained with UKIRT in November, 1981, (L1551) and with NASA IRTF in November, 1982 (L1455). The results are presented in tables and graphs, and L1455 and L1551 are compared with other objects in terms of central-star parameters, clouds, and overflows. The characteristics calculated for L1455 and L1551 include luminosity 1.5 and 23 solar luminosity, size less than 7 x 10 to the 16th cm, H2 density greater than or equal to 4 x 10 to the 5th and 1 x 10 to the 6th/cu cm, and 35-K dust cores of 0.2 and 0.7 solar mass, respectively. The bipolar appearance of the L1551 outflow is attributed to circumstellar material only.

Davidson, J. A.↗
NASA NTRS1982

Airborne far-infrared and submillimeter spectroscopy

This paper is a review of airborne spectroscopic observations in the wavelength range 18-800 microns, and the instruments on the NASA Kuiper Airborne Observatory with which they were carried out. Recent measurements of spectral lines of ions, atoms and molecules are presented and discussed.

Watson, D. M.↗
NASA NTRS1984

Characterization of a dual-mode horn for submillimeter wavelengths

A simple dual-mode conical horn has been developed and tested at 0.5, 1.4, 3.1, and 34.2 mm. The horn has nearly equal beam shape in the E and H plane far-field patterns, with a 3-dB half angle of 6 deg. At 34.2 mm, the waveguide reflection loss and the phase center have been determined.

Pickett, H. M.↗
NASA NTRS1984

The millimeter and submillimeter laboratory spectrum of methyl formate in its ground symmetric torsional state

Over 200 rotational lines of methyl formate in its ground (v sub t = 0), symmetric (A) torsional state have been measured in the frequency range 140-550 GHz. Analysis of these and lower frequency transitions permits accurate prediction (below 0.1 MHz) of over 10,000 transitions at frequencies below 600 GHz with angular momentum J lower than 50. The measured spectral lines have permitted identification of over 100 new methyl formate lines in Orion.

Plummer, G. M.↗
NASA NTRS1984

Temporal variations in the solar submillimeter continuum

Observations of local intensity variations in the 300-800 micron solar continuum are presented. Two-beam difference observations were used to determine power spectrum statistics of small temporal variations over the frequency range 0.1-20 mHz. A significant enhancement in spectral power (about 5 K rms) is found for frequencies between 3 and 7 mHz. These and higher frequency variations are attributed to adiabatic response of the chromospheric medium to compression waves.

Kaminski, C.↗
NASA NTRS1984

Laboratory submillimeter transition frequencies of Li-7H and Li-6H

The fundamental (J = 1 - 0) rotational transition frequencies of Li-7H and Li-6H in their ground (v = 0) vibrational states and of Li-7H in its first excited (v = 1) vibrational state have been measured in the laboratory. Use of these transition frequencies should permit astronomical investigations of LiH abundances in red giant stars of high lithium abundance.

Plummer, G. M.↗
NASA NTRS1984

Cryogenic metal mesh bandpass filters for submillimeter astronomy

The design and performance of a tunable double-half-wave bandpass filter centered at 286 microns (Delta lambda/lambda = 0.16) and operating at cryogenic temperatures (for astronomy applications) are presented. The operating principle is explained, and the fabrication of the device, which comprises two identical mutually coupled Fabry-Perot filters with electroformed Ni-mesh reflectors and is tuned by means of variable spacers, is described. A drawing of the design and graphs of computed and measured performance are provided. Significantly improved bandpass characteristics are obtained relative to the single Fabry-Perot filter.

Dragovan, M.↗
NASA NTRS1984

Far-infrared and submillimeter survey of the galactic plane from l = 11.5 deg to l = 17.5 deg

Medium resolution (11 min) maps of the galactic plane are presented from l = 11.5 deg to l = 17.5 deg at wavelengths of 93 microns, 154 microns, and 190 microns. The maps are interpreted in terms of the temperature and spatial structure of diffuse far-infrared/submillimeter sources associated with evolved H II regions and a continuous ridge of galactic emission. The emission regions are found to be more extended at the longer wavelengths which implies that there must be a range of dust temperatures in the sources. The properties of the galactic ridge are similar to those of the sources.

Campbell, M. F.↗