Engineering topics

Warner, J. W.

Publications and source records attributed to Warner, J. W..

9 records

NASA NTRS1999

Thin Film Ba(x) Sr(1-x)TiO3 Coupled Microstrip Ku- and K-band Phase Shifters

In this report authors found that the: (1) Best room temperature CMPS performance seen on 1% Mn-doped Ba(0.6)Sr(0.4)TiO3 annealed films on MgO: K = 74 C/dB. Phase Shift/coupled length: 1427 C/cm (2) Attempt to improve phase shifters through thicker as-deposited films stymied by declining film quality with film thickness. Annealing may alleviate this problem. (3) CMPS phase shift at Ku-band didn't experience the great rise in tunability seen in 1 MHz epsilon(sub r)(0) data. (4) While CMPS circuits may be well suited for arrays, simpler circuits like CPW would be more useful for characterizing epsilon(sub r) and tan(delta) at Ku-and K-band. (5) New substrates and designs are being tested.

VanKeuls, F. W.↗

NASA NTRS1982

R associations. VI - The reddening law in dust clouds and the nature of early-type emission stars in nebulosity from a study of five associations

Positions, identification charts, UBVRIKLMN photometry and spectral types are given for stars, illuminating reflection nebulae that are visible on the POSS prints, which have been identified in five associations. With a ratio of total to selective extinction of 4.2, the reddening law applicable to the dust clouds in which the stars are embedded is steeper than normal. The five associations exhibit 18 early-type stars with circumstellar shells, of which those with spectral types earlier than B5 characteristically have weak IR excesses, in contrast to the strong excesses indicative of circumstellar dust, of later-type stars. Color-magnitude charts show a distribution lying above the ZAMS by up to about 2 mag for both the circumstellar shell stars and those classified as rapid rotators. It is suggested that (1) rapid rotation accounts for the scatter in the color-magnitude diagram, and (2) many of the nebulous early-type emission-line stars are rapid rotators rather than pre-main sequence objects.

Herbst, W.↗

NASA NTRS1981

Two young stars in L 43

Optical and infrared photometry has been obtained for the two stars (RNO 90 and RNO 91) illuminating reflection nebulae in the small, filamentary dust cloud L 43. Spectrograms of RNO 90 in the blue and red have also been obtained, which show that it is a T Tauri star. Both stars have strong infrared excesses, placing them firmly in the 'dust' position of the H - K, K - L diagram. The absorption reversals superimposed on the Balmer lines from H-alpha to H-delta in RNO 90 display an interesting effect. They appear to move progressively redward from a position near the blue edge of the emission line at H-alpha to a nearly central location at H-delta. L 43 is located near the star-forming end of the Sco OB2 association, but is relatively isolated from the major center of activity, the Rho Oph cloud. There are a large number of similar-looking small clouds in its vicinity, only one of which is known to have an associated T Tauri star (AS 209). The complexity of this, the nearest star-forming region in an OB association, is illustrated.

Herbst, W.↗

NASA NTRS1980

A very large space telescope for optical/UV astronomy

A concept is presented for a Ritchey-Chretien optical-UV telescope to be deployed in orbit using a preassembled segmented primary mirror of 8 meter aperture, carried into orbit inside the modified interstage of the Space Shuttle External Tank. Shuttle revisits allow major assembly tasks to proceed such as the installation of the light shield, fine alignment of the system and attachment of scientific instrument modules to the instrument adapter. Prime technology requirements for the VLST are assessed in this paper.

Nein, M. E.↗

NASA NTRS1980

Super-size space telescope

A class of space telescopes for astronomical observations with a resolution and collecting capability more than one order of magnitude better than what is expected from the 2.4 m Space Telescope is discussed. To this purpose aplanatic two-mirror systems of coplanar primary/secondary mirror arrangements with approximately 45 deg angles of incidence and an overall diameter of about 100 m have been designed and analyzed. The main advantages of these systems are their compactness and the associated minimization of the moment of inertia in two axes. Two opposing secondary arrangements, one forward-reflecting and the other backward-reflecting are analyzed and compared.

Korsch, D.↗

NASA NTRS1979

Scientific Research with the Space Telescope: International Astronomical Union Colloquium No. 54

The application of the space telescope for extragalactic astronomy, planetary research, and stellar, interstellar, and galactic structural problems is discussed. Topics include investigations of small solar system objects, the physical characteristics of ionized gaseous nebulae, the central regions of active galaxies and quasars, problems of cosmology, and the distribution and composition of interstellar matter.

Longair, M. S.↗

NASA NTRS1978

Photometric and spectral properties of some T Tauri stars

Photometric and spectroscopic data have been obtained for selected T Tauri members of the Taurus-Aurigae cloud and the Orion complex. A correlation between the intensity ratio of calcium and hydrogen emission lines and the infrared excess at 3.5 microns is found for these stars, which indicates a causal relationship between 'chromospheric activity' and emission processes in the circumstellar shells. It is argued that a comparison with properties of well-studied novae could lead to a better understanding of the physical structure of T Tauri stars.

Warner, J. W.↗

NASA NTRS1978

The spectral-flux distribution /0.36-3.5 microns/ of nonstellar light from the broad-line radio galaxies 3C 227 and 3C 382

Optical-infrared (0.36-3.5 microns) photometric data of the radio galaxy 3C 382, obtained in 1976, show a distinct excess at the longest wavelengths, an ultraviolet excess, and a significant increase in brightness since previous photometry by Sandage (1972). A flux excess at infrared wavelengths has also been observed from 3C 227. These properties demonstrate the presence of emission not attributable to stars, probably originating in the nucleus, extending into the infrared portion of the spectrum.

Odell, S. L.↗

NASA NTRS1977

Development of a spectral break in the nonthermal emission of AO 0235+164

Results are reported for braod-band photometry of the BL Lac object AO 0235+164 carried out over the spectral range from 0.36 to 3.5 microns in December 1975 and in October and November 1976. It is found that the continuum of this object steepened at visible wavelengths between December 1975 and October 1976, but maintained a relatively constant slope in the near-IR despite a factor-of-ten decrease in flux from the maximum level. Visible-wavelength data are cited which appear to suggest that the steepening of the visible spectrum occurred in less than 300 days, while the near-IR level may have been nearly constant. It is shown that the observed change in the spectral shape of the visible-wavelength continuum cannot be explained in terms of a 'composite' model consisting of an unchanging galaxy and a varying nonthermal source with constant spectral index. Two other general classes of models are considered: intrinsic variability and extrinsic modulation.

Odell, S. L.↗