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NASA NTRS1987

System architecture of MMIC-based large aperture arrays for space application

The persistent trend to use millimeter-wave frequencies for satellite communications presents the challenge to design large-aperture phased arrays for space applications. These arrays, which comprise 100 to 10,000 elements, are now possible due to the advent of lightwave technology and the availability of monolithic microwave integrated circuits. In this paper, system aspects of optically controlled array design are studied. In particular, two architectures for a 40 GHz array are outlined, and the main system-related issues are examined: power budget, synchronization in frequency and phase, and stochastic effects.

Herczfeld, P. R.↗

NASA NTRS1987

Star formation in Carina OB1: Observations of a giant molecular cloud associated with the eta Carinae Nebula

A giant molecular cloud associated with the eta Carinae nebula was fully mapped in CO with the Columbia Millimeter-Wave Telescope at Cerro Tololo. The cloud comples has a mass of roughly 700,000 solar mass and extends about 140 pc along the Galactic plane, with the giant Carina HII region situated at one end of the complex. Clear evidence of interaction between the HII region and the molecular cloud is found in the relative motions of the ionized gas, the molecular gas, and the dust; simple energy and momentum considerations suggest that the HII region is responsible for the observed motion of a cloud fragment. The molecular cloud complex appears to be the parent material of the entire Car OB1 Association which, in addition to the young clusters in the Carine nebula, includes the generally older cluster NGC 3325, NGC 3293, and IC 2581. The overall star formation efficiency in the cloud complex is estimated to be approximately 0.02.

Grabelsky, D. A.↗

NASA NTRS1987

Maps of millimeter wave emission from three galactic star-forming regions

In order to investigate the gas dynamics around young stellar objects, three sources were mapped which exhibit supersonic velocities in the 115 GHZ, J = 1-0 transition of CO. The maps, made with the Owens Valley Radio Observatory Millimeter Interferometer, are the highest spatial resolution images currently available of millimeter-wave continuum and line emission from the sources S106, S87, and LkHalpha101. Observations were made in the CS (J = 2-1) and C-13O (J = 1-0) transitions. In all the sources, the observations indicate that the ionized stellar wind is sweeping up ambient molecular gas. The molecular gas is found adjacent to the outer edges of the ionized winds, which originate in embedded infrared sources. From the observations presented, it may be inferred that the outflowing ionized winds are channeled by the surrounding dense, neutral gas.

Barsony, Mary↗

NASA NTRS1986

Laboratory detection of the C5H radical

The new linear molecule reported by Cernicharo et al. (1986) has been found in the same laboratory discharge in which C3H is observed, establishing conclusively that the molecule is C5H in its 2Pi ground state. Six rotational transitions in the 2Pi(1/2) ladder and four in the 2Pi(3/2), each split by lambda doubling, were observed. The twenty millimeter-wave lines were simultaneously fit by a standard Hamiltonian with five free parameters: the fine-structure constant, the rotational constant, the centrifugal distortion constant, and two lambda-doubling constants.

Gottlieb, C. A.↗

NASA NTRS1986

Spectroscopic evidence for infall around an extraordinary IRAS source in Ophiuchus

Millimeter-wave continuum observations and spectral line observations of the J = 5-4 and J = 2-1 transitions of CS toward IRAS 16293-2422, an extremely cold infrared source associated with a high-velocity molecular outflow in the Rho Ophiuchi molecular cloud, are reported. The observations indicate that this source is a dust-enshrouded object embedded in a dense, elongated configuration of molecular gas whose major axis is roughly orthogonal to the direction of the double bipolar outflow observed in it. The observations appear to provide spectroscopic evidence for significant mass infall motions associated with a young stellar object, and suggest that IRAS 16293-2422 is a true protostar.

Walker, Christopher K.↗

NASA NTRS1986

Microwave performance of a quarter-micrometer gate low-noise pseudomorphic InGaAs/AlGaAs modulation-doped field effect transistor

Excellent dc and millimeter-wave performance is reported in In0.15Ga0.85As/Al0.15Ga0.85As pseudomorphic modulation-doped field effect transistors (MODFET's) with 0.25-micron-length gates. Extrinsic transconductances as high as 495 mS/mm at 300 K and unprecedented power performance in the 60-GHz range were observed. Although not yet optimized, excellent low noise characteristics, 0.9 dB, with an associated gain of 10.4 dB at 18 GHz, and a noise figure of 2.4 dB with an associated gain of 4.4 dB at 62 GHz were obtained. This is the best noise performance ever reported for a MODFET in this frequency range. These results clearly demonstrate the superiority of pseudomorphic MODFET structures in high-frequency applications.

Henderson, T.↗

NASA NTRS1986

Conceptual design of high power Ka-band radar transmitter

A proposed conceptual design of a 400-kW CW Ka-band transmitter and associated microwave components to be used for planetary radar and serve as a prototype for future spacecraft uplinks is discussed. System requirements for such a transmitter are presented. Performance of the proposed high-power millimeter-wave tube, the gyroklystron, is discussed. Parameters of the proposed power amplifier, beam supply, and monitor and control devices are also presented. Microwave transmission-line components consisting of signal-monitoring devices, mode converter, and an overmoded corrugated feed are discussed. Finally, an assessment of the state-of-the-art technology to meet the system requirements is given, and possible areas of difficulty are summarized.

Bhanji, Alaudin↗

NASA NTRS1987

Laboratory and astronomical spectroscopy of C3H2, the first interstellar organic ring

The first laboratory and astronomical observations of the carbene ring molecule C3H2 briefly reported in a recent Letter are described in detail. In the laboratory, 22 millimeter-wave lines have been measured in a He and C2H2 discharge. From these the three rotational constants and the five fourth-order centrifugal distortion constants of C3H2 have been determined to high precision, allowing, in turn, calculation to 0.1 km/s of the most important lines in the radio and far-IR spectrum; 123 lines in the rotational spectrum with E/K less than 100 K are tabulated. Eleven astronomical transitions have been identified, and in Sgr B2 and Orion KL, rotational temperatures and column densities were derived and compared with those of other hydrocarbons with a similar number of C atoms.

Vrtilek, J. M.↗

NASA NTRS1987

The radio spectrum of cyclopropene

Twenty-eight millimeter-wave lines in the rotational spectrum of the three-membered hydrocarbon ring cyclopropene, C3H4, have been measured in the laboratory to high precision. When combined with previous measurements, these determine the rotational and centrifugal distortion constants of C3H4 sufficiently well to allow its entire radio spectrum to be calculated to an accuracy adequate for foreseeable astronomical applications, i.e., to an equivalent radial velocity of 0.1 km/s or better. With the recent discovery that the related ring C3H2 is widespread in the Galaxy, cyclopropene has become a plausible candidate for astronomical detection. Upper limits in Sgr B2 and TMC-1 indicate that in these sources C3H4 cannot be much more abundant than C3H2.

Vrtilek, J. M.↗

NASA NTRS1987

Tunable diode laser measurements of formaldehyde foreign-gas broadening parameters and line strengths in the 9-11-micron region

A tunable diode laser spectrometer has been used to determine pressure broadening coefficients due to collision with the foreign gases air, H2, O2, and N2 in the nu4 and nu6 bands of H2CO between 9 and 11 microns. Absolute line strengths for twenty-eight transitions have also been determined. The broadening coefficients are very similar to theoretical literature values in the cases of air, N2, and O2. The H2-H2CO values are in good agreement with earlier experimental millimeter-wave results.

Nadler, Shachar↗

NASA NTRS1987

Abundances in red giant stars - Carbon and oxygen isotopes in carbon-rich molecular envelopes

Millimeter-wave observations have been made of isotopically substituted CO toward the envelopes of 11 carbon-rich stars. In every case, C-13O was detected and model calculations were used to estimate the C-12/C-13 abundance ratio. C-17O was detected toward three, and possibly four, envelopes, with sensitive upper limits for two others. The CO-18 variant was detected in two envelopes. New results include determinations of oxygen isotopic ratios in the two carbon-rich protoplanetary nebulae CRL 26688 and CRL 618. As with other classes of red giant stars, the carbon-rich giants seem to be significantly, though variably, enriched in O-17. These results, in combination with observations in interstellar molecular clouds, indicate that current knowledge of stellar production of the CNO nuclides is far from satisfactory.

Wannier, P. G.↗

NASA NTRS1985

V-band IMPATT power amplifier

This program is the result of the continuing demand and future requirement for a high data rate 60-GHz communications link. A reliable solid-state transmitter which delivers the necessary power over a wide bandwidth using the present IMPATT diode technology required the development of combining techniques. The development of a 60-GHz IMPATT power combiner amplifier is detailed. The results form a basis from which future wideband, high-power IMPATT amplifiers may be developed. As a result, several state-of-the-art advancements in millimeter-wave components technology were achieved. Specific achievements for the amplifier integration were: development of a nonresonant divider/combiner circuit; reproducible multiple junction circulator assemblies; and reliable high power 60-GHz IMPATT diodes. The various design approaches and tradeoffs which lead to the final amplifier configuration are discussed. A detailed circuit design is presented for the various amplifier components, and the conical line combiner, radial line combiner, and circulator development are discussed. The performance of the amplifier, the overall achievement of the program, the implications of the results, and an assessment of future development needs and recommendations are examined.

Schell, S. W.↗

NASA NTRS1987

Mass loss

Observational evidence for mass loss from cool stars is reviewed. Spectra line profiles are used for the derivation of mass-loss rates with the aid of the equation of continuity. This equation implies steady mass loss with spherical symmetry. Data from binary stars, Mira variables, and red giants in globular clusters are examined. Silicate emission is discussed as a useful indicator of mass loss in the middle infrared spectra. The use of thermal millimeter-wave radiation, Very Large Array (VLA) measurement of radio emission, and OH/IR masers are discussed as a tool for mass loss measurement. Evidence for nonsteady mass loss is also reviewed.

Goldberg, Leo↗

NASA NTRS1987

Photochemistry and molecular ions in oxygen-rich circumstellar envelopes

A theory for the ionization of the circumstellar envelopes around O-rich red giants is developed from the photochemical model. The main source of ionization is photoionization of H2O, OH, and C by the interstellar UV radiation field, supplemented by cosmic-ray ionization of hydrogen. Significant amounts of H3O(+) and HCO(+) are produced, with peak abundances of about 10 to the -7th at intermediate distances from the star. Although H3O(+) may be difficult to detect with current instrumentation, HCO(+) is probably detectable in nearby O-rich envelopes with large millimeter-wave telescopes.

Mamon, G. A.↗

NASA NTRS1987

Ozone over McMurdo Station, Antarctica, austral spring 1986 - Altitude profiles for the middle and upper stratosphere

In the austral spring of 1986, a program of measurements of the ozone altitude profile (for the z values between 25 and 55 km), relevant to an understanding of the ozone hole, was conducted at McMurdo Station, Antarctica. The measurements were performed using ground-based millimeter-wave spectrometry. It was found that the ozone mixing ratio peaked at altitudes ranging from 28 to 34 km, with peak values between 5 and 9 ppm by volume. During the period between September 12 and October 29, the ozone mixing ratio decreased, with great variability, by about 15 percent at 25 km, with no significant decrease at higher altitudes. The observation of the depletion occurring only below 25 km is consistent with ozone-sonde observations during previous years.

Connor, Brian J.↗

NASA NTRS1987

System architecture of MMIC-based large aperture arrays for space applications

Herczfeld, P. R.↗

NASA NTRS1987

Progress in MMIC technology for satellite communications

NASA's Lewis Research Center is actively involved in the development of monolithic microwave and millimeter-wave integrated circuits (MMICs). The approach of the program is to support basic research under grant or in-house, while MMIC development is done under contract, thereby facilitating the transfer of technology to users. Preliminary thrusts of the program have been the extension of technology to higher frequencies (60 GHz), degrees of complexity, and performance (power, efficiency, noise figure) by utilizing novel circuit designs, processes, and materials. A review of the progress made so far is presented.

Haugland, Edward J.↗

NASA NTRS1961

Lunar Brightness Variations with Phase at 4.3-MM Wave Length

The lunar radio observations and interpretations of Piddington and Minnett (1949) and Gibson (1958) show that the lunar brightness variation with phase at millimeter wave lengths can be used to determine the physical properties of the lunar surface. They found that the millimeter-wave brightness lagged the optical phase, and their interpretation was that the millimeter radiation originates below a surface layer that is a very good thermal insulator. The thickness of this layer could not be determined from observations at one frequency. Observations at different frequencies give different results because of the wave-length dependence of the radio absorption by the surface material. The attenuation in the material increases with decreasing wave length, and therefore it is possible, in principle, to determine surface layer thickness from radio observations at several wave lengths. For this reason, observations of lunar radiation were started at the Naval Research Laboratory at a wave length of 4.3 mm. This is half the wave length used by Gibson (1958) in his earlier studies. The radio telescope used for these observations has been described in detail in a previous publication (Coates 1958). The antenna is a parabolic reflector 10 feet in diameter, and it has a beam width of 6.7 minutes of arc at the wave length of 4.3 mm. This is about one-fifth the diameter of the moon. The receiver was a Dicke-type radiometer.

Coates, Robert J.↗