Engineering topics
Publications and source records attributed to Miller, D..
Accurate disturbance models are necessary to predict the effects of vibrations on the performance of precision space-based telescopes, such as the Space Interferometry Mission (SIM).
We present the development of a low noise superconductor insulator superconductor (SIS) mixer for the 1.1 - 1.25 THz heterodyne receiver of FIRST space radiotelescope. The quasi-optical SIS mixer has two NbTiN/AlN/Nb junctions with critical current density 30 kA/sq cm. The individual junction area is close to 0.65 square micrometers. The SIS junctions are coupled to the optical input beam through a planar double slot antenna and a Si hyperhemispherical lens. The minimum DSB receiver noise temperature is 650 K, about 12 hv/k.
We prevent the development of a low noise SIS mixer for the 1.1-1.25 THz heterodyne receiver of FIRST space radiotelescope.
The holographic scanning lidar HARLIE made continuous measurements of aerosol and cloud one-micron backscatter and derived the horizontal wind speed and direction at cloud height over the ARM (SGP) site during the water vapor campaign WVIOP, September 17 - October 6, 2000. Whenever possible, these measurements were compared with Loran-C winds as measured by the routine launches of Vaisala radiosonde balloons scheduled by the ARM project. Taken overall, the agreement between these two types of observation is excellent, which could be taken merely as a validation of the relatively new HARLIE technique. However, the detailed comparison for a given sonde launch clearly requires that, out of the HARLIE data which are taken all the time at all altitudes, one must select those segments that match the altitude-time trajectory of the sonde. Moreover, the conical HARLIE scan at a 45 deg. elevation angle covers a wide area that is more representative of the average wind conditions above the site than the isolated track of the sonde's ascent. We suggest that the HARLIE instrument offers a more general and improved representation of the horizontal wind profile whenever there is sufficient backscatter by clouds and aerosols for lidar operation. HARLIE is a rugged and compact lidar that operates from aircraft as well as from the ground and has been used in several meteorological campaigns. As a "direct detection" lidar, HARLIE does not require the complexity of a coherent detection system. The data reduction algorithms facilitate the rapid and accurate determination of wind speed and direction at all altitudes. Wind measurements and HARLIE performance data from WVIOP 2000 and other campaigns will be presented.
Accurate disturbance models are necessary to predict the effects of vibrations on the performance of precision space-based telescopes, such as the Space Interferometry Mission (SIM).
We have developed a low-noise 850 GHz superconductor-insulator-superconductor (SIS) quasi-particle mixer with NbTiN thin-film microstrip tuning circuits and hybrid Nb/AlN/NbTiN tunnel junctions. The mixer uses a quasioptical configuration with a planar twin-slot antenna feeding a two-junction tuning circuit. At 798 GHz, we measured an uncorrected double-sideband receiver noise temperature of T(sub RX) = 260 K at 4.2 K bath temperature. This mixer outperforms current Nb SIS mixers by a factor of nearly 2 near 800 GHz. The high gap frequency and low loss at 800 GHz make NbTiN an attractive material with which to fabricate tuning circuits for SIS mixers. NbTiN mixers can potentially operate up to the gap frequency, 2(delta)/h is approximately 1.2THz.
In 1996 and 1997 the Galileo Ultraviolet Spectrometer (UVS) obtained the first measurements of Jupiter's nightside midultraviolet (MUV) polar auroral spectrum from 1620 to 3231 A at 13 A resolution.
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In 1996 during the first four orbits of the satellite tour the Galileo ultraviolet spectrometer (UVS) (1130-4320 A) and extreme ultraviolet spectrometer (EUVS)(540-1280 A) performed near-simultaneous observations of the Jupiter aurora in both the north and south polar regions.
There are three general approaches to evaluating sleep disturbance in regards to noise: subjective, behavioral, and physiological. Subjective methods range from standardized questionnaires and scales to self-report measures designed for specific research questions. There are two behavioral methods that provide useful sleep disturbance data. One behavioral method is actigraphy, a motion detector that provides an empirical estimate of sleep quantity and quality. An actigraph, worn on the non-dominant wrist, provides a 24-hr estimate of the rest/activity cycle. The other method involves a behavioral response, either to a specific probe or stimuli or subject initiated (e.g., indicating wakefulness). The classic, gold standard for evaluating sleep disturbance is continuous physiological monitoring of brain, eye, and muscle activity. This allows detailed distinctions of the states and stages of sleep, awakenings, and sleep continuity. Physiological delta can be obtained in controlled laboratory settings and in natural environments. Current ambulatory physiological recording equipment allows evaluation in home and work settings. These approaches will be described and the relative strengths and limitations of each method will be discussed.
We have detected the 626 GHz J = 1 approaches 0 transition of hydrogen chloride (H(sup 35)Cl) in absorption against the blending of the three hyperfine components of this transition by the velocity profile of Sgr B2 observed in other species. The apparent optical depth of the line is tau approximately equal to 1, and the minimum HCl column density is 1.6 x 10(exp 14)/sq cm. A detailed radiative transfer model was constructed which includes collisional and radiative excitation, absorption and emission by dust, and the radial variation of temperature and density. Good agreement between the model and the data is obtained for HCl/H2 approximately 1.1 x 10(exp -9). Comparison of this result to chemical models indicates that the depletion factor of gas-phase chlorine is between 50-180 in the molecular envelope surrounding the SgrB2(N) and (M) dust cores.
We discuss airborne observations of rotational transitions of various hydride molecules in the interstellar medium, including H2O-18 and HCl. The detection of these transitions is now feasible with a new, sensitive submillimeter receiver which has been developed for the NASA Kuiper Airborne Observatory (KAO) over the past several years.
We have constructed a sensitive submillimeter receiver for the NASA Kuiper Airborne Observatory (KAO) which at present operates in the 500-750 GHz band. The DSB receiver noise temperature is about 5 h nu/k(sub B) over the 500-700 GHz range. This receiver has been used to detect H2O(18)O, HCl, and CH in interstellar molecular clouds, and also to search for C(+) emission from the highly redshifted galaxy (z = 2.3) IRAS 10214.
Technically speaking, an acronym is an abbreviation that is pronounced as word, made up of the first letters of first parts of the words in a term, while an initialism is an abbreviation that is not pronounced as a word, made up of the first letters of the words in a term. So what really determines whether an abbreviation in an acronym or an initialism? I am going to call all these abbreviations acronyms(omega)s does the rest of the world.
Many questions of lunar science remain unanswered because of a lack of specific data. With the potential for returning humans to the Moon and establishing a long-term presence there, a new realm of exploration is possible. Numerous plans have been outlined for orbital and surface missions. The capabilities and objectives of a small class of rovers to be deployed on the lunar surface are described. The objective of these small rovers is to collect detailed in situ information about the composition and distribution of materials on the lunar surface. Those data, in turn, would be applied to a variety of lunar geoscience questions and form a basis for planning human activities on the lunar surface.
The Isothermal Dendritic Growth Experiment, which is expected to fly on the Space Shuttle to study dendritic solidification of molten metals such as iron and aluminum, is examined. Succinonitrile and pivalic acid are substitued for metals to permit visualiztion of dendritic growth. The technical features of the apparatus are described, including temperature control, the photographic system, and slow scan television. The teleoperations techniques for the experiment are discussed in detail.
A dynamic test loop is designed to evaluate the thermal stability of an organic Rankine cycle working fluid, toluene, for potential application to the Space Station power conversion unit. Samples of the noncondensible gases and the liquid toluene were taken periodically during the 3410 hour test at 750 F peak temperature. The results obtained from the toluene stability loop verify that toluene degradation will not lead to a loss of performance over the 30-year Space Station mission life requirement. The identity of the degradation products and the low rates of formation were as expected from toluene capsule test data.
The differential flux of the hydrogen and helium isotopes was measured using an instrument on the ISEE-3 spacecraft during solar quiet time periods from August 1978 through December 1983. These measurements cover the energy range from 26 MeV/nucleon through 138 MeV/nucleon for both H-1 and He-4, from 24 to 89 MeV/nucleon for H-2, and from 43 to 146 solar activity varied from near minimum to maximum conditions causing the observed flux of galactic cosmic rays to modulate by an order of magnitude. To describe the propagation in the galaxy, it was found that the standard leaky box approximation with an escape path length of 6.7 g/sq cms forms a self consistent model for the light cosmic ray nuclei at the observed energies.