Molecular absorption of light in Jupiter's atmosphere and the surface structure of the planetary cloud layer
Molecular absorption bands and surface structure of Jupiter atmosphere
Teifel, V. G.↗
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An Improved Solution for Integrated Array Optics in Quasi-Optical mm and Submm Receivers: the Hybrid Antenna
The hybrid antenna discussed here is defined as a dielectric lens-antenna as a special case of an extended hemi-spherical dielectric lens that is operated in the diffraction limited regime. It is a modified version of the planar antenna on a lens scheme developed by Rutledge. The dielectric lens-antenna is fed by a planar-structure antenna, which is mounted on the flat side of the dielectric lens-antenna using it as a substrate, and the combination is termed a hybrid antenna. Beam pattern and aperture efficiency measurements were made at millimeter and submillimeter wavelengths as a function of extension of the hemi- spherical lens and different lens sizes. An optimum extension distance is found experimentally and numerically for which excellent beam patterns and simultaneously high aperture efficiencies can be achieved. At 115 GHz the aperture efficiency was measured to be (76 4 +/- 6) % for a diffraction limited beam with sidelobes below -17 dB. Results of a single hybrid antenna with an integrated Superconductor-Insulator-Superconductor (SIS) detector and a broad-band matching structure at submillimeter wavelengths are presented. The hybrid antenna is diffraction limited, space efficient in an array due to its high aperture efficiency, and is easily mass produced, thus being well suited for focal plane heterodyne receiver arrays.
Buttgenbach, Thomas H.↗
Survey of Coherent Approximately 1 Hz Waves in Mercury's Inner Magnetosphere from MESSENGER Observations
We summarize observations by the MESSENGER spacecraft of highly coherent waves at frequencies between 0.4 and 5 Hz in Mercury's inner magnetosphere. This survey covers the time period from 24 March to 25 September 2011, or 2.1 Mercury years. These waves typically exhibit banded harmonic structure that drifts in frequency as the spacecraft traverses the magnetic equator. The waves are seen at all magnetic local times, but their observed rate of occurrence is much less on the dayside, at least in part the result of MESSENGER's orbit. On the nightside, on average, wave power is maximum near the equator and decreases with increasing magnetic latitude, consistent with an equatorial source. When the spacecraft traverses the plasma sheet during its equatorial crossings, wave power is a factor of 2 larger than for equatorial crossings that do not cross the plasma sheet. The waves are highly transverse at large magnetic latitudes but are more compressional near the equator. However, at the equator the transverse component of these waves increases relative to the compressional component as the degree of polarization decreases. Also, there is a substantial minority of events that are transverse at all magnetic latitudes, including the equator. A few of these latter events could be interpreted as ion cyclotron waves. In general, the waves tend to be strongly linear and characterized by values of the ellipticity less than 0.3 and wave-normal angles peaked near 90 deg. Their maxima in wave power at the equator coupled with their narrow-band character suggests that these waves might be generated locally in loss cone plasma characterized by high values of the ratio beta of plasma pressure to magnetic pressure. Presumably both electromagnetic ion cyclotron waves and electromagnetic ion Bernstein waves can be generated by ion loss cone distributions. If proton beta decreases with increasing magnetic latitude along a field line, then electromagnetic ion Bernstein waves are predicted to transition from compressional to transverse, a pattern consistent with our observations. We hypothesize that these local instabilities can lead to enhanced ion precipitation and directly feed field-line resonances.
ultra-low-frequency↗
Four-Way Ka-Band Power Combiner
A waveguide structure for combining the outputs of four amplifiers operating at 35 GHz (Ka band) is based on a similar prior structure used in the X band. The structure is designed to function with low combining loss and low total reflected power at a center frequency of 35 GHz with a 160 MHz bandwidth. The structure (see figure) comprises mainly a junction of five rectangular waveguides in a radial waveguide. The outputs of the four amplifiers can be coupled in through any four of the five waveguide ports. Provided that these four signals are properly phased, they combine and come out through the fifth waveguide port.
Perez, Raul↗
Development of highly reliable capsule type slip ring assemblies final summary report
Design materials and processes for improvement of slip ring capsule assemblies
CAPSULE↗
Discovering Jupiter. I
The current state of knowledge regarding the planet Jupiter is examined, taking into account data obtained with the aid of the spacecraft Pioneer 11. A description is given of Jupiter's weather. The Pioneer 11 pictures show that the planet's banded cloud structure breaks down above 50 deg latitude, and turns into relatively small, mostly circular cloud features in the polar regions. Attention is given to Jupiter's heat balance, aspects of internal heat flow, questions of atmospheric circulation, the turbulence in Jupiter's atmosphere, the effects of coriolis forces, Jupiter's upper atmosphere, the Great Red Spot, and the Jovian magnetosphere and radiation belts.
Source record↗
Comparative radiation resistance calculation for graded- and constant-composition n Al/x/Ga/1-x/As-p Al/z/Ga/1-z/As solar cells
The performance and radiation resistance of a new double-graded-band-gap solar cell are theoretically determined. The performance of this device is similar to that of the single-graded-band-gap cell. The power-conversion efficiencies of both graded-band-gap structures are shown to be less sensitive to minority-carrier lifetime degradation than a similar constant-composition heteroface cell.
Hutchby, J. A.↗
Directional reflectance factor distributions of a cotton row crop
The directional reflectance factor distribution spanning the entire exitance hemisphere was measured for a cotton row crop (Gossypium barbadense L.) with 39 percent ground cover. Spectral directional radiances were taken in NOAA satellite 7 AVHRR bands 1 and 2 using a three-band radiometer with restricted 12 deg full angle field of view at half peak power points. Polar co-ordinate system plots of directional reflectance factor distributions and three-dimensional computer graphic plots of scattered flux were used to study the dynamics of the directional reflectance factor distribution as a function of spectral band, geometric structure of the scene, solar zenith and azimuth angles, and optical properties of the leaves and soil. The factor distribution of the incomplete row crops was highly polymodal relative to that for complete vegetation canopies. Besides the enhanced reflectance for the antisolar point, a reflectance minimum was observed towards the forwardscatter direction in the principle plane of the sun. Knowledge of the mechanics of the observed dynamics of the data may be used to provide rigorous validation for two- or three-dimensional radiative transfer models, and is important in interpreting aircraft and satellite data where the solar angle varies widely.
Kimes, D. S.↗
GaAsP on GaP top solar cells
GaAsP on GaP top solar cells as an attachment to silicon bottom solar cells are being developed. The GaAsP on GaP system offers several advantages for this top solar cell. The most important is that the gallium phosphide substrate provides a rugged, transparent mechanical substrate which does not have to be removed or thinned during processing. Additional advantages are that: (1) gallium phosphide is more oxidation resistant than the III-V aluminum compounds, (2) a range of energy band gaps higher than 1.75 eV is readily available for system efficiency optimization, (3) reliable ohmic contact technology is available from the light-emitting diode industry, and (4) the system readily lends itself to graded band gap structures for additional increases in efficiency.
Mcneely, J. B.↗
Lidar observations of banded convection during BLX83
Lidar observations of clear-air convection during the 1983 Boundary Layer Experiment (BLX83) reveal the presence of elongated, parallel regions of updrafts marked by enhanced aerosol backscattering. These linear (banded) aerosol structures were observed over a 2-hr period during a cloud-free morning. During this period, the depth of the convective boundary layer (CBL) increased from 100 to 1300 m. Wind speeds averaged over the depth of the CBL varied between 0 and 2 m/s, while the wind direction varied over a range of 160 deg. The CBL instability parameter, -Zi/L, increased from approximately 25 (weakly unstable) to 250 (strongly unstable). The spacings of the elongated, parallel plumes scaled with the CBL height. These findings suggest that secondary circulations in the form of horizontal roll vortices were present under conditions not normally associated with roll vortices. The lines of aerosol structures aligned much more closely (within 15 deg) with the direction of the vertical shear to the horizontal wind through the depth of the CBL than with either the surface wind, mean CBL wind, or the wind at an altitude of 1.1 Zi.
Ferrare, R. A.↗
The nu(sub 6), nu(sub 7), nu(sub 8), and nu(sub 10) Bands of HO2NO2
Two new fundamental vibration-rotation bands have been observed for HO2NO2 and assigned. They are nu(sub 7) at 648 1/cm and nu(sub 8) at 466 1/cm. On the basis of these assignments the previously observed bands at 722, 801.5, and 919 1/cm are assigned to nu(sub 10), nu(sub 7) + nu(sub 12), and 2 nu(sub 8), respectively. A partial rotational analysis of the atmospherically relevant nu(sub 6) band has been carried out, and the effects of tunneling, Coriolis interactions, and hot bands on the rotational structure have been characterized.The band origin derived from this analvsisis 8O2.54(sub 3) 1/cm.
Friedl, Randall R.↗
Wave Number Selection for Incompressible Parallel Jet Flows Periodic in Space
The temporal instability of a spatially periodic parallel flow of an incompressible inviscid fluid for various jet velocity profiles is studied numerically using Floquet Analysis. The transition matrix at the end of a period is evaluated by direct numerical integration. For verification, a method based on approximating a continuous function by a series of step functions was used. Unstable solutions were found only over a limited range of wave numbers and have a band type structure. The results obtained are analogous to the behavior observed in systems exhibiting complexity at the edge of order and chaos.
Miles, Jeffrey Hilton↗
Jupiter's Deep Flowing Thermocline
The observed banded wind structure of Jupiter and Saturn remains an outstanding problem in planetary fluid dynamics. Both planets exhibit super-rotational equatorial jets (exceeding the underlying rotation of the magnetic fields tied to their deep fluid interiors), with speeds of some 100 and 400m/s, respectively, and counter-flowing lots at higher latitudes;. Recent analyses of the 1995 Galileo probe measurements, Hubble Telescope observations of the 1994 Shoemaker-Levy9 comet crash, and Earth-based infrared mapping provide evidence for a variably stratified, deeply seated flow layer. A now conceptual model for the jovian current system is proposed, in some ways resembling the oceanic thermocline, assuming a mixed distribution of potential vorticity atop a tropospheric wind layer of latitudinally variable stratification. A simple analytic version of the model links the strength, shape, and direction of the alternating zonal currents on Jupiter and Saturn to a single parameter equivalent to the internal deformation scale for an inferred deep stable region.
Allison, Michael↗
A Dynamical Model for The Jupiter Thermocline
A new conceptual model for the observed banded wind structure of the giant outer planets is proposed, assuming a smoothly distributed potential vorticity (PV) atop a layer of deeply seated, latitudinally variable stratification. With a vanishing horizontal entropy contrast presumably enforced at the bottom of the flow layer by the underlying convection, the thermal-wind balance of observed cloud-top motions implies a mapping of constant potential temperature surfaces, nearly vertical at upper tropospheric levels, down to a deeper, flatter, but variably sloped 'thermocline.' For a generally colder-poleward distribution of isentropes consistent with the strong equatorial jets of both Jupiter and Saturn, this kind of mapping would also imply a poleward decreasing static stability. The proposed temperature-stability distribution is just the reverse of the Earth's troposphere, where the strongest latitudinal potential temperature gradients are at the bottom instead of the top, with static stability generally increasing toward the pole. The warmer-stabler correlation for Jupiter would be consistent, however, with a nearly monotonic distribution of PV from low to high latitudes, over planetary scales for which the planetary vorticity dominates the relative vorticity of the jets. In this way efficient PV mixing for the isentropically bounded thermocline can account for the dynamical maintenance of the cyclonic flanks of the equatorial jet. Over latitudinal intervals comparable to the internal deformation scale, however, the gradient of the absolute vorticity is dominated by the flow curvature, with the local latitudinal gradient of the static stability proportional to the local potential temperature gradient and therefore the local variation in geostrophic velocity. The resulting correlation of velocities and vorticity gradients implies an alternation of the flow over the internal deformation radius set by the vertical entropy contrast.
Allison, Michael↗
Kilometric Continuum Radiation
Kilometric continuum (KC) is the high frequency component (approximately 100 kHz to approximately 800 kHz) of nonthermal continuum (NTC). Unlike the lower frequency portion of NTC (approximately 5 kHz to approximately 100 kHz) whose source is around the dawn sector, the source of KC occurs at all magnetic local times. The latitudinal beaming of KC as observed by GEOTAIL is, for most events, restricted to plus or minus 15 degrees magnetic latitude. KC has been observed during periods of both low and strong geomagnetic activity, with no significant correlation of wave intensity with K(sub p), index. However statistically the maximum observed frequency of KC emission tends to increase with K(sub p) index, the effect is more pronounced around solar maximum, but is also detected near solar minimum. There is strong evidence that the source region of KC is from the equatorial plasmapause during periods when a portion of the plasmapause moves significantly inwards from its nominal position. Case studies have shown that KC emissions are nearly always associated with plasmaspheric notches, shoulders, and tails. There is a recent focus on trying to understand the banded frequency structure of this emission and its relationship to plasmaspheric density ducts and irregularities in the source region.
Green, James L.↗
EIT in resonator chains: similarities and differences with atomic media
We theoretically study a parallel configuration of two interacting whispering gallery mode optical resonators and show a narrow-band modal structure as a basis for a widely tunable delay line. For the optimum coupling configuration the system can possess an unusually narrow spectral feature with a much narrower bandwidth than the loaded bandwidth of each individual resonator.
electromagnetically induced transparency↗
Cratering Equations for Zinc Orthotitanate Coated Aluminum
The final STS-125 servicing mission (SM4) to the Hubble Space Telescope (HST) in May of 2009 saw the return of the 2nd Wide Field Planetary Camera (WFPC2) aboard the shuttle Discovery. This hardware had been in service on HST since it was installed during the SM1 mission in December of 1993 yielding one of the longest low Earth orbit exposure times (15.4 years) of any returned space hardware. The WFPC2 is equipped with a 0.8 x 2.2 m radiator for thermal control of the camera electronics (Figure 1). The space facing surface of the 4.1 mm thick aluminum radiator is coated with Z93 zinc orthotitanate thermal control paint with a nominal thickness of 0.1 0.2 mm. Post flight inspections of the radiator panel revealed hundreds of micrometeoroid/orbital debris (MMOD) impact craters ranging in size from less than 300 to nearly 1000 microns in diameter. The Z93 paint exhibited large spall areas around the larger impact sites (Figure 2) and the craters observed in the 6061-T651 aluminum had a different shape than those observed in uncoated aluminum. Typical hypervelocity impact craters in aluminum have raised lips around the impact site. The craters in the HST radiator panel had suppressed crater lips, and in some cases multiple craters were present instead of a single individual crater. Humes and Kinard observed similar behavior after the WFPC1 post flight inspection and assumed the Z93 coating was acting like a bumper in a Whipple shield. Similar paint behavior (spall) was also observed by Bland2 during post flight inspection of the International Space Station (ISS) S-Band Antenna Structural Assembly (SASA) in 2008. The SASA, with similar Z93 coated aluminum, was inspected after nearly 4 years of exposure on the ISS. The multi-crater phenomena could be a function of the density, composition, or impact obliquity angle of the impacting particle. For instance, a micrometeoroid particle consisting of loosely bound grains of material could be responsible for creating the multiple craters. Samples were obtained from the HST largest craters for examination by electron microscope equipped with x-ray spectrometers to determine impactor source (micrometeoroid or orbital debris). In an attempt to estimate the MMOD particle diameters that produced these craters, this paper will present equations for spall diameter, crater depth and crater diameter in Z93 coated aluminum. The equations will be based on hypervelocity impact tests of Z93 painted aluminum at the NASA White Sands Test Facility. Equations inputs for velocities beyond the testable regime are expected from hydrocode simulations of Z93 coated aluminum using CTH and ANSYS AUTODYN.
Hyde, James↗
High Speed Intensified Video Observations of TLEs in Support of PhOCAL
The third observing season of PhOCAL (Physical Origins of Coupling to the upper Atmosphere by Lightning) was conducted over the U.S. High Plains during the late spring and summer of 2013. The goal was to capture using an intensified high-speed camera, a transient luminous event (TLE), especially a sprite, as well as its parent cloud-to-ground (SP+CG) lightning discharge, preferably within the domain of a 3-D lightning mapping array (LMA). The co-capture of sprite and its SP+CG was achieved within useful range of an interferometer operating near Rapid City. Other high-speed sprite video sequences were captured above the West Texas LMA. On several occasions the large mesoscale convective complexes (MCSs) producing the TLE-class lightning were also generating vertically propagating convectively generated gravity waves (CGGWs) at the mesopause which were easily visible using NIR-sensitive color cameras. These were captured concurrent with sprites. These observations were follow-ons to a case on 15 April 2012 in which CGGWs were also imaged by the new Day/Night Band on the Suomi NPP satellite system. The relationship between the CGGW and sprite initiation are being investigated. The past year was notable for a large number of elve+halo+sprite sequences sequences generated by the same parent CG. And on several occasions there appear to be prominent banded modulations of the elves' luminosity imaged at >3000 ips. These stripes appear coincident with the banded CGGW structure, and presumably its density variations. Several elves and a sprite from negative CGs were also noted. New color imaging systems have been tested and found capable of capturing sprites. Two cases of sprites with an aurora as a backdrop were also recorded. High speed imaging was also provided in support of the UPLIGHTS program near Rapid City, SD and the USAFA SPRITES II airborne campaign over the Great Plains.
Lyons, Walter A.↗