X-band phase calibration generator coupler

A new type of phase calibration generator (PCG) coupler was developed for the Deep Space Network (DSN) X-band antennas that can be located directly behind the feedhorn. The advantage of this is that the calibration includes more of the system. The disadvantage is that the overmoded waveguide at this location must be coupled in a mode-selective manner. Low-power and high-power PCG couplers have been successfully produced, and the RF test results from a PCG coupler are given

Calculated 70-meter antenna performance for offset L-band and C-band feeds

A series of calculations that were carried out in order to determine the performance of the new dual-shaped 70 meter antenna for feeds that are displaced from the focal ring are summarized. Calculations were carried out at 1.68 GHz (L-band) and 5.0 GHz (C-band) for a number of feed/subreflector configurations. The effects of feed displacement, feed pointing angle, subreflector tilt, and lateral subreflector movement are summarized. Of specific interest are gain, beam squint, and spillover noise temperature for each of the feed/subreflector configurations described above

SETI low-frequency feed design study for DSS 24

The Search for Extraterrestrial Intelligence Sky Survey project requires operation from 1 to 10 GHz on the beam waveguide (BWG) antenna DSS 24. The BWG reflectors are undersized in the 1- to 3.02-GHz range, resulting in poor performance. Horn designs and a method for implementing 1- to 3.02-GHz operation on DSS 24 are presented. A combination of a horn and a shaped feed reflector placed above the main reflector is suggested. The horn and feed reflector could be hidden in the RF shadow of the subreflector and struts. Results from computer analysis of this design indicate that adequate performance could be achieved

Harmonic measurements of the Galileo spacecraft X-band transmitter system

Harmonics of X-band (8.4 GHz) spacecraft transmitter systems can be used to measure the performance characteristics of higher frequency deep space communication links. The Galileo X-band transmitter system was measured at the second, third, and fourth harmonics (16.8, 25.2, and 33.6 GHz, respectively). The effective isotropic radiated power was determined to be approximately 52 dBm at 16.8 GHz, 47 dBm at 25.2 GHz, and 25 dBm at 33.6 GHz. These values can be useful, depending upon the sensitivity of the Earth-based receiving system and the distance of the spacecraft from Earth

Experimental and modal verification of an integral equation solution for a thin-walled dichroic plate with cross-shaped holes

In order to add the capability of an X-band uplink onto the 70-m antenna, a new dichroic plate is needed to replace the Pyle-guide-shaped dichroic plate currently in use. The replacement dichroic plate must exhibit an additional passband at the new uplink frequency of 7.165 GHz, while still maintaining a passband at the existing downlink frequency of 8.425 GHz. Because of the wide frequency separation of these two passbands, conventional methods of designing air-filled dichroic plates exhibit grating lobe problems. A new method of solving this problem by using a dichroic plate with cross-shaped holes is presented and verified experimentally. Two checks of the integral equation solution are described. One is the comparison to a modal analysis for the limiting cross shape of a square hole. As a final check, a prototype dichroic plate with cross-shaped holes was built and measured

X/X/Ka-band prime focus feed antenna for the Mars Observer beacon spacecraft

The results of an X/X/Ka-band feed design concept demonstration are presented. The purpose is to show the feasibility of adding a Ka-band beacon to the Mars Observer spacecraft. Scale model radiation patterns were made and analyzed

Reliability of perceptions of voice quality: evidence from a problem asthma clinic population

<p>Introduction: Methods of perceptual voice evaluation have yet to achieve satisfactory consistency; complete acceptance of a recognised clinical protocol is still some way off.</p> <p>Materials and methods: Three speech and language therapists rated the voices of 43 patients attending the problem asthma clinic of a teaching hospital, according to the grade-roughness-breathiness-asthenicity-strain (GRBAS) scale and other perceptual categories.</p> <p>Results and analysis: Use of the GRBAS scale achieved only a 64.7 per cent inter-rater reliability and a 69.6 per cent intra-rater reliability for the grade component. One rater achieved a higher degree of consistency. Improved concordance on the GRBAS scale was observed for subjects with laryngeal abnormalities. Raters failed to reach any useful level of agreement in the other categories employed, except for perceived gender.</p> <p>Discussion: These results should sound a note of caution regarding routine adoption of the GRBAS scale for characterising voice quality for clinical purposes. The importance of training and the use of perceptual anchors for reliable perceptual rating need to be further investigated.</p&gt

The L-/C-band feed design for the DSS 14 70-meter antenna (Phobos mission)

A dual-frequency (1.668 and 5.01 GHz) feed was designed for the Deep Space Station (DSS) 14 70-m antenna to support the Soviet Phobos Mission. This antenna system was capable of supporting telemetry, two-way Doppler, and very long baseline interferometry (VLBI). VLBI and two-way Doppler information on the Phobos spacecraft was acquired with this antenna in 1989

An Investigation into the Effects of Dry Etching Techniques on Changing Halftone Dot-Sizes

The purpose of this research was to investigate the effects of dry etching techniques on changing halftone dotsizes. Dry etching, or photographic color correction, has emerged in recent years as an alternative to traditional dot etching for making local corrections to color separation halftones. This study examines six factors related to dry etching. First, three types of original halftone dots were considered: laser formed (hard) dots from a Hell DC-300B scanner, laser formed (semi-hard) dots from a P.D.I, scanner, and contact screen (soft) dots from a Crosfield 510 Magnascan scanner. Second, the original dot-sizes being treated were fixed as close as possible to five target dot-sizes (5$, 25$, 50$, 75$, and 95$). Third, three types of dry etching treat ments were applied a technique of overexposure; the use of a 4-mil clear spacer film; and a technique of exposing through the base. Fourth, sixteen levels of corrective treatment were applied ranging from 1 times dot-for-dot exposure to 100 times. Fifth, two types of graphic arts films were test ed lith film and rapid access. Sixth, two generations of contact printing were compared original positive-to-inter mediate negative and intermediate negative-to-duplicate positive

Coupling of Waves, Turbulence and Thermodynamics Across the Marginal Ice Zone

LONG TERM GOALS: Long term goals are to observe and model processes controlling ice retreat in the marginal ice zone (MIZ), the narrow strip between open ocean and the ice pack where the seasonal retreat of the main ice pack takes place. It is a highly variable sea ice environment, usually comprised of many individual floes of variable shape and size and made of mixed ice types, from young forming ice to fragmented multiyear ice. The presence of sea ice significantly affects the transport of energy and momentum between the atmosphere and ocean. Deformation of sea ice absorbs atmospheric surface stress acting on the ocean surface and resulting surface features affect aerodynamic drag. Ice cover prevents the local formation of surface gravity waves and attenuates and scatters waves that propagate from the open ocean. As a result, wave motions and wave-driven flows, such as Langmuir circulations, are greatly diminished below pack ice. The albedo of sea ice is large compared to open water, and most of the incoming solar radiation incident on sea ice is reflected back to the atmosphere. The thermal conductivity of sea ice is small, so sensible energy transport between ocean and atmosphere is limited in the presence of sea ice. Specialized Autonomous Ocean Flux Buoys have been developed to study wave effects, thermodynamic responses and turbulent coupling across the coupled ocean – ice – atmosphere system in the context of the larger MIZ DRI program.Award#: N0001412WX20737 , N0001412WX2112