摘要:

ADA is an instrument the principle of which is based on empirical relations among rainfall rate, reflectivity, and attenuation. It is used in connection with a weather radar which provides a display of the attenuation due to rain at 10 GHz over the radar line of sight. With ADA a large amount of data applicable to the assessment and design of satellite communication systems can be accumulated in a relatively short period of time. It is estimated that the ADA‐measured attenuations, expressed in decibels, are accurate to within a factor of tw

ISSN:0048-6604    

DOI:10.1029/RS007i006p00619

年代:1972

数据来源: WILEY

摘要:

Calculations of the propagation delay due to the atmosphere in satellite‐to‐earth communication are reported for the frequency range 1 to 15 GHz. A spherically symmetric, smoothly varying model is assumed for the atmosphere, and the techniques of geometrical optics are employed. The difference between the actual propagation delay and the delay which would occur in free space is presented for the lower atmosphere, the ionosphere, and the composite atmosph

ISSN:0048-6604    

DOI:10.1029/RS007i006p00625

年代:1972

数据来源: WILEY

摘要:

Attenuation due to rain at 10 GHz over the radar line of sight has been measured automatically during the past three summer seasons. Data from five months were analyzed to give statistics on the frequency of occurrence, the extent in azimuth, the duration, and the dependence on elevation angle of 5‐ and 10‐db attenuation events. Results show that the frequency of occurrence diminishes rapidly as the elevation increases from horizontal to 10°, and is essentially constant from there on to 20°. 5 db is exceeded 10 hours per year at 3° elevation, 4 hours per year at 10°, and 3.5 hours per year at 20°. At all elevations 10 db is exceeded about one‐fifth as frequently as 5 db.The azimuth extents of attenuating rain regions vary from 1°, the narrowest extent measurable, to values exceeding 60°. At low elevations the distributions of azimuth extent are strongly peaked at the narrow end. With increasing elevation the distributions flatten. The average azimuth extent of a 5‐db region increases approximately linearly from 10° at an elevation of 3° to 33° at an elevation of 20°. For all elevations the average 10‐db extents are about half the 5‐db extents. The average duration of a 5‐db event decreases from about 30 min at near‐horizontal paths to less than 10 min at an elevation of 20°. For all elevations the average duration of a 10‐db event is about two‐thirds that of the 5‐db event. These results indicate the characteristics of rain attenuation to be expected over satellite‐to‐ground comm

ISSN:0048-6604    

DOI:10.1029/RS007i006p00631

年代:1972

数据来源: WILEY

摘要:

The lower wall of the Antarctic earth‐ionosphere waveguide is composed of rock covered by an ice sheet, the depth of which can be an appreciable fraction of a wavelength at very low frequencies. The complex permittivity of the ice cap is therefore an important parameter in connection with the prediction of propagation velocities and attenuation in the guide over long paths on the Antarctic continent. This paper describes an experiment conducted near Byrd Station during November, 1971, in which the properties of the surface magnetic field between 5 and 20 kHz were measured in the immediate vicinity of a buried 34‐km dipole antenna just under the surface of the snow. The related analytical problem and data reduction process are described briefly to clarify the means for converting the data into bulk average values of the complex permittivity parameter of the ice over the frequency range of interest. The resulting dielectric and loss parameters are new and have not been determined before in connection with the Antarctic ice sh

ISSN:0048-6604    

DOI:10.1029/RS007i006p00645

年代:1972

数据来源: WILEY

摘要:

Average ionospheric reflection heights are deduced for a trans‐Antarctic propagation path between Byrd Station and Scott Base. A technique is described for making relative phase measurements on VLF transmissions at several phase‐locked frequencies. Results are interpreted using waveguide mode theory which accommodates a horizontal dipole source and the effect of an anisotropic polar ionosphere. Reflection heights are presented for illustration during a period of solar activity in March 1969 and a quiet period in September of the same year; correlations are made with other indicators of ionospheric activ

ISSN:0048-6604    

DOI:10.1029/RS007i006p00651

年代:1972

数据来源: WILEY

摘要:

For monostatic radar measurements of the correlation function in the lower ionosphere, suitably spaced short pulses must be transmitted in order to obtain adequate height resolution. The efficiency of the measurement is greatly increased if several (five or more) pulses, rather than the usual pair, are transmitted with a particular irregular spacing. With this procedure many delays (10 or more) can be studied simultaneously. The increase in number of lags more than compensates for the increase in clutter. Various such multipulse schemes are described and their merits compared. The rather formidable amount of data processing associated with these procedures often cannot be done with a general purpose computer but can easily be handled by special purpose digital devices.

ISSN:0048-6604    

DOI:10.1029/RS007i006p00661

年代:1972

数据来源: WILEY

摘要:

The construction of aKu‐band radio interferometer and some preliminary observations are reported. The interferometer was built for the purpose of mapping discrete radio sources like the Crab Nebula, Cassiopeia A, and Cygnus A. It has two 8‐ft parabolic antennas operating at 17.128 GHz (1.75 cm). The maximum baseline of 100 m corresponds to a resolution of 35 sec of arc. A PDP‐8 computer is incorporated in the system and is used for pointing, tracking, delay compensation, and real‐time data analysis. The phase stability of the system was better than 10° over a period of 2 hours. Consistent fringe components were obtained from the Crab Nebula with a baseline se

ISSN:0048-6604    

DOI:10.1029/RS007i006p00667

年代:1972

数据来源: WILEY

摘要:

A solution is given for the boundary value problem of a wave propagating along a thin wire parallel to the interface between two homogeneous half‐spaces. A general modal equation is derived for the propagation constant of the transmission current on the wire. It is shown how this result reduces to earlier known solutions obtained under more restrictive condition

ISSN:0048-6604    

DOI:10.1029/RS007i006p00675

年代:1972

数据来源: WILEY

摘要:

In this paper, some properties of the steepest descent path of the integral describing transient plane wave propagation in anisotropic cold plasmas are determined. The relationship of the steepest descent method to the possible arrival of evanescent waves is illustrated by a numerical example. Also, it is shown through error estimates that the result obtained by the steepest descent method is valid for finitezand larget.

ISSN:0048-6604    

DOI:10.1029/RS007i006p00681

年代:1972

数据来源: WILEY

摘要:

Using an idealized model, the attenuation rate of the lowest order mode is calculated for a range of deep crustal conductivities. It is shown that attenuation rates may be as low as 1 db/100 km at 1 Hz for a waveguide conductivity less than 10−6mhos m

ISSN:0048-6604    

DOI:10.1029/RS007i006p00689

年代:1972

数据来源: WILEY