摘要:

The amplitudes and differential Doppler of two radio signals transmitted to Mariner 5 as it was occulted by Venus are utilized to derive the dayside and nightside ionization distributions in the upper atmosphere, and the temperature and pressure profiles of the lower atmosphere. Both sides of Venus have ionization peaks near the 140‐km altitude level; the daytime peak is 30 times greater in electron number density. The nightside ionosphere extended up to an altitude of at least 1000 km, and the dayside ionization terminated in a plasmapause near an altitude of 500 km. There may be a wake of planetary ionization extending a great distance in the antisolar direction. The neutral atmosphere was probed down to within 35 km of the planetary surface. Differences in the temperature and pressure profiles for the nightside and dayside, and apparent kilometer‐size structure in the atmosphere, are discus

ISSN:0048-6604    

DOI:10.1029/RS004i010p00879

年代:1969

数据来源: WILEY

摘要:

The refractivity of carbon dioxide has been measured at 2.26 GHz under simulated Martian conditions and at standard temperature and pressure. In the temperature range of 150° to 190°K, at pressures from 2 to 25 millibars, the refractivity per molecule per cm2is 1.78 × 10−17± 0.06 when scaled by the ideal gas law. The measurements include pressures and temperatures which are within 30°C of the sublimation curve. This result is slightly lower than the best measurements previously obtained near standard temperature and pressure at other frequencies (1.8345 × 10−17± 0.0003) and at 2.26 GHz under standard conditions by the authors (1.8413 × 10−17± 0.005). It is concluded that the scaled refractivity of CO2in the range of temperatures and pressures stated above may be a few percent lower than under standard conditions. These results do not significantly alter the conclusions regarding the atmosphere of Mars as measured by the radio occu

ISSN:0048-6604    

DOI:10.1029/RS004i010p00899

年代:1969

数据来源: WILEY

摘要:

Transhorizon propagation techniques and their usefulness in determining atmospheric parameters are discussed. It is concluded that the state or structure of the atmosphere cannot be inferred unambiguously from individual measurement techniques used in experiments reported to date. However, because of the sensitivity of the transhorizon radio signals to changes in the parameters of the troposphere, it is suggested that combinations of available techniques be pursued to determine the parameters uniquely.

ISSN:0048-6604    

DOI:10.1029/RS004i010p00905

年代:1969

数据来源: WILEY

摘要:

It was shown by G. D. Thayer and J. J. Freeman that corrections to refraction‐induced errors can be expressed in terms of error functions for propagation in an exponential model atmosphere. Using Freeman's equations as an example, we replace the error functions by their asymptotic expressions, thereby giving closed form equations. To extend the usefulness of these functions for short ranges and small elevation angles, an empirical adjustment is mad

ISSN:0048-6604    

DOI:10.1029/RS004i010p00927

年代:1969

数据来源: WILEY

摘要:

Single‐pulse and double‐pulse methods for measuring the cross‐correlation (two polarizations transmitted and received) or auto‐correlation (one polarization only) function of the scattered signal are described. The statistical errors associated with various forms of multi‐bit (no quantization errors in the sampling process), one‐bit, and hybrid estimators of the correlation function are calculated and compared, both for large and small signal‐to‐noise ratios. Roughly speaking, when the signal correlation is small, the hybrid estimators require π/2 and the one‐bit π2/4 times as many independent samples as the multi‐bit estimators to achieve the same statistical accuracy, but this disadvantage is often more than compensated for by an increase in the effective sampling rate. When the correlation is 0.5 or more, there may be a substantial difference between estimators of the same class (multi‐bit, for example). Systematic distortions of the correlation function and limitations on resolution associated with the finite receiver bandwidth and transmitted pulse length are calculated. The effect of a refractive index slightly less

ISSN:0048-6604    

DOI:10.1029/RS004i010p00935

年代:1969

数据来源: WILEY

摘要:

Studies of radio waves (2.22–2.66 MHz) partially reflected from the lower ionosphere (50–90 km) have been used to calculate the magnitudes of the Fresnel irregularities required to give the observed signal strengths. These irregularities require 1–18% perturbations in electron density and show a distinctive seasonal variation, having a minimum in summer and a maximum in winter. Recently published electron‐density profiles obtained from rocket probes have revealed fine‐scale structure comparable in magnitude and vertical dimension to these calculated perturbations. The reflection coefficients and the magnitudes of the equivalent Fresnel irregularities are calculated for individual irregularities and are shown to be only 3 to 4 times less than those required by the radio‐wave data. Reflections from several of these closely spaced irregularities should give rise to signals comparable with the observations. It appears that the fine structure in these profiles is real and has much smaller vertical dimension than any other published measurements of mesospheric

ISSN:0048-6604    

DOI:10.1029/RS004i010p00955

年代:1969

数据来源: WILEY

摘要:

Several diffraction problems whose solutions involve incomplete Airy functions are briefly described; general and asymptotic characteristics of these functions are summarized. A uniform asymptotic representation, in which the incomplete Airy functions serve as canonical functions, is given for the class of integrals characterized by two saddle points arbitrarily positioned relative to an end point. Proceeding from an appropriate boundary‐layer expansion, the functions and their properties are applied in a detailed analysis of the fields near the point of confluence of the caustic of a converging wave and the shadow boundary resulting from the presence of an opaque obstacl

ISSN:0048-6604    

DOI:10.1029/RS004i010p00959

年代:1969

数据来源: WILEY

摘要:

The input resistance of a Hertzian electric dipole located over a homogeneous conducting half‐space is considered. It is shown that the functional dependence of the input resistance on the ‘loss tangent’ of the half‐space is consistent with electrostatic concepts, provided the frequency is sufficiently low. On the other hand, at the higher frequencies, the results are compatible with the surface impedance formulations based on the compensation theorem. The results have possible application to remote sensing of planetary surfaces from an elevated

ISSN:0048-6604    

DOI:10.1029/RS004i010p00971

年代:1969

数据来源: WILEY

摘要:

A relativistic formulation for the fields of sources in a uniformly moving, isotropic, dispersionless, conducting medium is developed in terms of Green's functions. Solutions are found in closed form for the cases of stationary charge sources and harmonic current sources. Cerenkov phenomena are observed and discussed. The work differs from former treatments in that a self‐consistent scheme is given which accounts for relaxation effects involving conduction charges. The results apply for all values of conductivit

ISSN:0048-6604    

DOI:10.1029/RS004i010p00977

年代:1969

数据来源: WILEY

ISSN:0048-6604    

DOI:10.1029/RS004i010p00982

年代:1969

数据来源: WILEY