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Berge, G. L.

Publications and source records attributed to Berge, G. L..

27 records · Page 2
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NASA NTRS1976

Earth-based radio observations of Jupiter - Millimeter to meter wavelengths

The historical development of the study of Jupiter radio emission is considered and a description of the observational data is presented, taking into account the spectrum of the continuous microwave radiation, the polarization of the microwave radiation, the brightness distribution, the rotation-related variability, variations related to the zenocentric declination of the earth, and other time variations. The separation of radio emission into thermal and nonthermal components is discussed and interpretations of the two components are provided. A comparison of earth-based radio measurements with Pioneer 10 and 11 data is conducted and the future of earth-based radio observations is evaluated.

Berge, G. L.↗
NASA NTRS1975

Callisto - Disk temperature at 3.71-centimeter wavelength

We observed the radio emission of Callisto with a three-element interferometer at the time of the 1973 opposition of Jupiter. Special care was taken to remove the residual, unresolved contribution from Jupiter itself in the antenna side lobes. The resulting disk temperature at a wavelength of 3.71 centimeters, assuming a radius of 2500 + or - 75 kilometers for Callisto, was 101 + or - 25 K. This temperature is much more consistent with emission from a simple dielectric sphere than the considerably higher temperatures that have been reported for wavelengths of 3.5 and 8.2 millimeters.

Berge, G. L.↗
NASA NTRS1973

High-angular-resolution observations of Saturn at 21.1-centimeter wavelength.

Saturn was observed with an interferometer at a wavelength of 21.1 cm in an effort to determine whether any of the emission at this wavelength originates from outside the area of the visible disk. The result, in terms of upper limits, is that no more than 6% can come from the visible rings nor more than 5% from a radiation belt, assuming certain brightness distribution models that are described. The latter limit implies that the volume emissivity of a hypothetical Saturn radiation belt has an upper limit of only about 1% of that for Jupiter in corresponding regions. The measured disk temperature is 232 plus or minus 18 K.

Berge, G. L.↗
NASA NTRS1973

The brightness temperature of Venus and the absolute flux-density scale at 608 MHz.

The disk temperature of Venus was measured at 608 MHz near the inferior conjunction of 1972, and a value of 498 plus or minus 33 K was obtained using a nominal CKL flux-density scale. The result is consistent with earlier measurements, but has a much smaller uncertainty. Our theoretical model prediction is larger by a factor of 1.21 plus or minus 0.09. This discrepancy has been noticed previously for frequencies below 1400 MHz, but was generally disregarded because of the large observational uncertainties. No way could be found to change the model to produce agreement without causing a conflict with well-established properties of Venus. Thus it is suggested that the flux-density scale may require an upward revision, at least near this frequency, in excess of what has previously been considered likely.

Muhleman, D. O.↗
NASA NTRS1972

Some recent observations and interpretation of the Jupiter decimeter emission

The decimetric emission consists partly of thermal radiation from the planetary disk and partly of nonthermal radiation from a region of larger angular extent and is thought to result from synchrotron emission by relativistic electrons in the magnetic field. Four topics relating to the decimetric emission are discussed. (1) A comparison is made of maps giving detailed brightness contours. One was obtained for epoch 1963.8 and was at a wavelength of 10.4 cm. The second was for epoch 1967.2 at 21.3 cm. (2) Interferometric data at 21.1 cm taken in April 1968 and May 1979 indicate that the emission centroid is fixed in Jupiter and rotates with it. (3) Circular polarization observations are described and are used to obtain a surface magnetic field strength at the equator between 3.2 and 15.2 gauss. (4) An upper limit on the Faraday rotation is used to set an upper limit on the density of thermal electrons surrounding Jupiter, and uncertainties in the results are discussed.

Berge, G. L.↗