Data from the European Space Agency's ERS 1 satellite synthetic aperture radar (SAR) covering the region of the East Australian Current during late 1991 have been analyzed in conjunction with ship and airborne data and infrared imagery. Apart from wind effects, the largest differences in backscatter seem to be associated with different water masses, these differences probably being caused by wave damping due to natural surfactants. Slicklike features in the Tasman Sea are common, even in the deep ocean, when the winds are light. Ocean currents are often visible but as relatively subtle features. It is unlikely that changes in atmospheric boundary layer stability due to changing sea surface temperature are the dominant mechanism for radar imaging of ocean currents. It is suggested that C band radar backscatter will prove to be more directly correlated with biological activity (and ocean color) than with sea surface temperature, particularly at higher latitudes. Surfactants could cause errors of 20% or more in wind speeds derived from satellite scatterometers.
Considerable doubt is cast on the validity of past satellite measurements of micrometeoroid fluxes in which piezoelectric microphones have been used as detectors. Data have been obtained from satellite and laboratory experiments which show that the microphone crystals emit noise when subject to slowly varying temperatures. The rate of noise is consistent with past flight data which have previously been interpreted on the basis of micrometeoroid impacts. These measurements have given rise to the theory that the earth is surrounded by a cloud of dust, although no satisfactory mechanism has yet been found to explain this apparent phenomenon. On the basis of the results reported here, it now appears that whether or not a concentration of dust exists in the vicinity of the earth, the data from satellite microphone measurements should not be used to support such a hypothesis.
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