The impulsive noise that the plasma wave and radio astronomy instruments detected during the Voyager 2 swing by Saturn was attributed to dust grains striking the spacecraft. This report presents a reanalysis of the dust impacts recorded by the plasma wave instrument using an improved model for the response of the electric antenna to dust impacts. The fundamental assumption used in this analysis is that the voltage induced on the antenna is proportional to the mass of the impacting grain. Using the above assumption and the antenna response constants used at Uranus and Neptune, the following conclusions can be reached. The primary dust distribution consists of a “disk” of particles that coincides with the equator plane and has a north‐south thickness of 2Δz = 962 km. A less dense “halo” with a north‐south thickness of 2Δz = 3376 km surrounds the primary distribution. The dust particle sizes are of the order of 10 µm, assuming a mass density of 1 g/cm³. The corresponding particle masses are of the order of 10−9 g, and maximum number densities are of the order of 10−2 m−3. Most likely, the G ring is the dominate source since the particles were observed very close to that ring, namely at 2.86 RS. Other sources, like nearby moons, are not ruled out especially when perturbations due to electromagnetic forces are included. The calculated optical depth differs by about a factor of 2 from photometric studies. The current particle masses, radii, and the effective north‐south thickness of the particle distribution are larger than what Gurnett et al. (1983) reported by about 2, 1, and 1 orders of magnitude, respectively. This is attributed to the fact that the collection coefficient used in this study is smaller than what was used in Gurnett et al.'s earlier publication.

No abstract

The Rough Evaporation Duct experiment aimed to see if the effects of ocean waves account for errors in modeling the ranges at which radar and infrared can detect low-flying targets. When radars first came into operation during the late 1930s, they were not expected to detect targets much beyond the geometrical horizon. These early radars, operating at a wavelength of 13 m, generally met expectations. As new radars were rapidly developed, operating at shorter and shorter wavelengths for better target detection, observations of anomalous propagation effects became more frequent. When 10-cm radars were installed along the south coast of England during World War II, they were often able to see the coast of France, even though the coast was well beyond the geometric horizon (Booker 1948). These anomalous propagation effects also became more pronounced as the operating area became more tropical. For example, a 1.5-mwavelength radar operating in Bombay, India, re-

Wideband waveform data obtained by the plasma wave instruments onboard the Voyager 1 and 2 spacecraft have been used to study micron‐sized dust particles in the vicinity of Jupiter. The technique used was developed during the fly by s of Saturn, Uranus, and Neptune, and makes use of the fact that a particle striking the spacecraft at 10–20 km/s causes a voltage pulse in the plasma wave receiver. The waveform of the voltage pulse is much different than the waveform of plasma waves and provides a highly reliable method of detecting micron‐sized dust particles. Although the dust impact rate observed in the vicinity of Jupiter is much lower than the rates at Saturn, Uranus, and Neptune, the particles are easily detectable. Approximately 1200 48‐second frames of wideband waveform data were examined in the vicinity of Jupiter. Dust impact signatures were found in approximately 20% of these frames. The peak impact rates are about 1 impact per second, and the peak number densities are about 10−5 m−3. Most of the impacts occurred near the equatorial plane at radial distances less than about 35 RJ from Jupiter. Analysis of the detection threshold indicates that the particles have masses greater than 10−11 g, which corresponds to particles with diameters of a few micrometers or larger.

The application of long-range infrared observation systems is challenging, especially with the currently available high spatial resolution infrared camera systems with resolutions comparable with their visual counterparts. As a result of these developments, the obtained infrared images are no longer limited by the quality of system but by atmospheric effects instead. For instance, atmospheric transmission losses and path radiance reduce the contrast of objects in the background and optical turbulence limits the spatial resolution in the images. Furthermore, severe image distortion can occur due to atmospheric refraction, which limits the detection and identification of objects at larger range. EOSTAR is a computer program under development to estimate these atmospheric effects using standard meteorological parameters and the properties of the sensor. Tools are provided to design targets and to calculate their infrared signature as a function of range, aspect angle, and weather condition. Possible applications of EOSTAR include mission planning, sensor evaluation and selection, and education. The user interface of EOSTAR is fully mouse-controlled, and the code runs on a standard Windows-based PC. Many features of EOSTAR execute almost instantaneous, which results in a user friendly code. Its modular setup allows its configuration to specific user needs and provides a flexible output structure.