Saturn's Rings: pre-Cassini Status and Mission Goals

Theoretical and observational progress in studies of Saturn's ring system since the mid-1980s is reviewed, focussing on advances in configuration and dynamics, composition and size distribution, dust and meteoroids, interactions of the rings with the planet and the magnetosphere, and relationships between the rings and various satellites. The Cassini instrument suite of greatest relevance to ring studies is also summarized, emphasizing how the individual instruments might work together to solve outstanding problems. The Cassini tour is described from the standpoint of ring studies, and major ring science goals are summarized. This revised version was published online in August 2006 with corrections to the Cover Date.     

The Lunar Reconnaissance Orbiter Diviner Lunar Radiometer Experiment

The Diviner Lunar Radiometer Experiment on NASA’s Lunar Reconnaissance Orbiter will be the first instrument to systematically map the global thermal state of the Moon and its diurnal and seasonal variability. Diviner will measure reflected solar and emitted infrared radiation in nine spectral channels with wavelengths ranging from 0.3 to 400 microns. The resulting measurements will enable characterization of the lunar thermal environment, mapping surface properties such as thermal inertia, rock abundance and silicate mineralogy, and determination of the locations and temperatures of volatile cold traps in the lunar polar regions.     

Interplanetary shock waves: Recent developments

Direct and indirect observations of interplanetary shock waves have been extended to the study of (i) the shock structure itself; (ii) the disturbed solar wind in its wake; (iii) additional discontinuities such as reverse shocks and pistons; and (iv) the shock's kinematic behavior. The last item — the trajectory — has benefited by the procedure (suggested by Pintér) of matching type II radio drift-inferred velocities with indirectly-inferred initial velocities found from at least two successive measurements in space. The significance of making type II observations at hectometric and kilometric wavelengths (as made, for example, by Slysh and Malitson, Feinberg and Stone) cannot be over-emphasized due to this technique's ability to make unambiguous solar terrestrial relationships. More direct and physically-meaningful observations, however, are still dependent uponin situ plasma and magnetic field measurements. Additional emphasis is presently being placed on numerical modeling of shock-induced disturbances in the solar wind as generated by both flares and stream-stream interactions. The former mechanism is emphasized in this review with several recommendations for further research: (a) further numerical modeling for shocks, starting when they are born within relatively low-Alfvén speed coronal regions; (b) expanded synoptic studies by spacecraft at various heliocentric longitudes, radii, and (eventually) latitudes with coordinated diagnostics; and (c) extended patrol of natural probes, such as comets, augmented with theoretical studies of possible shock-induced mechanical and chemical effects.     

Bengt Hultqvist and Marit Oieroset (eds.), Transport Across the Boundaries of the Magnetosphere

Space Science Reviews -     

Victor A. Brumberg and Eugene V. Brumberg,Celestial Dynamics at High Eccentricities

Space Science Reviews -     

R. von Steiger,R. Lallement,and M.S. Lee (eds.). The Heliosphere in the Local Interstellar Medium

Space Science Reviews -     

Can space exploration survive the end of the Cold War?

The first, heroic age of space exploration was drived by national rivalry between the USA and USSR. There have indeed been recent achievements, but as the Cold War ends the superpowers are turning their attention to domestic issues and the prospect looms of a prolonged hiatus in space exploration. The only way forward is through international cooperation, but this will never happen without a serious investment of political will. A well-planned, long-term strategy for the exploration of Mars could provide the necessary focus.     

The einstein observatory medium sensitivity survey

Results are presented from an X-ray survey of 50 square degrees of the high galactic latitude sky at sensitivities in the range 7·10^–14 – 5·10^–12 erg/cm² sec (0·3–3·5 keV) carried out with the Imaging Proportional Counter (IPC) aboard the Einstein Observatory. The extragalactic sample consists of 48 sources which have been used to determine the number flux relation. The content of the sample is analyzed in terms of types of sources and is found to be significantly different from the content of similar samples selected at higher fluxes.