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The EU DEMO Tokamak is foreseen to be equipped with an electron cyclotron (EC) system for plasma heating, magnetohydrodynamic (MHD) control, and thermal instability suppression. Up to six launchers will be installed into equatorial ports with the aim to inject a maximum of 130 MW millimeter wave power at frequencies of 136/170/204 GHz toward dedicated positions into the plasma. This article presents the current layout of the typical EC system launcher components within the available space reservation areas in the equatorial level of the DEMO baseline model. Beside the general arrangement of the EC launcher components, preliminary design features of the launcher port plug modules, an active cooling system approach, integration concepts for mirrors and waveguides (WGs) of the optical system, the shielding component formation, and safety important elements of the first containment barrier of the launcher are presented. Furthermore, relevant aspects of assembly and potential remote maintenance (RM) procedures are discussed.

The divertor tokamak test (DTT) facility is designed to study the power exhaust methods in scenarios similar to those expected in future fusion plants like DEMO. The project foresees 45 MW of external additional heating power to the plasma, provided by electron cyclotron heating (ECH), ion cyclotron heating, and neutral beam injector. This article focuses on the present status of the design of the transmission lines (TLs) and antennas for the ECH system. In the first operational phase, the system shall include 16 gyrotrons (1 MW/170 GHz/100 s), grouped into two clusters of eight sources each. In a later stage, the total installed power shall be doubled for a total of four clusters. Quasi-optical TLs connect the EC sources, located in a dedicated building, to the tokamak, via mirrors transmitting the microwave beams inside vacuum pipes to reduce losses and risks of arcing in air. Each TL consists of three main sections: two single-beam (SB) sections with small mirrors dedicated to a single beam at the beginning and the end of the line and a midsection of multibeam (MB) mirrors for the transmission of all the eight beams of the cluster. The beams at the output of the TL match the antennas installed in the equatorial and upper ports of the same vacuum vessel sector, through corrugated circular waveguides (WGs). The WGs are needed to reduce the vacuum conductance between the DTT vessel and TLs environments, being the connection with the vacuum vessel managed by all-metal gate valves without diamond windows. The two antennas consist of independent launching modules for each beam composed by two mirrors, one fixed and one steerable. All the components of the system are actively water-cooled to limit deformations of the mirrors surface to ensure the required quality of the beams and to reduce the transmission losses.

Galileo images of Gaspra make it possible for the first time to determine a main-belt asteroid's photometric properties accurately by providing surface-resolved coverage over a wide range of incidence and emission angles and by extending the phase angle coverage to phases not observable from Earth. We combine Earth-based telescopic photometry over phase angles 2° ≤ α ≤ 25° with Galileo whole-disk and disk-resolved data at 33° ≤ α ≤ 51° to derive average global photometric properties in terms of Hapke's photometric model. The microscopic texture and particle phase-function behavior of Gaspra's surface are remarkably like those of other airless rocky bodies such as the Moon. The macroscopic surface roughness parameter, θ̄ = 29°, is slightly larger than that reported for typical lunar materials. The particle single scattering albedo, ώ0= 0.36 ± 0.07, is significantly larger than for lunar materials, and the opposition surge amplitude, B0= 1.63 ± 0.07, is correspondingly smaller. We determine a visual geometric albedo pv= 0.22 ± 0.06 for Gaspra, in close agreement with pv= 0.22 ± 0.03 estimated from Earth-based observations. Gaspra's phase integral is 0.47, and the bolometric Bond albedo is estimated to be 0.12 ± 0.03. An albedo map derived by correcting Galileo images with our average global photometric function reveals subdued albedo contrasts of ±10% or less over Gaspra's northern hemisphere. Several independent classification algorithms confirm the subtle spectral heterogeneity reported earlier (S. Mottola, M. DiMartino, M. Gonano-Beurer, H. Hoffman, and G. Neukum, 1993, Asteroids, Comets, Meteors,pp. 421-424; M. J. S. Belton et al., 1992, Science257, 1647-1652). Whole-disk colors (0.41 ≤ λ ≤ 0.99 μm) vary systematically with longitude by about ±5%, but color differences as large as 30% occur locally. Colors vary continuously between end-member materials whose areal distribution correlates with regional topography. Infrared: violet (0.99:0.41-μm) color ratios on Gaspra are strongly correlated with local elevation, being largest at lower elevations and smaller at higher elevations. No correlation was detected between elevation and the green:violet (0.56:0.41-μm) color ratio. Bright materials with a strong 1-μm absorption occur primarily in association with craters along ridges, while darker materials with 30% weaker 1-μm signatures occur downslope. The variations of color and albedo cannot be easily explained by grain-size effects alone or by differences in photometric geometry. The trends observed are consistent with those revealed by laboratory studies of the effects of comminution, glass formation, and segregation of metal from silicate components in chondritic meteorites and also in some silicate mixtures. The relative importance of these various processes on Gaspra remains to be determined.

Galileo SSI color data between 0.4 and 1.0 μm demonstrate that both Ida and Dactyl are S-type asteroids with similar, but distinct spectra. Small but definite color variations are also observed on Ida itself and involve both the blue part of the spectrum and the depth of the 1-μm pyroxene–olivine band. Ida's surface can be classified into two color terrains: Terrain A has a shallower 1-μm absorption and a steeper visible red slope than does Terrain B. Qualitatively, the color–albedo systematics of these two terrains follow those noted for color units on Gaspra and the variations in 1-μm band depth with weathering described by Gaffeyet al.(Gaffey, M. J., J. F. Bell, R. H. Brown, T. H. Burbine, J. Piatek, K. L. Reed, and D. A. Chaky 1993.Icarus106, 573–602). Terrain A, with its slightly lower albedo, its shallower 1-μm band, and its slightly steeper visible red slope relative to Terrain B could be interpreted as the “more processed,” “more mature,” or the “more weathered” of the two terrains. Consistent with this interpretation is that Terrain A appears to be the ubiquitous background on most of Ida, while Terrain B is correlated with some small craters as well as with possible ejecta from the 10-km Azzurra impact structure. Because of these trends, it is less likely that differences between Terrains A and B are caused by an original compositional inhomogeneity within the body of Ida, although they do fall within the range known to occur within the Koronis family.

Galileo imaging observations over phase angles 19.5° to 109.8° are combined with near-opposition Earth-based data to derive the photometric properties of Ida. To first order these properties are uniform over the surface and well modeled at λ = 0.55 μm by Hapke parameters ω0= 0.22,h= 0.020,B0= 1.5,g= −0.33, and θ = 18° with corresponding geometric albedop= 0.21±0.030.01and Bond albedoAB= 0.081±0.0170.008. Ida's photometric properties are more similar to those of “average S-asteroids” (P. Helfenstein and J. Veverka 1989,Asteroids II, Univ. of Arizona Press, Tucson) than are those of 951 Gaspra. Two primary color units are identified on Ida: Terrain A exhibits a spectrum with relatively shallower 1-μm absorption and a relatively steeper red spectral slope than average Ida, while Terrain B has a deeper 1-μm absorption and a less steep red slope. The average photometric properties of Ida and Terrain A are similar while those of Terrain B differ mostly in having a slightly higher value of ω0(0.22 versus 0.21), suggesting that Terrain B consists of slightly brighter, more transparent regolith particles. Galileo observations of Ida's satellite Dactyl over phase angles 19.5° to 47.6° suggest photometric characteristics similar to those of Ida, the major difference being Dactyl's slightly lower albedo (0.20 compared to 0.21).

The scientific value of unmanned rovers for continued lunar exploration is considered in light of Apollo findings which suggest that the Moon's surface is more heterogeneous than expected. A set of major questions and investigations involving composition, internal structure, and thermal history are presented that form a scientific rationale for use of unmanned rovers in the post-Apollo period of lunar exploration. Visual, petrologic, chemical and geophysical measurements that are essential for an unmanned rover traverse over previously unexplored lunar terrain are discussed. Unmanned rovers are well-suited for low-cost, low-risk preliminary reconnaissance where measurement of a few definitive parameters over a wide area is more important than obtaining a wide array of detailed results at a given site.

Uranium: helium ages are compared with Th230: U234ages and stratigraphic ages for selected Pleistocene and Tertiary shells and corals. Agreement is good except for those fossils for which independent criteria (for example, aragonite: calcite, Ra226: Th230, or U234: U238ratios) indicate a chemically open system. Certain of the Tertiary samples yield erroneously low ages which probably result from secondary addition of uranium. The helium geochronometer appears to yield reliable minimum ages and may be applicable to direct dating of aragonitic fossils—especially those of Pleistocene age—when used in conjunction with other isotopic and geologic information.

The scientific value of unmanned rovers for continued lunar exploration is considered in light of Apollo findings which suggest that the Moon's surface is more heterogeneous than expected. A set of major questions and investigations involving composition, internal structure, and thermal history are presented that form a scientific rationale for use of unmanned rovers in the post-Apollo period of lunar exploration. Visual, petrologic, chemical and geophysical measurements that are essential for an unmanned rover traverse over previously unexplored lunar terrain are discussed. Unmanned rovers are well-suited for low-cost, low-risk preliminary reconnaissance where measurement of a few definitive parameters over a wide area is more important than obtaining a wide array of detailed results at a given site.

Laboratory measurements of the adsorption of CO2, H2O and Kr indicate that pulverized basalt has an extremely high internal surface area. This suggests that the Martian regolith may store an appreciable amount of adsorbed gas, and that the diurnal brightening of Mars may be caused by a fog of ice crystals formed from water molecules desorbed diurnally from the surface.