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The four spring lunations produced 105 acquisitions, including the 2000th range measurement made at McDonald Observatory. Statistics were normal for the spring months. Laser and electronics problems are noted. The Loran-C station delay was corrected. Preliminary doubles data is shown. New magnetic tape data formats are presented. R and D efforts include a new laser modification design.
A laser-optical instrument for use in determining the two-dimensional wave-slope spectrum of ocean capillary waves is described. The instrument measures up to a 35-deg tip angle of the surface normal by measuring the position of a refracted laser beam directed vertically upward through a water surface. A telescope, a continuous two-dimensional Schottky barrier photodiode, and a pair of analog dividers render the signals independent of water height and insensitive to laser-beam intensity fluctuations. Calibration is performed entirely in the laboratory before field use. Sample records and wave-slope spectra are shown for one-dimensional wave-tank tests and for two-dimensional ocean tests. These are presented along with comparison spectra for calm and choppy water conditions. A mechanical wave follower was used to adjust the instrument position in the presence of large ocean swell and tides.
An analysis of observations of the occultation of Epsilon Gem by Mars on April 8, 1976, is presented. The data were obtained by three neighboring telescopes at McDonald Observatory. Intensity fluctuations on time scales of the order of 100 ms were observed simultaneously at the three telescopes. As the observations compare well with predictions of turbulent scintillation theory, it is concluded that such fluctuations were probably largely the effect of stellar scintillations in the Martian atmosphere. The stellar diameter is included as a parameter in the theory but in a way which differs from previously published interpretations of occultations of extended sources by planetary atmospheres. Scintillations govern the experimental uncertainty in the deduction of the scale height of the high Martian atmosphere. A density scale height of 9.9 + or - 2.5 km is obtained at an altitude of 74 + or - 8 km above the mean surface. For CO 2 gas, this result corresponds to a temperature of 190 + or - 50 K.
It is noted that the variable Rb-Sr model ages of lunar highland rocks containing a significant amount of KREEP basalt may be best explained by some fractionation of Rb from Sr during metamorphism 3.9 billion years ago, but the uniformity of the KREEP-type trace-element pattern in different highland samples indicates that elements such as the rare earth were hardly fractionated at all during the metamorphic event. Data are presented which show that the Rb/Sr fractionation 3.9 billion years ago was due to Rb mobilization alone in most cases and that this fractionation can be accounted for by coupling of Rb to other, less volatile incompatible elements. Variations of Rb in lunar highland rocks are analyzed, a correction method is applied for the Rb/Sr fractionation, and results are evaluated separately for Apollo 16 VHA and KREEP basalts, Apollo 17 noritic breccias, Apollo 14 KREEP breccias, Apollo 15 KREEP basalts, and Apollo 15-KREEP-enriched breccias. Evidence for volatilization of alkalis from glasses of impact origin is summarized, and an apparent correlation is discussed between meteoritic component (as given by the Ir/Au ratio) and rock type (as given by the U or Rb content) for many lunar highland samples.
The paper analyzes the meteoritic material at five multikilometer craters: Clearwater (Lac a l'Eau Claire) East and West (22 and 32 km), Manicouagan (70 km) and Mistastin (28 km), all in Canada; and Lake Bosumtwi (10.5 km), Ghana, which is associated with Ivory Coast tektites. Radiochemical neutron activation analysis is applied to 16 crater samples for the siderophile trace elements Ir, Os, Pd, Ni, Ge, and Re, which are depleted to varying degrees in the earth's crust but are abundant in all meteorites except achondrites. It is found that only two samples, both from Clearwater, exhibit a strong meteoritic signal. The remaining ones fall within or slightly above the range for terrestrial rocks, and therefore at best contain only small meteoritic components. Clearwater East is the first terrestrial impact crater to be associated with a stony meteorite (a C1 or C2 chondrite).
Of the 33 lunar samples considered in the investigation, 31 came from the North Ray Crater. The relationship between meteoritic component and rock type is studied. There appears to be some correlation between the meteoritic component, as given by the Ir/Au ratio, and the rock type, as given by the U content. The relation of ancient meteoritic components to basins and craters is examined, taking into account the resolution of groups, the relative ages from clast-matrix relations, assignments to specific basins or craters, and the relation between meteoritic components and Woenke's 'primary matter'. A table shows seven meteorite-free samples which are all low-alkali cataclastic anorthosites, or anorthositic clasts in light-matrix breccias. The origin of ancient meteoritic bodies are also investigated. The latest data strengthen earlier conclusions that the basin-forming objects were genetically related to the moon.
Radiochemical neutron activation analyses for Ag, Au, Bi, Br, Cd, Cs, Ge, In, Ir, Ni, Os, Pd, Rb, Re, Sb, Te, Tl, U and Zn were carried out on 11 samples from the Apollo 11 and 12 sites (two samples of rock 12013, one granitic and one KREEPy; 4 KREEP fragments from 2-4 mm soil 12033,2; 4 anorthositic fragments from 1-3 mm soil 10085,104; 1 sample of 'Luny' rock-felsite-KREEP breccia 12013 10085,31 LR-1). Most Apollo 12 samples were found to have an Imbrium meteoritic component; others, typified by the Luny breccia, apparently contain a new meteoritic component of low Re content. Components of higher Ir/Au ratio (3L, 5L and 7) were found in Apollo 11 anorthositic samples; the fact that their enrichment in meteoritic siderophiles parallels that of Fe, Mg, REE and other KREEP elements is consistent with progressive contamination of an anorthositic crust. The Luny rock was tentatively classified Group 2, supporting the assignment of this group to Serenitatis.
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Seven documented and fresh glassy selvages from ocean floor basalt pillows were analyzed for trace elements including Ag, Au, Bi, Br, Ni, Pd, and Zn using radiochemical activation analysis. Glasses from DSDP leg 24, site 238 in the Indian Ocean have a trace element pattern which reflects secondary processes at a shallow depth. Chemical fractionations in petrogenesis of tholeiitic basalts indicate that (Ir, Os), Au, Pd, Ni, and Re are strongly fractionated in igneous processes; the unfractionated chondritic mantle pattern thus imposes constraints on mantle evolution models. Finally, the limited Rb/Cs fractionation in oceanic tholeiites reflects the low abundance of volatiles and hydrous silicates in normal ocean ridge basalts.
An analysis of impact melt samples from a drill hole at the Brent crater in Ontario for siderophile trace elements indicative of meteoritic contamination, has resulted in 823-857 m-deep basalt melt zone samples enriched in Ir, Os, Pd, Ni, Co, Cr and Se over basement. The abundance pattern suggests a chondritic projectile and, from a Ni-Cr correlation of 10 melt samples, an L or LL chondrite is inferred. Data from the Manicouagan, Mitastin, and Zhamanshin craters are also assessed, and large differences in siderophile element concentrations are found among the tektites which otherwise have similar chemical compositions. There are now four known craters formed by chondrites, with Brent being the smallest among them.
One nemesis of the structural dynamist is the tedious task of reviewing large quantities of data. This data, obtained from various types of instrumentation, may be represented by oscillogram records, root-mean-squared (rms) time histories, power spectral densities, shock spectra, 1/3 octave band analyses, and various statistical distributions. In an attempt to reduce the laborious task of manually reviewing all of the space shuttle orbiter wideband frequency-modulated (FM) analog data, an automated processing system was developed to perform the screening process based upon predefined or predicted threshold criteria.
Computer analysis was used to determine the AMO conversion efficiency of single-junction crystalline cells, two-cell and three-cell crystalline tandem structures operating under 100 suns and at 80 C. For optimally designed devices, the calculated efficiencies are 24% for single-junction cells, 33 to 35% for two-cell tandem structures, and 37 to 39% for three-cell tandem structures. Practical efficiencies are expected to be about 15 relative percentage points lower in each case.
The results of a study of the small achondrite found in 1974 near Brachina, Australia are presented and discussed. Trace element data for Brachina were found to be quite different from that for Chassigny. The major differences are higher FeO/MnO, Ge/Al, and K/La ratios, W depletion, high siderophile content, near-horizontal REE pattern at about 1 x chondrite level, high refractory/nonrefractory metal ratios (e.g., Ir/Au), and chalcophile element depletion. Brachina's 4.5 billion year age and oxygen isotropic signature within the eucritic field further suggest that it is not related to Chassigny or SNC meteorites, though it may be related to primitive meteorites, such as silicate inclusions in IAB irons and winonaites.
Computer analysis indicates that a substantial increase in solar cell conversion efficiencies can be achieved by using two-cell, multi-bandgap tandem structures instead of single-junction cells. Practical AM1 efficiencies of about 30 percent at one sun and over 30 percent at multiple suns are to be expected. The further increases in efficiency calculated for a three-cell tandem structure are much smaller and may not justify the added complexity. For inexpensive two-cell tandem modules, Si is preferred for the bottom cell, and the top-cell material should have a bandgap of 1.75 to 1.80 eV. The GaAs-AlAs and GaAs-GaP systems are very attractive candidates for the top cell. Significant advances have been achieved in growing GaAs on Ge-coated Si substrates (for the two-terminal, two-cell structure) and in growing free-standing ultrathin GaAs layers (for the two-terminal or four-terminal structures). These advances should be transferable to the GaAs-AlAs and GaAs-GaP systems.
An algorithm is presented for using a robot system with a single camera to position in three-dimensional space a slender object for insertion into a hole; for example, an electrical pin-type termination into a connector hole. The algorithm relies on a control-configured end effector to achieve the required horizontal translations and rotational motion, and it does not require camera calibration. A force sensor in each fingertip is integrated with the vision system to allow the robot to teach itself new reference points when different connectors and pins are used. Variability in the grasped orientation and position of the pin can be accomodated with the sensor system. Performance tests show that the system is feasible. More work is needed to determine more precisely the effects of lighting levels and lighting direction.
Observations of a convective planetary boundary layer (PBL) were made with an airborne, downward-looking lidar system over the Atlantic Ocean during a cold air outbreak. The lidar data revealed well-organized, regularly spaced cellular convection with dominant spacial scales between two and four times the height of the boundary layer. It is demonstrated that the lidar can accurately measure the structure of the PBL with high vertical and horizontal resolution. Parameters important for PBL modeling such as entrainment zone thickness, entrainment rate, PBL height and relative heat flux can be inferred from the lidar data. It is suggested that wind shear at the PBL top may influence both entrainment and convective cell size.
The detection of Antarctic meteorites of Lunar and perhaps Martian origin, belongs to the most important discoveries in planetology during the last years. There is such a wealth of new information on differentiated and undifferentiated planetary bodies deduced from Antarctic meteorites that it is at present not possible to even qualitatively foresee the impact that these meteorites will have on the understanding of the formation and differentiation of large and small planets in the solar system. Martian meteorites, Lunar meteorites, meteorites from the parent body of basaltic achondrites, and chrondritic meteorites are discussed.
The application of an airborne downward-looking lidar to the study of organized cellular convection in the planetary boundary layer (PBL) over the ocean is described. The lidar consisted of a frequency doubled Nd-YAG 530 mm-wavelength laser whose axis was aligned colinearly with the optical axis of an all-reflecting 40 mm-diameter Newtonian telescope. The airborne lidar provided a unique observation of both microscale and mesoscale variations of the PBL top. The lidar data, presented as constant backscatter isopleth soundings, provide a visual indication of the presence of vertically organized convection cells. Comparisons of the lidar-derived PBL structure with both a conceptual model of the PBL and laboratory simulations of Deardorf et al. (1980) of a developing convective PBL showed that the observations are consistent with a model of mixing in the PBL, which involves a field of organized updrafts separated by downdrafts.