The dependence of the level-sensitivity on the position and length of the bubble on the wild T-4 theodolite     

G. L. Barnes  I. I. Mueller 《Journal of Geodesy》1966,40(3):277-286

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Rb-Sr whole-rock age of the contact aureole of the Stillwater Igneous Complex,Montana     

Paul A. Mueller  Joseph L. Wooden 《Earth and Planetary Science Letters》1976,29(2):384-388

Fourteen whole-rock samples from three traverses through the contact aureole of the Stillwater Complex were analyzed for Rb, Sr and⁸⁷Sr/⁸⁶Sr. Twelve of these samples yielded an age of 2750 ± 45m.y.; (⁸⁷Sr/⁸⁶Sr)₀ = 0.705 ± 0.003 (2σ). In addition one whole rock and a biotite separate derived from it gave an age of 2544 m.y.; (⁸⁷Sr/⁸⁶Sr)₀ = 0.714. These data support a minimum age of 2750 m.y. for the intrusion of the complex.  相似文献   

Earth rotation and network geometry optimization for very long baseline interferometers     

A. Dermanis  Ivan I. Mueller 《Journal of Geodesy》1978,52(2):131-158

Very Long Baseline Interferometry (VLBI) is one of the new techniques which will probably dominate geodesy and geophysics in the near future. Its main advantage lies in the fact that it brings the accuracy of direction measurements to a level previously possible only for range measurements. This closes the gap between powerful range determination techniques such as laser ranging and the much less accurate determination of directions through photographic tracking of artificial earth satellites. The technique is geometric in the sense that the relevant observations are independent of the gravity field of the earth. However, the “orbits” of the observed extragalactic radio sources with respect to an earth-fixed system are dominated and perturbed by the rotation of the earth with respect to inertial frame. This allows the determination of polar motion, precession-nutation and length-of-the-day variations, and the technique becomes also “dynamic” in this respect. The capability of determining the geometry of a network of stations within a short time interval and with a centimeter level accuracy also allows the study of the variation of network geometry with time caused by earth tides and other periodic or secular station drifts. The main objective of the present work is the exploration of the capabilities of VLBI for the recovery of earth rotation and network geometry parameters. For this purpose, a number of characteristic experimental designs based on present and candidate for the near future station locations is chosen. The results from the analysis of simulated observations for each particular design are presented in the paper. Presented at IAG International Symposium on “Optimization of Design and Computation of Control Networks”, Sopron, Hungary, 4–10 July 1977.  相似文献   

Detection of crustal motion using spaceborne laser ranging systems     

Muneendra Kumar  Ivan I. Mueller 《Journal of Geodesy》1978,52(2):115-130

The spaceborne laser ranging (or lasering) system provides a method of precise positioning of a large number of points on the earth's surface in a short period of time. That is, a measure of the relative location of geodetic markers from a space platform can maintain horizontal and vertical control to 2 to 5 cm. At this level of control, small earth surface crustal motions should be detectable. Development of a model for the strain field can be constructed. Furthermore, the spaceborne lasering system can survey an area in a very short period of time (one to two weeks) and resurvey the area as required. System design parameters are now being established by NASA for a possible test flight aboard the Shuttle in 1982. These include design specifications of economical corner cubes for ground retroreflectors coupled with the evolution of engineering model to flight model development. If the experiment of the Shuttle proves to be successful, it is hoped to put the laser in a free flight satellite. This paper presents the results of a simulated analysis for this latter case. The system is conceived as an orbiting ranging device with a ground base grid of reflectors or transponders (spacing 10 to 30 km), which are projected to be of low cost (maintenance-free and unattended) and which will permit the saturation of a local area to obtain data useful to monitor crustal movements. The test network includes 75 stations with roughly half of them on either side of the San Andreas fault zone. Critical study comparatively evaluates various observational schemes and statistically analyzed crustal motion recovery. The study considers laser radar as the main ranging system pending final selection from many possible candidates. The satellite orbit is inclined at 110° and slightly eccentric (e=0.04) with orbital altitudes varying from 370 km to 930 km. The results indicate that the geometric mode (simultaneous ranging) with a minimum of five grid and three distant (fundamental) stations and mixed ranging to satellite and airplane seems to be most promising. The fundamental stations are distinguished from the grid station in their location and this location should be “distant” enough from the area of crustal movement so that they can be considered stationary over the time span of the motion involved. Presented at the 1977 I.A.G. International Symposia on Satellite Geodesy, Budapest, Hungary, June 28–July 1, and on Recent Crustal Movements, Palo Alto, California, USA, July 25–30.  相似文献   

A hybrid simulation of Mercury’s magnetosphere for the MESSENGER encounters in year 2008     

Y.-C. Wang  J. Mueller  W.-H. Ip 《Icarus》2010,209(1):46-52

The latest measurements from the two encounters of the MESSENGER spacecraft in year 2008 have discovered several interesting features of the magnetosphere of Mercury. We have performed high-resolution 3D hybrid model calculations to simulate the solar wind interaction with the Hermean magnetosphere during the first two Mercury encounters of the MESSENGER spacecraft in 2008. It is found that the global structure of the Hermean magnetosphere is significantly controlled by the direction of the interplanetary magnetic field. The bow shock size and shape and the magnetotail configuration have very large differences in these two encounters with northward-pointing and southward-pointing interplanetary magnetic field, respectively. Comparisons are also given with the observed magnetic field profiles and the computational results. In general, good agreement can be found including the interesting feature of the relatively thick magnetopause current layer at outbound measurements. Our work shows that 3D hybrid simulation is a promising method to study in detail the Hermean magnetosphere in parallel with the post-MOI observations of the MESSENGER spacecraft and the Bepi-Colombo mission in future.  相似文献   

Rapid growth of an Archean continent by arc magmatism     

Paul A. Mueller  Joseph L. Wooden  David W. Mogk  Darrell J. Henry  Donald R. Bowes 《Precambrian Research》2010

The voluminous Meso- to Neoarchean rocks exposed in the Beartooth Mountains of the northern Wyoming Province of western North America comprise the Long Lake Magmatic Complex (LLMC), a variably metamorphosed and deformed association of igneous and meta-igneous plutonic rocks with SiO₂ ranging from at least 52 to 78 wt%. Within this compositional range, rock types include lineated amphibolites to hornblende-bearing gneisses of intermediate composition and multiple generations of foliated to unfoliated granitoids. Emplacement ages range between approximately 2.79 and 2.83 Ga, based on U–Pb zircon geochronology (SHRIMP). Field relations, elemental compositions, and geochronology indicate that these rocks do not represent a single fractional crystallization sequence, but rather, the LLMC was constructed by injection of numerous, discrete magmas as sill-like bodies over an ∼40 Ma period. Although there is a continuum of compositions in the LLMC, trace element abundances can be used to distinguish distinct sources and petrogenetic processes that can be broadly extrapolated to at least 3 compositional groupings: (1) trondhjemitic to granitic intrusive rocks with SiO₂ >70 wt%, (2) variably metamorphosed granodioritic orthogneisses with SiO₂ between 63 and 70 wt%, and (3) amphibole-bearing mafic to intermediate gneisses with SiO₂ between 52 and 63 wt%. Despite the range of SiO₂ contents, maximum LREE abundances are similar across the compositional range and, consequently, exhibit a wide range of (La/Yb)_n ratios (∼20–130). All LLMC rocks share a relative depletion in HFSE abundances similar to modern convergent margin magmas. Initial Sr and Nd isotopic compositions across the compositional range are consistently offset from typical bulk silicate earth (BSE) values and preclude unaltered derivation from primitive or depleted mantle. Common Pb isotopic data define a single array that lies above model crustal growth curves and, along with the Nd and Sr data, suggest relatively uniform interaction with, or derivation from, older lithosphere. The combined isotopic and elemental data suggest the LLMC resulted from simultaneous, rapid, and voluminous production of diverse magmas that represent melting of isotopically similar, but compositionally distinct, crustal and mantle sources. Dynamically, Meso- to Neo-archean crustal growth in the northern Wyoming Province appears to require an environment similar to a modern ocean–continent convergent margin with a comparable rate of crustal production and diversity of magma series. The resultant crust and associated mantle lithosphere (keel) appear to have suffered little-to-no modification prior to Laramide (Cretaceous) uplift and exposure.  相似文献   

Spin Axis Direction of Comet 19p/Borrelly Based on Observations from 2000 and 2001     

Samarasinha  Nalin H.  Mueller  Béatrice E. A. 《Earth, Moon, and Planets》2002,90(1-4):473-482

We calculate the direction of the rotational angular momentum vector,M, of comet 19P/Borrelly based on rotational lightcurve data from 2000, groundbased imaging of the coma during the Deep Space 1encounter, and the basic near-nucleus coma morphology as revealed by the Deep Space 1 spacecraft. For the most likely direction, we derivea family of solutions (with center at RA = 221°, Dec = -7°) if the direction of M is towards the sunward hemisphere during the Deep Space 1 encounter, whereas if the rotation is of opposite sense, the diametrically opposite family of solutions (with center at RA = 41°, Dec = 7°) would result. We argue that the coma morphology in September 2001 is consistent with the nucleus being a principal axis rotator or one observationally indistinguishable from it. Therefore, for all practical purposes, the direction of the rotational angular momentum vector coincides with the spin axis. We also discuss why the determination of the spin axis direction based on observations from the last apparition is in disagreement with the current result.  相似文献   

Development of an In Situ Ion-Exchange Technique for the Determination of Free Cd,Co, Ni,and Zn Concentrations in Freshwaters     

A. Crémazy  S. Leclair  K. K. Mueller  B. Vigneault  P. G. C. Campbell  C. Fortin 《Aquatic Geochemistry》2015,21(2-4):259-279

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In-flight calibration of the HIFI diplexers     

Michael Mueller  Willem Jellema  Bertrand Delforge  David Teyssier  Martin Eggens  Robert Huisman  Geert Keizer 《Experimental Astronomy》2014,37(2):369-379

HIFI is a heterodyne spectrometer aboard the Herschel Space Observatory, providing high-spectral-resolution capabilities. Of its seven frequency bands, four (bands 3, 4, 6, and 7) employ Martin-Puplett diplexers to combine sky signal and local oscillator at the two linear polarizations H and V, prior to feeding them into the mixers (receivers). The optical path difference in each of these 8 diplexers must be tuned to the observed frequency. The required actuator currents were determined in flight before the start of routine science observations. We here report on regular (roughly quarterly) engineering test observations to validate the repeatability of the HIFI diplexers during the routine phase of Herschel operations. We find the optical path difference to be stable to within 0.4 % of the relevant wavelength, typically at the sub-micron level. We conclude that the repeatability and precision of the diplexer tuning mechanism are so high that science data are in no way negatively affected. With the diplexer calibration established and validated, this line of reasoning can be reversed, and the diplexers can be used as relative spectrometers to measure the local-oscillator frequency, i.e., to check the spectral purity of the local oscillator across the diplexer bands. This was done from before launch out to the last months of cryogenic operations in space.  相似文献   

R- and J-band photometry of Comets 2P/Encke and 9P/Tempel 1     

Carl W. Hergenrother  Beatrice E.A. Mueller  N.H. Samarasinha 《Icarus》2006,181(1):156-161

Near-simultaneous R- and J-band photometric measurements of the short-period Comets 2P/Encke and the Deep Impact mission target 9P/Tempel 1 were obtained. The resulting R-J colors are +0.82±0.08 mag and +1.46±0.13 mag for Encke and Tempel 1, respectively. Tempel 1's color is redder than the solar R-J color index of +0.76. The Tempel 1 observations directly detected the nucleus while the Encke observations likely suffered from coma contamination.  相似文献