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Zipf's Law is a mathematical expression of the relationship between size and rank orders of some discrete phenomena. We have used this relationship to predict the undiscovered viable copper reserves for the Zambian Copperbelt. This prediction has been reinforced by canvassing geological opinion. As two semi-numerate exploration geologists, we naively risk predicting the undiscovered gold resources of the West Australian shield.This paper was presented at Symposium 116.3, Quantitative Strategy for Exploration, held as part of the 25th International Geological Congress, Sydney, Australia, August 1976. 相似文献
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Lunar gravity field determination using SELENE same-beam differential VLBI tracking data 总被引:2,自引:0,他引:2
S. Goossens K. Matsumoto Q. Liu F. Kikuchi K. Sato H. Hanada Y. Ishihara H. Noda N. Kawano N. Namiki T. Iwata F. G. Lemoine D. D. Rowlands Y. Harada M. Chen 《Journal of Geodesy》2011,85(4):205-228
A lunar gravity field model up to degree and order 100 in spherical harmonics, named SGM100i, has been determined from SELENE and historical tracking data, with an emphasis on using same-beam S-band differential VLBI data obtained in the SELENE mission between January 2008 and February 2009. Orbit consistency throughout the entire mission period of SELENE as determined from orbit overlaps for the two sub-satellites of SELENE involved in the VLBI tracking improved consistently from several hundreds of metres to several tens of metres by including differential VLBI data. Through orbits that are better determined, the gravity field model is also improved by including these data. Orbit determination performance for the new model shows improvements over earlier 100th degree and order models, especially for edge-on orbits over the deep far side. Lunar Prospector orbit determination shows an improvement of orbit consistency from 1-day predictions for 2-day arcs of 6 m in a total sense, with most improvement in the along and cross-track directions. Data fit for the types and satellites involved is also improved. Formal errors for the lower degrees are smaller, and the new model also shows increased correlations with topography over the far side. The estimated value for the lunar GM for this model equals 4902.80080±0.0009 km3/s2 (10 sigma). The lunar degree 2 potential Love number k 2 was also estimated, and has a value of 0.0255 ± 0.0016 (10 sigma as well). 相似文献
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N. J. Rowlands P. G. Blight D. M. Jarvis C. C. von der Borch 《Australian Journal of Earth Sciences》2013,60(1-2):55-68
We have reconstructed the depositional environment of sulphate‐dolomite‐sand‐mud sequences of the Callanna Beds of the late Proterozoic Adelaidean System in three areas of the Willouran Ranges, South Australia. We interpret the Callanna Beds which represent the earliest Adelaidean sediments as having been deposited in a series of discrete shallow cratonic basins. The sequences in all three areas consist of cyclic hypersaline sand‐shale‐carbonate sheets and wedges. Hypersalinity has been inferred from a study of evaporites and their pseudomorphs, which imply basin evolution in sabkha and playa palaeoenvironments. We interpret the Callanna Beds in the Willouran Ranges to have been formed in playa lake or prograding sabkha complexes, that formed in a series of yoked half‐grabens within the tectonic setting of the Adelaide palaeorift. 相似文献
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Influence of age,size and condition factor on lipid concentration in the snapper Chrysophrys auratus
Survival, growth rates and functionality of larvae have been hypothesised to correlate with higher lipid provisioning in older teleosts. To test the lipid provisioning part of this hypothesis, we investigated the total and relative (mg/g) lipid (triglyceride) concentration in both the source (liver) and sink (gonad) lipidation organs of female snapper Chrysophrys auratus across age, size and condition factor throughout its spawning season. Age, size and condition factor had little discernible effect on the total or relative lipid concentration in either liver or gonadal tissue. Therefore, if oocyte quality (based on triglyceride concentration) is comparable across a population, research on the relationship between lipidomics and reproductive success needs to move beyond highlighting correlations to elucidating causation by focusing on the biochemical mechanisms of egg quality and larval survival, identifying maternal parameters associated with consistent lipid provisioning, and partitioning of phenotypic and genotypic maternal influences. 相似文献
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Erwan?MazaricoEmail author David?D.?Rowlands Terence?J.?Sabaka Kenneth?M.?Getzandanner David?P.?Rubincam Joseph?B.?Nicholas Michael?C.?Moreau 《Journal of Geodesy》2017,91(10):1141-1161
The goal of the OSIRIS-REx mission is to return a sample of asteroid material from near-Earth asteroid (101955) Bennu. The role of the navigation and flight dynamics team is critical for the spacecraft to execute a precisely planned sampling maneuver over a specifically selected landing site. In particular, the orientation of Bennu needs to be recovered with good accuracy during orbital operations to contribute as small an error as possible to the landing error budget. Although Bennu is well characterized from Earth-based radar observations, its orientation dynamics are not sufficiently known to exclude the presence of a small wobble. To better understand this contingency and evaluate how well the orientation can be recovered in the presence of a large 1\(^{\circ }\) wobble, we conduct a comprehensive simulation with the NASA GSFC GEODYN orbit determination and geodetic parameter estimation software. We describe the dynamic orientation modeling implemented in GEODYN in support of OSIRIS-REx operations and show how both altimetry and imagery data can be used as either undifferenced (landmark, direct altimetry) or differenced (image crossover, altimetry crossover) measurements. We find that these two different types of data contribute differently to the recovery of instrument pointing or planetary orientation. When upweighted, the absolute measurements help reduce the geolocation errors, despite poorer astrometric (inertial) performance. We find that with no wobble present, all the geolocation requirements are met. While the presence of a large wobble is detrimental, the recovery is still reliable thanks to the combined use of altimetry and imagery data. 相似文献
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Evaluation and validation of mascon recovery using GRACE KBRR data with independent mass flux estimates in the Mississippi Basin 总被引:1,自引:1,他引:0
S. Klosko D. Rowlands S. Luthcke F. Lemoine D. Chinn M. Rodell 《Journal of Geodesy》2009,83(9):817-827
The direct recovery of surface mass anomalies using GRACE KBRR data processed in regional solutions provides mass variation
estimates with 10-day temporal resolution. The approach undertaken herein uses a tailored orbit estimation strategy based
solely on the KBRR data and directly estimates mass anomalies from the GRACE data. We introduce a set of temporal and spatial
correlation constraints to enable high resolution mass flux estimates. The Mississippi Basin, with its well understood surface
hydrological modelling available from the Global Land Data Assimilation System (GLDAS), which uses advanced land surface modeling
and data assimilation techniques, and a wealth of groundwater data, provides an opportunity to quantitatively compare GRACE
estimates of the mass flux in the entire hydrological column with those available from independent and reliable sources. Evaluating
GRACE’s performance is dependent on the accuracy ascribed to the hydrological information, which in and of itself is a complex
challenge (Rodell in Hydrogeol J, doi:, 2007). Nevertheless, the Mississippi Basin is one of the few regions having a large hydrological signal that can support
a meaningful GRACE comparison on the spatial scale resolved by GRACE. The isolation of the hydrological signal is dependent
on the adequacy of the forward mass flux modeling for tides and atmospheric pressure variations. While these models have non-uniform
global performance they are excellent in the Mississippi Basin. Through comparisons with the independent hydrology, we evaluate
the effect on the solution of changing correlation times and distances in the constraints, altering the parameter recovery
for areas external to the Mississippi Basin, and changing the relative strength of the constraints with respect to the KBRR
data. The accuracy and stability of the mascon solutions are thereby assessed, especially with regard to the constraints used
to stabilize the solution. We show that the mass anomalies, as represented by surface layer of water within regional cells
have accuracy estimates of ±2–3 cm on par with the best hydrological estimates and consistent with our accuracy estimates
for GRACE mass anomaly estimates. These solutions are shown to be very stable, especially for the recovery of semi-annual
and longer period trends, where for example, the phase agreement for the dominant annual signal agrees at the 10-day level
of resolution provided by GRACE. This validation confirms that mascons provide critical environmental data records for a wide
range of applications including monitoring ground water mass changes. 相似文献
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Orbit determination of the Lunar Reconnaissance Orbiter 总被引:3,自引:1,他引:2
Erwan?MazaricoEmail author D.?D.?Rowlands G.?A.?Neumann D.?E.?Smith M.?H.?Torrence F.?G.?Lemoine M.?T.?Zuber 《Journal of Geodesy》2012,86(3):193-207
We present the results on precision orbit determination from the radio science investigation of the Lunar Reconnaissance Orbiter
(LRO) spacecraft. We describe the data, modeling and methods used to achieve position knowledge several times better than
the required 50–100 m (in total position), over the period from 13 July 2009 to 31 January 2011. In addition to the near-continuous
radiometric tracking data, we include altimetric data from the Lunar Orbiter Laser Altimeter (LOLA) in the form of crossover
measurements, and show that they strongly improve the accuracy of the orbit reconstruction (total position overlap differences
decrease from ~70 m to ~23 m). To refine the spacecraft trajectory further, we develop a lunar gravity field by combining
the newly acquired LRO data with the historical data. The reprocessing of the spacecraft trajectory with that model shows
significantly increased accuracy (~20 m with only the radiometric data, and ~14 m with the addition of the altimetric crossovers).
LOLA topographic maps and calibration data from the Lunar Reconnaissance Orbiter Camera were used to supplement the results
of the overlap analysis and demonstrate the trajectory accuracy. 相似文献