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[en] The most challenging difficulty of streamer marine 4D seismic technology is repeating a given acquisition geometry with high precision. This challenge does not exist onshore, and it should then be possible to aim for higher 4D sensitivity needed to observe changes in carbonated reservoirs. The different categories of 4D noises are first examined and the focus is then given to the necessary positioning accuracy of source and receiver deployment. On synthetic data, it is demonstrated that the effect of positioning inaccuracy on 4D noise depends on ]apparent velocity. It is small on fast velocities, large on slow velocities. For this reason, it cannot be compensated for by application of a 1-D matching filter. Therefore, seismic positioning requirements must be re-assessed to increase land 4D sensitivity. A field experiment confirms the previous synthetic examples, leading to the conclusions oas follows:- A 1-m relative accuracy (difference between base and monitor) on the array's centre of gravity is adequate (but also necessary) if the frequency in the target area does not exceed 50 Hz, the dips are relatively small (less than (15) and a -20dB 4D noise is acceptable. Otherwise, relative accuracy requirements should be increased. -Moreover, in the process of ground roll, extreme care should be taken in repeating the arrays themselves. This second requirement is obviously easier to fulfill with simple and short arrays. This remark suggests that the conventional 50-m 3D group interval (and array size) may constitute another reason for the slow development of 4d seismic technology on land
[en] Complete text of publication follows. While high-degree global models of the gravity field have been produced for decades, the break-through for magnetic models has only been achieved in the last few years. This is primarily due to three reasons: (1) Long wavelength control for a global model requires highly accurate satellite measurements at low orbital altitudes. These have only recently become available with the ongoing CHAMP mission. (2) Due to the secular change of the Earth's core field, marine and airborne magnetic surveys have unknown offsets which make it difficult to integrate 60 years of surveys into a common global field model. (3) The geopotential can conveniently be inferred from measurements of the gravity acceleration by direct integration. In contrast, the magnetic potential is not completely determined by measurements of the anomaly of the total intensity, and it has to be estimated in an iterative scheme. Here, we present our modeling approach starting with the determination of the long-wavelength lithospheric field from CHAMP data then merging the marine and aeromagnetic data into the EMAG2 global magnetic anomaly grid which then provides the basis for the estimation of the NGDC-720 model (http://geomag.org).
[en] We introduce a novel method to measure the masses of galaxy clusters at high redshift selected from optical and IR Spitzer data via the red-sequence technique. Lyman-break galaxies are used as a well-understood, high-redshift background sample allowing mass measurements of lenses at unprecedented high redshifts using weak lensing magnification. By stacking a significant number of clusters at different redshifts with average masses of ∼(1-3) x 1014 Msun, as estimated from their richness, we can calibrate the normalization of the mass-richness relation. With the current data set (area: 6 deg2) we detect a magnification signal at the >3σ level. There is good agreement between the masses estimated from the richness of the clusters and the average masses estimated from magnification, albeit with large uncertainties. We perform tests that suggest the absence of strong systematic effects and support the robustness of the measurement. This method-when applied to larger data sets in the future-will yield an accurate calibration of the mass-observable relations at z ∼> 1 which will represent an invaluable input for cosmological studies using the galaxy cluster mass function and astrophysical studies of cluster formation. Furthermore, this method will probably be the least expensive way to measure masses of large numbers of z > 1 clusters detected in future IR-imaging surveys.
[en] The Spitzer Extended Deep Survey (SEDS) is a very deep infrared survey within five well-known extragalactic science fields: the UKIDSS Ultra-Deep Survey, the Extended Chandra Deep Field South, COSMOS, the Hubble Deep Field North, and the Extended Groth Strip. SEDS covers a total area of 1.46 deg2 to a depth of 26 AB mag (3σ) in both of the warm Infrared Array Camera (IRAC) bands at 3.6 and 4.5 μm. Because of its uniform depth of coverage in so many widely-separated fields, SEDS is subject to roughly 25% smaller errors due to cosmic variance than a single-field survey of the same size. SEDS was designed to detect and characterize galaxies from intermediate to high redshifts (z = 2-7) with a built-in means of assessing the impact of cosmic variance on the individual fields. Because the full SEDS depth was accumulated in at least three separate visits to each field, typically with six-month intervals between visits, SEDS also furnishes an opportunity to assess the infrared variability of faint objects. This paper describes the SEDS survey design, processing, and publicly-available data products. Deep IRAC counts for the more than 300,000 galaxies detected by SEDS are consistent with models based on known galaxy populations. Discrete IRAC sources contribute 5.6 ± 1.0 and 4.4 ± 0.8 nW m–2 sr–1 at 3.6 and 4.5 μm to the diffuse cosmic infrared background (CIB). IRAC sources cannot contribute more than half of the total CIB flux estimated from DIRBE data. Barring an unexpected error in the DIRBE flux estimates, half the CIB flux must therefore come from a diffuse component.
[en] This study presents a search for infrared (IR) excess in the 3.4, 4.6, 12, and 22 μ m bands in a sample of 216 targets, composed of solar sibling, twin, and analog stars observed by the Wide-field Infrared Survey Explorer ( WISE ) mission. In general, an IR excess suggests the existence of warm dust around a star. We detected 12 μ m and/or 22 μ m excesses at the 3 σ level of confidence in five solar analog stars, corresponding to a frequency of 4.1% of the entire sample of solar analogs analyzed, and in one out of 29 solar sibling candidates, confirming previous studies. The estimation of the dust properties shows that the sources with IR excesses possess circumstellar material with temperatures that, within the uncertainties, are similar to that of the material found in the asteroid belt in our solar system. No photospheric flux excess was identified at the W1 (3.4 μ m) and W2 (4.6 μ m) WISE bands, indicating that, in the majority of stars of the present sample, no detectable dust is generated. Interestingly, among the 60 solar twin stars analyzed in this work, no WISE photospheric flux excess was detected. However, a null-detection excess does not necessarily indicate the absence of dust around a star because different causes, including dynamic processes and instrument limitations, can mask its presence.
[en] The article discusses the patterns of the polarization processes flowing in different types geo electric models under external electrical influence by the differential time mode, intended for direct measurements of the transitional characteristic second derivative of induced polarization at different configurations and parameters of the excitation. On the basis of the complex analysis of the characteristics of the amplitude time parameters of IP and the established regularities of the electrochemical charging of the geo electrical medium, are presented the main ways of the optimizing methods for performing such electrical prospecting studies
[en] During the Space Shuttle Endeavour mission in October 1994, a remote-sensing campaign was carried out with the objectives of both radiometric and polarimetric calibration and ground truth data acquisition of bare soils. This paper presents the results obtained in the experiment. Polarimetric cross-talk and channel imbalance values, as well as radiometric calibration parameters, have been found to be within the science requirements for SAR images. Regarding ground truth measurements, a wide spread in the height rms values and correlation lengths has been observed, which was motivated a critical revisiting of surface parameters descriptors
[en] We present initial results from the Wide-field Infrared Survey Explorer (WISE), a four-band all-sky thermal infrared survey that produces data well suited for measuring the physical properties of asteroids, and the NEOWISE enhancement to the WISE mission allowing for detailed study of solar system objects. Using a NEATM thermal model fitting routine, we compute diameters for over 100,000 Main Belt asteroids from their IR thermal flux, with errors better than 10%. We then incorporate literature values of visible measurements (in the form of the H absolute magnitude) to determine albedos. Using these data we investigate the albedo and diameter distributions of the Main Belt. As observed previously, we find a change in the average albedo when comparing the inner, middle, and outer portions of the Main Belt. We also confirm that the albedo distribution of each region is strongly bimodal. We observe groupings of objects with similar albedos in regions of the Main Belt associated with dynamical breakup families. Asteroid families typically show a characteristic albedo for all members, but there are notable exceptions to this. This paper is the first look at the Main Belt asteroids in the WISE data, and only represents the preliminary, observed raw size, and albedo distributions for the populations considered. These distributions are subject to survey biases inherent to the NEOWISE data set and cannot yet be interpreted as describing the true populations; the debiased size and albedo distributions will be the subject of the next paper in this series.
[en] We consider the results of a comparison of the two approaches to determine the coordinates of earthquake hypocenters. Various examples show that the determination of earthquakes hypocenters coordinates on the basis of minimizing the functional residuals hypocentral distances gives more accurate and consistent results comparedto the approach based on the minimization of the functional residuals of the travel time seismic waves
[en] The aim of true-amplitude imaging is to restore the amplitude information partially disappeared during different processing steps of the seismic data. In this paper, we try to develop a unified approach to the true-amplitude (TA) migration and partial migration (DMO) for two basic F-K and integral methods in 3D constant-offset data space. We, first, establish the connection between F-K and integral methods for TA migration in a 3D constant-offset medium. Secondly, we extend our analysis to unify the treatment of the TA migration and TA DMO within the same theoretical formulations for both F-K and integral approaches. Starting from the very general formulas obtained for F-K and integral methods in a 3D constant-offset environment, the amplitude preservation terms related to different acquisition configurations are derived as the special cases of the general formulation. Examples applied on synthetic and field data are given. Theoretical expectations are confirmed by the performance of the proposed method