Observatorio National

Brazil

Observatorio National

Brazil
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Carlos D.U.,VALE S.A. | Uieda L.,Observatorio National | Barbosa V.C.F.,Observatorio National | Braga M.A.,VALE S.A. | Gomes A.A.S.,VALE S.A.
SEG Technical Program Expanded Abstracts | Year: 2011

We have interpreted the airborne gravity gradiometry data from Quadrilátero Ferrífero, an iron ore province in southeastern Brazil. Aiming at retrieving the geometry of the iron body, we have used a fast and novel gravity inversion method for estimating a 3D density-contrast distribution defined on a grid of prisms. This inversion approach combines robust data-fitting with an iterative procedure that does not require the solution of a large equation system. By using a systematic search algorithm, the estimated mass grows around prismatic elements called "seeds". The interpreter specifies the locations and the associated density contrasts of the seeds. Automatically, the inversion method fits the observations and favors compact gravity sources closest to the seeds. To produce a more robust data fitting than least-squares fit, the inversion method minimizes the L1 - norm of the residuals. Hence, it allows the presence of large residuals, so that outliers produced by non-targeted bodies can be handled. By using 126 seeds which were assigned density contrasts of 0.5 g.cm-3 and whose locations were based on our knowledge about the QF area, we have retrieved a continuous elongated iron body that fits the observed components of the gravity gradient. Our inversion result agrees reasonably with previous geophysical interpretations. In addition, our result honors the borehole information about the iron body depth. © 2011 Society of Exploration Geophysicists.


Honscheid K.,Ohio State University | Elliott A.,Ohio State University | Annis J.,Fermi National Accelerator Laboratory | Bonati M.,U.S. National Optical Astronomy Observatories | And 14 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

The Dark Energy Camera (DECam) is a new 520 Mega Pixel CCD camera with a 3 square degree field of view designed for the Dark Energy Survey (DES). DES is a high precision, multi-bandpass, photometric survey of 5000 square degrees of the southern sky. DECam is currently being installed at the prime focus of the Blanco 4-m telescope at the Cerro-Tololo International Observatory (CTIO). In this paper we describe SISPI, the data acquisition and control system of the Dark Energy Camera. SISPI is implemented as a distributed multi-processor system with a software architecture based on the Client-Server and Publish-Subscribe design patterns. The underlying message passing protocol is based on PYRO, a powerful distributed object technology system written entirely in Python. A distributed shared variable system was added to support exchange of telemetry data and other information between different components of the system. We discuss the SISPI infrastructure software, the image pipeline, the observer console and user interface architecture, image quality monitoring, the instrument control system, and the observation strategy tool. © 2012 SPIE.


Honscheid K.,Ohio State University | Eiting J.,Ohio State University | Elliott A.,Ohio State University | Annis J.,Fermi National Accelerator Laboratory | And 20 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

In this paper we describe the data acquisition and control system of the Dark Energy Camera (DECam), which will be the primary instrument used in the Dark Energy Survey (DES). DES is a high precision multibandpath wide area survey of 5000 square degrees of the southern sky. DECam currently under construction at Fermilab will be a 3 square degree mosaic camera mounted at the prime focus of the Blanco 4m telescope at the Cerro-Tololo International Observatory (CTIO). The DECam data acquisition system (SISPI) is implemented as a distributed multi-processor system with a software architecture built on the Client-Server and Publish-Subscribe design patterns. The underlying message passing protocol is based on PYRO, a powerful distributed object technology system written entirely in Python. A distributed shared variable system was added to support exchange of telemetry data and other information between different components of the system. In this paper we discuss the SISPI infrastructure software, the image pipeline, the observer interface and quality monitoring system, and the instrument control system. © 2010 SPIE.


Honscheid K.,Ohio State University | Elliott A.,Ohio State University | Bonati M.,U.S. National Optical Astronomy Observatories | Buckley-Geer E.,Fermi National Accelerator Laboratory | And 20 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2014

The Dark Energy Camera (DECam) is a new 520 Mega Pixel CCD camera with a 3 square degree field of view built for the Dark Energy Survey (DES). DECam is mounted at the prime focus of the Blanco 4-m telescope at the Cerro-Tololo International Observatory (CTIO). DES is a 5-year, high precision, multi-bandpass, photometric survey of 5000 square degrees of the southern sky that started August 2013. In this paper we briefly review SISPI, the data acquisition and control system of the Dark Energy Camera and follow with a discussion of our experience with the system and the lessons learned after one year of survey operations. © 2014 SPIE.


Oliveira V.C.,Observatorio National | Barbosa V.C.F.,Observatorio National
SEG Technical Program Expanded Abstracts | Year: 2011

We present a new 3D gravity-inversion approach that retrieves the geometry of an isolated geologic source with known density contrast and depth of the top. We approximate the source by an interpretation model formed by an ensemble of vertically juxtaposed right prisms whose horizontal cross-sections are described by unknown polygons. The vertices of the polygon of each prism are described by polar coordinates with an unknown origin within the prism. Our method estimates the radii associated with the vertices of each polygon and the horizontal Cartesian coordinates of the unknown origin. The depth of the bottom of the interpretation model is estimated by a new criterion based on the curve of the estimated total-anomalous mass versus the data-misfit measure. Applications to both synthetic and field data sets show that our method obtains stable solutions that recover the geometry of the 3D source and fit the data, even in the case of a complex simulated body with variable dips and strikes. Our method has the advantage of requiring no constraints favoring homogeneity and compactness, which makes it operationally simple. © 2011 Society of Exploration Geophysicists.


Uieda L.,Observatorio National | Barbosa V.C.F.,Observatorio National
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

We present a new gravity gradient tensor inversion for estimating a 3D density-contrast distribution defined on a user-specified grid of prisms. Our method consists of an iterative algorithm that does not require the solution of large equation system. Instead, the solution grows systematically around user-specified prismatic elements called "seeds". Each seed can have a different density contrast, allowing the interpretation of multiples bodies with different density contrasts. The compactness of the solution is imposed by means of a regularizing function that favors compact bodies closest to the priorly specified seeds. The solution grows by accreting neighboring prisms of the current solution. The prisms for the accretion are chosen by systematically searching the set of current neighboring prisms. Therefore, this approach allows that the columns of the Jacobian matrix be calculated on demand. This is a known technique from computer science called "lazy evaluation", which greatly reduces the demand of computer memory and processing time. Test on synthetic data from multiple buried sources at different depths and on real data collected over iron deposits located in the Quadrilatáre Ferrífero, southeastern region of Brazil, confirmed the ability of our method in detecting sharp and compact bodies.


Oliveira Jr. V.C.,Observatorio National | Barbosa V.C.F.,Observatorio National
73rd European Association of Geoscientists and Engineers Conference and Exhibition 2011: Unconventional Resources and the Role of Technology. Incorporating SPE EUROPEC 2011 | Year: 2011

We present a new 3D gravity-inversion approach that retrieves the geometry of an isolated geologic source with density contrast and depth of the top known. We approximate the source by an ensemble of vertically juxtaposed 3D right prisms whose horizontal cross-sections are described by polygons and thicknesses are fixed. The polygon vertices of each prism are described by polar coordinates with an unknown origin within the prism. Our method estimates the horizontal Cartesian coordinates of the unknown origin and the radii of the vertices of each polygon. To obtain stable estimates we impose constraints on the source shape. The estimated solution, despite being stable and fitting the data, will depend on the maximum depth assumed for the set of 3D prisms. We also propose a new criterion to determine the optimum depth-to-bottom estimate of the source based on the curve of the estimated total-anomalous mass versus estimated data-misfit measure for the range of different tentative maximum depths considered. Applications to both synthetic and field data show that our method obtains stable solutions that recover the geometry of the 3D source and fit the data, even in the case of a complex simulated body with variable dips and strikes.

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