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Poedjono B.,Schlumberger | Chandrasekharan M.,National Geophysical Data Center
Society of Petroleum Engineers - Arctic Technology Conference 2014 | Year: 2014

In measurement while drilling (MWD), wellbore azimuth is determined relative to the direction of the geomagnetic field. Converting this magnetic azimuth to a true azimuth requires accurate knowledge of the direction of the geomagnetic field at the point of measurement downhole. In the Arctic, MWD processing must include corrections for rapid changes in the geomagnetic field caused by auroral electrojet currents. The auroral zone, those latitudes at which the aurora borealis (or the northern lights) occurs, is a region where the electric field of the magnetosphere precipitates along magnetic field lines into the ionosphere. At 100 km above the surface, this electric field drives auroral electrojet currents in the east/west direction, generating the strongest magnetic field disturbances on the planet. The direction of the geomagnetic field in the auroral zone can change by several degrees in less than an hour. Data from geomagnetic observatory and variometer stations can be analyzed to characterize the auroral electrojets and compensate for the disturbance. Knowledge of the spatial structure of the electrojets' magnetic signature is essential for deploying a ground network of monitoring stations in the Arctic. This network provides the real-time geomagnetic infrastructure essential to support MWD operations, making it the most cost-effective technology available to achieve accurate wellbore placement in horizontal, relief well, and extended reach drilling, as well as in collision-avoidance applications. In one case study using historical data from two nearby observatories from 1995 to the present, the disturbance field was characterized and a time series of maximum disturbances was derived and extrapolated to the year 2020. Maximum disturbance in the magnetic field was found to lag the maximum of solar activity by approximately two years, predicting the next maximum in 2015-2019. Copyright 2014, Offshore Technology Conference.


Alken P.,University of Colorado at Boulder | Alken P.,National Geophysical Data Center | Maus S.,University of Colorado at Boulder | Maus S.,National Geophysical Data Center | And 4 more authors.
Earth, Planets and Space | Year: 2015

The International Geomagnetic Reference Field (IGRF) is a model of the geomagnetic main field and its secular variation, produced every 5 years from candidate models proposed by a number of international research institutions. For this 12th generation IGRF, three candidate models were solicited: a main field model for the 2010.0 epoch, a main field model for the 2015.0 epoch, and the predicted secular variation for the five-year period 2015 to 2020. The National Geophysical Data Center (NGDC), part of the National Oceanic and Atmospheric Administration (NOAA), has produced three candidate models for consideration in IGRF-12. The 2010 main field candidate was produced from Challenging Minisatellite Payload (CHAMP) satellite data, while the 2015 main field and secular variation candidates were produced from Swarm and Ørsted satellite data. Careful data selection was performed to minimize the influence of magnetospheric and ionospheric fields. The secular variation predictions of our parent models, from which the candidate models were derived, have been validated against independent ground observatory data. © 2015 Alken et al.; licensee Springer.


Tuttle B.T.,University of Denver | Anderson S.J.,University of South Australia | Sutton P.C.,University of South Australia | Sutton P.C.,University of Denver | And 2 more authors.
Photogrammetric Engineering and Remote Sensing | Year: 2013

Nighttime satellite imagery from the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) has a unique capability to observe nocturnal light emissions from sources including cities, wild fires, and gas flares. Data from the DMSP OLS is used in a wide range of studies including mapping urban areas, estimating informal economies, and estimations of population. Given the extensive and increasing list of applications a repeatable method for assessing geolocation accuracy would be beneficial. An array of portable lights was designed and taken to multiple field sites known to have no other light sources. The lights were operated during nighttime overpasses by the DMSP OLS and observed in the imagery. An assessment of the geolocation accuracy was performed by measuring the distance between the GPS measured location of the lights and the observed location in the imagery. A systematic shift was observed and the mean distance was measured at 2.9 km. © 2013 American Society for Photogrammetry and Remote Sensing.


Tuttle B.T.,University of Denver | Anderson S.,University of South Australia | Elvidge C.,National Geophysical Data Center | Ghosh T.,University of Colorado at Boulder | And 3 more authors.
Remote Sensing | Year: 2014

Nighttime satellite imagery from the Defense Meteorological Satellite Programs' Operational Linescan System (DMSP OLS) is being used for myriad applications including population mapping, characterizing economic activity, disaggregate estimation of CO2 emissions, wildfire monitoring, and more. Here we present a method for in situ radiance calibration of the DMSP OLS using a ground based light source as an active target. We found that the wattage of light used by our active target strongly correlates with the signal measured by the DMSP OLS. This approach can be used to enhance our ability to make intertemporal and intersatellite comparisons of DMSP OLS imagery. We recommend exploring the possibility of establishing a permanent active target for the calibration of nocturnal imaging systems. © 2014 by the authors.


Miller S.D.,Colorado State University | Straka W.,University of Wisconsin - Madison | Mills S.P.,Renaissance Man Engineering | Elvidge C.D.,National Geophysical Data Center | And 5 more authors.
Remote Sensing | Year: 2013

Daytime measurements of reflected sunlight in the visible spectrum have been a staple of Earth-viewing radiometers since the advent of the environmental satellite platform. At night, these same optical-spectrum sensors have traditionally been limited to thermal infrared emission, which contains relatively poor information content for many important weather and climate parameters. These deficiencies have limited our ability to characterize the full diurnal behavior and processes of parameters relevant to improved monitoring, understanding and modeling of weather and climate processes. Visible-spectrum light information does exist during the nighttime hours, originating from a wide variety of sources, but its detection requires specialized technology. Such measurements have existed, in a limited way, on USA Department of Defense satellites, but the Suomi National Polar-orbiting Partnership (NPP) satellite, which carries a new Day/Night Band (DNB) radiometer, offers the first quantitative measurements of nocturnal visible and near-infrared light. Here, we demonstrate the expanded potential for nocturnal low-light visible applications enabled by the DNB. Via a combination of terrestrial and extraterrestrial light sources, such observations are always available-expanding many current existing applications while enabling entirely new capabilities. These novel low-light measurements open doors to a wealth of new interdisciplinary research topics while lighting a pathway toward the optimized design of follow-on satellite based low light visible sensors.© 2013 by the authors; licensee MDPI, Basel, Switzerland.


Weigel R.S.,George Mason University | Zhizhin M.,Russian Academy of Sciences | Mishin D.,Russian Academy of Sciences | Kokovin D.,Russian Academy of Sciences | And 2 more authors.
Earth Science Informatics | Year: 2010

The recent Heliophysics Virtual Observatory (VxO) effort involves the development of separate observatories with a low overlap in physical domain or area of scientific specialization and a high degree of overlap in metadata management needs. VxOware is a content and metadata management system. While it is intended for use by a VxO specifically, it can also be used by any entity that manages structured metadata. VxOware has many features of a content management system and extensively uses the W3C recommendations for XML (Extensible Markup Language), XQuery (XML Query), and XSLT (Extensible Style Sheet Language Transformations). VxOware has features such as system and user administration, search, user-editable content, version tracking, and a wiki. Besides virtual observatories, the intended user-base of VxOware includes a group or an instrument team that has developed a directory structure of data files and would like to make this data, and its associated metadata, available in the virtual observatory network. One of the most powerful features of VxOware is the ability to link any type of object in the observatory to other objects and the ability for every object to be tagged. © 2010 Springer-Verlag.


Getmanov V.G.,Russian Academy of Sciences | Gvishiani A.D.,Russian Academy of Sciences | Stroker K.,National Geophysical Data Center | Mungov G.,National Geophysical Data Center
Izvestiya, Physics of the Solid Earth | Year: 2012

The problem of recognizing the time intervals with Rayleigh-wave disturbances in the signals from the depth pressure transducers of the ocean-bottom seismic stations (OBS) is considered in the context of the tsunami-warning problem. A new recognition algorithm, which makes use of the frequency-time distribution functions (FTD) of the OBS signals, and the decision-making procedure based on the comparison of the calculated and reference FTD functions are developed. The results of recognizing the Rayleigh wave disturbances in the OBS signals are presented. The suggested approach can serve as an efficient means for solving the problems of recognition and classification of the disturbances in the time series of various geophysical observations. © 2012 Pleiades Publishing, Ltd.


PubMed | University of Michigan, University of Colorado at Boulder, National Geophysical Data Center, Applied Physics LaboratoryJohns Hopkins UniversityLaurelMarylandUSA and 2 more.
Type: Journal Article | Journal: Earth and space science (Hoboken, N.J.) | Year: 2016

In this data report we discuss reprocessing of the Space Technology 5 (ST5) magnetometer database for inclusion in NASAs Coordinated Data Analysis Web (CDAWeb) virtual observatory. The mission consisted of three spacecraft flying in elliptical orbits, from 27 March to 27 June 2006. Reprocessing includes (1) transforming the data into the Modified Apex Coordinate System for projection to a common reference altitude of 110km, (2) correcting gain jumps, and (3) validating the results. We display the averaged magnetic perturbations as a keogram, which allows direct comparison of the full-mission data with the solar wind values and geomagnetic indices. With the data referenced to a common altitude, we find the following: (1) Magnetic perturbations that track the passage of corotating interaction regions and high-speed solar wind; (2) unexpectedly strong dayside perturbations during a solstice magnetospheric sawtooth oscillation interval characterized by a radial interplanetary magnetic field (IMF) component that may have enhanced the accompanying modest southward IMF; and (3) intervals of reduced magnetic perturbations or calms, associated with periods of slow solar wind, interspersed among variable-length episodic enhancements. These calms are most evident when the IMF is northward or projects with a northward component onto the geomagnetic dipole. The reprocessed ST5 data are in very good agreement with magnetic perturbations from the Defense Meteorological Satellite Program (DMSP) spacecraft, which we also map to 110km. We briefly discuss the methods used to remap the ST5 data and the means of validating the results against DMSP. Our methods form the basis for future intermission comparisons of space-based magnetometer data.

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