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