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At least 415 records · Page 23

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NASA NTRS2013

Combinations of Earth Orientation Measurements: SPACE2011, COMB2011, and POLE2011

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2011, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to July 13, 2012, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2011 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2011, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to July 13, 2012, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2011, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 21, 2012, at 30.4375-day intervals.

Ratcliff, J. T.↗

NASA NTRS2013

Unit-Sphere Anisotropic Multiaxial Stochastic-Strength Model Probability Density Distribution for the Orientation of Critical Flaws

Models that predict the failure probability of monolithic glass and ceramic components under multiaxial loading have been developed by authors such as Batdorf, Evans, and Matsuo. These "unit-sphere" failure models assume that the strength-controlling flaws are randomly oriented, noninteracting planar microcracks of specified geometry but of variable size. This report develops a formulation to describe the probability density distribution of the orientation of critical strength-controlling flaws that results from an applied load. This distribution is a function of the multiaxial stress state, the shear sensitivity of the flaws, the Weibull modulus, and the strength anisotropy. Examples are provided showing the predicted response on the unit sphere for various stress states for isotropic and transversely isotropic (anisotropic) materials--including the most probable orientation of critical flaws for offset uniaxial loads with strength anisotropy. The author anticipates that this information could be used to determine anisotropic stiffness degradation or anisotropic damage evolution for individual brittle (or quasi-brittle) composite material constituents within finite element or micromechanics-based software

Nemeth, Noel↗

NASA NTRS2013

Combinations of Earth Orientation Measurements: SPACE2012, COMB2012, and POLE2012

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2012, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to April 26, 2013, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2012 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2012, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to April 26, 2013, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2012, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to May 22, 2013, at 30.4375-day intervals.

Ratcliff, J. T.↗

NASA NTRS2015

Combinations of Earth Orientation Measurements: SPACE2013, COMB2013, and POLE2013

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2013, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to June 30, 2014, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2013 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2013, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to June 30, 2014, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2013, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2014, at 30.4375-day intervals.

Ratcliff, J. T.↗

NASA NTRS2015

Combinations of Earth Orientation Measurements: SPACE2014, COMB2014, and POLE2014

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2013, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to June 30, 2014, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2013 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2013, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to June 30, 2014, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2013, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2014, at 30.4375-day intervals.

Ratcliff, J. T.↗

NASA NTRS2017

Combinations of Earth Orientation Measurements: SPACE2016, COMB2016, and POLE2016

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2016, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to June 30, 2017, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2016 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2016, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to June 30, 2017, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2016, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2017, at 30.4375-day intervals.

Ratcliff, J. T.↗

NASA NTRS2018

Combinations of Earth Orientation Measurements: SPACE2017, COMB2017, and POLE2017

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2017, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to June 29, 2018m at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2017 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2017, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962 to June 29, 2018, at daily intervals and which are also available inversions with epochs given at either midnight or noon; and (2) POLE2017, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1990, to June 22, 2018, at 30.4375-day intervals.

VLBI↗

NASA NTRS2019

Combinations of Earth Orientation Measurements: SPACE2018, COMB2018, and POLE2018

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2018, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to June 28, 2019, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2018 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2018, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to June 28, 2019, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2018, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2019, at 30.4375-day intervals.

VLBI↗

NASA NTRS2020

SNPP and N20 VIIRS Solar Vector Orientation Knowledge Error Detected by SDSM Sun Views

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a passive scanning Earth observing satellite radiometer. The VIIRS has 22 spectral bands with design center wavelengths from 0.41 to 12.01 μm, providing data to generate more than 20 Earth’s biogeophysical parameters. Fourteen of the 22 VIIRS bands are the reflective solar bands (RSBs), detecting Earth reflected sunlight. To ensure data quality, regular on-orbit radiometric calibrations of the RSBs are performed, mainly through observations of an onboard solar diffuser (SD). The spectral radiance provided by the sunlit SD depends on the SD screen transmittance which is a function of the solar vector orientation. Additionally, on orbit the SD’s bidirectional reflectance distribution function (BRDF) changes its value due to solar bombardment. The BRDF change is derived from the SD stability monitor (SDSM) measurements. The SDSM views the Sun through a screen with through holes (the SDSM screen) and the SD at almost the same time. The time series of the ratio of the signal strengths is a measure of the SD BRDF on-orbit change. Hence the measurements of the on-orbit SD BRDF change depends on the SDSM screen relative transmittance which is also solar vector orientation dependent. In this paper for both the SNPP and the NOAA-20 VIIRS instruments we examine the solar vector orientation knowledge error through matching the SDSM screen relative effective transmittances derived from the calibration data collected on the yaw maneuver and the regular orbits.

SNPP↗

NASA NTRS2004

Combinations of Earth orientation measurements : SPACE2003, COMB2003, and POLE2003

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the global positioning system have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2003, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28.0, 1976 to January 31.0, 2004 at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2003 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2003, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20.0, 1962 to January 31.0, 2004 at daily intervals and which is also available in versions whose epochs are given at either midnight or noon, and (2) POLE2003, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900 to January 21, 2004 at 30.4375-day intervals.

Gross, Richard↗

NASA NTRS2009

Combinations of Earth orientation measurements : SPACE2007, COMB2007, and POLE2007.

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2007, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to March 29, 2008, at daily intervals and is available in versions whose epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2007 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2007, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to March 29, 2008, at daily intervals and which is also available in versions whose epochs are given at either midnight or noon; and (2) POLE2007, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to March 22, 2008, at 30.4375-day intervals.

Gross, R. S.↗

NASA NTRS2010

Combinations of Earth orientation measurements : SPACE2008, COMB2008, and POLE2008

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2008, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to July 2, 2009, at daily intervals and is available in versions whose with epochs are given at either midnight or noon. The space-geodetic measurements used to generate SPACE2008 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2008, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to July 2, 2009, at daily intervals and which areis also available in versions whose with epochs are given at either midnight or noon; and (2) POLE2008, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2009, at 30.4375-day intervals..

Gross, R. S.↗

NASA NTRS2011

Combinations of Earth Orientation Measurements : SPACE2010, COMB2010, and POLE2010

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2010, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to July 15, 2011, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2010 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2010, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to July 15, 2011, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2010, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to June 22, 2011, at 30.4375-day intervals.

Gross, R. S.↗

NASA NTRS2013

Combinations of Earth Orientation Measurements: SPACE2011, COMB2011, and POLE2011

Gross, R. S.↗

NASA NTRS2015

Combinations of Earth orientation measurements: SPACE2014, COMB2014, and POLE2014

Independent Earth orientation measurements taken by the space-geodetic techniques of lunar and satellite laser ranging, very long baseline interferometry, and the Global Positioning System have been combined using a Kalman filter. The resulting combined Earth orientation series, SPACE2014, consists of values and uncertainties for Universal Time, polar motion, and their rates that span from September 28, 1976, to April 14, 2015, at daily intervals and is available in versions with epochs given at either midnight or noon. The space-geodetic measurements used to generate SPACE2014 have then been combined with optical astrometric measurements to form two additional combined Earth orientation series: (1) COMB2014, consisting of values and uncertainties for Universal Time, polar motion, and their rates that span from January 20, 1962, to April 14, 2015, at daily intervals and which are also available in versions with epochs given at either midnight or noon; and (2) POLE2014, consisting of values and uncertainties for polar motion and its rate that span from January 20, 1900, to March 23, 2015, at 30.4375-day intervals.

Gross, R.S.↗

NASA NTRSDate not supplied

How Discipline-Oriented DAACs Collaborate to Support Interdisciplinary Earth Science

The Earth system is made of multiple complex subsystems. While scientists tend to specialize in single subsystems or even portions of a subsystem, to fully understand the physical, chemical and biological processes occurring on the Earth, we must understand how these systems interact. Thus, scientists need to be able to expand beyond their chosen field and collaborate across disciplines. The NASA Earth Observing System Data and Information System (EOSDIS) is focusing on new capabilities to make interdisciplinary science easier. The EOSDIS DAACS are responsible for archiving and distributing NASA’s rapidly growing collection of satellite, airborne and field data. Like the scientists they serve, the DAACs are discipline oriented. This has many advantages. Scientists are able to interact with experts on data in their domain and receive data appropriate for their research. However, discipline-oriented services may be confusing to cross-disciplinary users who may not know how to get started. Fortunately, collaboration across scientific communities is a specialty of the DAACs who support interdisciplinary users with a collaborative culture and technology that empowers the open sharing of data, information, and knowledge within the scientific community and the wider public to accelerate scientific research and understanding. This presentation will discuss the capabilities of a discipline-oriented approach to support future Earth science goals including those of Open Science and cross-disciplinary collaboration.

Sara Lubkin↗

NASA NTRSDate not supplied

Autonomous Stabilization and Orientation Control of Hoisted Payloads

An orientation control system prototype has been developed for hoisted payloads. This system will allow payloads to be lifted off inclined surfaces while maintaining orientation control, allowing removal of tightly packed payloads without colliding with adjacent objects. For this concept, the payload is hoisted with a crane using a rigging system composed of a cable routed through two capstans and three or four attachment points on the payload. Motors rotate the capstans to adjust the cable lengths to the payload, and thereby control the orientation of the payload. Initial testing of the prototype was completed using manual control, however the algorithms necessary to fully automate the system are presented in this paper.

control↗

DOE OSTI2022

MODELLING FIBER ORIENTATION DURING ADDITIVE MANUFACTURING COMPRESSION MOLDING PROCESSES

The production of high-performance thermoplastic composites reinforced with short carbon fibers can be achieved by a novel “additive manufacturing-compression molding” technique. An advantage of such combination is two-fold: controlled fiber orientation in additive manufacturing and less void content by compression molding. In this study, a computational fluid dynamics model has been developed to predict the behavior of printed layers during fiber-reinforced thermoplastic extrusion and subsequent compression molding. The fiber orientation was modelled with a simple quadratic closure model. The interaction between the fibers is included using a rotary diffusion coefficient which becomes significant in concentrated regimes. Finally, the second order orientation tensor is coupled with the momentum equation as an anisotropic part of the stress term. The effect of processing parameters on the behavior of printed layers was investigated to determine the favorable printing scenarios. The developed numerical model enables design of high-performance composites with tunable mechanical properties.

Seta, Berin↗