Engineering topics
Heflin, Michael
Publications and source records attributed to Heflin, Michael.
Improving UAVSAR results with GPS, radiometry, and QUAKES topographic imager
UNKNOWN
Improving UAVSAR results with GPS, radiometry, and QUAKES topographic imager
UAVSAR is NASA’s airborne interferometricsynthetic aperture radar (InSAR) platform. The instrument has been used to detect deformation from earthquakes, volcanoes, oil pumping, landslides, water withdrawal, landfill compaction, and glaciers. It has been used to detect scars from wildfires and damage from debris flows. The instrument performs well for large changes or for local small changes. Determining subtle changes over large areas requires improved instrumentation and processing. We are working to improve the utility of UAVSAR by including GPS station position results in the processing chain, and adding a topographic imager to improve estimates of topography, 3D change, and damage. We are also exploring the benefit of microwave radiometry to mitigating error from water vapor path delay. A goal is to determine 3D tectonic deformation to millimeters per year at ~100 km plate boundary scales and to understand surface processes in areas of decorrelated radar imagery.
Improving UAVSAR Results with GPS, Radiometry, and QUAKES Topographic Imager
UNKNOWN
Use of Reference Frames for Interplanetary Navigation at JPL
Navigation of interplanetary spacecraft is typically based on range, Doppler, and differential interferometric measurements made by ground-based telescopes. Acquisition and interpretation of these observations requires accurate knowledge of the terrestrial reference frame and its orientation with respect to the celestial frame. Work is underway at JPL to reprocess historical VLBI and GPS data to improve realizations of the terrestrial and celestial frames. Improvements include minimal constraint alignment, improved tropospheric modeling, better orbit determination, and corrections for antenna phase center patterns.
Combining JPL/GPS and JPL/DORIS weekly free-network solutions for geodetic purposes: preliminary answers on local ties accuracy and reference frame stability
Explore the source record for details and available documents.
Rate Change Observed at JPLM after the Northridge Earthquake
Geodetic time series detemined with the Global Positioning System indicate that the geodetic rate of a permanent site in Pasadena, Califonia (JPLM) changed significantly after the 17 January 1994 Northridge California earthquake.
The International GPS Service (IGS) as a Continuous Reference System for Precise GPS Positioning
The International GPS Service for Geodynamics (IGS) is an organization which operates under the auspices of the International Association of Geodesy (IAG) and has been operational since January 1994. The primary objective of the IGS is to provide precise GPS data and data products to support geodetic and geophysical research activities.
Direct Comparison of GPS and VLBI Velocity Estimates
Considerable effort has been made to collocate permanent GPS and VLBI sites for comparison. The global GPS solution is derived from daily measurements spanning four years while the VLBI solution is based on monthly measurements spanning more than 10 years. Current WRMS agreement of velocities is 3-5 mm/yr for horizontal rates and 6-10 mm/yr for vertical rates. Comparison of velocities is limited by the time span of GPS data. Positions agree at the level of 1-2 cm and their comparison is limited by the quality of the site ties. Best and worst agreement will be discussed along with possible sources of systematic error.