Robust Real-Time Wide-Area Differential GPS Navigation

The present invention provides a method and a device for providing superior differential GPS positioning data. The system includes a group of GPS receiving ground stations covering a wide area of the Earth's surface. Unlike other differential GPS systems wherein the known position of each ground station is used to geometrically compute an ephemeris for each GPS satellite. the present system utilizes real-time computation of satellite orbits based on GPS data received from fixed ground stations through a Kalman-type filter/smoother whose output adjusts a real-time orbital model. ne orbital model produces and outputs orbital corrections allowing satellite ephemerides to be known with considerable greater accuracy than from die GPS system broadcasts. The modeled orbits are propagated ahead in time and differenced with actual pseudorange data to compute clock offsets at rapid intervals to compensate for SA clock dither. The orbital and dock calculations are based on dual frequency GPS data which allow computation of estimated signal delay at each ionospheric point. These delay data are used in real-time to construct and update an ionospheric shell map of total electron content which is output as part of the orbital correction data. thereby allowing single frequency users to estimate ionospheric delay with an accuracy approaching that of dual frequency users

Use of Radio Occultation to Evaluate Atmospheric Temperature Data from Spaceborne Infrared Sensors

With its high accuracy, stability, and worldwide coverage GPS radio occultation offers an attractive means of independently validating and calibrating the world's premier weather and climate sensors. These include such instruments as AIRS, AMSU, and MODIS on NASA's EOS platforms, and similar systems on operational weather satellites. GPSRO also offers a valuable comparison standard for global weather analyses, such as those produced by NOAA's National Center for Environmental Predictions (NCEP) and the European Centre for Medium-RangeWeather Forecasts (ECMWF)

Integration of space geodesy: a US National Geodetic Observatory

In the interest of improving the performance and efficiency of space geodesy a diverse group in the U.S., in collaboration with IGGOS, has begun to establish a unified National Geodetic Observatory (NGO)

From Data to Knowledge in Earth Science, Planetary Science, and Astronomy

This paper examines three NASA science data archive systems from the Earth, planetary, and astronomy domains, and discusses the various efforts underway to provide their science communities with not only better access to their holdings, but also with the services they need to interpret the data and understand their physical meaning. The paper identifies problems common to all three domains and suggests ways that common standards, technologies, and even implementations be leveraged to benefit each other

"A Riotous Spray of Words": Rethinking the Medieval Theory of Satire

This article offers a reconsideration of the theory of satire found in medieval exegesis. While acknowledging the importance of recent scholarship on the subject, such as the studies by Paul Miller and Udo Kindermann, it also seeks to develop the findings of this criticism further. Particular attention is paid to commentaries that offer more unusual remarks on classical satire. It is argued that these observations constitute a second tendency in the medieval response to satire, which identifies more scurrilous and disruptive potential in the genre