Search

Ponencia expuesta online en el 8th International Radio Occultation Working Group Meeting (2021) celebrado del 7 al 9 de abril, Ground and satellite based GNSS Remote Sensing (GNSS-RS) developed during the recent two decades into a very powerful and versatile tool for Earth System Research. A highlight of these developments is the operational use of spaceborne GNSS Radio Occultation (RO) data from several satellite missions to improve day-by-day global weather predictions. GNSS Remote Sensing is briefly introduced with selected applications. One prominent example is the improvement of regional and global weather forecasts. GNSS signals, reflected from water, ice and land surfaces (GNSS-Reflectometry, GNSS-R) can usefully complement the observation capabilities of GNSS-RO mission and enable versatile additional geophysical applications such as observation of wind speed and precipitation over oceans, which are illustrated. Finally, selected aspects for a comprehensive GNSS based Earth Observation with small satellite constellations are presented.

Experimental work with high intensity lasers at the Rutherford Appleton Laboratory has led to the production of both XUV laser and XUV harmonic sources with extreme brightness. In particular an efficient XUV laser source has been developed based on collisionally excited neon -like Ge XXIII(J=0-1) at 19.6 nm using the high power glass laser Vulcan generating 75 ps pulses. With Vulcan operating in sub -ps CPA mode, extremely powerful and short wavelength XUV high harmonic sources have been obtained by irradiation of solid targets and recombinant laser action with high gain has been demonstrated with fibre targets. An ultra-bright Krypton-fluoride laser system, Sprite(recently upgraded to a new configuration Titania) has produced the shortest harmonic wavelength (6.7 nm) and has been used to assess the possibilities of optical field ionised recombinant laser action with gas jet targets. The Ge XUV laser has been successfully applied in fusion research for radiographic measurements of the effect of laser speckle on the hydrodynamic stability of laser accelerated thin foils. The present status of the work, the comparative performance of the XUV laser and harmonic sources and near-term future directions are reviewed.

We report on measurements of a saturated single frequency Ne-like Ge XUV laser on the J = 0->1 transition at 19.6 nm from a refraction compensating double target driven by 150 J of energy from 75 ps Nd-laser pulses. The 19.6 nm line completely dominated the laser output. The output energy was measured to be 0.9 mJ, corresponding to a conversion efficiency of 6x10(-6).

Polysilicon fuses are one time programmable memory elements which allow the calibration of integrated circuits at wafer and package level. We present a zero dimensional lumped parameter model of the programming of fuses made from a combination of tungsten silicide and polycrystalline silicon. The components of the model are an electrical model, a thermal model and a flow model. The electrical model describes the temperature and geometry dependent resistance of the fuse. The thermal model describes the heating and melting of the fuse and its surroundings. The flow model describes the disconnection of the fuse by electromigration driven flow of silica. The model generates quantitatively accurate results and reproduces trends with applied voltage and fuse size., Comment: 3 pages, 4 figures, 1 table

The GPS radio occultation experiment within the German geoscience CHAMP (Challenging Minisatellite Payload) satellite mission has been activated now for more than 3 years. More than 250,000 occultation measurements are expected as of April 2004. Since the life time of the CHAMP satellite is predicted to last longer than 2007, the first and unique long-term set of GPS occultation data is anticipated. GFZ provides results of an operational occultation data analysis via the Information System and Data Center (ISDC). The results are available at different processing levels: atmospheric excess phase data, bending angles and vertical profiles of refractivity. Due to the ambiguity of dry and wet component to the refractivity, the bending angles and refractivity profiles are currently used to provide additional information for the data assimilation to improve the numerical weather forecast. First impact studies already demonstrated the ability of the CHAMP refractivity data to improve the global forecasts. The temperature profiles, provided at ISDC, are calculated assuming that the air is dry. The resulting dry temperature profiles are almost identical with the real temperature at altitudes above 10 km, where the wet component of the refractivity can be neglected. However, vertical profiles of the tropospheric temperature and water vapor can only be derived using ancillary atmospheric information from e.g. meteorological analyses (either temperature or water vapor). Tropospheric water vapor and temperature profiles are derived using the improved version (005) of GFZ’s operational refractivity profiles, which will be provided via ISDC by about mid 2004. The Full Spectrum Inversion (FSI) technique is used for the data analysis in the lower troposphere. To combine the measurements with the ancillary meteorological information in a statistically optimal way an operational 1Dvar retrieval code is used for the water vapor profiling. The results are validated with ECMWF analyses and radiosonde data.

An alternative to the traditional retrieval algorithms currently used in the retrieval of temperature and moisture profiles from GPS based radio occultation are retrieval methods based on optimal estimation principles. Such variational algorithms have become a quasi-standard in most fields of remote sensing data, since they have been proven to be comparatively robust against errors in both observational and a priori data. In addition, sensible error estimates of the derived geophysical quantities can be obtained. Theoretical investigations of their merits in the field of GPS based radio occultations have been presented by Healy and Eyre (2001) and Palmer et al (2001). There is, however, only limited practical experience with this type of retrieval algorithms in a quasi-operational environment for large volumes of data. We discuss the 1D variational retrieval developed for CHAMP radio occultation data. Results from the variational retrieval are compared with those from the traditional one, and comparisons with independent meteorological measurements (especially radiosondes) will be presented.

We report on measurements of the saturated single frequency output of a Ge XXIII x-ray laser on the J=0→1 transition at 19.6 nm from a refraction compensating double target driven by 150 J of energy from 75-ps Nd-glass laser pulses. The 19.6-nm line completely dominated the laser output. The output energy was measured to be 0.9 mJ in a beam of 6.6×30 mrad2 divergence, corresponding to a conversion efficiency of 6 ×10-6.

Experimental work with high intensity lasers at the Rutherford Appleton Laboratory has led to the production of both XUV laser and XUV harmonic sources with extreme brightness. In particular an efficient XUV laser source has been developed based on collisionally excited neon -like Ge XXIII(J=0-1) at 19.6 nm using the high power glass laser Vulcan generating 75 ps pulses. With Vulcan operating in sub -ps CPA mode, extremely powerful and short wavelength XUV high harmonic sources have been obtained by irradiation of solid targets and recombinant laser action with high gain has been demonstrated with fibre targets. An ultra-bright Krypton-fluoride laser system, Sprite(recently upgraded to a new configuration Titania) has produced the shortest harmonic wavelength (6.7 nm) and has been used to assess the possibilities of optical field ionised recombinant laser action with gas jet targets. The Ge XUV laser has been successfully applied in fusion research for radiographic measurements of the effect of laser speckle on the hydrodynamic stability of laser accelerated thin foils. The present status of the work, the comparative performance of the XUV laser and harmonic sources and near-term future directions are reviewed.

We report on measurements of a saturated single frequency Ne-like Ge XUV laser on the J = 0->1 transition at 19.6 nm from a refraction compensating double target driven by 150 J of energy from 75 ps Nd-laser pulses. The 19.6 nm line completely dominated the laser output. The output energy was measured to be 0.9 mJ, corresponding to a conversion efficiency of 6x10(-6).

This paper will investigate the different spaces and different times of radio and the Internet. This is part of the wider question of how sound art is playing out in digital culture. I will look specifically at the project Checklist for an Armed Robber, which was both an ABC radio drama and an associated ABC new media online work.