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Hermann Lühr - One of the best experts on this subject based on the ideXlab platform.
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CHAMP Mission 5 Years in Orbit
Observation of the Earth System from Space, 2020Co-Authors: Christoph Reigber, Hermann Lühr, L. Grunwaldt, Christoph Förste, Rolf König, Heiner Massmann, Carsten FalckAbstract:In the summer of 2000 the geo-research satellite CHAMP was launched into orbit. Its innovative payload arrangement and its low injection altitude allow CHAMP to simultaneously collect almost uninterrupted measurement series relating to the Earth gravity and magnetic fields at low altitude. In addition, CHAMP sounds the neutral atmosphere and ionosphere using GPS observations onboard. After 60 months in orbit one arrives at a very positive conclusion for the CHAMP mission. The CHAMP satellite and its instruments have been operated almost uninterruptedly since launch. The great performance of the satellite subsystems and of the mission operation specialists has made it possible to keep CHAMP in the science operation mode for most of the time and in addition to lift its orbit two times. After a series of calibration and validation activities in the course of the mission, which included a number of onboard software updates and parameter adjustments, CHAMP has been providing excellent measurements from its state of the art instruments for now more than 4 years. The effective and steadily functioning of the CHAMP Science Data System and the supporting tracking networks has made it possible to provide large quantities of pre-processed data, precision data products and auxiliary information to hundreds of registered users in an almost uninterrupted manner. This was only possible due to the funding of the project DACH (CHAMP Data Acquisition and Data Use) within the ‘GEOTECHNOLOGIEN’ R+D programme of the BMBF. With the orbit altitude being presently about 60 km higher than originally planned for mid 2005, CHAMP will very likely orbit the Earth for another 3 years at quite low altitude. This mission extension at low altitude will make CHAMP a pioneering long-duration mission for geo-potential research and sounding of the atmosphere.
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first CHAMP mission results for gravity magnetic and atmospheric studies
Springer Press, 2003Co-Authors: Kathy Whaler, Ch. Reigber, Hermann Lühr, P SchwintzerAbstract:I Orbit and Earth Gravity Field.- CHAMP Orbit and Gravity Instrument Status.- On Board Evaluation of the STAR Accelerometer.- Determination of CHAMP Accelerometer Calibration Parameters.- CHAMP Accelerometer and Star Sensor Data Combination.- CHAMP Clock Error Characterization.- Determination of the CHAMP GPS Antenna with Respect to Satellite's Mass Center.- Spaceborne GPS for POD and Earth Science.- The CHAMP Orbit Comparison Campaign.- CHAMP Orbit Determination with GPS Phase-Connected, Precise Point Positioning.- Kinematic and Dynamic Determination of Trajectories for Low Earth Satellites Using GPS.- CHAMP Double-Difference Kinematic POD with Ambiguity Resolution.- Approaches to CHAMP Precise Orbit Determination.- STAR Accelerometer Contribution to Dynamic Orbit and Gravity Field Model Adjustment.- Impact of Different Data Combinations on the CHAMP Orbit Determination.- CHAMP Rapid Science Orbit Determination - Status and Future Prospects.- Orbit Predictions for CHAMP - Development and Status.- Thermospheric Events in CHAMP Precise Orbit Determination.- New Global Gravity Field Models from Selected CHAMP Data Sets.- First Insight into Temporal Gravity Variablility from CHAMP.- CHAMP Gravity Field Recovery with the Energy Balance Approach.- Preliminary Analysis of CHAMP State Vector and Accelerometer Data for the Recovery of the Gravity Potential.- CHAMP Precise Orbit Determination and Gravity Field Recovery.- Gravitational Field Modelling from CHAMP-Ephemerides by Harmonic Splines and Fast Multipole Techniques.- Evaluation of Geoid Models with GPS/Levelling Points in Sweden and Finland.- Geophysical Impact of Field Variations.- CHAMP, Mass Displacements and the Earth's Rotation.- CHAMP Gravity Anomalies over Antarctica.- Assimilation of Altimeter and Geoid Data into a Global Ocean Model.- Total Density Retrieval with STAR.- II Earth Magnetic Field.- CHAMP ME Data Processing and Open Issues.- Ion Drift-Meter Status and Calibration.- CO2 - A CHAMP Magnetic Field Model.- Decadal and Subdecadal Secular Variation of Main Geomagnetic Field.- Modelling the Earth's Magnetic Field: Wavelet Based and Standard Methods.- Improved Parameterization of External Magnetic Fields from CHAMP Measurements.- Monitoring Magnetospheric Contributions using Ground-Based and Satellite Magnetic Data.- Unraveling the Magnetic Mystery of the Earth's Lithosphere: The Background and the Role of the CHAMP Mission.- A Comparison of Global Lithospheric Field Models Derived from Satellite Magnetic Data.- Mapping the Lithospheric Magnetic Field from CHAMP Scalar and Vector Magnetic Data.- Improving the Definition of Cratonic Boundaries Utilizing the Lithospheric Magnetic Field derived from CHAMP Observations.- Crustal Magnetisation Distribution Deduced from CHAMP Data.- Multiscale Downward Continuation of CHAMP FGM-Data for Crustal Field Modelling.- CHAMP Enhances Utility of Satellite Magnetic Observations to Augment Near-Surface Magnetic Survey Coverage.- Comparing Magsat, Orsted and CHAMP Crustal Magnetic Anomaly Data over the Kursk Magnetic Anomaly, Russia.- CHAMP, Orsted and Magsat Magnetic Anomalies of the Antarctic Lithosphere.- Separation of External Magnetic Signal for Induction Studies.- Two-Dimensional Spatiotemporal Modelling of Satellite Electromagnetic Induction Signals.- Night-Time Ionospheric Currents.- Multiscale Determination of Radial Current Distribution from CHAMP FGM-Data.- Ionospheric Currents from CHAMP Magnetic Field Data - Comparison with Ground Based Measurements.- Mapping of Field-Aligned Current Patterns during Northward IMF.- Field-Aligned Currents Inferred from Low-Altitude Earth-Orbiting Satellites and Ionospheric Currents Inferred from Ground-Based Magnetometers - Do They Render Consistent Results?.- III Neutral Atmosphere and Ionosphere.- GPS Radio Occultation with CHAMP.- Validation and Data Quality of CHAMP Radio Occultation Data.- Global Climate Monitoring based on CHAMP/GPS Radio Occultation Data.- Initial Results on Ionosphere/Plasmasphere Sounding based on GPS Data Obtained On Board CHAMP.- Backpropagation Processing of GPS Radio Occultation Data.- Combination of NOAA16/ATOVS Brightness Temperatures and the CHAMP Data to get Temperature and Humidity Profiles.- An Improvement of Retrieval Techniques for Ionospheric Radio Occultations.- Validation of Water Vapour Profiles from GPS Radio Occultations in the Arctic.- Comparison of DMI-Retrieval of CHAMP Occultation Data with ECMWF.- The Assimilation of Radio Occultation Measurements.- Status of Ionospheric Radio Occultation CHAMP Data Analysis and Validation of Higher Level Data Products.- NWP Model Specific Humidities Compared with CHAMP/GPS and TERRA/MODIS Data.- Analysis of Gravity Waves from Radio Occultation Measurements.- GPS Atmosphere and Ionosphere Methods used on Orsted Data and Initial Application on CHAMP Data.- Combining Radio Occultation Measurements with Other Instruments to Map the Ionospheric Electron Concentration.- Vertical Gradients of Refractivity in the Mesosphere and Atmosphere Retrieved from GPS/MET and CHAMP Radio Occultation Data.- Observation of Reflected Signals in MIR/GEO and GPS/MET Radio Occultation Missions.- Assimilation Experiments of One-dimensional Variational Analyses with GPS/MET Refractivity.- Monitoring the 3 Dimensional Ionospheric Electron Distribution based on GPS Measurements.- Comparison of Three Different Meteorological Datasets (ECMWF, Met Office and NCEP).- Radio Occultation Data Processing at the COSMIC Data Analysis and Archival Center (CDAAC).- Verification of CHAMP Radio-Occultation Observations in the Ionosphere Using MIDAS.- Approach to the Cross-Validation of MIPAS and CHAMP Temperature and Water Vapour Profiles.- Author Index.- Keyword Index.
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sounding of the topside ionosphere plasmasphere based on gps measurements from CHAMP initial results
Geophysical Research Letters, 2002Co-Authors: Susanne Heise, A Wehrenpfennig, Norbert Jakowski, Ch. Reigber, Hermann LührAbstract:[1] Beside the GPS radio occultation measurements of the troposphere and ionosphere, the CHAMP satellite tracks presently up to 8 GPS satellites simultaneously for navigation. The received dual frequency GPS signals provide valuable information on the ionization state of the topside ionosphere and plasmasphere. This paper briefly describes a new developed model assisted technique to improve the three dimensional electron density estimation above the CHAMP orbit from these GPS measurements. Application of this assimilation algorithm provides a 2-D electron density slice of the ionosphere/plasmasphere system within the CHAMP orbit plane from the CHAMP altitude up to GPS orbit heights. We estimate the accuracy of the GPS TEC calibration and perform a first validation by comparing the retrieved electron density of the ionosphere/plasmasphere slice at CHAMP altitude to simultaneous electron density measurements of the Langmuir Probe onboard CHAMP.
Heinz Juergen Steinhoff - One of the best experts on this subject based on the ideXlab platform.
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salt driven equilibrium between two conformations in the hamp domain from natronomonas pharaonis the language of signal transfer
Journal of Biological Chemistry, 2008Co-Authors: Meike Doebber, Johann P. Klare, Martin Engelhard, Nadine Mennes, Julia Holterhues, Swetlana Martell, Enrica Bordignon, Lin Li, Heinz Juergen SteinhoffAbstract:Abstract HAMP domains (conserved in histidine kinases, adenylyl cyclases, methyl-accepting chemotaxis proteins, and phosphatases) perform their putative function as signal transducing units in diversified environments in a variety of protein families. Here the conformational changes induced by environmental agents, namely salt and temperature, on the structure and function of a HAMP domain of the phototransducer from Natronomonas pharaonis (NpHtrII) in complex with sensory rhodopsin II (NpSRII) were investigated by site-directed spin labeling electron paramagnetic resonance. A series of spin labeled mutants were engineered in NpHtrII157, a truncated analog containing only the first HAMP domain following the transmembrane helix 2. This truncated transducer is shown to be a valid model system for a signal transduction domain anchored to the transmembrane light sensor NpSRII. The HAMP domain is found to be engaged in a “two-state” equilibrium between a highly dynamic (dHAMP) and a more compact (CHAMP) conformation. The structural properties of the CHAMP as proven by mobility, accessibility, and intra-transducer-dimer distance data are in agreement with the four helical bundle NMR model of the HAMP domain from Archaeoglobus fulgidus.
William B Guggino - One of the best experts on this subject based on the ideXlab platform.
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epac1 mediates protein kinase a independent mechanism of forskolin activated intestinal chloride secretion
The Journal of General Physiology, 2010Co-Authors: Kazi Mirajul Hoque, William B Guggino, Owen M Woodward, Damian B Van Rossum, Nicholas C Zachos, Linxi Chen, George P H Leung, Sandra E GugginoAbstract:Intestinal Cl− secretion is stimulated by cyclic AMP (cAMP) and intracellular calcium ([Ca2+]i). Recent studies show that protein kinase A (PKA) and the exchange protein directly activated by cAMP (Epac) are downstream targets of cAMP. Therefore, we tested whether both PKA and Epac are involved in forskolin (FSK)/cAMP-stimulated Cl− secretion. Human intestinal T84 cells and mouse small intestine were used for short circuit current (Isc) measurement in response to agonist-stimulated Cl− secretion. FSK-stimulated Cl− secretion was completely inhibited by the additive effects of the PKA inhibitor, H89 (1 µM), and the [Ca2+]i chelator, 1,2-bis-(o-aminophenoxy)-ethane- N , N , N ’, N ’-tetraacetic acid, tetraacetoxymethyl ester (BAPTA-AM; 25 µM). Both FSK and the Epac activator 8-pCPT-2’-O-Me-cAMP (50 µM) elevated [Ca2+]i, activated Ras-related protein 2, and induced Cl− secretion in intact or basolateral membrane–permeabilized T84 cells and mouse ileal sheets. The effects of 8-pCPT-2’-O-Me-cAMP were completely abolished by BAPTA-AM, but not by H89. In contrast, T84 cells with silenced Epac1 had a reduced Isc response to FSK, and this response was completely inhibited by H89, but not by the phospholipase C inhibitor U73122 or BAPTA-AM. The stimulatory effect of 8-pCPT-2’-O-Me-cAMP on Cl− secretion was not abolished by cystic fibrosis transmembrane conductance (CFTR) inhibitor 172 or glibenclamide, suggesting that CFTR channels are not involved. This was confirmed by lack of effect of 8-pCPT-2’-O-Me-cAMP on whole cell patch clamp recordings of CFTR currents in Chinese hamster ovary cells transiently expressing the human CFTR channel. Furthermore, biophysical characterization of the Epac1-dependent Cl− conductance of T84 cells mounted in Ussing chambers suggested that this conductance was hyperpolarization activated, inwardly rectifying, and displayed a Cl−>Br−>I− permeability sequence. These results led us to conclude that the Epac-Rap-PLC-[Ca2+]i signaling pathway is involved in cAMP-stimulated Cl− secretion, which is carried by a novel, previously undescribed Cl− channel.
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membrane trafficking of the cystic fibrosis gene product cystic fibrosis transmembrane conductance regulator tagged with green fluorescent protein in madin darby canine kidney cells
Journal of Biological Chemistry, 1998Co-Authors: Bryan D Moyer, Johannes Loffing, Erik M Schwiebert, Dominique Loffingcueni, Patricia A Halpin, Katherine H Karlson, Iskandar I Ismailov, William B Guggino, George M Langford, Bruce A StantonAbstract:Abstract The mechanism by which cAMP stimulates cystic fibrosis transmembrane conductance regulator (CFTR)-mediated chloride (Cl−) secretion is cell type-specific. By using Madin-Darby canine kidney (MDCK) type I epithelial cells as a model, we tested the hypothesis that cAMP stimulates Cl− secretion by stimulating CFTR Cl− channel trafficking from an intracellular pool to the apical plasma membrane. To this end, we generated a green fluorescent protein (GFP)-CFTR expression vector in which GFP was linked to the N terminus of CFTR. GFP did not alter CFTR function in whole cell patch-clamp or planar lipid bilayer experiments. In stably transfected MDCK type I cells, GFP-CFTR localization was substratum-dependent. In cells grown on glass coverslips, GFP-CFTR was polarized to the basolateral membrane, whereas in cells grown on permeable supports, GFP-CFTR was polarized to the apical membrane. Quantitative confocal fluorescence microscopy and surface biotinylation experiments demonstrated that cAMP did not stimulate detectable GFP-CFTR translocation from an intracellular pool to the apical membrane or regulate GFP-CFTR endocytosis. Disruption of the microtubular cytoskeleton with colchicine did not affect cAMP-stimulated Cl− secretion or GFP-CFTR expression in the apical membrane. We conclude that cAMP stimulates CFTR-mediated Cl− secretion in MDCK type I cells by activating channels resident in the apical plasma membrane.
Markus Rothacher - One of the best experts on this subject based on the ideXlab platform.
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Comparison of Water Vapor and Temperature Results From GPS Radio Occultation Aboard CHAMP With MOZAIC Aircraft Measurements
IEEE Transactions on Geoscience and Remote Sensing, 2008Co-Authors: Stefan Heise, Jens Wickert, Georg Beyerle, Torsten Schmidt, Herman Smit, Jean-pierre Cammas, Markus RothacherAbstract:Global positioning system (GPS) radio occultation (RO) observations aboard low earth orbiting (LEO) satellites provide a powerful tool for global atmospheric sounding. Almost continuously activated since mid-2001, the challenging minisatellite payload (CHAMP) GPS RO experiment provides up to 200 vertical atmospheric profiles per day. In this paper, we intercompare CHAMP RO humidity results and analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF) with coinciding measurement of ozone and water vapor by airbus in-service aircraft (MOZAIC) data collected during aircraft ascents and descents. About 320 coinciding profiles with CHAMP were found from 2001 to 2006 (coincidence radius: 3 h, 300 km). Between about 650 and 300 hPa, the CHAMP-MOZAIC humidity bias is smaller than the ECMWF-MOZAIC bias. On the other hand, the standard deviation between MOZAIC and CHAMP humidity is slightly higher than that between MOZAIC and ECMWF through the entire altitude range. Apart from the water vapor validation (ascent and descent data), we also compare MOZAIC cruise data at an altitude of typically 10-11 km with CHAMP refractivity and temperature results (dry retrieval), and corresponding ECMWF analysis data. Whereas refractivity data from MOZAIC, CHAMP, and ECMWF show excellent agreement, the CHAMP temperature exhibits a cold bias of about 0.9 K in comparison to MOZAIC and ECMWF.
Bruce A Stanton - One of the best experts on this subject based on the ideXlab platform.
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membrane trafficking of the cystic fibrosis gene product cystic fibrosis transmembrane conductance regulator tagged with green fluorescent protein in madin darby canine kidney cells
Journal of Biological Chemistry, 1998Co-Authors: Bryan D Moyer, Johannes Loffing, Erik M Schwiebert, Dominique Loffingcueni, Patricia A Halpin, Katherine H Karlson, Iskandar I Ismailov, William B Guggino, George M Langford, Bruce A StantonAbstract:Abstract The mechanism by which cAMP stimulates cystic fibrosis transmembrane conductance regulator (CFTR)-mediated chloride (Cl−) secretion is cell type-specific. By using Madin-Darby canine kidney (MDCK) type I epithelial cells as a model, we tested the hypothesis that cAMP stimulates Cl− secretion by stimulating CFTR Cl− channel trafficking from an intracellular pool to the apical plasma membrane. To this end, we generated a green fluorescent protein (GFP)-CFTR expression vector in which GFP was linked to the N terminus of CFTR. GFP did not alter CFTR function in whole cell patch-clamp or planar lipid bilayer experiments. In stably transfected MDCK type I cells, GFP-CFTR localization was substratum-dependent. In cells grown on glass coverslips, GFP-CFTR was polarized to the basolateral membrane, whereas in cells grown on permeable supports, GFP-CFTR was polarized to the apical membrane. Quantitative confocal fluorescence microscopy and surface biotinylation experiments demonstrated that cAMP did not stimulate detectable GFP-CFTR translocation from an intracellular pool to the apical membrane or regulate GFP-CFTR endocytosis. Disruption of the microtubular cytoskeleton with colchicine did not affect cAMP-stimulated Cl− secretion or GFP-CFTR expression in the apical membrane. We conclude that cAMP stimulates CFTR-mediated Cl− secretion in MDCK type I cells by activating channels resident in the apical plasma membrane.