Christoph Reigber

Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ | GFZ · Department of Geodesy and Remote Sensing

During the first Central and South America GPS Campaign (CASA/UNO) in January/February 1988, five stations were occupied along the Boconó Fault in Western Venezuela. The stations form a quadrangle of about 100 km to 180 km lateral length and are placed nearly parallel on both sides of the fault in order to monitor compressive as well as strike-slip...

Satellite tracking data accumulated since the beginning of the space age, that is optical, laser and doppler measurements, combined into 106 arcs of 5 to 25 days have been analyzed to derive about 200 000 observation equations for spherical harmonic coefficients of the Earth’s gravity field expansion. To these were added : (I) equations for zonal h...

Since Kepler, Newton and Huygens in the seventeenth century, geodesy has been concerned with determining the figure, orientation and gravitational field of the Earth. With the beginning of the space age in 1957, a new branch of geodesy was created, satellite geodesy. Only with satellites did geodesy become truly global. Oceans were no longer obstac...

Time-resolved satellite gravimetry has revolutionized understanding of mass transport in the Earth system. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled monitoring of the terrestrial water cycle, ice sheet and glacier mass balance, sea level change and ocean bottom pressure variations, as well as understanding response...

Nur wenigen Gelehrten einer Wissenschaftsdisziplin ist es vergönnt, mit ihrem Namen in dieser Disziplin verewigt zu werden. Für die Geodäsie trifft dies auf F. R. Helmert zu, dessen Todestag sich am 15. Juni 2017 zum 100. Mal jährt. Dies ist Anlass genug, sich erneut mit Lebensweg und herausragendem Schaffen dieses europäischen Meisters der Geodäsi...

Die Geodäsie beschäftigt sich seit Kepler, Newton und Huygens im 17. Jahrhundert mit der Bestimmung von Figur, Orientierung und Gravitationsfeld der Erde. Mit dem Beginn des Raumfahrtzeitalters im Jahr 1957 entstand ein neuer Zweig der Geodäsie, die Satellitengeodäsie. Erst durch den Einsatz von Satelliten wurde die Geodäsie wirklich global, Ozeane...

Radio occultation concept, first tested on planetary satellite missions, can also be applied to Low-Earth-Orbiting (LEO) satellites with GPS occultation receivers. Successfully demonstrated for the first time by the GPS/MET experiment in 1995 [27] , GPS occultation technique shows great prospective to provide accurate pressure, temperature and wate...

Measurements at ∼400 campaign-style GPS points and another 14 continuously recording stations in central Asia define variations in their velocities both along and across the Kyrgyz and neighboring parts of Tien Shan. They show that at the longitude of Kyrgyzstan the Tarim Basin converges with Eurasia at 20 ± 2 mm/yr, nearly two thirds of the total...

During 8 years of very successful operation in orbit, the US-German GRACE mission has demonstrated in a very impressive way its outstanding capability to monitor mass motions in the Earth system with unprecedented accuracy and temporal resolution. These results have stimulated many novel research activities in hydrology, oceanography, glaciology, g...

After more than 6 years of very successful operation in orbit, the US-German GRACE mission has demonstrated in a very impressive way its outstanding capability to monitor mass motions in the Earth system with unprecedented accuracy and temporal resolution. These results have stimulated many novel research activities in hydrology, oceanography, glac...

With the help of STAR (Spatial Triaxial Accelerometer for Research) accelerometer measurements on board CHAMP (Challenging Minisatellite Payload), the global distributions of total mass density changes at about 400 km height during major magnetic storms are studied, aiming to improve the capability of current thermospheric model for predicting the...

TerraSAR-X, to be launched at the end of May, 2007, carries the tracking, occultation and ranging (TOR) Category A payload instrument package. The TOR consists of a high-precision dual-frequency GPS receiver, called integrated GPS occultation receiver (IGOR), for precise orbit determination and atmospheric sounding and a laser retro-reflector (LRR)...

This study aims at the calibration of the formal variance covariance matrices of monthly GRACE-only gravity models that are known to give too optimistic accuracy measures for derived grav?ity functionals respectively surface mass anomalies. Based on 16 monthly solutions generated at GFZ Potsdam, a simple degree-dependent scaling of given variance-c...

The global positioning system radio occultation (GPS RO) technique provides a powerful tool for atmospheric sounding which requires no calibration, is not affected by clouds, aerosols or precipitation, and provides an almost uniform global coverage. The paper deals with application of GPS RO measurements from CHAllenging Minisatellite Payload (CHAM...

The Gravity Recovery and Climate Experiment (GRACE) is a dedicated satellite mission whose objective is to map the global gravity field with unprecedented accuracy over a spatial scales approaching 200 km. The Grace measurements of mass flux are significant for climate related Earth System Studies and have been a major contributor to satellite dete...

A 3-D velocity model of the Tien Shan crust and upper mantle is constructed through the inversion of the receiver functions of P and S waves together with teleseismic traveltime anomalies at nearly 40 local seismic stations. It is found that in the vast central region, where no strong earthquakes have been known over the past century, the S wave ve...

Gravity recovery and climate experiment (GRACE)-derived temporal gravity variations can be resolved within the μgal (10−8 m/s 2) range, if we restrict the spatial resolution to a half-wavelength of about 1,500 km and the temporal resolution to 1 month. For independent validations, a comparison with ground gravity measurements is of fundamental inte...

Numerical models are presented that simulate several active tectonic processes. These models include a continent that is thermally and mechanically coupled with viscous mantle flow. The assumption of rigid continents allows use of solid body equations to describe the continents' motion and to calculate their velocities. The starting point is a quas...

Signatures between monthly global Earth gravity field solutions obtained from GRACE satellite mission data are analyzed with respect to continental water storage variability. GRACE gravity field models are derived in terms of Stokes' coefficients of a spherical harmonic expansion of the gravitational potential from the analysis of gravitational orb...

An analysis of atmospheric refractivity profiles observed by the georesearch satellite CHAMP between May 2001 and October 2004 reveals a negative bias compared to ECMWF meteorological fields at altitudes below 5 km. In order to separate bias contributions caused by critical refraction from contributions induced by the receiver tracking process a co...

The German CHAMP (CHAllenging Minisatellite Payload) satellite provides continuously GPS radio occultation data since February 2001. The measurements are analyzed by an operational orbit and occultation processing system at GFZ. In total ∼170 000 high quality globally distributed vertical profiles of refractivity, temperature and water vapor are pr...

Within the national German geoscientific research and development programme "GEOTECHNOLOGIEN", funded by the Federal Ministry of Education and Research (BMBF) and the German Research Foundation (DFG), the research theme "Observation of the System Earth from Space" was selected as one of 13 key areas in this programme. During the first research phas...

The German CHAMP (CHAllenging Minisatellite Payload) satellite provides continuously GPS radio occultation data since February 2001. The measurements are analyzed by an operational satellite orbit and occultation processing system at GFZ. In total, more than 200,000 precise globally distributed vertical profiles of refractivity, temperature and wat...

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 ionosp...

High frequency temporal gravity changes on sub-monthly time scales are caused by Earth's mass transport primarily originating from tidal and nontidal atmospheric and oceanic motions. Exploitation of precise GRACE satellite-to-satellite ranging measurements now makes it possible to monitor these changes on a global scale with a moderate spatial reso...

Based on the GRACE mission data, a new era of static and time-variable gravity models with unprecedented resolution and accuracy have been generated by the GRACE Science Data System teams. In general, the spatial resolution of the field from pre-CHAMP satellite only models of about 1000 km can be increased by a factor of 5 – 6 thanks to the microme...

GRACE, CHAMP and LAGEOS tracking data have recently been reprocessed at GFZ Potsdam based on improved processing standards, models and data screening resulting in time series of several years of weekly to monthly gravity field solutions with varying spatial resolution, maximum up to degree and order 150. These time series have been combined in orde...

High-resolution global mean gravity field models can be derived from the combination of satellite tracking and surface data. With the CHAMP and GRACE satellite missions, a new generation of such global gravity field models became available. Here the latest results of the processing of GRACE, CHAMP and SLR satellite tracking are presented and compar...

New global models of the gravity field derived from data of the CHAMP and GRACE satellites are described. These models open new possibilities for the study of density inhomogeneities and tectonics of the Earth. A uniform (for the entire planet) distribution of the gravitational potential and gravity up to the 120th spherical harmonic is obtained fo...

A detailed knowledge of the thickness of the lithosphere in the north Atlantic is an important parameter for understanding plate tectonics in that region. We achieve this goal with as yet unprecedented detail using the seismic technique of S-receiver functions. Clear positive signals from the crust–mantle boundary and negative signals from a mantle...

A local mechanism for strong ionospheric effects on radio occultation (RO) global positioning satellite system (GPS) signals is described. Peculiar zones centered at the critical points (the tangent points) in the ionosphere, where the gradient of the electron density is perpendicular to the RO ray trajectory, strongly influence the amplitude and p...

In this study the global lapse-rate tropopause (LRT) pressure, temperature, potential temperature, and sharpness are discussed based on Global Positioning System (GPS) radio occultations (RO) from the German CHAMP (CHAllenging Minisatellite Payload) and the U.S.-Argentinian SAC-C (Satelite de Aplicaciones Cientificas-C) satellite missions. Results...

The Gravity Recovery And Climate Experiment (GRACE) is in the 3rd year of its nominal 5-year operating lifetime. GRACE data have been providing unprecedented insights into the mass distribution and variability evident through measurements of the Earth's gravity field variations. The mean geoid errors have been reduced to less than 1-cm to harmonic...

CHAMP (CHAllenging Minisatellite Payload) and GRACE (Gravity Recovery And Climate Experiment) formed a satellite configuration for precise atmospheric sounding during the first activation of the GPS (Global Positioning System) radio occultation experiment aboard GRACE on 28 and 29 July 2004. 338 occultations were recorded aboard both satellites, pr...

In this paper, we demonstrate that biases in the GPS satellite antenna phase center offsets could lead to scale biases in global network solutions, which change along with the observed satellite constellation. To validate the IGS standard offset values, satellite-specific offsets are estimated from GPS data and the network solutions are re-adjusted...

A new medium-wavelength gravity field model has been calculated from 110 days of GRACE tracking data, called EIGEN-GRACE02S. The solution has been derived solely from satellite orbit perturbations and is independent from oceanic and continental surface gravity data. This model that resolves the geoid with an accuracy of better than 1 mm at a resolu...

The canonical transform (CT) and full spectrum inversion (FSI) method together with their heuristic sliding spectral modifications are validated using end-to-end simulation data and one week of CHAMP observations. In general, we observe a pronounced correlation between small refractivity biases and enhanced penetration altitudes. Processing of simu...

Atmospheric sounding with the German CHAMP (CHAllenging Minisatellite Payload) satellite is successfully performed since February 2001. In total similar to145,000 precise globally distributed vertical profiles of refractivity. temperature and, water vapor were provided as of April 2004. The operational occultation infrastructure from GFZ allows for...

In this paper an overview of the temperature structure in the tropical upper troposphere and lower stratosphere (UTLS) region is given using Global Positioning System (GPS) radio occultation (RO) data front the German CHAMP (CHAllenging Minisatellite Payload) satellite mission. Several climatologgies for tropopause parameters based on radiosonde da...

In this paper a description of the CHAMP atmospheric processing system for radio occultation data at GFZ Potsdam is given. The generation of radio occultation products, as e.g. atmospheric excess phases, vertical profiles of refractivity, temperature or water vapour is a complex process. Besidess the scientific challenge the design and installation...

The knowledge of the transmitter and receiver differential code biases (DCB) plays a key role for the calibration of GPS based measurements of total electron content (TEC). To estimate the DCB of the CHAMP receiver concerning the zenith looking antenna a model assisted technique has been developed which takes advantage of the known CPS biases and c...

Successfully launched in mid-March 2002, the GRACE (Gravity Recovery & Climate Experiment) mission currently provides monthly maps of the variations of the geo-potential, at the unprecedented resolution of 200–300 km (max. degree ∼100–120). Tiny time variations of the Earth’s gravity field (a few of mm in terms of geoid height) measured by GRACE ar...

We showed that the amplitude of GPS occultation signal is important indicator of the ionospheric activity. Amplitude is more sensitive to small-scale ionospheric disturbances than the phase of the radio occultation (RO) signals. Local mechanism of strong ionospheric influence oil the amplitude and phase of RO GPS signals is described. Critical poin...

The analysis of the amplitude of the GPS/MET and CHAMP radio occultation (RO) events revealed clusters (quasi-regular structures) with a vertical size of about 10 km and an interior vertical period of ∼0.8 to 2 km in the tropopause and lower stratosphere. The height interval of the clusters changes from 10 to 40 km. Restored from the RO amplitude d...

GPS-CHAMP satellite-to-satellite and accelerometry data covering 25 years of the CHAMP mission period were exploited to generate the global gravity field model EIGEN-3p revealing considerable improvements in both accuracy and resolution with respect to the previous model EIGEN-2. For the year 2001. CHAMP and satellite laser ranging data of four sat...

The technique of using the evolution of a satellite orbit through resonance to determine the values of appropriate lumped geopotential harmonic coefficients has recently been revived, and applied to the triple passage of the Champ orbit through 31:2 resonance. Preliminary results for four pairs of coefficients have been derived rapidly, without usi...

The GeoForschungsZentrum Potsdam (GFZ) operationally provides CHAMP orbit products for various purposes. Here the rapid and ultra-rapid orbits are highlighted. Significant developments in Precise Orbit. Determination (POD) for Low Earth Orbiters (LEOs), in particular SAC-C and GRACE besides CHAMP, are described. GFZ also started to generate CHAMP-l...

The behaviour of the space-borne CHAMP GPS receiver clock over nearly three years is inspected by the results of the Rapid Science Orbit, (RSO) determination and the on-board navigation solution (NAV). The analysis completes and enhances the results of the clock characterization study carried out earlier oil a limited number of data. It is shown, t...

The long-wavelength part of non-isostatic topography is supposed to be generated by mantle dynamics and is LIP to now not well studied. In order to separate the dynamic part from the residual topography (that part of the Earth's topography which is not explained by the crustal model providing isostatic compensation) a correlation analysis is perfor...

In the summer of 2000 the German geo-research satellite CHAMP was launched into orbit. Its innovative payload arrangement and the low initial orbit allow CHAMP to simultaneously collect and almost continuously analyse precise data relating to gravity and magnetic fields at low altitude. In addition, CHAMP also measures the neutral atmosphere and io...

Recently Tyler et al. (2003) demonstrated that the magnetic fields generated by the lunar semidiurnal (M2) ocean flow can be clearly identified in magnetic satellite observations. They compared their numerical simulations of magnetic fields due to the M2 tide with CHAMP observations and found close agreement between observations and predictions. Th...

New satellite data have led to increased resolution models of the geomagnetic secular variation (SV). Simple plots of the spectra of these models suggest an unphysical source depth above the core-mantle boundary (CMB). By taking a ratio of the main field and SV spectra, we argue that this result comes from the chosen spectral definition. The models...

Recently Olsen & Kuvshinov (2003) presented an approach for modelling the ocean effect of geomagnetic storms by solving the induction equation given the conductivity distribution of the Earth's interior and the time-space structure of the storm. The results for several major storms show much better agreement between the observed and the simulated m...

The magnetic crustal thickness of Greenland and the surrounding area is determined by inversion of gridded values of the magnetic radial component as given by the IDEMM model, which is based on CHAMP and Ørsted data alone, and by the Comprehensive Model (CM4), which is based on satellite and observatory data. After correcting for the remanent magne...

The classification of the effect of ionospheric disturbances on the radio occultation signal amplitude has been introduced based on an analysis of more than 2000 seances of radio occultation measurements performed with the help of the CHAMP German satellite. The dependence of the histograms of variations in the radio occultation signal amplitude on...

The double difference technique is the standard processing method of challenging minisatellite payload (CHAMPs), global positioning system (GPS) occultation data to correct for satellite clock errors. In order to apply this technique, the implementation of a global fiducial GPS ground network is required. This network (“High Rate and Low Latency Ne...

The availability of GPS (Global Positioning System) radio signals has introduced a new promising remote sensing technique for the Earth’s atmosphere. GPS-based radio occultation exploits GPS signals received onboard a Low Earth Orbiting (LEO) satellite for atmospheric limb sounding. Temperature and water vapour profiles with high accuracy and verti...

1] The noisy and impulsive fluctuations in the CHAMP radio occultation (RO) amplitude data are similar to the C-type and S-type ionospheric amplitude scintillations formerly observed at 1.5 GHz in the mid-latitude region in satellite-to-Earth Inmarsat links. These amplitude scintillations can be associated with different types of ionospheric struct...

Based on the analysis of various factors controlling isostatic gravity anomalies and geoid undulations, it is concluded that it is essential to model the lithospheric density structure as accurately as possible. Otherwise, if computed in the classical way (i.e. based on the surface topography and the simple Airy compensation scheme), isostatic anom...

The Global Positioning System (GPS) radio occultation (RO) technique offers a valuable new data source for global and continuous monitoring of the Earth's atmosphere. Refractivity, temperature and water vapor profiles with high accuracy and vertical resolution can be derived from this method. The GPS RO technique requires no calibration, is no...

Radio occultation events recorded on 28-29 July 2004 by a GPS receiver aboard the GRACE-B satellite are analyzed. The stability of the receiver clock allows for the derivation of excess phase profiles using a zero difference technique, rendering the calibration procedure with concurrent observations of a reference GPS satellite obsolete. 101 refrac...

Various types of observations, such as space-borne Global positioning system (GPS) code and phase data, accelerometer data, K-band range and range-rate data, and ground-based satellite laser ranging data of the CHAllenging Minisatellite Payload (CHAMP) and GRAvity Climate Experiment (GRACE) satellite missions, are used together with ground-based GP...

To obtain an image of the deep structure of the Tien Shan in central Asia, we invert P and S receiver functions jointly for almost 40 local broad-band seismograph stations. The inversion is performed using a simulated annealing technique. The combined inversion is an improvement on earlier studies, where P and S receiver functions were inverted sep...

The temperature structure in the tropical upper troposphere and lower stratosphere (UTLS) region is discussed based on Global Positioning System (GPS) radio occultation (RO) data from the German CHAMP (CHAllenging Minisatellite Payload) satellite mission. Several climatologies for tropopause parameters based on radiosonde data and model analyses ha...

The GRACE mission is designed to track changes in the Earth's gravity field for a period of five years. Launched in March 2002, the two GRACE satellites have collected nearly two years of data. A span of data available during the Commissioning Phase was used to obtain initial gravity models. The gravity models developed with this data are more than...

The Gravity Recovery and Climate Experiment (GRACE) is a dedicated satellite mission whose objective is to map the global gravity field with unprecedented accuracy over a spectral range from 500 km to 40,000 km. The measurement precision will support gravity field solutions in this frequency range that are between 10 and 1000 times better than our...

Within the framework of the Helmholtz Association Strategy Project “GPS Atmosphere Sounding” (GASP), an operational monitoring of integrated water vapor was established using 170 GPS sites in Germany and neighboring countries. The product, which can be obtained within 12-15 minutes of computer time on a single Linux PC, is generated each hour with...

The operational data analysis of the GPS radio occultation experiment aboard the German CHAMP (CHAllenging Minisatellite Payload) satellite mission is described. Continuous Near-Real-Time processing with average time delay of ∼5 hours between measurement and provision of analysis results is demonstrated. A delay of less than 3 hours is reached for...

Validation studies of current GPS radio occultation experiments using meteorological analyses consistently report on a negative refractivity bias in the lower troposphere. End-to-end simulations including the GPS receiver's signal tracking process suggest that receiver-induced phase deviations contribute to this observed bias. We propose a heuristi...

Ground based GPS measurements are well proved in terms of monitoring the vertical Total Electron Content (TEC) of the ionosphere. The GPS receivers installed on board of LEO (Low Earth Orbiting) satellites such as CHAMP and SAC-C provide a rather new data source for ionospheric remote sensing on global scale. Both satellites CHAMP and SAC-C track p...

Please note: This is a preprint version of the paper "Near Real Time GPS Water Vapor Monitoring for Numerical Weather Prediction in Germany", Journal of the Meteorological Society of Japan 82:361-370 (2004). Within the framework of the German Project "GPS Atmosphere Sounding" (GASP) an operational monitoring of integrated water vapor using 170 GPS...

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