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Cross-calibration for 20 years satellite altimetry

Climate studies require long data records extending the lifetime of a single remote sensing satellite mission. Precise satellite altimetry exploring global and regional evolution of the sea level has now completed a two decade data record. A consistent long-term data record can only be constructed from a sequence of different, partly overlapping altimeter systems by means of a careful cross-calibration.

At DGFI, satellite altimeter cross-calibrations are routinely performed with all available altimeter systems including mission phases from geodetic and drifting orbits. The methodology of this calibration is described in detail in a new Remote Sensing paper giving also selected results from the latest computation run.

The paper compiles – for the first time – a complete list of range biases between all relevant altimeter systems of the last 20 years, from ERS-1 to SARAL including less prominent missions such as GFO, ICESat, or HY-2A (cf. Table). Moreover, the computations provide time series of radial errors and allow to estimate empirical auto-covariance functions, systematic variations in the geo-centering of altimeter satellite orbits, as well as geographically correlated mean errors for all altimeter systems.

For more details see:

Bosch W, Dettmering D, Schwatke C.: Multi-Mission Cross-Calibration of Satellite Altimeters: Constructing a Long-Term Data Record for Global and Regional Sea Level Change Studies. Remote Sensing. 2014; 6(3):2255-2281 (available via open-access)

Dr. Manuela Seitz receives the Young Author Award 2012 of the International Association of Geodesy (IAG)

The Young Author Award 2012 of the International Association of Geodesy (IAG) was presented to DGFI scientist Dr. Manuela Seitz during the IAG Scientific Assembly 2013 in Potsdam for her paper “The 2008 DGFI Realization of the ITRS: DTRF2008” (DOI:10.1007/s00190-012-0567-2) that she published together with her colleagues from DGFI D. Angermann, M. Bloßfeld, H. Drewes and M. Gerstl.

With the Young Author Award IAG honors important publications of young authors in the Journal of Geodesy. The prize is granted at each IAG General or Scientific Assembly.

The award-winning paper deals with the realization of the International Terrestrial Reference System (ITRS) in the frame of DGFI's ITRS Combination Centre of the International Earth Rotation and Reference Systems Service (IERS). It explains in detail the computation strategy applied at DGFI and provides a comprehensive discussion of the results.

Marco Limberger received the Young Scientist Award of the Asia-Pacific Radio Science Conference 2013

(c) AP-RASC

Marco Limberger from the Technische Universität München (TUM) was honored with one of the Young Scientist Awards (YSA) of the Asia-Pacific Radio Science conference 2013 (AP-RASC'13) for his contribution with co-authors from DGFI "The combination of space-geodetic observation techniques to determine key parameters of the F2 Chapman layer" of Marco Limberger, U. Hugentobler, M. Schmidt, D. Dettmering, W. Liang, N. Jakowski, M. Hoque, T. Gerzen and J. Berdermann.

The AP-RASC is the Asia-Pacific regional Union of Radio Science (URSI) conference held between the URSI General Assemblies and Scientific Symposia. Winners of the YSA are selected by peer-review of the submitted papers.

The list of recipients and further information can be found on the conference website at http://aprasc13.ntu.edu.tw/.

Mathis Bloßfeld is awarded with the Bernd Rendel Prize 2013 of the German Research Foundation (DFG)

(c) University of Tuebingen

Mathis Bloßfeld won one of the Bernd Rendel Prizes of 2013. The prize is awarded by the Deutsche Forschungs-gemeinschaft (DFG, German Research Foundation) and honours early career researchers who have made important and original contributions to basic geosciences research before obtaining their doctorates. The prize is awarded annually since 2002.

More information about the Bernd Rendel Prize and a list of the previous winners can be found on the DFG website.

Photo from left to right: Yannick Bussweiler, Laura Klüpfel, Mathis Bloßfeld, Matthias Alberti., Prof. Dr. Astrid Holzheid (Deutsche Mineralogische Gesellschaft), Dr. Birgit Scheibner-Münker, Prof. Dr. Ralf Littke (Geologische Vereinigung)

Two scientists of DGFI won the Student's Best Talk Award at the IAG Scientific Assembly 2013

The first and second price of the IAG Student's Best Talk Award have been granted to Mathis Bloßfeld and Wenjing Liang in recognition of two excellent oral presentations at the IAG Scientific Assembly 2013 held in Potsdam, Germany, 1-6 September 2013.

The presentation of Wenjing Liang, M. Schmidt, D. Dettmering, U. Hugentobler, M. Limberger, N. Jakowski, M. Hoque, V. Wilken, T. Gerzen and J. Berdermann was entitled "Combination of GNSS observations and electron density profiles from Radio Occultation data for the determination of a multi-scale regional ionosphere model". 

The first presentation of Mathis Bloßfeld, M. Seitz and D. Angermann was entitled "Epoch reference frames as short-term realizations of the ITRS - recent developments and challenges".

The second presentation of Mathis Bloßfeld, V. Stefka, H. Mueller and M. Gerstl was entitled "Satellite Laser Ranging - a tool to realize GGOS?".

 

The presentations will be available online through the conference website soon.

Verena Lieb is awarded with the Outstanding Student Poster Award at the EGU 2013

The prize for the Outstanding Student Poster (OSP) of the Geodesy division at the general assembly 2013 of the European Geosciences Union (EGU) is this year awarded to Verena Lieb. She presented a poster about “Using the full tensor of GOCE gravity gradients for regional gravity field modelling” (Lieb V., Bouman J., Dettmering D., Fuchs M., Schmidt M.). The award honours not only the scientific quality of the poster, but also the ability of young scientists in presenting their work and answering questions at international conferences.

Consistent realization of ITRS and ICRS

For the first time, DGFI realizes the International Terrestrial Reference System (ITRS) and the International Celestial Reference System (ICRS) together with the Earth Orientation Parameters, which allow for a transformation between both systems, consistently in one adjustment. So far, ITRS and ICRS are realized independently at different computation centres.

In our computation, we considered data of Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS). The parameter considered in the realization are station coordinates, quasar coordinates and the EOP, i.e. the coordinates of the terrestrial and the celestial pole (polar motion and nutation) and UT1-UTC and their derivation in time. Alltogether about 45,000 parameters are solved. The results are presented at different international conferences and first results are already published [more].

 

Lithospheric modelling using GOCE

ESA's gravity mission GOCE measures the Earth's mean gravitational field with unprecedented accuracy with a spatial resolution of 100 km or better. Comparing GOCE gravity gradients with gradients from geophysical modelling for the North-East Atlantic (NEA) margin shows that the spatial patterns are similar, but that the amplitudes differs. This indicates that even in well-surveyed areas, such as the NEA, GOCE data may contribute to improved modelling of the Earth's interior. [more]

Dynamic ocean topography time series with meso-scale pattern resolved

Combining the most recent GOCE gravity fields and multi-mission satellite altimetry allow for the first time to estimate meso-scale features of the dynamic ocean topography (DOT). The “profile method” of DGFI even generates DOT profiles on individual ground tracks of any altimeter satellite which can be subsequently  gridded  to construct  (e.g. with 10 day sampling) a DOT time series spanning the period 1993 up to now. The animation shows the geostrophic velocity field of this time series for the South Atlantic and the Agulhas Counter Current with intensive Eddy formation. [more…]

Baroclinic tides from multi-mission altimetry

Multi-mission altimetry processing at DGFI has demonstrated the potential to provide a complete mapping of baroclinic tides (due to internal waves with density variations). With some 100-150 km the wavelength of baroclinic tides are much shorter than for barotropic tides. Moreover, the baroclinic surface signal remains small (~ 2-5 cm amplitude), although the internal waves may reach amplitudes of several tens of meters. The figure shows the amplitudes of the M2 baroclinic tide … [more]

Multi-mission cross-calibration extended to Cryosat-2

The first data of Cryosat-2, an altimeter mission primarily dedicated to ice observations, has now been included in DGFI’s multi-mission crossover calibration (MMXO). The analysis reveals a good quality of Level 2 Low Resolution Mode (LRM) data, a global mean range bias of about -0.59 m and a timing error of app. 11 ms. With 2.6 cm RMS of the radial errors, the data quality is very promising but not yet comparable to Jason and Envisat missions. [more]

Establishment of the “Centre for Geodetic Earth System Research” (CGE)

Foto: A. Heddergott

On October 28, 2010 a contract was signed for the establishment of the Centre for Geodetic Earth System Research (CGE) in Munich. DGFI, the division Geodesy of the BAdW Commission on Geodesy and Glaciology (KEG), the Institute for Astronomical and Physical Geodesy (IAPG) and the Research Establishment for Satellite Geodesy (FESG) of TUM integrate their research in one common CGE programme. The principal objectives are investigations on global change by measuring variations in the solid Earth, oceans, ice covers and atmosphere, and analysing those variations with respect to the generating physical processes. [More]

Geodetic results of the earthquake in Chile (2010-02-27)

To estimate the impact of the Chile earthquake in the Reference Frame for the Americas (SIRGAS), the SIRGAS Analysis Centre at DGFI estimated daily station positions between February 21 and March 6, 2010, for selected continuously operating SIRGAS stations. Results show that the GPS station CONZ (Concepción, Chile) initially moved 2,9 m in the south-west direction (on 27-02-2010). In the week following the first earthquake, post-seismic movements of more than 10 cm were detected. Additional GPS stations located between latitudes 30°S to 40°S from the Pacific to the Atlantic coast also present larger displacements. [More]

 

Free oscillations of the Earth

The free oscillations of the Earth caused by the displacement from the position of rest will be excited by earthquakes with a magnitude larger than 6.5 on the momentum scale. After the huge Offshore Maule earthquake in Chile on Februar 27, 2010 with magnitude 8.8 on the momentum scale the free oscillations were excited.

The frequency domain of free oscillations is between 0.3 mHz, i.e. a period of 54 minutes and 20mHz i.e. a period of 50 seconds. [More]

ITRF2008 solution of DGFI (DTRF2008) is now available

DGFI as one of the ITRS Combination Centres of International Earth Rotation and Reference System Service (IERS) has completed the computation of the International Terrestrial Reference Frame 2008 (DTRF2008). DTRF2008 is an independent solution, based on the same input data as ITRF2008, which is computed by the IERS Combination Centre at IGN, Paris, and provided by the IERS Product Centre at IGN in May 2010. The difference between both solutions is the combination strategy: while a combination of solutions is performed at IGN, DGFI computation is based on the combination of normal equations.

The DTRF2008 is a global terrestrial reference frame containing the station coordinates of 559 GPS, 106 VLBI, 122 SLR and 132 DORIS stations. The reference epoch for station positions is 2005-01-01, 0:00 UTC. Earth orientation parameters (EOP), i.e., coordinates of the terrestrial and the celestial pole, UT1-UTC and length of day (LOD), are simultaneously solved with the station coordinates. The time series of EOP covers the period from 1983 until the end of 2008. The solution is available in different file formats at ftp.dgfi.badw.de/pub/DTRF2008. A short description of the solution is given in the local SINEX file.


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