Advanced Technologies in Earth Sciences Frank Flechtner Nico Sneeuw Wolf-Dieter Schuh Editors Observation of the System Earth from Space - CHAMP, GRACE, GOCE and Future Missions GEOTECHNOLOGIEN Science Report No. 20 Advanced Technologies in Earth Sciences Series Editors Ute Münch Ludwig Stroink Volker Mosbrugger Gerold Wefer For furthervolumes: http://www.springer.com/series/8384 Frank Flechtner Nico Sneeuw • Wolf-Dieter Schuh Editors Observation of the System Earth from Space - CHAMP, GRACE, GOCE and Future Missions GEOTECHNOLOGIEN Science Report No. 20 123 Editors Wolf-Dieter Schuh Frank Flechtner Instituteof Geodesy and Geoinformation Department forGeodesy andRemote Universityof Bonn Sensing Bonn GFZ GermanResearch Centre Germany forGeosciences Wessling Germany Nico Sneeuw Instituteof Geodesy Universityof Stuttgart Stuttgart Germany ISSN 2190-1635 ISSN 2190-1643 (electronic) ISBN 978-3-642-32134-4 ISBN 978-3-642-32135-1 (eBook) DOI 10.1007/978-3-642-32135-1 SpringerHeidelbergNewYorkDordrechtLondon LibraryofCongressControlNumber:2013938165 (cid:2)Springer-VerlagBerlinHeidelberg2014 Thisworkissubjecttocopyright.AllrightsarereservedbythePublisher,whetherthewholeorpartof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation,broadcasting,reproductiononmicrofilmsorinanyotherphysicalway,andtransmissionor informationstorageandretrieval,electronicadaptation,computersoftware,orbysimilarordissimilar methodology now known or hereafter developed. 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The books in this series deal with research results from different innovative geoscientific research areas, interlinking a broad spectrum of disciplines with a view to documenting System Earth as a whole, including its various sub-systems and cycles. The research topics are predefined to meet sci- entific, socio-political and economic demands for the future. Ute Münch Ludwig Stroink Volker Mosbrugger Gerold Wefer v Preface ObservingtheEarthfromspacehasundergonerapiddevelopmentsinrecentyears and has a prominent position in geo-related scientific research today. Research satellitesareindispensabletoolsforstudyingprocessesontheEarth’ssurfaceand withintheSystemEarth.Theviewfromspaceallowstheobservationoftheentire planet uniformly in near-real-time. At the same time the resulting time series of measurementsallowthedetectionandmonitoringofchangesinthisverycomplex system. SatelliteslikeChallengingMini-satellitePayload(CHAMP),GravityRecovery and Climate Experiment (GRACE) and Gravity Field and steady state Ocean CirculationExplorer(GOCE)measurethegravityandmagneticfieldsoftheEarth with unprecedented accuracy and resolution (in time and space) and provide the metrological basis for oceanography, climatology, glaciology, global change and geophysics in general. These missions have been—and continue to be—instru- mental to establish a new segment of the Earth system science. Basedonthesedataitispossibletoexploreandmonitorchangesrelatedtothe Earth’s surface, the boundary layer between atmosphere and solid Earth, oceans andiceshields.Thisboundarylayerisourhabitatandthereforeinthefocusofour interests. The Earth’s surface is exposed to anthropogenic changes, to changes driven by Sun, Moon and planets, and to processes in the Earth system. The state parameters and their changes are best monitored from space. The theme ‘‘ObservationoftheSystemEarthfromSpace’’offerscomprehensiveinsightsinto a broad range of research topics relevant to geodesy, oceanography, atmosphere science (from meteorology to climatology), hydrology and glaciology, and to society as a whole. The volume Observation of the System Earth from Space-CHAMP, GRACE, GOCEandFutureMissionsdocumentsthethirdphaseofthetopicObservationof thesystemEarthfromspace.Asopposedtothefirsttwophasestherangeoftopics was narrowed down to the projects LOTSE-CHAMP/GRACE (led by Frank Flechtner), REAL GOCE (led by Wolf-Dieter Schuh) and Future Gravity Field Satellite Missions (led by Nico Sneeuw). This structure is also mirrored by the table of contents in the volume. Three seminars, the status seminarsat the Universityof Bonn inOctober 2010 andattheUniversityofStuttgartinOctober2011andthefinalpresentationsatthe GFZ, German Research Centre for Geosciences in Potsdam in May 2012 were vii viii Preface organizedtokeep trackoftheprogressandtodrawtheconclusionoftheworkof thethirdfundingphase,respectively.Theadvisoryboardthoroughlyreviewedthe progress at the status seminars in Bonn and in Stuttgart and made its recom- mendations for the completion of the work in two reports, which were made available to the involved scientists. Itisratherunusual—andasviewedfromtheoutside—extraordinarythatatopic of GEOTECHNOLOGIEN is funded over three phases and so for more than 10 years. The third phase could only be approved based on the very strong recom- mendation submitted by the international advisory committee consisting at that time of Alain Geiger, ETH, Zürich, Robert Weber, Technical University of Vienna,SuzannaZerbini,UniversityofBologna,KathrinA.Whaler,Universityof Edinburgh, and Gerhard Beutler from University of Bern (chair), on the occasion of the status seminar of phase 2 in Munich in November 2007. The recommen- dation in 2007 was based on the insights that • the three space missions CHAMP, GRACE and GOCE would have a tremen- dous impact on the advance of Earth system science, • the funding through GEOTECHNOLOGIEN was of paramount importance to create a strong, internationally competitive science community in Germany, • aterminationoffundingin2008wouldhaveadevastatingimpactonGermany’s standing in this important field of science. It was, in particular clear, that a terminationwouldendangertheGermanparticipationintheGRACEfollowon mission (GRACE-FO). The advisory committee is convinced that the Coordination Committee GEOTECHNOLOGIENmadetherightdecisionatits22ndmeetingonMarch17, 2008, in Potsdam to approve the third phase of Observation of the System Earth from Space with the focus on the three space missions CHAMP, GRACE and GOCE. The reduced breadth of the project in the third phase allowed it to reduce the size advisory committee—Alain Geiger, Robert Weber and Gerhard Beutler (chair) accompanying the third phase. Meanwhile, history has proven that the decision taken in 2008 was absolutely right: • The GOCE satellite was successfully launched on March 17, 2009. The scien- tific exploitation of this mission proved to be a full success, not least thanks to thestrongsupportofthethirdphaseoftheGEOTECHNOLOGIENprogramme. • After very long andat times tiresome negotiations, the German participationin theGRACE-FOmission,slatedforlaunchin2017,couldbesecured.Partofthe work documented in the section future gravity field missions is related to GRACE-FO. It would have been close to impossible to achieve this participa- tionwithoutthestrongsupportandstandingoftheunitedscientistsdocumented by this volume. Preface ix Thereportwehaveinourhandsnownotonlydocumentstheoutstandingwork performed by German scientists in this last phase using the data of CHAMP, GRACE and GOCE, it also marks the end of the topic Observation of the Earth from Space within the GEOTECHNOLOGIEN programme. AnewchapterofEarthmonitoringfromspaceisabouttobeginwiththelaunch of the US/German mission GRACE-FO. Let us hope that this new era—which musteventuallybefollowedbyapermanentmonitoringoftheEarth’sgravityand magnetic fields—will be accompanied in Germany by a science programme to matchthatrelatedtotheexploitationofCHAMP,GRACEandGOCE.Itwilltake dedicationonthepartofscienceandwisdomonthepoliticalsidetoinvokesucha development in Germany. Ute Münch Head of the GEOTECHNOLOGIEN coordination office Gerhard Beutler Chair, advisory committee of the R&D Programme GEOTECHNOLOGIEN Professor emeritus and former Director of the Astronomical Institute of University of Bern (AIUB) Acknowledgments The authors gratefully acknowledge the financial support of the German Federal Ministry of Education and Research (BMBF) in the frame of LOTSE-CHAMP/ GRACE (Grants 03G0728A-D), REAL GOCE (Grants 03G0726A-H) and FUTURE MISSINONS (Grants 03G0729A-G) within the R&D programme GEOTECHNOLOGIENandtheGermanResearchFoundation(DFG)forfunding the Cluster of Excellence ‘‘Integrated Climate System Analysis and Prediction’’ (CliSAP) of the University of Hamburg. TheauthorsaregratefultotheCHAMP,GRACE,TerraSAR-XandTanDEM-X teams for their efforts to maintain the availability of gravity field, magnetic field and/or GPS radio occultation data. The German Weather Service provided EC- MWF data. N. K. Pavlis (NGA) is acknowledged for providing the topographic database DTM2006.0.Furthermore,theauthorswouldliketothankX.Luo(KIT) sincerelyforhisgreatsupportinperformingthewavelettransformandproducing the wavelet spectrograms. The GOCE-Team is very thankful for the support by ESAGOCEHPF(contractNo.18308/04/NL/MM)andthecomputationperformed ontheJUROPAsupercomputerattheResearchCenterJülich.Thecomputingtime was granted by the John von Neumann Institute for Computing (project HBN15). xi Contents Part I LOTSE-CHAMP/GRACE 1 LOTSE-CHAMP/GRACE: An Interdisciplinary Research Project for Earth Observation from Space . . . . . . . . . . 3 Frank Flechtner 2 Improvement in GPS Orbit Determination at GFZ . . . . . . . . . . . 9 Grzegorz Michalak, Daniel König, Karl-Hans Neumayer and Christoph Dahle 3 Using Accelerometer Data as Observations . . . . . . . . . . . . . . . . . 19 Karl-Hans Neumayer 4 GFZ RL05: An Improved Time-Series of Monthly GRACE Gravity Field Solutions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 Christoph Dahle, Frank Flechtner, Christian Gruber, Daniel König, Rolf König, Grzegorz Michalak and Karl-Hans Neumayer 5 GRACE Gravity Modeling Using the Integrated Approach . . . . . 41 Daniel König and Christoph Dahle 6 Comparison of Daily GRACE Solutions to GPS Station Height Movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Annette Eicker, Enrico Kurtenbach, Jürgen Kusche and Akbar Shabanloui 7 Identification and Reduction of Satellite-Induced Signals in GRACE Accelerometer Data . . . . . . . . . . . . . . . . . . . . . . . . . 53 Nadja Peterseim, Anja Schlicht, Jakob Flury and Christoph Dahle 8 Reprocessing and Application of GPS Radio Occultation Data from CHAMP and GRACE . . . . . . . . . . . . . . . . . . . . . . . . 63 Stefan Heise, Jens Wickert, Christina Arras, Georg Beyerle, Antonia Faber, Grzegorz Michalak, Torsten Schmidt and Florian Zus xiii