Torsten Mayer-Gürr Institute of Geodesy, NAWI Graz Technische Universität Graz

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1 GGOS and Reference Systems Introduction Torsten Mayer-Gürr Institute of Geodesy, NAWI Graz Technische Universität Graz Torsten Mayer-Gürr 1

2 Course and exam Lecture Monday 14:00 16:00, A111 (ST01044) Slides (PPT and PDF) available; partly based on slides by Oliver Baur. TeachCenter: Oral examination (ca. 25 min) About 2 dates per month Registration: itsg.tugraz.at/education/exams Contact: mayer-guerr@tugraz.at Lab Monday 16:00-17:00, A111 (ST01044) Starts after announcement Materials: TeachCenter: Marking: written elaborations Torsten Mayer-Gürr 2

3 GGOS Global Geodetic Observing System GGOS is the Observing System of the International Association of Geodesy (IAG). GGOS works with the IAG components to provide the geodetic infrastructure necessary for monitoring the Earth system and for global change research. The mission of GGOS is to provide the observations needed to monitor, map and understand changes in the Earth s shape, rotation and mass distribution to provide the global frame of reference that is the fundamental backbone for measuring and consistently interpreting key global change processes and for many other scientific and societal applications to benefit science and society by providing the foundation upon which advances in Earth and planetary system science and applications are built. Torsten Mayer-Gürr 3

4 GGOS structure Torsten Mayer-Gürr 4

5 GGOS Global Geodetic Observing System Torsten Mayer-Gürr 5

6 The three pillars of geodesy Torsten Mayer-Gürr 6

7 The dynamic system Earth gravity field of the Earth geometry of the Earth orientation of the Earth Torsten Mayer-Gürr 7

8 sun, moon, planets solid Earth tides ocean tides The dynamic system Earth ocean currents atmospheric tides atmosphere currents gravity field of the Earth ground water postglacial rebound plate tectonic vulkanism geometry of the Earth ocean loading ocean angular momentum atmosphere loading atmos. angular momentum mass distribution rotation deformation Earth quakes vegetation core, mantel... torque orientation of the Earth inertia tensor Torsten Mayer-Gürr 8

9 Solid Earth Tides Sun Moon Torsten Mayer-Gürr 9

10 Ocean tides Torsten Mayer-Gürr 10

11 Atmosphere Torsten Mayer-Gürr 11

12 sun, moon, planets solid Earth tides ocean tides The dynamic system Earth ocean currents atmospheric tides atmosphere currents gravity field of the Earth ground water postglacial rebound plate tectonic vulkanism geometry of the Earth ocean loading ocean angular momentum atmosphere loading atmos. angular momentum mass distribution rotation deformation Earth quakes vegetation core, mantel... torque orientation of the Earth inertia tensor Torsten Mayer-Gürr 12

13 Modeling and monitoring of the system Earth Torsten Mayer-Gürr 13

14 Early warning systems Torsten Mayer-Gürr 14

15 Sea level rise Torsten Mayer-Gürr 15

16 Torsten Mayer-Gürr 16

17 Sea level rise? G. Liebsch, BKG Torsten Mayer-Gürr 17

18 Reference system z x,y Torsten Mayer-Gürr 18

19 Reference system z x,y Not distinguishable wether the Earth is moving relative to the reference system or the reference system is moving relative to the Earth. Torsten Mayer-Gürr 19

20 Reference system Need of a global, precise, long time stable reference systems! Actually, need of at least two reference systems - An Earth fixed, rotating reference system (Terrestrial Reference Frame (TRS)) - Terrestrial observations - Geophysical processes - Position of observation stations - A space fixed, quasi-intertial reference system (Celestial Reference system (CRS)) - Satellite motion - Position of planetary objects - Quasi-inertial system Torsten Mayer-Gürr 20

21 System vs. Frame Reference system: conceptual definition of how a coordinate system is formed; definition of origin and base vectors Conventional reference system: reference system in combination with numerical constants, models and algorithms Reference frame: realization of a reference system, i.e., a set of precise station position coordinates and station velocities at a specific epoch regulary updated: ITRF2005, ITRF2008, (ITRF2014 is in preparation) Torsten Mayer-Gürr 21

22 Plate motion: Model Nuvel-1A Torsten Mayer-Gürr 22

23 Rotation of the Earth Torsten Mayer-Gürr 23

24 Rotation of the Earth Length of day Torsten Mayer-Gürr 24

25 Earth rotation Torsten Mayer-Gürr 25

26 Location of the 937 ITRF 2008 sites Torsten Mayer-Gürr 26

27 Location of the 937 ITRF 2008 sites Torsten Mayer-Gürr 27

28 Fundamental station Wettzell (Germany) Torsten Mayer-Gürr 28

29 LAGEOS Fundamental station Wettzell (Germany) Very Long Baseline Interferometry (VLBI) Satellite Laser Ranging (SLR) Global Navigation Satellite System (GNSS) Torsten Mayer-Gürr 29

30 Observatorium Graz-Lustbühel Torsten Mayer-Gürr 30

31 Observatorium Graz-Lustbühel Torsten Mayer-Gürr 31

32 Observatorium Graz-Lustbühel Torsten Mayer-Gürr 32

33 Observatorium Graz-Lustbühel Torsten Mayer-Gürr 33

34 Observation techniques SLR: Satellite Laser Ranging LLR: Lunar Laser Raning VLBI: Very Long Baseline Interferometry GNSS: Global Navigation Satellite Systems (e.g. GPS) DORIS: Doppler Orbitography and Radio positioning Integrated by Satellite Torsten Mayer-Gürr 34

35 Satellite Laser Ranging (SLR) Torsten Mayer-Gürr 35

36 Dedicated SLR satellites (Geodetic satellites) Torsten Mayer-Gürr 36

37 Data coverage ( ) Torsten Mayer-Gürr 37

38 Very Long Baseline Interferometry (VLBI) space-geodesy.nasa.gov/techniques/vlbi.html Torsten Mayer-Gürr 38

39 GPS Space segement Torsten Mayer-Gürr 39

40 Global Navigation Satellite Systems Torsten Mayer-Gürr 40

41 DORIS Doppler Orbitography and Radio positioning Integrated by Satellite Bases on the Doppler effect Torsten Mayer-Gürr 41

on stable frequencies; on-board receiver measures Doppler count Beacons broadcast

42 DORIS Doppler Orbitography and Radio positioning Integrated by Satellite French development (CNES, IGN, GRGS) One-way Doppler tracking system: ground beacons transmit on stable frequencies; on-board receiver measures Doppler count Beacons broadcast continuously and omnidirectionally Current 5 satellites equipped with DORIS receivers Torsten Mayer-Gürr 42

43 Realization Torsten Mayer-Gürr 43

44 Realization Torsten Mayer-Gürr 44

45 Modelling of the observations Prediction of the observations by a model: y( t) f (??? ) Observations: to multiple satellites from serveral stations at different times Torsten Mayer-Gürr 45

multiple satellites from serveral stations at different times Station position Earth fixed Corrections - Biases

46 Modelling of the observations Prediction of the observations by a model: y( t) f ( t, r ( t), r, R ( t), x, ) sat station Earth corrections Time Satellite position Depends on the orbit dynamic x sat Observations: to multiple satellites from serveral stations at different times Station position Earth fixed Corrections - Biases - Atmospheric delays - Earth rotation Described by the Earth Orientation Parameters (EOPs) x EOP Torsten Mayer-Gürr 46

47 Modelling of the observations Prediction of the observations by a model: y( t) f ( t, r ( t), r, R ( t), x, ) sat station Earth corrections Linearization by a truncated Taylor series y f ( x0) x x x f 0 0 Torsten Mayer-Gürr 47

Modelling of the observations Prediction of the observations by a model: y( t) f ( t, r ( t), r, R ( t), x, ) sat station Earth corrections Linearization by a truncated Taylor series y f ( x0) x x x

48 Modelling of the observations Prediction of the observations by a model: y( t) f ( t, r ( t), r, R ( t), x, ) sat station Earth corrections Linearization by a truncated Taylor series y f ( x0) x x x f 0 0 Linear, overdetermined system of equations l A x Solution by minimizing the weighted quadratic sum of residuals l A x xˆ 2 P min T 1 T A PA A P l Unknown parameters x: - Station coordinates - Satellite orbit (described by a few dynamic parameters) - Earth rotation - Calibration parameters Torsten Mayer-Gürr 48

49 Services maintained by the IAG Torsten Mayer-Gürr 49

50 International organizations related to ITRF Torsten Mayer-Gürr 50

51 Overview over the course 1. Newton mechanics & rotating reference systems - centrifugal, coriolis, euler force 2. Physics of Earth rotation - Angular momentum, Torques, Inertia tensor - Euler-Liouville equation 3. Planetary motion - Osculating Kepler elements 4. Celestial & terrestrial reference systems 5. Earth rotation: Transformation between TRF and CRF 6. Time systems (UTC, TAI, GMST, ) 7. Space techniques (SLR, VLBI, GNSS, DORIS) - observation equations - corrections 8. Orbit dynamics - variational equations Torsten Mayer-Gürr 51

Fundamental Station Wettzell - geodetic observatory -

Fundamental Station Wettzell - geodetic observatory - Wolfgang Schlüter Bundesamt für Kartographie und Geodäsie, Fundamental Station Wettzell Germany Radiometer Workshop, Wettzell, 10.10.06 Evolvement