1. 1 Satellite geodesy (ge-2112) Applications E. Schrama

2. 2 Applications Global Positioning System –Precise point positioning services –Detection of platetectonics –estimation of wet tropospheric delay International Earth Rotation Service –Earth rotation parameters + LOD –Interpretation of these Earth rotation variables (AAM) Satellite altimetry –status 2002, where are we, how did it emerge, results Results from gravity missions

3. 3 GPS: precise point positioning Concept of differencing –Single differencing –Double differencing –Triple differencing Software –Bernse software –GIPSY JPL –Other software

4. 4 Concept of differencing In the GPS system, many observations are made at the “same” time by difference receivers. All receivers collect pseudo range data, carrier phase data and navigation messages The Pseudo range navigation allows you to get a approximate solution for receiver coordinates (approx 3 m) More importantly is that the pseudo range navigation solution allows to synchronize all receiver clocks to the (approx 10 nano seconds, nsec). The pseudo-range solution requires orbit information The dual frequency concept results in ionospheric free ranges and carrier phase estimates From this point on we start to work with “differencing techniques”,

5. 5 Broadcast Ephemeris GPS

6. 6 Broadcast ephemeris GPS (2)

7. 7 Single differences SAT(1)SAT(2) RCV(a) r1ar1a r2ar2a Single Difference = r 1 a - r 2 a

8. 8 Double differences SAT(1)SAT(2) RCV(a) r1ar1a r2ar2a Double Difference = (r 1 a - r 2 a ) - (r 1 b -r 2 b ) r2br2b r1br1b RCV(b)

9. 9 Difference data processing Single differences (as shown two sheets before this one) are insensitive to receiver clock errors Double differences are insensitieve to all receiver and satellite clock errors Triple differences (= differences of double differences at consequetive epochs) reveal jumps in carrier phase data. Differencing techniques as described above result in observation equations that allow one to solve for coordinate delta’s (improvements) Available software to do this: GIPSY (JPL) + Bernese SW

10. 10 GPS to observe deformation around a vulcano on Hawaii Ref: http://www.unavco.org/research_science/science_highlights/kilauea/kilauea.html

11. 11 Plate Tektonics Source: Unavco Brochure

12. 12 GPS: Wet troposphere (cm) http://www.gst.ucar.edu/gpsrg/realtime.html

13. 13 Ionosphere from GPS (TEC) http://www.gst.ucar.edu/gpsrg/realtime.html

14. 14 IERS Earth rotation parameters

15. 15 X-pole solution

16. 16 Y-pole solution

17. 17 IERS: Length of day variations The atmosphere (left) and the ocean tides (right) correlate with space geodetic observations of the length of day (LOD) source: NASA

18. 18 Satellite Altimetry By means of a nadir looking radar we measure the reflection of short pulse in the footprint. This footprint is about 4 to 8 kilometer in diameter. Source: JPL

19. 19 Pulse reflection time power time power Sent Received

20. 20 Radar footprint simulation

21. 21 Significant wave height (JPL)

22. 22 Scalar wind speed (JPL)

23. 23 Ionospheric delay (JPL)

24. 24 Radiometric water vapor (JPL)

25. 25 Technical evolution SKYLAB1972NASA 20 m GEOS-31975-1978NASA 3 m SEASAT1978NASA 2 m GEOSAT1985-1990US Navy 30 cm ERS-11991-1996ESA 4-10 cm ERS-21995-ESA 4 cm T/P1992-NASA/CNES 2 - 3 cm GFO 2000- US Navy JASON2001-NASA/CNES 2 - 3 cm ENVISAT2002-ESA

26. 26 Geosat (1985-1990) ERS-1 1991-1996 ERS-2 1995- Recent and operational systems Topex/Poseidon 1992 -

27. 27 Doris tracking network Source: CNES

28. 28 ERS-1/2 tracking + cal/val Source: DEOS

29. 29 122 T/P sampling 121 120 119

30. 30 Topex/Poseidon groundtrack

31. 31 Mesoscale Variability

32. 32 Gulf stream (altimeter)

33. 33 Thermal image Gulf stream

34. 34 Permanent currents

35. 35 Schematic overview ocean currents

36. 36 Ship observations (1)

37. 37 To show how difficult it sometimes is at sea (2)

38. 38 More Detail in Gulf Steam

39. 39 Four Seasons from Altimetry

40. 40 El Niño Southern Oscillation

41. 41

42. 42 Speed Kelvin/Rossby waves

43. 43 Kelvin and Rossby waves Equator: 2.8 m/s20 N: 8.5 cm/s

44. 44 Pacific decadal oscillation 1977-1999 Since 1999

45. 45 Examples of ocean tides This shows a 7 meter tidal height difference in Brittany France (Pentrez Plage)

46. 46 M2 tide observed by altimeter

47. 47 Tides in the South China Sea M2 wave

48. 48 K1 tidal component (23h 56m)

49. 49 Tide constants along the shores

50. 50 Tidal energy dissipation

51. 51 Gravity from satellite altimetry

52. 52 January 98August 98

53. 53 Quickscat You can also observe wind speed AND direction from space with a so-called scatterometer. (A different instrument that looks and works much like a radar altimeter.)

54. 54 Tutorial quickscat under the radar Side lobes

55. 55 Global windfield patterns

56. 56 Extreme wind conditions (Hurricane DORA)

57. 57 ICE/wind

58. 58 Decade of the Geopotentials CHAMP: a satellite equipped with acceleromters and a spaceborn version of GPS GRACE: two CHAMP flying after one another GOCE: four “champs” inside a satellite

59. 59 CHAMP 1

60. 60 CHAMP 2

61. 61 CHAMP launch

62. 62 CHAMP 4

63. 63 CHAMP 5

64. 64 Gravity field improvement