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Overview of Presentation

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Overview of Presentation

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  1. Improved Homogeneous Orbits of ERS SatellitesMichiel Otten1, Pieter Visser2, Sergei Rudenko3, Remko Scharroo4, Franz-Heinrich Massmann3.1The Navigation Support Office, ESA/ESOC, Darmstadt, Germany2DEOS, Delft University of Technology, Delft, The Netherlands3GFZ German Research Centre for Geosciences, Potsdam, Germany4Altimetrics LLC, Cornish, New Hampshire, USAESA Living Planet Symposium, Bergen, Norway 02/07/2010.

  2. Overview of Presentation The REAPER orbit processing objectives and goals The new ERS orbit processing standards First orbit comparison results First altimeter results Conclusions and Outlook Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 2

  3. The REAPER Project 1/2 An important role in the overall reprocessing of the ERS-1 and ERS-2 altimeter data is the reprocessing of the ERS satellites orbits. For the REAPER project the ERS-1 orbit were reprocessed from August 1991 until July 1996 and for ERS-2 from May 1995 until July 2003. Three different centres were selected to produce three independent solutions for each of the satellites (but using common processing standards). These centres are: Helmholtz Centre Potsdam (GFZ), Delft University (DEOS) and the ESA/ESOC Navigation Support Office. The availability of three different solutions allows for rigorous validation and detection of systematic errors in any of the solutions. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 3

  4. The REAPER Project 2/2 Orbit reprocessing is performed in an iterative manner so that individual centres can enhance their processing based on initial validation results. Four different solutions are generated: the three solutions from the processing centres and a combination solution based on the three individual solutions. The final selection of the orbit used within the REAPER project is based on evaluation on the entire orbit reprocessing period performed by an independent party (Remko Scharroo from Altimetrics). All solutions will be made available to the user community at the end of the REAPER project. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 4

  5. ERS Processing Standards 1/2 At the same time as the ERS reprocessing is taking place a similar reprocessing is being performed for ENVISAT and Jason-1. To maximise the homogeneity between all altimeter missions it was decided to align the ERS specifications as much as possible with those of Envisat and Jason-1. Thus the orbit reprocessing standards are as much as possible inline with the CNES GDR-C standards. Beside the orbit models to be used the orbit processing centres are free to choose the orbit parameterisation that best fits with each centres POD software. The orbit solutions are based on SLR, altimeter data and PRARE (for ERS-2) tracking data. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 5

  6. ERS Processing Standards 2/2 The three processing centres use different software package namely: EPOS (GFZ), GEODYN (DEOS) and NAPEOS (ESA/ESOC) Using the latest IERS2003 Conventions SLR station coordinates LPOD2005 v11 (kept fixed) PRAPE station coordinates estimated Static gravity field EIGEN-GL04S plus varying part (annual+semi annual) variation from EIGEN-GL04S-ANNUAL FES2004 Ocean tides for ocean loading displacement and gravity Atmospheric gravity included (either NCEP or ECMWF fields) Surface forces either box/wing model or ANGARA Atmospheric density MSIS86/90 Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 6

  7. ERS-1 Orbit Comparison 1/2 RMS orbit difference for ERS-1 between the DEOS solution and the GFZ solution Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 7

  8. ERS-1 Orbit Comparison 2/2 RMS orbit difference for ERS-1 between the DEOS solution and the combination solution Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 8

  9. ERS-2 Orbit Comparison 1/2 RMS orbit difference for ERS-2 between the GFZ solution and the ESOC solution Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 9

  10. ERS-2 Orbit Comparison 2/2 RMS orbit difference for ERS-2 between the ESOC solution and the combination solution Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 10

  11. Altimeter Improvements 1/5ERS-2 Geographical Difference (Asc-Des) ERS-2 averaged crossover difference showing the anti-correlated orbit Error. This plot is from the existing ERS-2 DGM-E04 orbits. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 11

  12. Altimeter Improvements 2/5ERS-2 Geographical Difference (Asc-Des) ERS-2 averaged crossover difference showing the anti-correlated orbit Error. This plot is from the new ERS-2 REAPER orbits. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 12

  13. Altimeter Improvements 3/5ERS-2 Altimeter XO improvements ERS-2 crossovers over time for the DGM-E04 and GFZ REAPER orbits showing the clear improvement over the entire ERS-2 reprocessing period. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 13

  14. Altimeter Improvements 4/5ERS-2 Altimeter XO improvements ERS-2 crossovers change for the ESOC REAPER solution and the combination solution. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 14

  15. Altimeter Improvements 5/5ERS-1 Altimeter XO improvements ERS-1 crossovers change for the GFZ and DEOS REAPER solution. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 15

  16. Conclusions and Outlook 1/2 First reprocessed solution from the three POD centres show a large improvement for ERS-1 and ERS-2 over existing POD solutions. First validation results indicate a radial orbit error of 21mm for ERS-1 phase C-G and ERS-2 (excluding 2000-2001). Compared to 50mm for the DGM-E04 orbits. The availability of three different solution proves to be a major benefit allowing for rigorous validation and detection of systematic errors in any of the solutions. Initial validation has been performed over the entire processing period guaranteeing that no unexpected problems/results will arise later on. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 16

  17. Conclusions and Outlook 2/2 All centres will/are generating a second solution based on the initial validation results. The second iteration will focus on the periods were the reprocessed solutions shows the least improvement over the existing solution: ERS-1 period from 1991-1992 and ERS-2 period from 2000-2001 Final selection among the four solutions to be used in the reprocessing chain (GFZ,DEOS,ESOC and combination) will be made by Altimeterics but all four solutions will be made available to the user community as part of the REAPER project. Michiel Otten | ESA Living Planet Symposium | 02/07/2010 | Pag. 17

  18. Thank you Michiel Ottenmichiel.otten@esa.int

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