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Improved Method for Measuring the Satellite-to-Satellite TEC in the Ionosphere by S. Syndergaard

Improved Method for Measuring the Satellite-to-Satellite TEC in the Ionosphere by S. Syndergaard H.-H. Benzon G. B. Larsen M. B. Sørensen P. Høeg Atmosphere Ionosphere Remote Sensing Division Danish Meteorological Institute. Setting the scene: Ionosphere occultation principle.

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Improved Method for Measuring the Satellite-to-Satellite TEC in the Ionosphere by S. Syndergaard

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  1. Improved Method for Measuring the Satellite-to-Satellite TEC in the Ionosphere by S. Syndergaard H.-H. Benzon G. B. Larsen M. B. Sørensen P. Høeg Atmosphere Ionosphere Remote Sensing Division Danish Meteorological Institute

  2. Setting the scene: Ionosphere occultation principle

  3. Ionosphere tomography combining ground and space measurements Convenient to assume straight lines

  4. GPS observables and traditional TEC measure Disregarding troposphere, clocks & ambiguity bias: • On occultation links the traditional measure is not exactly the straight line TEC • Discrepancy becomes appreciable for large electron density gradients

  5. Occultation geometry

  6. S-S TEC with first order dispersion correction (“major” term) (“minor” term) • Mainly proportional to the square of vertical TEC gradients • Accuracy depends on validity of spherical symmetry assumption

  7. Simulated TEC residuals, double Chapman layers E-layer: Max. dens.: 2·1011 m-3 Scale height: 5 km F-layer: Max. dens.: 3·1012 m-3 Scale height: 60 km

  8. GPS/MET ionosphere profile, occ. 641, Feb 20 1997 Local time: 12:30 Latitude: 36 N Longitude: 144 E Solar flux: 73

  9. GPS/MET TEC profile, occ. 641, Feb 20 1997 Local time: 12:30 Latitude: 36 N Longitude: 144 E Solar flux: 73

  10. GPS/MET estimated TEC residuals, occ. 641, Feb 20 1997

  11. Ørsted ionosphere profile, April 18 1999 Local time: 14:45 Latitude: 33 S Longitude: 13 W Solar flux: 113

  12. Ørsted TEC profile, April 18 1999 Local time: 14:45 Latitude: 33 S Longitude: 13 W Solar flux: 113

  13. Ørsted estimated TEC residuals, April 18 1999

  14. Alternative estimate of straight line S-S TEC ) ( traditional combination for comparison • Corrects for first order dispersion effects • Not sensitive to spherical asymmetry • Drawback: clocks and POD needs to be solved (removed)

  15. Simulated TEC residuals, spherical asymmetry conditions

  16. Summary • Satellite-to-satellite TEC  L1 - L2 may give TEC errors • of order 10 TECU • Not a big problem at low solar activity or night time • (error < 1 TECU) • May be a problem at day time, solar maximum • Dispersion correction reduce errors depending on • spherical symmetry assumption • Alternative dual frequency combination can be applied, • but then one needs to solve for clocks and POD • Results can be used in ionosphere tomography to obtain more • accurate straight-line satellite-to-satellite TEC

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