Simula'ons of COSMIC Follow On Sounding Distribu'ons and Data Latency for OSSE Studies

Transcription

1 Simula'ons of COSMIC Follow On Sounding Distribu'ons and Data Latency for OSSE Studies Bill Schreiner Bill Kuo, Chris Rocken, Sergey Sokolovskiy UCAR/COSMIC Project Office

2 Outline RO sounding distribugon study RO data latency study COSMIC observagon error esgmates NOT for lower troposphere Summary

3 RO Geometry Ray Tangent Point GPS Height of Straight Line (-200 to 150km) a r tp a α LEO Earth

4 SpacecraN Geometry View from Side v fore Limb Antenna POD Antennas Spacecraft v aft Limb Antenna Side Antenna View from Top Azimuth Angle +v fore aft -v Side Antennas

5 Constella'on Requirements Uniform RO global sampling Uniform RO local Gme sampling Minimize RO data latency Minimize deployment Gme Maximize GPS tracking data

6 Simula'on Inputs

7 Simula'on Outputs Times at start/end of occultagon LaGtude/Longitude at start of occultagon LaGtude/Longitude at end of occultagon Rise/set flag OccultaGon azimuth angle in local level frame Azimuth of occultagon plane projected onto surface of Earth Horizontal smear LEO/GPS prn numbers

8 Number of Orbit Planes planes Inc = 90 ΔΩ=180/n= planes Inc = 72 ΔΩ=180/n= planes Inc = 24 ΔΩ=180/n= planes Inc = 24 ΔΩ=360/n=90 1 2

9 Inclina'on vs. Precession rate Ω = -1.5 (µ/a 3 ) 1/2 (R E /a) 2 cos(i) J2/(1- e 2 ) 2 Final orbit 800 km Parking orbit 525 km

10 Geographic Coverage

11 Local Time Coverage Noon Midnight

12 Azimuth and Horizontal Smear Inc = 72 Inc = 24 Inc = 0 ~30% more soundings for 72 inc when azimuth angles > 45 considered 100% more ionospheric data when azimuth angles > 45 considered

13 Occulta'on Density vs. Inclina'on Azimuth < 45 InclinaGon > 68 required to capture every ½ orbit dump from (Fairbanks, Tromso, McMurdo, TrollSat)

14 Occulta'on Density vs. Constella'on Op'ons IIA 8/72 & 4/24 IIB 12/72 IIC 6/72 & 6/24 IID 4/72 & 8/24 Actual COSMIC Good tracking period

15 COSMIC Data Latency Timelines Current COSMIC LOS min Occultation Events 2-5 min Downlink 3 min PTP 1 m FTP 5 min CDAAC 2.5 min Wait FTP to NESDIS AOS LOS Latency of Occultation COSMIC-II AOS + 8 min Occultation Events 2 min Downlink 1 m FTP 5 min CDAAC FTP to NESDIS AOS Latency of Occultation

16 COSMIC II Average Data Latency Worst Case: Current COSMIC 15 deg elevagon cutoff Data to CDAAC = LOS + 4 min CDAAC processing Gme = 7.5 min Best Case: RealisGc COSMIC II 5 deg elevagon cutoff Data to CDAAC = AOS + 3 min CDAAC processing Gme = 5 min 15 sites: Fairbanks, Tromso, McMurdo, TrollSat, Guam, Hawaii, Vandenberg, Colorado, NewHampshire, DiegoGarcia, England, Thule, Bangalore, MauriGus, Taiwan Network COSMIC (Fairbanks, Tromso) COSMIC +McMurdo COSMIC +McMurdo +TrollSat LEO Inclina'on (deg) Worst Case Average Latency (min) Best Case Average Latency (min) StaGons StaGons

17 Current COSMIC Latency Ave = 86 min Ave = 96 min Simulation Ave = 68 min Current (one orbit) Latency: Fairbanks (FBSK01) = 72 min Norway (NORTG5) = 74 min Ave = 85 min

18 Refrac'vity Precision Collocated (Tangent points within 10km, same PRN) refracgvity profiles are differenced to esgmate precision (Schreiner et al., GRL, 2007, doi: /2006gl027557) Magnitude similar to theoregcal esgmates from Kursinski et al. (1997) Profile precision ~0.1% between 10 and 20 km RepresentaGveness errors not included These errors can be mapped to non local linear excess phase observable (Sokolovskiy et al, MWR, 2005)

19 Bending Angle Precision Collocated (Tangent points within 10km, same PRN) raw bending angle profiles from COSMIC3 are differenced with COSMIC4 at common impact heights Daterange = ranges of impact height are shown for visibility 15 to 60 km 0 to 15 km Legend: Mean = Black, STD = Green, STD of mean = Red, Count = Blue Profile precision < 0.2% above 20 km 15km < Impact height < 60km STD ~ 2.5e-6 rad 0km < Impact height < 15km

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21 TEC Errors Absolute TEC good to ~ 3 TECU RelaGve TEC ~ TECU Actual COSMIC reference link data ~ TECU at 1 Hz sampling ( )

22 Summary Most uniform RO sampling provided by constellagon with 8 s/c at 72 inc and 4 s/c at 24 inc Slightly increase plane separagon for 8/72 component to minimize local Gme hole Plane separagon for 4/24 component should be 90 Perform sampling error study (similar to B. Pirscher) to quangfy errors Side viewing antennas (originally proposed to UCAR by Prof. Tsuda) COSMIC II should consider adding side looking antennas (100% increase in ionosphere data) COSMIC should consider side viewing test SimulaGon and current COSMIC data latency agree reasonably well Best case 32 min average latency for 72 constellagon from polar RTSs Best case 37 min average latency for 24 constellagon from 15 RTSs Demonstrated COSMIC precision very high Simulated sounding locagons and data latency data available upon request (schrein@ucar.edu)

23 Acknowledgments NSF Taiwan s NSPO NASA/JPL, NOAA, USAF, ONR, NRL Broad Reach Engineering