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Formosat3 / COSMIC The Ionosphere as Signal and Noise

Formosat3 / COSMIC The Ionosphere as Signal and Noise. Christian Rocken, Bill Schreiner, Sergey Sokolovskiy, Doug Hunt, Stig Syndergard UCAR COSMIC Project. FORMOSAT-3. Status of Constellation April 23, 2008. Ionosphere as signal. Ionosphere is noise. Radio Occultation.

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Formosat3 / COSMIC The Ionosphere as Signal and Noise

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  1. Formosat3 / COSMICThe Ionosphere as Signal and Noise Christian Rocken, Bill Schreiner, Sergey Sokolovskiy, Doug Hunt, Stig Syndergard UCAR COSMIC Project FORMOSAT-3

  2. Status of Constellation April 23, 2008

  3. Ionosphere as signal Ionosphere is noise Radio Occultation

  4. Over 1 Million Profiles 4/21/06-4/15/08 Neutral Atmosphere Ionosphere

  5. We estimate systematic ionospheric error by computing the “mean of the iono-free bending angle minus neutral bending angle (from climatology) in the 60-80 km height bin”. We compare this quantity “smean” for daytime vs. nighttime soundings. COSMIC Days 0-120, 2007 -20 < Lat. < 20 DAY (11<LT<15) smean= -1.19 e-7 rad NIGHT (2<LT<6) smean=-0.37e-7 rad Ionospheric Calibration We can see the day vs. night iono bias change we expect that we can monitor the change of this bias to better than 0.5e-7 rad during the 11-year solar cycle.

  6. Relationship of F10.7 / Bending Bias/ Temperature The bending angle change of +3 e-7 rad due to change in solar activity would cause a apparent stratospheric warming of: 0.6 / 0.4 / 0.2 deg K at 30 / 25 / 20 km. F10.7 BA Bias

  7. Ionosphere as “Noise” Summary • In RO the ionosphere is corrected by forming the “standard” dual frequency linear combination of L1 and L2 bending angles • This correction does not completely eliminate the ionospheric effect • Significant random noise remains which can affect profiles for weather forecasting down to 25 km altitude • The residual ionosphere also introduces a bias, which - if left uncorrected -could introduce a significant spurious “warming with decreasing solar activity” signal at 30 km in the stratosphere of ~ 0.6 deg K with the 11 year solar cycle. • Methods have been developed to minimize the “ionosphere as noise” so that it becomes largely insignificant below 25 km. • At altitudes 25-40 km the ionosphere remains the most significant noise source for RO

  8. Amount of COSMIC-observed Trans Ionospheric TEC Data Quality of abs. TEC ~2 TECU COSMIC trans-ionospheric radio links for a 100-min period, June 29, 2007

  9. Location of Low-Latency TEC Arcs Current Latency of COSMIC TEC Data Most data are downloaded from Satellites < 100 m Processing at CDAAC takes ~ 20 minutes

  10. Comparisons with ground-based data Courtesy of Jiuhou Lei

  11. COSMIC - Ionosonde ComparisonJan. 2008, distance < 500 km, time difference < 15 min, colors indicate ionosondes F0F2 rms=0.60 MHz HMF2 rms=57 km

  12. Scintillation Sensing with COSMIC No scintillation S4=0.005 Scintillation S4=0.113 GPS/MET SNR data

  13. Amplitude scintillations (S4 index based on 50-Hz observations) E-Layer scintillation: Occurs at all local times except near sun-rise (3-7 LT), strongest near sun-set (14-19 LT). Most active between 20-60 deg north and south latitude More pronounced in NH than SH Stronger S4 than F-layer scintillation

  14. Amplitude scintillations (S4 index based on 50-Hz observations) F-Layer scintillation: Occurs sunset to sunrise (19 - 5 LT). Most active in equatorial region (+/- 30 degrees). Weaker S4 than E-layer scintillation

  15. What comes after COSMIC? • Several Options for a follow - on mission are discussed and considered by US agencies • Participation in a Taiwan 6+ satellite follow on mission (2012) • Iridium has proposed to use (some of) its 64 future communication satellites as a platform for RO observations (2013 ?) • CICERO plans to launch 24 satellites (starting in 2011) and to sell data • Planned improvements compared to COSMIC • Plan for lower data latency. Goal of 10-15 minutes (more ground stations, or real-time satellite to satellite downlink) • Observations of GPS and Galileo (Glonass?, Compass?) • More TEC arcs and soundings • Community feedback on requirements and secondary space weather payloads for future mission should be provided to UCAR

  16. Summary • In the 2 years since launch COSMIC has generated and distributed over 1.3 million ionospheric profiles and TEC arcs • COSMIC is now also generating a large amount of scintillation observations • COSMIC ionospheric observations are of high quality and most products are available within < 120 minutes of on-orbit collection, some within < 30 minutes • All data are available from www.ucar.cosmic.edu • Follow on missions for COSMIC are now in planning stages and input from the space weather community is needed • UCAR COSMIC program is presently looking for a scientist to take charge of our ionospheric processing

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