Formosat3 / COSMIC The Ionosphere as Signal and Noise

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Formosat3 / COSMICThe Ionosphere as Signal and
Noise

• Christian Rocken, Bill Schreiner, Sergey
  Sokolovskiy, Doug Hunt, Stig Syndergard
• UCAR COSMIC Project

FORMOSAT-3
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Status of Constellation April 23, 2008
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Radio Occultation
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Over 1 Million Profiles 4/21/06-4/15/08
Neutral Atmosphere
Ionosphere
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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.
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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
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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

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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
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Current Latency of COSMIC TEC Data
Most data are downloaded from Satellites lt 100
m Processing at CDAAC takes 20 minutes
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Comparisons with ground-based data
Courtesy of Jiuhou Lei
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COSMIC - Ionosonde ComparisonJan. 2008, distance
lt 500 km, time difference lt 15 min, colors
indicate ionosondes
F0F2 rms0.60 MHz
HMF2 rms57 km
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Scintillation Sensing with COSMIC
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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

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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
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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

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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 lt
  120 minutes of on-orbit collection, some within lt
  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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