1. Formosat3 / COSMIC The 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. Radio Occultation
Ionosphere as signal
Ionosphere is noise

4. Over 1 Million Profiles 4/21/06-4/15/08
Neutral Atmosphere
Ionosphere
The number of ionospheric soundings have decreased recently because of some satellite troubles, especially antenna problems which have prompted us to us use the forward-facing POD antenna--this cuts out many ionospheric occultations.

5. Ionospheric Calibration
We estimate systematic ionospheric error by computing the “mean of the iono-free bending angle minus neutral bending angle (from climatology) in the 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= 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 / 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 km the ionosphere remains the most significant noise source for RO

10. 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

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

13. Comparisons with ground-based data
Courtesy of Jiuhou Lei
Ionospheric profile from COSMIC (red) compared to Incoherent Scatter Radar data at Millstone Hill and ionosondes at Millstone Hill and in Boulder.

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

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

17. 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 deg north and south latitude
More pronounced in NH than SH
Stronger S4 than F-layer scintillation
Half a year of scintillation data ( )
Includes high altitude satellites only ( km)
Dots are at the locations and local time of the tangent point
S4 values are the maximum for each arc/track of a GPS satellite (from either OCC or POD antennas)
S4 values are based on 9 second averages; the CDAAC level1b data allows the calculation of S4 values based on user-defined n-sec averages
Most E-layer scintillations occur in the afternoon/evening sector at mid latitudes; note north-south asymmetry (this is January-June 2007)
Most F-layer scintillations occur in the evening/morning sector at low latitudes
Dots in boxes in upper panels correspond to dots in boxes in lower panels

18. Amplitude scintillations (S4 index based on 50-Hz observations)
F-Layer scintillation:
Occurs sunset to sunrise ( LT).
Most active in equatorial region (+/- 30 degrees).
Weaker S4 than E-layer scintillation
Half a year of scintillation data ( )
Includes high altitude satellites only ( km)
Dots are at the locations and local time of the tangent point
S4 values are the maximum for each arc/track of a GPS satellite (from either OCC or POD antennas)
S4 values are based on 9 second averages; the CDAAC level1b data allows the calculation of S4 values based on user-defined n-sec averages
Most E-layer scintillations occur in the afternoon/evening sector at mid latitudes; note north-south asymmetry (this is January-June 2007)
Most F-layer scintillations occur in the evening/morning sector at low latitudes
Dots in boxes in upper panels correspond to dots in boxes in lower panels

20. 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 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

21. 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
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