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Status of GPS Radio occultation with CHAMP
J. Wickert, N. Jakowski2, G. Beyerle, T.
Schmidt, R. König, Ch. Marquardt3, and Ch.
Reigber GeoForschungsZentrum Potsdam 2German
Aerospace Center, Neustrelitz 3Met Office,
Bracknell, U.K.
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Content

• Status of the CHAMP occultation experiment
• Operational data processing (GFZ Potsdam, DLR)
• Validation application (Neutral atmosphere
  GPS reflections)
• Validation Ionosphere
• Summary

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First occultation measurements
February 11, 2001, 1933 UTC Antarctica
Occultation Nr. 4
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SNR CHAMP AS on
Viewing angle 23
Occ. No. 2, Feb 11, 2001
Optimized occultation antenna
L1 (50 Hz)
L2 (1 Hz)
JPLs BlackJack
Data analysis not restricted to AS off
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Neutral atmosphere Occultations 2001
217 days 36,514 occultations (168 daily)
24,658 profiles (64.6)
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Neutral atmosphere Occultations 2002
208 days 44,962occultations (216 daily) 33,036
profiles (73.5)
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First electron density profiles from CHAMP on
April 11, 2001
Ionosphere Profiling
First electron density profiles from CHAMP as
directly provided by the automatic working data
processing system
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Ionosphere Occultations 2001
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Ionosphere Occultations 2002
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Expected mission duration
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GPS Radio occultation at GFZ Potsdam
One major task Development of strategies and
methods for the determination of atmospheric and
ionospheric parameters in near real-time from
radio occultation data of forthcoming LEO
missions, in particular CHAMP and GRACE
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Occultation processing
Automated data processing systems for Neutral
atmosphere occultations (GFZ) and Ionosphere
occultation (DLR)
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GPS Ground station network
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GPS Ground Station Data Availability
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Ground antenna Ny Alesund
48 h real scenario
Contact every orbit 5-10 min Delay 90 min
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Recent CHAMP RSO USO Precision
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Ultra Rapid Science Orbits (USO)
182 profiles Doy 103/2002, processed using RSO
and USO
Real delay between measurement and Data
provision 3-6 hours for each profile
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Status information via WWW
CHAMP occultation statistics
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Validation Application

• Various validation studies,
• CHAMP
• Analyses (ECMWF, UKMO, NCEP)
• Radio sondes
• ATOVS (Single Comparisons)
• Regional analyses HRM (BALTEX-Region) HIRHAM
  (Arctic)
• Activities within German GPS Atmosphere Sounding
  Project

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Validation of 42,000 CHAMP profiles (ECMWF)
Dry temperature
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Validation Radio sondes
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Reflections
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Reflections
about 10,000 occultation events 30 contain
reflections signatures at high latitudes 80-90
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Comparison with ionosonde profile and TEC
Day-time profile retrieved from GPS Radio
occultation measurements onboard CHAMP during
HIRAC/SolarMax of IGS on 27 April 2001
Comparison with ionosonde vertical profile
measured in Juliusruh/IAP Kühlungsborn, with
the corresponding TEC map and planar Langmuir
probe data obtained on CHAMP
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Comparison with Vertical Sounding data Key
parameter NmF2 and hmF2 (percentage)
Ionosphere profiling
Vertical sounding stations that have been
included Athens (A. Belehaki) Boulder, Mawson,
Hobart, Canberra, Norfolk Is., Brisbane,
Townsville, Darwin (Phil Wilkinson)
El Arenosillo, Tortosa (G.Miro, D. Altadill,
B.A.de la Morena) Juliusruh (J. Mielich)
Rome (B. Zolesi, R.Vincenzo) COST 271 community
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Global distribution and amplitude of day-time
f0F2 data
Ionosphere profiling
Global distribution of the typical vertical
sounding parameters f0F2 and hmF2 on day-time
between 11 April and 12 August 2001 Possibility
to complete the global ionosonde network by IRO
data?
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Summary

• Quasi-continuous provision of GPS occultation
  data, operational CHAMP processing of CHAMP data
  at GFZ Potsdam and DLR Neustrelitz since
  February/April 2001 80,000 atmospheric profiles
  available, 30.0000 ionosphere profiles recent
  status via WWW
• Demonstration of Near-real-time occultation
  processing
• Extensive validation activities
• Neutral Atmosphere Warm-Bias Stratosphere,
  Negative refractivity bias troposphere,
• Ionosphere Promising first validation results,
  studies will be continued, COST 271 Action
• CHAMP GPS data are a good basis for a broad
  international cooperation

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Launch March 17, 2002