The Use of GPS Radio Occultation Data for Tropical Cyclone Prediction
Radio Occultation From GPS/MET to COSMIC
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Transcript of Radio Occultation From GPS/MET to COSMIC
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Radio Occultation From GPS/MET to COSMIC
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Background: Global Positioning System (GPS) Satellites
Low-Earth Orbit (LEO) Satellites• A GPS receiver in LEO can track GPS radio signals
that are refracted in the atmosphere
GPS Satellite
LEO Satellite
Radio Signal
LEO Orbit
Atmosphere
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Occultation Geometry
• During an GPS occultation a LEO ‘sees’ the GPS rise or set behind Earth limb while the signal slices through the atmosphere
Occultation geometry
• The GPS receiver on the LEO observes the change in the delay of the signal path between the GPS SV and LEO
• This change in the delay includes the effect of the atmosphere which delays and bends the signal
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Signals Abundant
GPS GlonassGalileo
---------------
60–90sourcesin space
T. Yunck, JPL
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1. High accuracy: Averaged profiles to < 0.1 K
Unique Attractions of GPS Radio Occultation
2. Assured long-term stability
3. All-weather operation
4. Global 3D coverage: stratopause to surface
5. Vertical resolution: ~100 m in lower trop
6. Independent height & pressure/temp data
7. Compact, low-power, low-cost sensor
T. Yunck, JPL
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Radio Occultation Mission OverviewJPL + StanfordUse RadioOccultation (RO) to Explore planetary atmospheres
CHAMP and SAC-C MissionsImproved Proof of Concept2000 - 2005
UCAR manages GPS-MET RO Mission - Proof of Concept1995 - 1997
COSMIC Operational Demonstration
2006-2011
METOP(COSMIC II)
Operations RO Missions
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COSMIC at a Glance Constellation Observing System for Meteorology Ionosphere
and Climate (ROCSAT-3) 6 Satellites launched in late 2005 Orbits: alt=800km, Inc=72deg, ecc=0 Weather + Space Weather data Global observations of:
● Pressure, Temperature, Humidity● Refractivity● TEC, Ionospheric Electron Density
● Ionospheric Scintillation
Demonstrate quasi-operational GPS limb sounding with global coverage in near-real time
Climate Monitoring Geodetic Research
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COSMIC Status
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Payloads•High-resolution (1 Hz) absolute total electron content (TEC) to all GPS satellites in view at all times (useful for global ionospheric tomography and assimilation into space weather models)
•Occultation TEC and derived electron density profiles (1 Hz below the satellite altitude and 50 Hz below ~140 km), in-situ electron density
•Scintillation parameters for the GPS transmitter–LEO receiver links
•Data products available within 15 - 120 minutes of on-orbit collection
Tri-band Beacon (TBB)•Phase and amplitude of radio signals at 150, 400, and 1067 MHz transmitted from the COSMIC satellites and received by chains of ground receivers.•TEC between transmitter and receivers•Scintillation parameters for LEO transmitter - receiver links
Tiny Ionosphere Photometer (TIP)•Nadir intensity on the night-side (along the sub-satellite track) from radiative recombination emission at 1356 Å•Derived F layer peak density•Location and intensity of ionospheric anomalies (Auroral Oval)
GPS Occultation receiver
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COSMIC System
6 Satellite COSMIC Microsat Constellation
C W B
TT&C NSPOMOC, MCC, SCC, FDF
UniversityScienceCenters
R.O. RTData E/S
(Fairbanks)
R.O. RTData E/S(Kiruna)
Real Time CDAAC (Boulder)
U.S. Universities & Mission
Teams
NESDIS
RT FiducalNetwork
OtherUsers
L b
an
d
S b
an
d
T1
Internet
S b
an
d
S b
an
d
Payload Commands and All Real-Time Data Products
S/C Telemetry
vBNSSTARTAPTanet, I2
Taiwan OPS
T1
Other Customers
TT&C
GPS s/c
TACCT1
LAN
Operational Centers
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Input
Data
CDAAC
NESDIS
GTS
NCEP
ECMWF
CWB
UKMO
Canada Met.
JMA
BUFR FilesWMO standard1 file / sounding
Getting COSMIC Results to Weather Centers
This system is currently under development by UCAR, NESDIS, + UKMOData available to weather centers within < 180 minutes of on-orbit collection
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Summary•Radio occultation is a new and promising remote sensing technique
•Technique was demonstrated and now COSMIC aims to:–Improve data quality in lower troposphere - new technology–Increase number of soundings –Show impact in operational models - work at NCEP, UKMO, ECMF
•COSMIC launch is on schedule for December of 2005
•COSMIC “operational demonstration” - should be followed by continuous operational missions