Transcript Radio occultation processing at the COSMIC Data Analysis

Radio Occultation
From GPS/MET to COSMIC
Background:
Calibrating GPS
10 sec
data
c
se
m
Occulting GPS
GPS Sat.
20
(LI
NK
3)
Global Positioning System (GPS) Satellites
Low-Earth Orbit (LEO) Satellites
1-s
ec
da
ta
GPS Sat.
GPS Sat.
ta
da
GPS Sat.
• A GPS
receiver
in LEO can
GPS radio signals that are
20 mtrack
secda
1t
a
s
(LIN
ta
K1
da
refracted inec dthe
atmosphere
)
c
at
se
K
IN
(L
10 sec da
ta
ulting LEO
a
Ionosphere
GPS Sat.
2)
10
ta
da
c
se
(L
IN
K
4)
Neutral atmosphere
Ground
receiver
10
10 sec da
ta
Occulting LEO
GPS Sat.
GPS Satellite
Earth
LEO Orbit
Atmosphere
Radio Signal
LEO Satellite
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
Signals Abundant
GPS
Glonass
Galileo
-------------60–90
sources
in space
T. Yunck, JPL
Unique Attractions of GPS Radio Occultation
1. High accuracy: Averaged profiles to < 0.1 K
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
Radio Occultation Mission Overview
JPL + Stanford
Use Radio
Occultation (RO) to
Explore planetary
atmospheres
UCAR manages GPS-MET
RO Mission - Proof of Concept
1995 - 1997
CHAMP and SAC-C Missions
Improved Proof of Concept
2000 - 2005
COSMIC
Operational Demonstration
2006-2011
METOP
(COSMIC II)
Operations RO Missions
COSMIC at a Glance
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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:
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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
COSMIC Status
Payloads
GPS Occultation receiver
•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
Tiny Ionosphere Photometer (TIP)
Tri-band Beacon (TBB)
•Nadir intensity on the night-side (along the subsatellite track) from radiative recombination emission
at 1356 Å
•Derived F layer peak density
•Location and intensity of ionospheric anomalies
(Auroral Oval)
•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
COSMIC System
Taiwan OPS
TT&C
TT&C
T1
NSPO
MOC, MCC,
SCC, FDF
T1
S/C Telemetry
CWB
TACC
Internet
Other
Customers
R.O. RT
Data E/S
(Fairbanks)
R.O. RT
Data E/S
(Kiruna)
GPS s/c
RT Fiducal
Network
Payload Commands and
All Real-Time Data Products
LAN
T1
S band
S band
L band
S band
6 Satellite COSMIC Microsat Constellation
University
Science
Centers
Real Time CDAAC (Boulder)
vBNS
STARTAP
Tanet, I2
U.S.
Universities
& Mission
Teams
NESDIS
Operational
Centers
Other
Users
QuickTime™ and a
decompressor
are needed to see this picture.
Getting COSMIC Results to Weather Centers
NCEP
I
n
p
u
t
D
a
t
a
C
D
A
A
C
BUFR Files
WMO standard
1 file / sounding
N
E
S
D
I
S
ECMWF
GTS
CWB
UKMO
JMA
Canada Met.
This system is currently under development by UCAR, NESDIS, + UKMO
Data available to weather centers within < 180 minutes of on-orbit collection
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