Download Altimetry and Oceanography

TOPEX and JASON SPACEBORNE
ALTIMETERS
Jean PLA
CNES, Toulouse, France
WMO Workshop, Geneva - March 20-21, 2006
J. PLA - CNES
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Summary
Scope of a spaceborne altimeter
Frequency plan for TOPEX and JASON
Usage of the data
Data Assimilation and forecasting
WMO Workshop, Geneva - March 20-21, 2006
J. PLA - CNES
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Topex-Jason Mission Objectives: Scope of a
spaceborne altimeter
• Ocean general circulation
• Intra-seasonal to interannual sea level variations
• Long term mean sea level changes
• Tide observation
• Wind speed mapping and significant wave height at the
ocean surface
WMO Workshop, Geneva - March 20-21, 2006
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Objectives of a spaceborne altimeter
WMO Workshop, Geneva - March 20-21, 2006
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TOPEX/POSEIDON
JASON 1
JASON 2
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TOPEX/POSEIDON
2500 kg
Jason-1
500 kg
performances
similar to in-flight T/P ones
7 Dec. 2001
TOPEX/POSEIDON (1992) ; JASON-1 (2001) ; JASON-2 (2007-2008)
WMO Workshop, Geneva - March 20-21, 2006
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Frequency plan of TOPEX/ JASON altimeters
•
C BAND: 5140 to 5460 MHz, 320 MHz bandwidth, linear frequency modulation
• Fc = 5.3 GHz, antenna gain = 32.2 dBi (3.4° at -3dB), peak power = 17 W,
mean power = 0.54 W, PRF = 300 Hz, pulse duration = 105.6 μs
• 5140 MHz to 5250 MHz, under 4.4: no allocation to EESS (active), no
recorded cases of interference
Services: Aeronautical Radionavigation
Fixed Satellite (Earth to Space): feeder links of
non- GSO satellites in the mobile satellite service
Mobile
• WRC(2003): extension from 5460 MHz to 5570 MHz
•
Ku BAND: 13415 MHz to 13735 MHz: 320 MHz bandwidth, linear frequency
modulation
• Fc = 13,575 GHz, antenna gain = 41.5 dBi (1.23° at -3 dB), peak power = 8 W,
mean power = 1.52 W, PRF = 1800 Hz, pulse duration = 105.6 μs
• 13250 MHz to 13750 MHz: allocation to EESS (active):
• Other services: Aeronautical Radionavigation
Space Research
•
For C and Ku BANDS: use of large bandwidths (320 MHz) to estimate ionospheric
delay and to get unprecendented accuracy: around 1 cm
WMO Workshop, Geneva - March 20-21, 2006
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JASON-1
Altitude = 1344 km, beam footprint = 77 km
WMO Workshop, Geneva - March 20-21, 2006
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Jason-1 Instrument
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Radiometer (JMR)
This instrument collects the natural emission by the
ground surface and in the atmosphere at three
different (18, 21 and 37 GHz) frequency bands. The
goal is to determine the water vapour content and in
liquid water in the atmosphere, when combining the
whole set of measurements within those bands.
Therefore, it is possible to know the correction to be
applied to the altimetric measurement. ( NASA)
WMO Workshop, Geneva - March 20-21, 2006
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From GEOS-3 to Jason-1
Centimeters
Error budget of altimeter missions
100
90
80
Orbit error
Alt. Instr. error
Ionosphere
Troposphere
EM Bias
70
60
50
40
30
Ocean signal
20
10
0
GEOS 3
SEASAT
GEOSAT
ERSI
T/P
(before launch)
T/P
(after launch)
Jason-1
(before launch)
WMO Workshop, Geneva - March 20-21, 2006
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TOPEX/POSEIDON RESULTS
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TOPEX/POSEIDON - JASON Achievements
WMO Workshop, Geneva - March 20-21, 2006
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MAIN RESULTS
• Rise of the mean sea level of about 3 cm within 10
years according to TOPEX-POSEIDON
• Complex interaction between the oceans and the
atmosphere. An example is El Niño event: warm
waters are pushed to the West coast of South
America, disrupting normal winter conditions
throughout the Pacific ocean. Reliable predictions of
El Niño occurrence will lead to better preparation for
its widespread impact.
WMO Workshop, Geneva - March 20-21, 2006
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El Niño/La Niña as seen by TOPEX/Poséidon (NASA/CNES)
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WMO Workshop, Geneva - March 20-21, 2006
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MERCATOR :
Towards an integrated, multi-parameter approach of
ocean modelling and operational forecasting
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OCEAN MODELLING & FORECASTING
OCEAN : turbulent & chaotic medium
Integrated approach necessary with :
–
–
–
–
Space based observations
in situ measurements
numerical models
multi-data analysis & assimilation
French initiative : MERCATOR
Process similar to weather forecast
.
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The MERCATOR mission was defined in 1996 by six partner
organizations. The project is pursuing three goals:
• Develop an operational oceanography system
• Develop downstream oceanography applications
Mercator Users :
• « Sea people »
• « Science people »
• « Climate people »
• « Coastal people »
WMO Workshop, Geneva - March 20-21, 2006
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Mercator, towards operational oceanography
2002
1/3°
1/15°
2003
1/15°
2°
1/4°
2004
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MERCATOR OBJECTIVES
• For its scientific users, MERCATOR is an operational ocean
observatory: by systematically combining, over several years, all
the information yielded from observations (measurements
reflecting reality) with that provided by the model (a threedimensional view and a memory of past states), it can produce
a view of the ocean that is continuous in both space and time.
This integrated view is extremely valuable, as it exists nowhere
else. It provides a reference state which can be examined or
enhanced … as well as the raw materials to do it.
• For the ocean, MERCATOR provides information of salinity,
state of surface down to 1000 m of depth thanks to the satellite
and to the in situ data. The forecast are valid for 2 weeks.
WMO Workshop, Geneva - March 20-21, 2006
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MERCATOR system
TOPEX, JASON, ...
CORIOLIS
WMO Workshop, Geneva - March 20-21, 2006
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Altimetry & Oceanography - Operational Organization
Research
Altimetry missions :
Jason, ENVISAT,
DORIS/SPOT
Other space data
(temperature, salinity,
colour)
Value-added
Products
Assimilation,
forecast :
MERCATOR
Users
In situ Data:
ARGO, CORIOLIS
WMO Workshop, Geneva - March 20-21, 2006
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WMO Workshop, Geneva - March 20-21, 2006
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OCEANOGRAPHY APPLICATIONS
Navy
"See without being
seen"
Routing
"Find the most
economical route"
Fishing
"Find fish"
Research
"Interesting structures to study"
WMO Workshop, Geneva - March 20-21, 2006
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Fisheries
Altimeter product from T/P and ERS-2
for fisheries in the Indian ocean
WMO Workshop, Geneva - March 20-21, 2006
• need to understand, model and predict
the effects of ocean conditions on fish
populations
• can help locate areas with a higher
probability of finding fish and reduce
search time and operation costs
• description of the upper ocean at high
space and time resolution needed
• start to use external information (e.g.
SST, ocean colour, altimetry).
• a global and integrated approach should
allow the development of improved
products for fisheries and a better
management of stocks
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MERCATOR : future activities
The MERCATOR mission seeks to develop and deploy a truly
operational oceanography system over the next five years
capable of analyzing and predicting ocean conditions around the
globe : the Centre for Operational Oceanography (C2O)
This system will describe and predict ocean conditions over the
whole ocean column continuously and in real time, at scales
ranging from global phenomena to regional areas.
WMO Workshop, Geneva - March 20-21, 2006
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