ET-3rd Indo-French Workshop on Megha-Tropiques, October 2005 1

ALTIKA / OCEANSAT3 ALTIKA / OCEANSAT3 ISRO / CNES missionISRO / CNES mission

Prepared by E. Thouvenot (CNES)

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International context for altimetry missionsInternational context for altimetry missions

• Need expressed by IGOS (Integrated Global Observing Strategy) &GODAE (Global Ocean Data Assimilation Experiment) since 2000:

« Continuity of high accuracy, high resolution near-real time observations of the ocean surface topography is required. At least, 2 simultaneous altimetry missions are required (including one of the Jason reference class)  »

• Consequence : need to prepare a post-ENVISAT mission that would fly at the same time as JASON2

• Additional requirements to take into account : - post-GODAE & IGOS needs about performance improvement (high resolution altimetry & coastal altimetry)- GMES needs

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Altimetry missions : from research to operationalAltimetry missions : from research to operational

In orbit Approved Planned/pending approval

97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12

03/2001

Proposed Scenario

66 deg inclinat ion

EUR-US M2

High inclination

ALTIMETRIC MEASUREMENTS: SSH, SWH, WIND SPEED AT NADIRPOSSIBLE SCENARIO FOR OPERATIONAL CONVERGENCE BETWEEN THE USA & EUROPE

G F O

GODAE

TOP EX-POS EIDON

ERS-2

ENVISAT

* An oc ea n circula tio n o bserv ing s ys te m requires tw o altim eter miss io ns s imultane ous ly in orbit fo r pro pe r s ampling/cove rag e .* US co ntribution to jo int o peratio nal sy stem part o f NPOESS (a ltimetry is part o f NPOES S base line)

JASON-1

JASON-2

US-Europe a nConverge nc e

on jointope ra tional sys te m

(2 orbits)

Po s t-Envis at (Alt iKa ?)

EUR-US M1

AltiKa Oceansat3

NPOESS,GMES (S3)

Possible gapin 2007

To-day : very good situation ! (5 satellites)

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CNES involvement in altimetryCNES involvement in altimetry

TOPEX/POSEIDON (CNES/NASA)

LauncherDORIS & POSEIDON

Mission Center

Reference missionOcean Large scale

Complementing missionmesoscale, ice

Earth reference system

SPOT2 (CNES)DORIS

SPOT3 (CNES)DORIS

SPOT4 (CNES)DORIS

SPOT5 (CNES)DORIS

1990

2000Jason-1 (CNES/NASA)

Satellite busDORIS & POSEIDON

Control & Mission Center

ERS-1 (ESA) Altimeter algorithm

ENVISAT (ESA)DORIS

Altimeter ProcessingArchive & distrib.

ERS-2 (ESA)

experiment

operational

CRYOSAT (ESA)DORIS

Jason-2 / OSTM (CNES/NASA/EUMETSAT/NOAA)

Satellite busDORIS & POSEIDON

Control & Mission Center

ALTIKA/OCEANSAT(CNES/ISRO)

Altimeter, radiometer, DORIS, Lra

Process, archive & distrib.

SALP : Altimetry and precise positioning service

MERCATOR : assimilation, forecastCNES / SHOM / METEOFRANCE / IFREMER / CNRS / IRD

PLEIADES (CNES)DORIS

2005

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ALTIKA System RequirementsALTIKA System Requirements

Orbit selection : Sun synchronous orbit Altitude range : 700 – 900 km Ground track repetitivity : <35 days, >15 days

Ground system : Altika payload near real time monitoring and commands : ISRO OCEANSAT control

center Altika Payload expertise and long term monitoring : CNES SALP Science and auxiliary telemetry recovery and distribution : ISRO OCEANSAT control

Center Sizing parameter : data latency

– Three hours max required between data measurements on-board and near real time distribution to operational users (for > 75% data)

– Implies science data dump once per orbit– One hour for data exchange and processing

Science Data Processing, Archive and distribution ISRO Mission Center CNES SALP (+ EUMETSAT TBC)

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Ka-band altimeter with enhanced bandwidth ionospheric effects are negligible better vertical resolution error budget improvement Ka-band (35 GHz) authorizes a compact, lightweight instrument easier to accommodate on a wide range of satellite buses

Dual-frequency radiometer (24/37 GHz) required for tropospheric correction derived from Madras (Megha-Tropiques) developments

Laser Retro-reflector Array useful for orbitography and system calibration

DORIS required for achieving adequate orbitography performances in low earth orbit (oceanography need) enable to have similar performance than reference missions like T/P, JASON, ENVISAT required for mean sea level analysis and coastal/inland applications (real-time coupling with altimeter)

AltiKa payloadAltiKa payload

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OrbitOrbitOrbitOrbit

Sea levelSea level

Doris BeaconDoris BeaconEarth ReferenceEarth ReferenceDoris BeaconDoris BeaconEarth ReferenceEarth Reference

Altimeter beam

EllipsoidEllipsoid

GeoidGeoid

Ionosphere

Troposphere

TopographyTopography

Altimetric measurement Altimetric measurement systemsystem

Altimeter measurementAltimeter measurementAltimeter measurementAltimeter measurementsatellitesatellite AltitudeAltitudesatellitesatellite AltitudeAltitude

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0 1 2 3 4 5 6 7 8 9 100.5

1

1.5

2

2.5

3

3.5

4

4.5

H1/3 (m)

Ran

ge n

oise

1 s

econ

d (

cm)

Ku/C320

Ku

Ka

AltiKa performanceAltiKa performance

Large improvement wrt current altimetry missions :- altimetrer noise 3 times better on ocean- very good coastal and inland (rivers, lakes) performance

Comparison of tracking performance on western Corsica coastline:-AltiKa alone (at left)-AltiKa + DIODE/DORIs (at right)

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Meso-ScaleMeso-ScaleVariabilityVariability

(Central Objective)(Central Objective)

Light rainfallLight rainfallclimatologyclimatology

MeanMeanSea LevelSea Level

InlandInlandIceIce

SeaSeaStateState

OperationalOperationalOceanographyOceanography

CoastalCoastalAltimetryAltimetry

GeodesyGeodesy

InlandInlandwaterswaters

AltiKa applicationsAltiKa applications

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Ocean heat influence on HurricanesOcean heat influence on Hurricanes

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Dec. 2004 Tsunami as seen by Jason 1Dec. 2004 Tsunami as seen by Jason 1

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Proposed OCEANSAT / ALTIKA Proposed OCEANSAT / ALTIKA Responsibility SharingResponsibility Sharing

ISRO responsibilities: Project Management Launch vehicle Satellite development, IRS bus Payload :

TBD Satellite integration and test Ground System & Operations

Satellite Operations Control Center Command & Data Acquisition Stations

(TBD) Near Real Time product processing Product distribution Archiving Ground network for housekeeping

data, science data and products exchange

User interface

ISRO responsibilities: Project Management Launch vehicle Satellite development, IRS bus Payload :

TBD Satellite integration and test Ground System & Operations

Satellite Operations Control Center Command & Data Acquisition Stations

(TBD) Near Real Time product processing Product distribution Archiving Ground network for housekeeping

data, science data and products exchange

User interface

CNES responsibilities: Project Management Payload

Nadir Ka band Altimeter Nadir microwave radiometer DORIS tracking receiver Laser retro reflector array

CNES support for Payload integration and test

Ground System & Operations Product processing tool development Off line global product processing and

distribution Archiving Ground network for housekeeping data,

science data and products exchange EUMETSAT responsibilities (TBC) :

– Near Real Time global product processing, archiving, distribution and user interface

User interface ALTIKA System Coordination with other

altimetry missions

CNES responsibilities: Project Management Payload

Nadir Ka band Altimeter Nadir microwave radiometer DORIS tracking receiver Laser retro reflector array

CNES support for Payload integration and test

Ground System & Operations Product processing tool development Off line global product processing and

distribution Archiving Ground network for housekeeping data,

science data and products exchange EUMETSAT responsibilities (TBC) :

– Near Real Time global product processing, archiving, distribution and user interface

User interface ALTIKA System Coordination with other

altimetry missions

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AltiKa development planAltiKa development plan AltiKa instruments are based on proven concepts and already developed

sub-systems: innovative & mature solutions

AltiKa payload development plan discussed with ISRO in the frame of OCEANSAT-3 mission

Launch planned on 1st semester 2009 Nominal lifetime : 3 years OCEANSAT3 payload not yet decided : candidates are OCM sensor (probably), TIR

sensor (possibly), Wind scatterometer (may be difficult to combine with AltiKa), ... AltiKa payload current status

Delta phase B : January 2005 to October 2005(Very fruitful technical meetings with ISRO on May 16-17)

Phase C/D : October 2005 to June 2008 DORIS Phase C/D started since January 2005

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CONCLUSION: The AltiKa Payload as CONCLUSION: The AltiKa Payload as a precursor to future altimetry systemsa precursor to future altimetry systems

• AltiKa has been designed to solve the « post-ENVISAT altimetry gap » issue and reach the mission objectives derived from post-GODAE/IGOS requirements, in complement to the operational Jason-2 mission

• At a longer time scale, AltiKa payload could be the core of a permanent, operational, high-resolution altimetry system, flying as a multi-microsatellite system embarking the same payload, or as a combination of microsatellites and minisatellites.