1. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 1 ALTIKA / OCEANSAT3 ISRO / CNES mission Prepared by E. Thouvenot (CNES)

2. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 2 International 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

3. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 3 Altimetry missions : from research to operational AltiKa Oceansat3 NPOESS, GMES (S3) Possible gap in 2007 To-day : very good situation ! (5 satellites)

4. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 4 CNES involvement in altimetry TOPEX/POSEIDON (CNES/NASA) Launcher DORIS & POSEIDON Mission Center Reference mission Ocean Large scale Complementing mission mesoscale, ice Earth reference system SPOT2 (CNES) DORIS SPOT3 (CNES) DORIS SPOT4 (CNES) DORIS SPOT5 (CNES) DORIS 1990 2000 Jason-1 (CNES/NASA) Satellite bus DORIS & POSEIDON Control & Mission Center ERS-1 (ESA) Altimeter algorithm ENVISAT (ESA) DORIS Altimeter Processing Archive & distrib. ERS-2 (ESA) experiment operational CRYOSAT (ESA) DORIS Jason-2 / OSTM (CNES/NASA/EUMETSAT/NOAA) Satellite bus DORIS & POSEIDON Control & Mission Center ALTIKA/OCEANSAT (CNES/ISRO) Altimeter, radiometer, DORIS, Lra Process, archive & distrib. SALP : Altimetry and precise positioning service MERCATOR : assimilation, forecast CNES / SHOM / METEOFRANCE / IFREMER / CNRS / IRD PLEIADES (CNES) DORIS 2005

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7. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 7 ALTIKA System Requirements  Orbit selection : Sun synchronous orbit Altitude range : 700 – 900 km Ground track repetitivity : 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)

8. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 8  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 payload

9. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 9 Orbit Sea level Doris Beacon Earth Reference Altimeter beam Ellipsoid Geoid Ionosphere Troposphere Topography Altimetric measurement system Altimeter measurement satelliteAltitude

10. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 10 0123456789 0.5 1 1.5 2 2.5 3 3.5 4 4.5 H1/3 (m) Range noise 1 second (cm) Ku/C320 Ku Ka AltiKa 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)

11. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 11 Meso-Scale Variability (Central Objective) Light rainfall climatology Mean Sea Level Inland Ice Sea State Operational Oceanography Coastal Altimetry Geodesy Inland waters AltiKa applications

12. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 12 Ocean heat influence on Hurricanes

13. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 13 Dec. 2004 Tsunami as seen by Jason 1

14. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 14 Proposed OCEANSAT / ALTIKA Responsibility 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

15. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 15 AltiKa 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

16. ET- 3rd Indo-French Workshop on Megha-Tropiques, October 2005 16 CONCLUSION: The AltiKa Payload as a 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.