AltiKa/SARAL project status

AltiKa/SARAL project status Jocelyne NOUBEL, CNES Pierre SENGENES, CNES

Summary • AltiKa/SARAL Mission features • SARAL Responsibility sharing • SARAL System overview • AltiKa/SARAL Mission requirements • Data products requirements • Products definition • SARAL Project summary

AltiKa/SARAL Mission features • SARAL Responsibility sharing • SARAL System overview • AltiKa/SARAL Mission requirements • Data products requirements • Products definition • SARAL Project summary

AltiKa/SARAL mission context • AltiKa/SARAL program is an answer to the need expressed by IGOS and GODAE since 2000 • « Continuity of high accuracy, high resolution near-real time observations of the ocean surface topography is required. At least, 2 simultaneous altimetric missions are required (including one of the Jason reference class) » • Program approved on December, 2005 • Altimetric Gap filler between ENVISAT & SENTINEL3 • Research oriented mission : - new, higher frequency, greater performance - potential new applications on ice, land, coast areas • …but with a consolidated architecture : conventional altimeter

AltiKa/SARAL mission scientific objectives • AltiKa/SARAL central objective • Ocean meso-scale variability studies with an improvement of vertical and spatial resolution • Data assimilation in a global ocean model • Contribution to : • Operational oceanography • Coastal altimetry • Continental waters • Inland ice sheet monitoring • Light rainfall and clouds climatology • Mean sea level • Sea state observation and forecasting • Geodesic reference system determination

AltiKa/SARAL mission and system highlights – Orbit • AltiKa/SARAL mission orbit : same as ERS and Envisat orbits • Polar (incl. = 98.55°) Sun-Synchronous orbit (6:00/18:00), 800 km altitude, low eccentricity • Ground track • repetitivity period : 35 days • ground-track stability : +/- 1 km • Complementary to Jason2 ground-track in terms of spatial & temporal sampling

AltiKa/SARAL mission and system highlights – Payload • A single frequency Ka-band altimeter (35.75 GHz +/- 250 MHz) • Improved vertical and spatial resolution • enhanced bandwidth (500 MHz) and increased PRF (~ 4kHz) • antenna footprint : 8.5 km in Ka-band, 12 km in K-band • reduced ionosphere effect in Ka-band authorizes mono-frequency altimeter • Ka-band limitations • no altimeter measurement for rain rate > 1.5 mm/h (data loss ~ 5% according to geographic areas) • Specific measurement processing required in case of clouds or low rain rate situations (~ 10%) • A dual-frequency radiometer ( 23.8 GHz +/- 200 MHz & 37 GHz +/- 500 MHz ) • required for wet troposphere correction on altimeter measurements • embedded in the altimeter instrument : share the same antenna • POD system to achieve high accuracy orbitography performances • DORIS • required for achieving high accuracy orbitography performances on low earth orbit in a precisely monitored reference frame (mean sea level analysis) • contribution to DORIS system performance and monitoring ( for the benefit of all altimetry missions using DORIS) • Laser Retro-reflector Array • POD system calibration and guarantees minimum orbitography • for coastal/inland applications, real-time coupling of the altimeter with DORIS

AltiKa/SARAL mission and system highlights – Mission Ground System • AltiKa Mission Ground System • same definition of ocean products between JASON2 and AltiKa products • Same constraints for near real-time products processing and distribution • important synergy with JASON2 SALP/SSALTO developments • Processing algorithms (retracking, radiometer troposphere correction,…) has to be defined by the end of 2007 for ocean products, and at the beginning of 2008 for non-ocean products

AltiKa/SARAL program status • AltiKa program has been approved by CNES Governing Board in December 2005 • Authorization for Altimeter & Radiometer phase C/D commitment • Funding for AltiKa development (AltiKa mission payload, CNES Mission Center upgrades, system and science support studies) and for a 3-year exploitation (phase C/D/E) • AltiKa payload was planned to be embarked on Oceansat3 ISRO satellite, for a launch foreseen in mid-2009. • But Oceansat3 launch is now postponed to 2011/12 … • May/June 2006 : CNES&ISRO proposition to embark AltiKa payload with Argos3 equipments, on a new platform, named SSB (Small Satellite Bus), which is being developed by ISRO • July/November 2006 : CNES&ISRO technical studies to assess the feasibility of this new satellite configuration SARAL satellite • December 2006 : CNES commitment to develop the Integrated Payload Module accommodating AltiKa and ARGOS-3 payloads • SARAL and ARGOS-3/SARAL MoUs signature by CNES and ISRO on February 23rd, 2007

Present AltiKa & Argos-3 payloads accommodation baseline on SSB platform : SARAL (SAtellite with ARgos and ALtika) ALTIKA ALTIMETER & RADIOMETER ANTENNA INTEGRATED PAYLOAD MODULE SARAL sat. characteristics # Mass : 350/400 kg - SSB platform : ~200kg - Payload Module : ~150 kg # Power : 570 W (end of life) - SSB platform : ~ 205 W - Payload Module: ~ 195 w # Size - 0.98m x 0.98m X 2.6 m -Solar panels : 1.2m x 1.4m (x2) STAR SENSORS LRA SSB PLATFORM DORIS ANTENNA TTC ANTENNA ARGOS L-BAND ANTENNA X-BAND ANTENNA ARGOS UHF ANTENNA MAGNETOMETER

ISRO responsibilities Project Management, shared with CNES Overall SARAL system engineering PSLV Launch vehicle and services SSB Platform SARAL Satellite integration and test Ground System & Operations Satellite Operations Control Center S-band network stations X-band Hyderabad station Data communication network NRT and OFL products processing and distribution to users within India Archiving User interface CNES responsibilities Project Management, shared with ISRO Overall SARAL system engineering Payload AltiKa payload ARGOS-3 payload Integrated Payload Module Support for SARAL Payload Module integration and test Ground System & Operations X-band stations Data communication network AltiKa Mission Center NRT and OFL product processing software development NRT product processing, archiving, distribution to users outside India with the support of EUMETSAT OFL product processing and distribution to users outside India DORIS product processing and distribution Archiving of all telemetry and products ARGOS3 Data Processing and Distribution System User interface ALTIKA System Coordination with other altimetry missions CNES/ISRO SARAL Responsibility Sharing

SARAL system overview SARAL Space Segment SARAL Payload Data Segment SARAL Satellite Auxiliary data providers DORIS Beacons Network Laser Community SARALS-Band Ground Stations Network Flight Operation Control Center Integrated Payload Module AltiKa & ARGOS3 Missions Centers CNES Payload Outside INDIA AltiKa Users EUMETSAT Center CNES Mission Center IDS Payload Interface Module AltiKa NRT AltiKa NRT ICU ARGOS User ARGOS User ARGOS User ARGOS Processing Center ARGOS Processing Center ISRO Center SSB AltiKa NRT Within INDIA AltiKa Users AltiKa OFL ARGOS L-Band Ground Stations Network SARAL X-Band Ground Stations Network PSLV Launch vehicle

AltiKa Data Products requirements • Data products • Operational Service Specification (OSS) products (ocean type products) • Near-Real Time (NRT) products : OGDR • Off-Line products (OFL) : IGDR, GDR • Non-OSS products • 1 product for coastal zone & inland waters (studies in progress to define specific ground retracking, content and format) • 1 product for inland ice • Data collection • The system shall be design to assure for each day that 80% of data collected on the satellite within 3 hours, and up to 100% of the data within 5 hours, can be made available to the users • Impact on on-board mass memory storage design, on ground station network design, set-up and operations, on communication network design, on ground processing performances • Data latency • Near-Real Time product (OGDR) • 75% of the data taken shall be made available to the users within 3 hours from acquisition • 95% of the data within 5 hours

AltiKa Data Products requirements - continued • Data availability • GDR shall contain 95% of all possible over-ocean data during the mission life time, without any systematic gaps, taking into account the Ka-band constraints • 5% of data loss due to rain rate > 1.5 mm/h according to geographic areas • 10% of data to be processed with a specific retracking algorithm

AltiKa/SARAL Products definition • Products definition closed to the Jason-2 one • All O/I/GDR products will have the same format and very close scientific content • IGDR vs. OGDR : • Orbit quality, improved pole location data, restituted DORIS USO frequency, improved altimeter/radiometer calibrations, analyzed meteorological fields, GIM ionospheric and dynamic atmospheric corrections applied • OGDR product not generated in case of altitude or time-tagging information from DORIS/DIODE not available • Fast Quality Control & Check for OGDR : elementary and automatic controls only, product delivered in any case • Quality Control & Check for IGDR : product not delivered in case of pbs detected; fully validated by DUACS processing; possible reprocessing • GDR vs. IGDR : • Orbit quality, more accurate pole location data, more accurate dynamic atmospheric corrections • GDR is fully validated by experts; dissemination to users only once validated • Taken into account Jason-1 heritage, products will be split into several files : • One file close to current Jason-1 NRT-SSHA, limited to 1Hz sampling • One file close to current Jason-1 I/GDR, containing 1Hz and 40Hz values • One file close to current Jason-1 SGDR, containing 1Hz, 40Hz and waveforms values. This file will not be generated in NRT

AltiKa/SARAL Product files

SARAL Project summary • AltiKa/SARAL system PDR : end of 2007 • Payload instruments delivery • Altimeter&Radiometer instrument (antenna, electronic boxes) Flight Model: August 2008 • DORIS receiver (BDR) Flight Model : April 2008 • DORIS/AltiKa antenna flight model available since October 2006 • LRA design and development phase : June 2007 to December 2008 • ARGOS-3 equipments flight models delivery : July 2008 to December 2008 • SARAL ICU and Payload Module design & development phase : July 07 to December 08 • SSB spacecraft simulator delivery by ISRO to CNES : March 2008 • CNES delivery of PIM electrical simulator to ISRO : July 2008 • CNES Payload Module AIT : January 2009 – June 2009 • CNES Payload Module delivery to ISRO : July 2009 • Development of AltiKa mission specific upgrades on the CNES altimetry multi-missions Center • Specification phase : until mid-2007 • Development phase : from mid-2007 until end of 2008 • Validation, Technical & Operational Qualification: until end of 2009 • Satellite AIT and launch campaign : July 2009 – December 2009

AltiKa/SARAL project status