Technologies / Trade-off studies CNES studies

1. Technologies / Trade-off studies CNES studies Jean-Claude Souyris – Juliette Lambin Altimetry and Radar Department, DCT/SI/AR – DCT/SI/IM Inputs from : Th. Amiot, B. Cugny, B. Lazard, N. Mognard, E. Thouvenot WATER HM Barcelona Meeting, July 25, 2007

2. CONTEXT • Past programmatic context • WSOA on-board Jason-2/OSTM (PhD Vivien Enjolras) • WatER proposal • Several R&D studies initiated; some still in progress • Current context: renewed perspectives for Wide-Swath altimetry • CNES-NASA plans for cooperations : on-going at agencies level  Study Re-activation (R&D, research groups, engineering studies)  New PASO study (Plateau d’Architecture des Systèmes Orbitaux) • Dedicated study/funding (phase 0) 2007-2008 • Specific actions + synthesis of other activities • Next stage would be a phase A study (2nd half 2008, TBC?) WATER HM Barcelona Meeting, July 25, 2007

3. CNES staff involved as of today … • CNES-LEGOS science team : Nelly Mognard, Anny Cazenave, Yves Ménard • Programmatics : Eric Thouvenot (Océan), Hervé Jeanjean (Land surfaces) • Coordinator of PASO study : Bruno Lazard • Mission engineering studies : Juliette Lambin • Payload technical team : Bruno Cugny, Jean-Claude Souyris, Alain Mallet WATER HM Barcelona Meeting, July 25, 2007

4. Reminder : WATER MISSION on a Sun-Sync. orbit WATER HM Barcelona Meeting, July 25, 2007

5. Reminder : WATER main figures • Dawn-Dusk orbit, 824 km, 16 days, (5 days sub-cycle), 98° • PRIMA platform – Payload mass : 360 kg (max on PRIMA : 1100 kg) • Mean PL power : 800 W • 1000 Gbits mass memory • 4 x 155 Mbit/s X band telemetry • Antennas : 3.8 x 0.28 m / Mast length : 10 m • Thermal noise errors : ~ 0.5 m for 10 m pixel • Wet tropospheric delays : RMS variability between 3 cm and 5 cm over 100 km – WATER HM Barcelona Meeting, July 25, 2007

6. Payload studies : CNES view • KaRIN : Need to understand and decline high level performance @ Sub-System level  Preliminary requirements for : antenna, interferometric arm, RF unit, calibration sub-system, on-board processing… • Preliminary definition of some of these equipments taking into account CNES/TAS (Thalès Alenia Space) heritage with Poseidon, AltiKa and SIRAL/SRAL  Critical analysis of sub-system RFU (Radio-Frequency Unit) + PCU (Processing Unit): feasibility, cost evaluation, phase stability performances, power consumption for the different modes • A priori exclusion of antennas, IF arm and Ka band HPA WATER HM Barcelona Meeting, July 25, 2007

7. Payload (cntd) • Processing unit • TM rate  what is the need ? • CNES state of the art : existing solutions (ex : Pléiades TMHD 3 x 150 Mbits.s-1 ) • Trade-off between on-board processing and data rate • Echo digitization and processing for the various configurations : ocean, coastal, hydro mode, calibration … • Assessment of a SAR mode to improve along-track resolution  Coordination with JPL needed WATER HM Barcelona Meeting, July 25, 2007

8. Satellite accommodation • Will require the PL inputs in terms of mass, consumption, telemetry needs • Available figures : • Non sun-synchronous orbit (78° inclinaison) : • 1000 W satellite (including Payload + Bus consumption)  solar panel : 21 m² • 1600 W satellite (including Payload + Bus consumption)  solar panel : 33 m² • a reasonable solar panel size: 15 m² - 20m² 800 W-1000W allowed • Reminder : JASON-1 : 400 W; JASON-2 : < 500 W • Recommendation : Design a satellite between800-1000 Wwith 500-700 Wfor PL • Sun-synchronous orbit : • 1600 W satellite easily achievable • Reminder : WATER (sun-sync. orbit) : 1420 W (PL only) WATER HM Barcelona Meeting, July 25, 2007

9. Satellite accomodation (cntd) • Trade-off study (?) between : 1- Sun-synchronous mission + “JASON-like” satellite on a non sun synchronous orbit vs. 2 – Non Sun – synchronous mission with limited power consumption (800 W– 1000 W) WATER HM Barcelona Meeting, July 25, 2007

10. Platform attitude (roll) corrections • R&D study with CLS : • 2005-2006 : context of oceanography • Corrections of WSOA roll errors using ocean ascending/descending crossing points from an accurate description of roll signal error covariance • Possible improvement using the synergy with standard altimetry nadir missions and pre-correction of interferometric signals from oceanic variability • 2007 (starting soon) : roll corrections in the context of coastal / hydrology – two techniques will be assessed • Use of control points from geo-referenced DEM (SRTM type) • Propagation of errors estimated from ocean crossing points WATER HM Barcelona Meeting, July 25, 2007

11. End-to-end simulator: principle • Tool developped using CNES R&D funding. Objective is to compare different multi-mission configurations of altimetry satellites (e. g., Jason- ENVISAT, WaterHM – Jason, Jason-TOPEX, Jason-TP-ENVISAT-GFO….) • Inputs : • Mission characteristics (orbit, nadir/swath, resolution, measurement errors…) • Core : • Ocean model (Mod2G, tides) • Generation of synthetic observations • Assimilation code • Output : • Performances assessment (assimilation output versus initial « truth ») • Several diagnostic levels WATER HM Barcelona Meeting, July 25, 2007

12. End-to-end simulator: present extensions • Plan to extend this simulator to tidal analysis • Impact of Water-HM in SSO associated with non-SSO nadir mission • Impact on mission if a non-SSO is selected (at the cost of instrument performance?) • Work plan (2007-2008) • Several adaptations needed (tides modeling, diagnostic) in progress • Study zone : North Atlantic European coast • Case studies (inferred from PASO instrument study) WATER HM Barcelona Meeting, July 25, 2007

13. Nadir tropospheric corrections • Assessment of tropospheric corrections using HF bands of AMSU-B/MHS (89, 150, 176.31, 180.31, 182.31 GHz) and a neural network. Spatial resolution ~ 10 km : • Open ocean : AMSU-B corrections more noisy (icy clouds?) than standard TMR corrections (18, 24, 36 GHz). • Under low humidity conditions comparisons on real measurements between (AMSU-A and TMR), and between (AMSU-B and TMR) have shown standard deviation of ~ 2 cm (same type of error between TMR and radio-sounding)  AMSU-B can be a potential solution, even a small degradation is expected with respect to TMR. • Coastal zones (< 50 km) AMSU-B less affected than TMR. From simulated brightness temperatures (ECMWF model), standard deviation : 0.47 cm WATER HM Barcelona Meeting, July 25, 2007

14. Nadir tropospheric corrections (cntd) • Coastal zones (cntd) : tropospheric correction using extrapolated or corrected (Bennartz model) Path delay WATER HM Barcelona Meeting, July 25, 2007

15. Nadir tropospheric corrections (cntd) • Based on past studies for radiometric correction over ocean, need for extension to land tropospheric corrections : • If a radiometer is on-board : • Combination of TMR-like and HF channels ? • Standard TMR channels + Bennartz correction (including a surface emissivity model) ? • Trade-off between the different approaches • Otherwise: • A long-wavelength correction can be provided by models (ECMWF) • Need for a short wavelenght correction term (DEM?) • Off-Nadir tropospheric corrections (interferometric mode) : to be investigated WATER HM Barcelona Meeting, July 25, 2007

16. Ka band studies • R&D study starting Sept. 2007 (ONERA) • Bibliography on Ka band backscattering of water and continental surfaces • Set-up of a probative measurement campaign including a calibration step. • Experimental data take @ polarizations VV and VH • Extension of an existing propagation model @ Ka band under low precipitation conditions (0.1 mm/h) • 2008 : Data take representative of Alti-Ka mission WATER HM Barcelona Meeting, July 25, 2007

17. Ka band studies ONERA-BUSARD (moto-glider) WATER HM Barcelona Meeting, July 25, 2007

18. Ka band studies (cntd) Future configuration : phased Array antenna : assessment of WATERHM-like measurements ? Current configuration : vertical vision @ Ka band WATER HM Barcelona Meeting, July 25, 2007