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 Spacecraft Techniques and Technology

WATER HM Barcelona Meeting, July 25, 2007 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 Spacecraft Techniques and Technology 1

WATER HM Barcelona Meeting, July 25, 2007 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 Spacecraft Techniques and Technology 1

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

WATER HM Barcelona Meeting, July 25, 2007 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

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

WATER HM Barcelona Meeting, July 25, 2007 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

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 between 800-1000 W with 500-700 W for 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

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

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

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

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

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

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

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

WATER HM Barcelona Meeting, July 25, 2007 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

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

WATER HM Barcelona Meeting, July 25, 2007 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