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
Spacecraft Techniques and Technology

2. 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)
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

3. 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

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

5. 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

6. Payload studies : CNES view
KaRIN : Need to understand and decline high level 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. 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

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 between W with 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

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 :
: 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 ( )
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, , , 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. WATER HM Barcelona Meeting, July 25, 2007
Ka band studies
R&D study starting Sept (ONERA)
Bibliography on Ka band backscattering of water and continental surfaces
Set-up of a probative measurement campaign including a calibration step.
Experimental data polarizations VV and VH
Extension of an existing propagation 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. WATER HM Barcelona Meeting, July 25, 2007
Ka band studies
ONERA-BUSARD (moto-glider)
WATER HM Barcelona Meeting, July 25, 2007

18. 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