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SWOTJet Propulsion Laboratory California Institute of Technology
SWOT Ground System
IGARSS – August 2011
Helene Vadon (CNES, Toulouse) Phil Callahan (Jet Propulsion Lab, California Institute of
Technology)
http://swot.jpl.nasa.gov
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SWOTJet Propulsion Laboratory California Institute of Technology
SWOT Ground System Outline
• Introduction– SWOT mission– Mission phases – Ground segment overview
• KaRIN Data Acquisition and Products– Acquisition characteristics– KaRIN processing – Data Products– Sizing estimates
• Joint Ground System Development – Commonality levels and approach for the processing development
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SWOT Mission
• Mission – Extraction of water surface heights over ocean and continental water
bodies– The principal instrument is KaRIN, a Ka-band interferometric SAR
system – Other instruments are a nadir altimeter, radiometer, and precision
tracking systems (classical Jason Altimeter suite)
• Main scientific requirements– Oceanography: Global coverage (< 78°) of oceans, sea surface height
precision < 2 cm at approximately 1 km resolution LR mode
– Hydrology: Global inventory of rivers > 100 m (50 m) and lakes > (250 m)2, water surface height precision of the order of 10 cm (averaged over 1 km2), slope precision 1 cm/km (averaged over 10 km); average posting 50 m HR mode
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Mission Phases
• Launch and Early Orbit Operations (~ 3 days) – Launch planned for late 2019
• Checkout / Commissioning (~ 30 - 45 days)
• Fast repeat orbit at 3 (or 1) days for ~90 (or 30) days – For ocean sub-mesoscale
• Calibration / Validation (Cal/Val) (3 – 6 months, covering Fast Repeat and Science Operations)
• Transition to Science Orbit, Operations (~ 15 days) – Non-sun-synchronous, 22 day exact repeat, 970 km altitude, 78 deg
inclination
• Science Observations (Requirement = 3 years; starts ~4.5 months after launch)
• Disposal and Ground System Closeout (= 3 months) 2011/07/25 s3 psc
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SWOT Ground System Challenges
• High precision for both ocean (1-2 cm) and hydrology (~10 cm)
– Complete, accurate algorithms – Use of instrument and spacecraft calibration data – External corrections; Ancillary information
• Large Data Volume – both telemetry and data products – Raw data downlink for land data. Requires >~ 600 Mbps X-band
downlink – Data products posted at fine resolution: LR = 500 m, HR = 50 m (~100
giga-samples per cycle for LR+HR)
• Likely Near Real Time requirements – Ocean from Jason suite similar to Jason series – Hydrology (floods, reservoirs) from KaRIN
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Architecture Diagram
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CNES
CNES X-band Network(also has S-band Uplink)
Science Processing Archive & Distribution
CNES ElementsNASA ElementsJoint Elements
S/C Control Center (SCC) (Contractor)
CNES S-band Network
KaRIN Science Data
Data exchangeJPL
Science Data Processing
Science Data Center
To CNES: Ack. successful downlink Payload commands
Karin
Radiometer
Nadir AltimeterPayload module
X bandTM
S/C Bus
UPLINK: S/C & P/L Cmd. DOWNLINK: Jason Suite Sci Data (Nadir Alt, Rad, GPS) and All Eng Telem
TBD Additional X-band Sta
JPL Science Data Archiving
& Distribution
X-band Network Center
Payload Operations Center
JPL Payload
Operations Center
To JPL: X-band data, S-band Sci, s/c Telemetry, TBD[KaRIN Eng]
To JPL: Jason Suite L2. Cal/val. To CNES: KaRIN TBD[L1b]. POD. Cal/val.
Ancillary Data: Tropo model(s), Iono info, Tide
model(s), DEM, SSH
To JPL: X-band data, TBD[KaRIN Eng]
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Ground System Elements (1 of 2)
• Tracking Stations – CNES S-band stations: Downlink for Nadir Alt, Radiometer, DORIS,
GPS (“Jason Altimeter Suite”, JAS); Engineering. Uplink commanding
– X-band network (620 Mbps (nominal, min)): Downlink for high rate science (KaRIN), and associated Engineering data
• Front End Networks – Network from X-band Data Center(s) to JPL and CNES operation
centers. Minimum data rate to return all downlink within approximately 20 mins is >~ 300 Mbps (similar to downlink)
– Network from CNES to JPL for S-band science and engineering data
• Spacecraft Control Center (SCC, CNES/Contractor) – Real time monitoring of s/c and p/l via S-band housekeeping telemetry
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Ground System Elements (2 of 2)
• Payload Operations Centers (POC) – JPL: Near Real Time health monitoring of KaRIN, GPS, Radiometer.
Determine X-band data quality, need for replay.– CNES: Near Real Time health monitoring of Jason Altimeter Suite
• Science Processing Centers – JPL: Processing of KaRIN, POD – CNES: Jason Suite, POD
• Data Archiving and Distribution Centers – JPL: PODAAC – CNES: AVISO
• Project Data Distribution Networks – JPL-CNES link – Science Processing Centers to Archiving/Distribution Centers
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SWOTJet Propulsion Laboratory California Institute of Technology
SWOT Ground System Outline
• Introduction– SWOT mission– Mission phases – Ground segment overview
• KaRIN Data Acquisition and Products– Acquisition characteristics– KaRIN processing – Data Products– Sizing estimates
• Joint Ground System Development – Commonality levels and approach for the processing development
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KaRIN Data Acquisition
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Vsat
KaRIN altimetry Resolution << Swath : (2.5m x 10m to 70m) << ~100km Almost full coverage
2.5 m70m max
20 km120 km
50km
50km
6 -10 km
Vsat
Classical Nadir Altimetry Resolution = Swath ( ~ 10km) Inter-track at equator ~ 100km
A few km
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KaRIN Processing Steps
• SAR processing (range and azimuth compression)
• Interferometric processing (co-registration, computation of interferometric phase and coherence)
• Application of acquisition geometry: geolocation, precise orbit determination, correction of roll, baseline variations
• Propagation corrections: tropospheric, ionospheric delay
• Interferogram flattening/correction, land phase unwrapping
• Estimation of geophysical parameters: water surface detection (HR only), computation of water surface heights, slopes etc.
• Establish/refine floodplain DEM (annually (goal) or mission)
• High-level and multi-temporal processing is a Science Team activity
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Data Products (1 of 4)
• Level 0 ( ~ 1 TB/day) – Ocean KaRIN: partial interferograms (Raw to partial interferograms
processing onboard)– Hydro KaRIN: raw data– Nadir altimeter and Radiometer data: instrument raw data– GPSP and DORIS data: POD raw data
• Level 1: Nadir Alt, Radiometer, KaRIN ( ~ 10-12 TB/day) – L1a: Engineering unit conversion, calibration data separated for
additional processing – L1b: Final instrument level data with calibrations appended
• Ocean: 9-11 onboard interferograms (1km x 1 km), correlations, amplitudes with instrument calibrations and phase variations corrected combined
• Hydro (HR): KaRIN phase flattened Interferograms• Altimeter, radiometer compliant with Jason-2 Science Data record
processing (SGDR)
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High Level Data Products (2 of 4)
• L2A– Ocean KaRIN : As L1B + Geophysical corrections. Nadir data
merged for cross calibration. – Ocean Crossover Attitude Correction: Estimate attitude errors
from ocean crossovers for correcting both ocean and land data. – Intermediate Hydro: L1B + water mask detection; rain, snow,
ice/frozen detections
• L2B (standard distributed products)Remark: Every field will be associated with an uncertainty estimate– Ocean (LR, fixed swath grid, 500 m; ~ 3 G-samples/day):
• Sea surface (SS) heights in latitude/longitude grid• SS slope at each point of the grid • Sigma 0• Wind speed• Ocean Sea Wave Height on same grid (goal)
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High Level Data Products (3 of 4)
• L2B (standard distributed products) (continued) – Hydrology (HR, regions, network, 50 m; TBD[80] GB/day):
• Geo-localized water mask (lakes > (250 m)^2, rivers >100 (50) m)• Estimated water elevations (same sampling as mask) -> Triangular
interpolated network (+ uncertainties)• Topographic map of the flood plain surrounding the water surface
and channel cross sections (requirement to be produced by the end of the mission; goal - annually)
– Ocean Nadir: Similar to current Jason-2 SGDR
• NRT (goal)– Ocean: as Level 2 products but with lower accuracy (quick-look orbit and
calibration using past cross-overs)– Hydro: Level 1 products (SLC + interferogram), no calibration data, use of
ancillary DEM for phase flattening– Nadir products: OGDR/ IGDR products (see Jason-2 OSS)
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High Level Data Products (4 of 4)
• POD – determined from GPS and DORIS
• Ancillary Data – updated daily – Atmospheric models: Dry Tropo (surface pressure), Wet Tropo (water
vapor) – Input to ionospheric model
• Geophysical Models – updated infrequently – Mean Sea Surface, Geoid – DEM, Water mask (a priori, then self derived) – Elastic Ocean Tides, Earth Tides, “Pole Tide”
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Sizing Considerations
• Global coverage, continuous acquisition• Acquisition hypothesis
– Sea 70%, Land 30% => In the average orbit, KaRIN will acquire 67 GB of data to be transmitted to
ground=> ~1 TB /day (~ 99% HR data)
• Archive Plan – Nominal mission duration: 3 years– Long term archive of (main contributors in terms of volume) Raw HR,
SLC (L1A), Interferograms + masks (L2A), Geo-localized hydro products (L2B) => ~10 000TBytes
• Comparison to other missions – CNES: more than 5 times Pleiades satellite archive (dual civilian/defense
optical imagery, to be launched soon)– NASA: similar to proposed DESDynI (Earth deformation and sea ice from
L-band Radar repeat pass interferometer) 2011/07/25 s3 psc
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SWOTJet Propulsion Laboratory California Institute of Technology
SWOT Ground System Outline
• Introduction– SWOT mission– Mission phases – Ground segment overview
• KaRIN Data Acquisition and Products– Acquisition characteristics– KaRIN processing – Data Products– Sizing estimates
• Joint Ground System Development – Commonality levels and approach for the processing development
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General Levels of Commonality
• Commonality between two processing systems may be achieved at different levels
– Commonality of the full production system (clone, e.g. Jason)
• Prevents existing systems reuse. Not necessary for SWOT development
– Commonality of the algorithms, software, and products
• Products are guaranteed 100% similar. May be the right level.
– Commonality of specification and reference data
• Independent developments. Risky because reference data does not cover all cases so products will not be 100% similar.
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General Algorithm Development Approach
• Science processing algorithms will be developed primarily by supplier of each instrument
• Algorithm flow will be iterated within entire development team
• Data product definitions will be iterated with Science Team • Algorithm testbed will be set up and prototype processing
developed – Testbed will read and write specified products – Test data will be (or emulate) specified products
• After initial development cycle, algorithm specifications will be written for review by System Engineering team and selected subset of Science Team
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CNES Usual Development Approach
• Algorithms prototyping activities and operational chain development are relatively independent The scope of prototype development may be larger than scope of
operational system development But not true the other way: prototypes are needed to build the reference
data for the validation of the operational chain
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Algorithmic prototyping
Operational chain development
GS Infrastructure development
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JPL Usual Development Approach
• Testbed prototype will incorporate as much of the processing framework as possible
• Notes: • NRT processing will be based on standard algorithms but may not use the
processing framework • Existing POD processing will be implemented in project environment
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Algorithmic prototyping
Operational chain development
GS Infrastructure development
Processing framework from previous projects will be leveraged
Algorithm and framework developers will agree on interfaces and control mechanisms
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Commonality Approach for SWOT
• Complementary prototyping activities will be conducted by JPL and CNES
• The order and nature of the processing steps of the operational LR and HR processing chains will be discussed and agreed on by JPL/NASA and CNES
• The detailed work share is not yet defined, but the operational algorithms and related binary code will be common
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BACKUP
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SWOT 40 month Mission Timeline
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Mission PhaseLaunch(02 Dec 2019)
2020 2021 2022 2019
EOM (Mar 2023)
Checkout / Commissioning (up to L + ~65 days)
LEOP ~3 days: nominal s/c state
Calibration/ Validation Period
OrbitInjection
ScienceDisposal
Calendar Years
22-day repeat, 78 deg, 970 km (non-sun-sync)
2023
Decommissioning( ~ 30 days)
Cal/Val
Eclipse Season (illustration only)
Fast Repeat
Science Observation (36 months)
TBD[3, 1 day; near 22 day]Science Processing Closeout
Fast sampling orbit acq 4 weeks
In-Flight Assessment Meeting
In-Flight Assessment Meeting
Operational Phase
Initial Phase
First Verification Workshop
~ 2-4 weeks Nominal Orbit Acquisition
Final Verification workshop (Sci Team meeting at L + 12 months
Backup or here ?
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Science Operations (1 of 1)
• Science data collection phase starts ~ 4.5 months after launch. Collect data for 3 full years in observational orbit
• Full validation period: 6 months of data in science orbit + 2 months processing, internal review
– Science Team meeting to assess initial data products ~ 12 months after launch – Processing update based on Science Team assessment implemented ~ 2 months after
meeting
• Ready to reprocess all data with updated system ~ 16 months after launch. • Science Requirements on Reprocessing (assume “caught up” at 24
months) puts requirements on total Processing Center throughput (Suggest project aggregate > 5x). Budget/scenario:
– Cal/val data (~3 months) – as science phase starts – Initial science phase data (~12 months +3 months cal/val) – within TBD [< 3]
months. Result: at ~20 months after launch version 2 of all usable data available. Support Science Team meeting at ~24 months to validate data
– End of nominal mission: Reprocess all data a second time with SDS update done from ~ 30 – 36 months after launch; takes 6 – 8 months (runs until 3 months after end of mission [assumes no extended mission])
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