Surface%20Water%20and%20Ocean%20Topography%20Mission%20Risk%20Reduction%20Activities - PowerPoint PPT Presentation

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Surface Water and Ocean Topography Mission Risk Reduction Activities Ernesto Rodr guez Jet Propulsion Laboratory California Institute of Technology – PowerPoint PPT presentation

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Title: Surface%20Water%20and%20Ocean%20Topography%20Mission%20Risk%20Reduction%20Activities


1
Surface Water and Ocean Topography MissionRisk
Reduction Activities
  • Ernesto Rodríguez
  • Jet Propulsion Laboratory
  • California Institute of Technology

2
Risk Reduction StudySelection Process
  • Mission Definition Studies required prior to
    mission start!
  • Define mission science requirements
  • Assess the feasibility of meeting the measurement
    requirements ( iterate)
  • Define mission implementation requirements
    (feasibility cost iterate)
  • Retire phenomelogy risks (Wet tropo, river
    backscatter/resolution, EM bias, iterate)
  • Mission definition plan iterated during November
    and December with SWG
  • Technology Risk Studies required to retire major
    mission technology risks prior to mission start
  • On NASA side Instrument Incubator Program (IIP)
    proposal
  • Programmatic goals
  • Coordinated progress between CNES phase zero
    studies and NASA studies
  • Mission Concept Review in FY 2009
  • Detailed discussions on the partnering
    responsibilities, schedule and milestones are
    ongoing and will be clarified in this meeting and
    a subsequent meeting (Monday) in Toulouse

3
Water HM Year 1 Objectives
  • The SWOT design must be tuned to meet the science
    requirements from both communities in the most
    efficient fashion.
  • This requires formalizing both the science
    requirements as well as the mission and
    instrument design, so as to deliver accurate
    performance, risk and cost assessments.
  • The proposed FY08 overall objectives are
  • Finalize science goals and derive level 1
    requirements
  • Formalize a mission and system design and assess
    its end-to-end performance.
  • Identify all instrument and mission risk areas
    and perform cost assessment.
  • These objectives are implemented as six separate
    tasks, described in the following viewgraphs.

4
Task 1 Oceanography science studies
  • Objective the Science Working Group will
    identify the mission Level 1 ocean science
    requirements and rationale with detailed
    science-cost trade-offs.
  • Rationale The science requirements constitutes
    the baseline that enables the mission definition
    team to start developing a mission and instrument
    design.
  • Approach
  • Definition of the science scope and significance
    for sub-mesoscale processes and translation into
    measurement requirements (April 2008 workshop)
  • Review and development of improved coastal and
    internal tide models.
  • Review of state-of-the-art mesoscale atmospheric
    water vapor modes and development of improved
    algorithms for conventional radiometer
    water-vapor retrieval in coastal areas.
  • Develop science questions in mesoscale air-sea
    interaction processes.
  • Deliverables
  • SWG report (10/2008).

5
Task 2 Hydrology science studies
  • Objective the Science Working Group will
    identify the mission Level 1 hydrology science
    requirements and rationale with detailed
    science-cost trade-offs.
  • Rationale The science requirements constitutes
    the baseline that enables the mission definition
    team to start developing a mission and instrument
    design.
  • Approach
  • Definition of the spatial and temporal sampling,
    spatial resolution, and height accuracies
    requirements for understanding water storage
    changes.
  • Studies coordinated with Virtual Mission studies
    funded by NASA terrestrial hydrology program
  • Studies also coordinated with ongoing studies at
    LEGOS and Bristol
  • Deliverables
  • SWG report (10/2008).

6
Key Outcome from Science Studies
  • Science definition document (Level-1
    requirements)
  • Instrument team (on both sides) need this by 2007
  • Although this goal may be a bit too aggressive
  • A preliminary working version would be nice, of
    course
  • Some important issues
  • Full coverage needed (no gaps, land or ocean)?
  • Temporal sampling requirements?
  • Required small and long wavelength accuracy?
  • Land Coastal mask?
  • Data product definition?
  • Data product latency?

7
Task 3 Mission Orbital Design Definition
Example Water HM sampling (9.95 days)
  • Objective To finalize an orbit selection that
    balances and satisfies the hydrology and
    oceanographic requirements and constraints
  • Rationale Finalizing the orbit selection is
    imperative as a key driver for many instrument
    and mission design decisions
  • Approach Due to tidal aliasing, a
    sun-synchronous orbit is not feasible. Candidate
    orbits with inclination gt 75o and altitudes
    ranging from 800-1000km are proposed that are
    acceptable in terms of sampling and coverage
    goals.
  • Down-select orbit based on mission (i.e. launch
    vehicle candidacy/cost), instrument (i.e. power)
    and scattering predictions (i.e. achievable swath
    based on geometry)
  • Deliverables
  • Orbit definition document (5/2008).

140 km
8
Key Outcome
  • Define orbit altitude, inclination, and subcycles
  • Needed to define calibration accuracy
  • Needed for instrument power
  • Needed for sizing antenna
  • Needed to define launch vehicle
  • Needed to define ground stations required

9
Task 4 Instrument Error Budget and Calibration
  • Objective Develop an integrated measurement
    error budget and calibration simulation tools
    capable of predicting mission performance for
    design trade-studies.
  • Rationale To optimize instrument performance by
    characterizing noise errors and developing
    necessary calibration schemes.
  • Approach Three primary subtasks will be
    developed
  • An integrated measurement error budget for the
    system that accounts for random and systematic
    instrument noise errors, as well as
    (uncompensated) wet-tropospheric delays and the
    impact of vegetation.
  • To develop and validate suitable calibration
    schemes (cross-over and DEM-based) using
    realistic errors sources and tailored to a) open
    ocean, b) coastal regions and c) large inland
    water bodies, and rivers, wetland, and small
    lakes.
  • Assess the impact of the nadir altimeter and
    multi-channel radiometer.
  • Deliverables
  • Instrument error budget (7/2008).
  • Calibration techniques for error mitigation
    (8/2008)
  • Nadir altimeter and radiometer system
    requirements document (8/2008)
  • Error budget for floodplain topography (9/2008).

Path delay (PD) error from 3-12 km as a function
of PD and cloud liquid water (CLW) standard
deviation
92, 130, 166 GHz
10
Ocean Cross-Over Calibration Concept
  • Roll errors are the dominant error source for
    WSOA and must be removed by calibration. Residual
    range and phase errors are also removed.
  • Assume the ocean does not change significantly
    between crossover visits (lt5 days)
  • For each cross-over, estimate the baseline roll
    and roll rate for each of the passes using
    altimeter-interferometer and interferometer-interf
    erometer cross-over differences, which define an
    over-constrained linear system.
  • Interpolate along-track baseline parameters
    between calibration regions by using smooth
    interpolating function (e.g, cubic spline.)

11
WSOA Distribution of Time Separation Between
Calibration Regions
The revisit statistics will change for SWOT due
to orbit changes
12
WSOA Sea Surface Height Performance
Input roll errors based on Alcatel 99 study 2
dominant components with 50 sec/97cm and 2 sec/2
cm periods/amplitudes - worst case assumption
since both error sources are inside the
1sec-80sec passband.
Pixel Size 14 km
Height error includes both random and residual
systematic errors
13
Height Error Performance for 14 km Resolution
LANL Model Variability
  • Error estimated based on T/P cycles 22-39
  • No smoothing to height data has been applied

Simulation Normalized Error
Simulation RSS Error
14
WSOA Velocity Estimation Error
LANL Model Geostrophic Velocity
Estimation window 45km
WSOA Simulated Geostrophic Velocity
15
V Component Velocity Error
Error estimated based on T/P cycles 22-39
16
Assessment of Wet-Tropo Errors
  • Use regional models to generate realistic
    wet-tropo signals (coast, inland rivers, large
    bodies)
  • Simulate instrument raw heights
  • Assess error magnitude and spatial scale
  • Does error need to be corrected?
  • Can error be corrected by large scale NWP wet
    tropo?
  • What is the impact of a radiometer?
  • How well does land calibration work?

17
Hydrology Issues
  • How well does land calibration work?
  • What is to be done with rivers above SRTM
    coverage?
  • Can high latitude frequent revisits be used so
    that DEM calibration is not required?
  • Can river bed/flood-plain topography be retrieved
    with significant accuracy?
  • Is this a mission data product?

18
Task 5 Mission and Instrument Definition Study
  • Objective To formalize an instrument and mission
    design that meets the science Level 1
    requirements
  • Rationale To mature the mission/instrument
    design to support a detailed mass/power/cost
    assessment in Year 2.
  • Approach
  • Definition of key instrument parameters.
  • Define the instrument to block diagram level, to
    identify its mechanical configuration, derive
    data rate budgets, and to identify key critical
    technology drivers.
  • Identify key spacecraft requirements and
    implementation solutions that meet power
    generation (for continuous science data
    collection in the selected orbit), data handling
    (examining on-board compression, Solid-State
    Recorders, downlink subsystems, and ground
    stations requirements), and attitude control
    system requirements (accounting for mast, antenna
    and solar panel dynamics error budgets).
  • Deliverables
  • Mission definition document (8/2008).
  • Instrument definition document (10/2008).

19
Key Issues
  • What are the measurement components?
  • Jason type altimeter AMR or AltiKA with
    integrated radiometers
  • What are the power requirements on the
    spacecraft?
  • What are the attitude roll requirements of the
    spacecraft? Which spacecraft meet these
    requirements?
  • What data rate is required?
  • How can we download it?
  • How can we process it?
  • Are there key technologies that need to be
    developed prior to mission start?

20
Task 6 Field Observations of Fresh Water Bodies
  • Objective Expand Ka-band field observations of
    fresh water bodies to a greater range of
    environmental conditions.
  • Rationale Initial observations indicate
    fundamental limits to the spatial resolution, and
    possibly swath loss at higher incidence angles
    (more pronounced at higher orbits). More
    comprehensive observations and analysis will help
    assess the extent of potential data compromise.
  • Approach Using the same radar system as the
    previous campaign we will redeploy for a longer
    duration to capture a greater range of
    conditions.
  • Observations will be coupled with wind and
    surface conditions to better define limiting
    cases
  • Predict mission impact or constraints
  • Deliverables
  • Scientific journal paper reporting observations
    and analysis (9/2008).
  • Question what about the EM bias for the ocean?

21
SWOT Mission Definition Year 2 Objectives
  • The overall objective for Year 2 is to ensure a
    FY10 start of Phase-A studies.
  • To this end, we proposed to perform the following
    tasks (to be refined after year 1 studies)
  • Provide a detailed mass and power breakdown with
    costing for the possible mission scenarios.
  • Refine bus and launch vehicle accommodation
    requirements.
  • Develop the suite of documents required for the
    Mission and System Readiness reviews.
  • Design the ground data system and mature key
    algorithms for the data processing system.
  • Retiring the critical risk items identified
    during the Year 1 studies.
  • Refine the science questions initiated during
    Year 1.
  • Define the science data products at levels 2 and
    3.

22
Technology Risk ReductionNASA IIP
  • The latest AO release of the NASA IIP was
    targeted for technology risk reduction of NRC
    decadal review missions
  • JPL submitted a SWOT IIP proposal
  • Lee Fu PI (Rodríguez, Alsdorf, Esteban, Brown,
    Hodges others co-Is)
  • Proposals expected to be adjudicated in Spring
    (or early summer?)

23
Technology Risk ReductionNASA IIP
  • Technologies addressed
  • On-board processor
  • Needs to do onboard range compression, SAR
    processing, interferometry, averaging
    (calibration?)
  • PRF is 10 faster than WSOA!
  • Ka-band antenna
  • Ka-band, long (4m) and skinny (15cm). What is
    the right architecture? Deployment? Multipath?
  • High-frequency radiometer
  • If one is needed, does it cover the swath? Nadir?
    How to implement it within current architectures?
  • Proposal details fall under ITAR restrictions for
    the moment
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