national aeronautics and space administration scatterometer algorithm simon yueh, adam freedman and...

National Aeronautics and Space Administration

Scatterometer Algorithm

Simon Yueh, Adam Freedman and Greg Neumann

Jet Propulsion Laboratory

Aquarius Science Algorithm Workshop

20-21 March 2007, GSFC

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20-21 July, 2006Aquarius Science Pre-CDR<scatterometer> <Yueh>

Outline

• Algorithm Overview (Day 1)– Requirements– ATBD– Algorithm flow overview– Development approach

• Simulator Status and Simulation (Day 1)• Remaining Tasks and Plans (Day 2)

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Key Scatterometer Data Processing Requirements

• Locate each Sigma0 on Earth.

• Convert the L1A Aquarius data from counts to calibrated normalized radar cross-sections (Sigma0)

• Generate an error estimate (Kpc) for Sigma0.

• Incorporate quality control flags (RFI, land fraction, etc)

• Generate Tb corrections for surface roughness effects (L2)

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Level 1 ATBD (Calibration Loop Data)

Define:

lbcL Loss through the Loop-back attenuator.

calL Loss through the variable attenuator during a loop-back calibration pulse.

opL Loss through the variable attenuator during measurement pulses.

calP The measured value of a loop-back pulse.

sP The signal power in the received radar echo

t rbp pB Bias terms to compensate for accumulated (but constant) measurement error

Then the measured power during a loop-back calibration pulse will be:

callbc

oprtcal LL

LGPP

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Level 1 ATBD (Calibration Equation) – Current Form

Define the following terms:

int 4r t

area

g g hdAX

R

22

34

pk

t r

cal lbc cal bp

calop T R bp p

P L L GX

L L L B

nes PPP

Then: 0int

s

cal

PX X

This is an expression for 0 in terms of parameters either measured by Aquarius or derivable from geometry and pre-launch test measurements.

• Ps= signa+noise data, Pn=noise only data and Pcal= cal-loop data.

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ATBD Forward Polarimetric Radar Equation Mueller Matrix and Stokes Vector Formulation

2 2 * *

2 2 * *

* * * * * *

* * * * * *

Re Im

Re Im

2 Re 2 Re Re Im

2 Im 2 Im Im Re

vv vh vh vv vh vv

hv hh hh hv hh hvg

vv hv vh hh vv hh vh hv vv hh vh hv

vv hv vh hh vv hh vh hv vv hh vh hv

G G G G G G

G G G G G GM

G G G G G G G G G G G G

G G G G G G G G G G G G

2 2

2 2

cos sin cos sin 0

sin cos cos sin 0

2 cos sin 2 cos sin cos 2 0

0 0 0 1

prM

2 2

2 2

* *

* *

2

3 4

2 Re 2Re

2 Im 2Im

(4 )

v v

h hr

v h v h

v h v hreceive transmit

gr pr s pt gtr

area

E E

E EM

E E E E

E E E E

hM M M M M dAM

R

20

3 4(4 )r t

r

area

hG G dAP

R

Scalar Radar Equation

Polarimetric Radar Equation

Re Im

Re Im

2 Re 2 Re Re Im

2 Im 2 Im Im Re

s

vvvv vhvh vhvv vhvv

hvhv hhhh hhhv hhhv

vvhv vhhh vvhh vhhv vvhh vhhv

vvhv vhhh vvhh vhhv vvhh vhhv

M

Mueller matrix for polarization rollMueller matrix for antenna gain

Mueller matrix for ocean scattering

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Algorithm Overview

• Level 1A-1B processing:– Interpolate ephemeris and attitude data

– Calculate geometric quantities. Cell locations Incidence angles and cell azimuth angles Polarization rotation angles

– Calculate radiometric quantities X_int (antenna pattern and geometry) X_cal (electronics gain and loss) P_s (signal-only power estimate) Sigma0 (Normalized radar cross section) Sigma0 uncertainty (Kpc)

– Pass data to level 2 processing

• Level 2 processing:– Average Sigma0 data over for matchup with each radiometer

data packet

– Derive roughness corrections from the collocated Sigma0

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Inputs to L1A-1B Processing

• Instrument telemetry– Science

– Engineering (temperature, current and voltage)

• Spacecraft ephemeris data– MJ2K or ECF or lat/lon/altitude

• Spacecraft attitude data– Quaternion or pitch, roll, and yaw

– Need to know the reference coordinate of spacecraft

– Need to know the sequence of rotations for either type of attitude data because we need to parameterize the pre-calculated Xint processing table as a function of pitch, roll and yaw.

– Need sample attitude data

• Pre-launch calibration data– Insertion losses versus temperature

– Thermistor DN-T conversion data

– Antenna peak gain and pattern

• Land and sea ice maps - Format and sample data

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Level 1 Output Parameters for Each Block

Items Per

block Parameter Comment

1 Time Time at the start of the block 3 Spacecraft location ( , ,x y z ) Position at the start of the block 3 Spacecraft velocity( , ,x y z ) Velocity at the start of the block 1 Spacecraft Roll At the start of the block 1 Spacecraft Yaw At the start of the block 1 Spacecraft Pitch At the start of the block 3 Doppler frequency shift At the start of the block* 3 Antenna azimuth relative to north At the start of the block* 3 Polarization roll angle At the start of the block* 3 Incidence Angle At the start of the block*

TBD Housekeeping At the start of the block* 3*4 The latitude of 4 points at the edge of the beam. Combination for the block*. 3*4 The longitude of 4 points at the edge of the beam. Combination for the block.*

8*3*4 Quality flag For each measurement** 8*3*4 0 For each measurement**

8*3*4 pcK For each measurement**

8*3*4 SNR For each measurement** 8*3*2 Noise Only For each measurement** 8*3*4 Latitude of the center of the echo return. For each measurement** 8*3*4 Longitude of the center of the echo return. For each measurement**

* Beam Number indicated by position in the file. ** Polarization and beam number indicated by position in the file.

• One block includes data from 1.44 sec window.• About 12-15MB for each orbit of L1B data file

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Development Approach

• Develop ATBD and prototype codes

• Develop scatterometer algorithm simulator – Algorithm simulator will include processing codes (inversion) and codes

for forward simulation

• Develop algorithm specifications document

• Test algorithms and prototype codes using the simulator

L1 and L2 processing codes

Scatterometer algorithm simulator (Forward and inversion)

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Issues

• Need to finalize the definition of ephemeris data– ECF x, y, and z will be more convenient for us

– MJ2K x, y, and z are ok for us, but require more codes for conversion

• Need to finalize the definition of s/c attitude and local coordiante system– Need confirmation from CONAE on the definition of pitch, roll, and yaw

and sequence of rotations

– If Quaternion is to be used, still need to know the sequence of rotations because we need to parameterize the Xint table as a function of attitude

– Need sample attitude data

• Who is going to provide the sea ice map? What will be the format?– Need sample ice map or ice edge data

• Need to finalize and document the land map

• Others


Aquarius Scatterometer Simulation and Data Inversion Software

Design and StatusAdam Freedman

Simon Yueh

Greg Neumann

March 21-22, 2007

Aquarius Data Processing System Algorithm Implementation Workshop

GSFC

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Topics

• Scatterometer Forward Simulator– Algorithms

– Block Diagram

– Results

– Present status and future plans

• Scatterometer Inversion L1A-L1B Testing Platform– Algorithms

– Block Diagram

– Results

– Present status and future plans

• Level 1A Processing– Results and status

• Pre-Launch Calibration– Requirements overview

– Testing overview

– Scatterometer block diagrams

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Simulator Algorithms

• Simulation broken up into– Xcal_sim

Instrument transmit chain effects Instrument receive chain effects

– Xint Integration of sigma-0 backscatter

over main beam (Sint) Integration of beam pattern

weighted by area and range (Xint)

– Pcal Loopback power computation

– Pnoise

Range gate and filtering effects.hTotal transmit loss (outsideloop-back)

LT

Slant rangeRLoss through attenuator forloop-back.

Llbc

Antenna patterngLoss through attenuator forecho

Lop

Fixed biasBbptprLoss through loop-backLcal

Peak antenna gainGbpLoop-back powerPcal

Total receive loss (outside loop-back)

LREcho power (minus noise-only)Ps

Pecho

Psignal

Pnoise

Pcnstnt

Psignal

P

t

Lt ,bp

0g2h

tdA

2 2R4

area

bp

Gbp2 2

2

Gr

Bbptr

Lr ,bp

Pcal

P

tG

r

LLB

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Simulator Block Diagram

Read antenna gain, output arrays of two-way relative and max gain

Read antenna gain, output arrays of two-way relative and max gain

Read orbit file, one record at a timeCompute x, v, at t in ECF

Read orbit file, one record at a timeCompute x, v, at t in ECF

Compute S/P nadir locationCompute S/P local frame orientation

Compute S/P nadir locationCompute S/P local frame orientation

Instrument SimulatorCompute Xcal_sim, LB power,

noise power, DC offset

Instrument SimulatorCompute Xcal_sim, LB power,

noise power, DC offset

Integration Over Beam PatternCompute Xint, beam-weighted sig-0,

Mean sig-0 over 3-dB footprint

Integration Over Beam PatternCompute Xint, beam-weighted sig-0,

Mean sig-0 over 3-dB footprint

Compute footprint location,Incidence, azimuth angles

Compute footprint location,Incidence, azimuth angles Write to output filesWrite to output files

Antenna beam pattern filesComplex Eco and Ecr,

(theta,phi,beam#,H/V-pol)

Antenna beam pattern filesComplex Eco and Ecr,

(theta,phi,beam#,H/V-pol)

Time, Echo, Noise-only, LB data per beam(power values; DN conversion not yet implemented)

Input simulator command optionsInput simulator command options

Orbit ephemeris fileS/P XYZ position vs time,

either ECF or MJ2K

Orbit ephemeris fileS/P XYZ position vs time,

either ECF or MJ2K

S/P Attitude fileS/P RPY vs time, or equivalent

S/P Attitude fileS/P RPY vs time, or equivalent

Scatterometer HW data fileTx power, gains, losses, etc.Scatterometer HW data file

Tx power, gains, losses, etc.

Compute simulated measurementHV,nV,VV,VH,nH,HH,LB,DC vs t

Compute simulated measurementHV,nV,VV,VH,nH,HH,LB,DC vs t

Next orbit position

Next beam

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Beam Integration Block Diagram

Initialize wind fieldInitialize wind field

Loop though beam pattern, for eachtheta (elevation) and phi (azimuth)Within range of thetas (±15°,±20°)

Loop though beam pattern, for eachtheta (elevation) and phi (azimuth)Within range of thetas (±15°,±20°)

Compute two-way gain matricesGh2,Gv2,Ghv,etc. for co- and cross-pol

Compute two-way gain matricesGh2,Gv2,Ghv,etc. for co- and cross-pol

Define corners of on-Earth grid square for integration. Compute area of grid

on spherical surface

Define corners of on-Earth grid square for integration. Compute area of grid

on spherical surface

Compute area and range-weightedGain (area*G2/range4)

Compute area and range-weightedGain (area*G2/range4)

Apply range gate factor if fullchirp not contained in Rx window

Apply range gate factor if fullchirp not contained in Rx window

Model function computation.Compute sig-0 at grid pt center

Adjust sig-0 for land flag

Model function computation.Compute sig-0 at grid pt center

Adjust sig-0 for land flag

NSCAT or equiv wind fieldU and V components

0.5 deg spacing or better

NSCAT or equiv wind fieldU and V components

0.5 deg spacing or better

Input viewing, geometry and beam pattern info for beam and epoch

Input viewing, geometry and beam pattern info for beam and epoch

Lookup ocean winds at grid pt. center

Lookup ocean winds at grid pt. center

Next theta, phi

Multiply weighted gain by sig-0Multiply weighted gain by sig-0

Sum sig-0 weighted gainSum weighted gain

Sum sig-0 in 3-dB regionSum area in 3-dB region

Sum sig-0 weighted gainSum weighted gain

Sum sig-0 in 3-dB regionSum area in 3-dB region

Exit and return integrated measurements

Exit and return integrated measurements

Completed integration

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Input Data Sets

• Antenna beam pattern files (JPL)– 3 beams, two polarizations, complex E fields, (theta,phi) currently– Ancillary info: boresight pointing of each beam in instrument coordinate system, and

polarization alignment in instrument C.S.

• Orbit ephemeris file (CONAE)– S/P position as function of time, either as XYZ position in ECF, or as XYZ in MJ2K– Currently use once per minute epochs; will ramp up to ~once per second.

• Attitude file (CONAE)– S/P attitude as function of time, in TBD format (no sample file yet)– Currently uses roll, pitch, yaw; values fixed over time.

• Scatterometer pre-launch calibration data (JPL)– Extensive set of gains, losses, mismatches, zero-state values and changes over

temp and time; probable tabular format

• Wind field (JPL or other)– Currently NSCAT winds at 0.5 deg spacing, zonal (U) and meridional (V)

components

• Land masks, ice masks, etc. TBD

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Beam Patterns

Beam 1 two-way gain patterns in dBElevation range ±15°

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Wind Field

NSCAT Wind Field11/20/96 00 UT0.5° resolutionU and V, m/sec

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Ocean Backscatter Over Footprint

Beam 1 Ocean Backscattersigma-0 in dBModel function (NSCAT winds)Land sig-0 set to -10 dBElevation range ±15°

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Ocean Backscatter Weighted by Beam Pattern

Beam 1 Ocean sigma-0 weightedby beam pattern, range loss,receive windowElevation range ±15°

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Measurements Over an Orbit

Simulated scatterometer measurements over about 3 orbits(HV barely visible above noise floor)

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Global Simulation

Simulated Global Coverageover 7 days, spacecraft position at 1 minute intervalsGround tracks for each beam

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Modeled Received Power Over Earth

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Present Status & Future Plans for Forward Simulation

• Simulator version 0 completed

• Simulator version 1 under development– Additional testing needed in antenna integration, orbit computation, etc.

– Modify form of Xint, Xcal, and other terms

– Implement polarimetric scattering matrix for generating all terms

– Add measurement noise, power-to-DN conversions

• Simulator version 2– Stand alone modules; improved efficiency and data flow

– Additional simulation capabilities (some pieces in version 1) Faraday rotation effects Effects of S/P attitude variations Temperature dependent HW variations and variable Tant effects; telemetry output products Updated ocean model function; accurate land and ice polarimetric backscatter Full timing sequence simulation @ ~10 ms

• Major modeling questions to address– How best to parameterize Xint for L1a-L1b processing, and how best to remove these

contaminating errors during processing Need to deal with altitude and pointing variations, land and ice masking, polarimetric misalignments,

Faraday rotation

– L2 (sigma-0 to Tb correction) methodology and design Sigma-0 to wind field algorithm Wind field to Tb algorithm

– Flag detection and response algorithms: rain, ice, RFI, extreme wind

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Scatterometer L1a-to-L1b Algorithms A

• Existing algorithm summarized in “Aquarius Ground System Radar Data Processing” (early draft version)

– Based on division of radar equation into Xint and Xcal– Formulation primarily for single polarization measurement; needs updating for

polarimetric measurements– Algorithm being re-examined and updated

0 Ps

X cal X int

22

34

pk

t r

cal lbc cal bp

calop T R bp p

P L L GX

L L L B

2

int 4area

g hdAX

R

Range gate and filtering effects.hTotal transmit loss (outsideloop-back)

LT

Slant rangeRLoss through attenuator forloop-back.

Llbc

Antenna patterngLoss through attenuator forecho

Lop

Fixed biasBbptprLoss through loop-backLcal

Peak antenna gainGbpLoop-back powerPcal

Total receive loss (outside loop-back)

LREcho power (minus noise-only)Ps

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Scatterometer L1a-to-L1b Algorithms B

• Module SB1: Have geometry routines – Tested and implemented

– Not yet stand-alone

– Attitude format uncertain; not fully implemented

• Module SB2: Not done (unimportant?)

• Module SB3: Have Xcal subroutine– Partially tested and implemented

– Evaluating alternative representations

• Module SB4: Kpc computation– Have placeholder routine

– Need to generate simulated data at higher time resolution with thermal/fading/speckle noise added.

• Module SB5: Have Xint subroutine– Not yet stand-alone, part of simulator

– Evaluating alternative representations

• Module SB6: Have sigma-0 inline algorithm– Currently testing

– Comparing to sigma-0 averaged over 3-dB beam width

• Modules SB7-SB10 not yet implemented

Module SB1: For each value of eP perform

geometric calculations to locate each measurement on the earth (with latitude and longitude).

Ephemeris Cubic Spline Coefficient file*

Level 1 Stage B Processing Flow

Module SB4: For each value of eP

estimate the best value for sP . Calculate

the SNR and pcK

Module SB6: Calculate 0 .

Module SB5: Look up

intX based on beam

number and orbit location.

Module SB3: For each value of eP

calculate the value of calX , using

temperature telemetry if necessary.

Module SB8: Set quality flags, land and ice flags, etc.

Module SB10: Write stage 2 output file(s).

Module SB7: Calculate the polarization roll angle.

Radar file

Temperature file*

PtGr file*

Noise only file*

Module SB2: Calculate Doppler Frequency Shift

Scatterometer Parameter file

Module SB9: Average 0 .

file*: This may be implemented as storage in RAM, if desired.

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Scatterometer Measurement Inversion Block Diagram

For each measurement epoch,And for each beam

For each measurement epoch,And for each beam

Compute Xcal (SB3)Compute Xcal (SB3)Time, temperature telemetry,Max reflector gains, LB power

Psig = Pecho - Pnoise - PdcSNR = Psig / Pnoise

Psig = Pecho - Pnoise - PdcSNR = Psig / Pnoise

Compute Kpc (SB4)Compute Kpc (SB4)

Compute Xint (SB5)Compute Xint (SB5)

Compute Sig-0Sig-0 = Psig - Xint - Xcal

Compute Sig-0Sig-0 = Psig - Xint - Xcal

Write to output fileWrite to output file

Read from measurements fileTime, echo power, LB power,

DC offset, telemetry

Read from measurements fileTime, echo power, LB power,

DC offset, telemetry

Xint value computed from simulator

Time, location, sigma-0,

quality flags

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Estimated Ocean Surface Backscatter

Over one orbit: Sigma-0 estimated from simulated measurements, vs. sigma-0 averaged over 3-dB footprint

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Estimated Sigma-0 and Error: Beam 1 VV

Simulated global measurementsover 7 days, spacecraft position at 1 minute intervals (400 km spacing).

Note stacking up of contours at land boundary (-10 dB land vs <-13 db ocean).Errors greatest at ocean/land boundary, as expected.Small positive bias to residuals.

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Estimated Sigma-0 and Error: Beam 2 HV


Note stacking up of contours at land boundary (-15 dB land vs <-40 db ocean).Errors greatest at ocean/land boundary, as expected.Errors much larger for HV than for HH or VV near land.

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Estimated Sigma-0 and Error: Beam 3 HH


Note stacking up of contours at land boundary (-10 dB land vs <-25 db ocean).Errors greatest at ocean/land boundary, as expected.Small positive bias to residuals.Beam 3 sigma-0 much smaller than beam 1, as expected.

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Present Status and Future Plans for L1A-L2 Processing

• Testing recovery of sigma-0.– Effects of beam patterns, wind speeds, polarization, land fraction, pointing errors, etc.

– Develop maximal polarimetric calibration using all measurements

• Exploring best methods to implement Xint computation in GS processing– Inline vs offline

• Need to verify format of incoming S/P ephemeris and attitude information, and conversions to implemented formats.

• Instrument module (Xcal) very simple at present– Need to update with latest HW loss measurements, loss vs. temp curves, reflection and mismatch

measurements, etc.

– Exploring alternative forms of Xcal implentation, in conjunction with Xint definition

• Will begin estimation and verification of Kpc after simulator generates appropriate data.

• DN to EU power and telemetry conversions from high-rate simulator data using coefficient lookup tables and other algorithms

• Working to modularize L1a-L1b processing, and allow it to function separately from simulator.

• Need to include data quality flag algorithms and formats (sea ice, land, instrument anomaly)

• Need to generate “total-power” measurement product

• Work on Faraday-rotation correction scheme for future simulation/testing

• Significant set of L1a-L1b and L2 processing questions to address

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Scatterometer L1a-to-L1b ProcessingTemporal Interpolation

• Module SA1 for interpolating ephemeris: exists, needs checking

• Reading of downlink data format and conversion to time, power (dBm), and voltage (mV): exists and tested

– Needed for SA2, SA3, etc.

• Reading, parsing, and converting telemetry from DN to EU: exists and tested

– Needed for SA4, etc.

• MATLAB implementation in use during scatterometer-ICDS IVT, and planned for use during Instrument I&T

Module SA1: Interpolate the Ephemeris using a cubic spline algorithm. Save the result for use in stage B processing.

Ephemeris: X,Y,Z positionX,Y,Z velocitySpacecraft AttitudeEvery TBD seconds.

Level 1 Stage A Processing Flow

Module SA2: Write Noise only data out to a separate file for use in stage B processing

Radar data:

Module SA3: Write loop-back calibration data out to a separate file for use in stage B processing. Include time, loop-back measurement, etc.

Module SA4: Convert temperature from data number to degree centigrade. Write temperature data out to a separate file for use in stage B processing. Include time and temperature(s).


Noise only file*

PtGr file*

Temperature file*

file*: This may be implemented as storage in RAM, if desired.

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Sample Data and Telemetry

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Sample DN-to-EU Telemetry Conversions

SSPA RF Deck temp deg C $POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SCG temp deg C $POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SBE LNA temp deg C $POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SBE Tx Chain temp deg C $POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SBE step attenuator temp deg C $POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SFE loopback attenuator temp deg C $POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SFE loopback switch temp deg C $POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SFE beam switch temp deg C $POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3

SFE Tx power monitor volts $*5/65536

SFE 15N voltage monitor volts $*5/256*(-5)

SBE PLM 1 tuning voltage (960) volts $*5/256

SBE PLM 2 tuning voltage (1256) volts $*5/256

SBE Tx Exciter Power Mon volts $*5/256

LVPS Converter Current volts $*5/256

SSPA output stage voltage volts $*5/256*10

SSPA intermediate stage voltage volts $*5/256*10

SSPA input stage voltage volts $*5/256*5

SFE +5V monitor volts $*5/256*2

SCG +5V monitor volts $*5/256*2

SBE +5V monitor volts $*5/256*2

SBE +12V monitor (non switched) volts $*5/256*4.8

CAL_RES1_RES 360

CAL_RES2_RES 460

CAL_RES3_RES 640

CAL_RES4_RES 550

GAIN_NORM ($CAL_RES3_RES - $CAL_RES1_RES) /($IE_ICDS_TLM_CAL_RES3 - $IE_ICDS_TLM_CAL_RES1)

GAIN_EXTENDED ($CAL_RES4_RES - $CAL_RES2_RES) /($IE_ICDS_TLM_CAL_RES4 - $IE_ICDS_TLM_CAL_RES2)

OFFSET_NORM $CAL_RES2_RES - ($IE_ICDS_TLM_CAL_RES2 * $GAIN_NORM)

OFFSET_EXTENDED $CAL_RES1_RES - ($IE_ICDS_TLM_CAL_RES1 * $GAIN_EXTENDED)

POLY0 -244

POLY1 0.4765

POLY2 1.39E-05

POLY3 1.88E-08


Pre-Launch Calibration Requirement

Adam Freedman

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Scat Pre-Launch Calibration Requirements A

3.3 Scatterometer Measurement Calibration

3.3.1 Antenna Subsystem Scatterometer CalibrationAll scatterometer calibration requirements apply at the scatterometer center frequency of 1.26 GHz.

3.3.1.1 Antenna Peak Gain Calibration: Zero-State Calibration: The antenna peak gain at the scatterometer frequency will be calculated to an absolute accuracy of 1 dB. The “Antenna Peak Gain” is defined to be the peak gain of the antenna referenced to the output of the OMT couplers. It includes antenna directivity, reflector loss, feed assembly loss, cabling losses, and the loss associated with the OMT coupler.

3.3.1.2 OMT Assembly Loss Calibration:Primary Calibration: The OMT Assembly (horn, isolator, OMT, cabling, coupler) Loss at the scatterometer frequency shall be determined as a function of temperature over the Performance Temperature Range of 0 to 30 degrees C for the OMT and -50 to 30 degrees C for the feed horn. The calibration shall be sufficiently accurate to ensure that the change in loss can be estimated to within 0.01 dB for any 1 degree C change in temperature over the Performance Temperature Range.

3.3.1.3 Antenna Pattern Data:Zero-State Calibration: Antenna pattern data shall be generated at the scatterometer frequency for each of the three beams. This antenna pattern data shall consist of the complex co-pol and cross-pol gains and cover 4 PI steriadians. Antenna pattern data shall be provided at a resolution of at least 0.5 degrees.

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Scat Pre-Launch Calibration Requirements B

3.3.2 Scatterometer Electronics Calibration

3.3.2.1 Loop-Back Path Calibration:Primary Calibration: The loss through the scatterometer loopback path within the SFE shall be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C. The loss of the adjustable attenuator within the SBE shall also be determined as a function of temperature for all values of the attenuator setting. The overall SBE and SFE loopback path calibration shall be sufficiently accurate to insure that changes in transmit power and receiver gain can be estimated to within 0.02 dB for any 4 degree C change in temperature over the Performance Temperature Range.

3.3.2.2 SFE Transmit Path Calibration:Primary Calibration: The loss through the SFE transmit path shall be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C. The calibration shall be sufficiently accurate to insure that changes in loss can be estimated to within 0.02 dB for any 4 degree C change in temperature over the Performance Temperature Range.

3.3.2.3 SFE Receive Path Calibration:Primary Calibration: The loss through the SFE receive path shall be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C. The calibration shall be sufficiently accurate to insure that changes in loss can be estimated to within 0.02 dB for any 4 degree C (TBC) change in temperature over the Performance Temperature Range.

3.3.2.4 SFE to Diplexer RF Cabling Loss:Primary Calibration: The loss through the RF cabling between the SFE and the Diplexer shall be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C. The calibration shall be sufficiently accurate to insure that changes in loss can be estimated to within 0.01 dB for any 2 degree C change in temperature over the Performance Temperature Range.

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Scat Pre-Launch Calibration Requirements C

3.3.2.5 Scatterometer TSFE Components:Primary Calibration: The loss through the scatterometer TSFE (temperature sensitive front-end) components (i.e., Diplexer and Diplexer-to-OMT coupler cabling) shall be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C. The calibration shall be sufficiently accurate to insure that changes in loss can be estimated to within 0.01 dB for any 1 degree C change in temperature over the Performance Temperature Range.

3.3.2.6 SSPA Transmit Power Monitor (TPM):Secondary Calibration: The SSPA transmit power monitor shall be calibrated to measure the transmit output power.

3.3.2.7 SSPA Transmit Power vs. Temperature:Secondary Calibration: The SSPA output power shall, as a goal, be determined as a function of temperature.

3.3.2.8 Scatterometer Receiver Gain:Secondary Calibration: The combined scatterometer receiver gain (SBE + ICDS) as referenced to the input of the SBE shall, as a goal, be determined as a function of temperature over the Performance Temperature Range of 0-30 degrees C.

3.3.2.9 Transmit Pulse Envelope:Primary Calibration: The scatterometer transmit pulse envelope, in terms of output power vs. time, shall be determined with respect to the SSPA RF gate signal as a function temperature.

3.3.2.10 Transmit Pulse Spectrum: Primary Calibration: The transmit pulse spectrum at the output of the SSPA shall be determined with respect to the carrier frequency as a function of temperature.

3.3.2.11 SBE Filter Response:Primary Calibration: The net, combined filter response of the SBE (measured from the input of the SBE to the output of the SBE) shall be determined with respect to the carrier frequency as a function of temperature.

41 of 27


Scat Pre-Launch Cal Planned Testing

SA18: OMT/Feedhorn Loss and Stability AnalysisRequirements Addressed: Cal-3.2.1.5, Cal-3.2.1.7, Cal-3.2.1.11, Cal-3.2.1.16, Cal-3.3.1.2Analysis Responsibility: Antenna SubsystemAnalysis Description: Perform numerical modeling analysis of OMT/Feed assembly over temperature. Perform analysis to estimate the contribution of the feedhorn to the overall OMT/feed loss, and estimate the behavior of this component of loss as a function of temperature. Estimate the change in OMT cross-pol, OMT phase, and OMT/feed return loss over temperature.

T9: Radiometer Functional Test, Responsibility: Instrument I&T, Radiometer Subsystem, Instrument EngineeringRequirements Addressed: Cal-3.2.1.8, Cal-3.3.2.3Verify interfaces prior to integration with ICDS per EICD.As passive front end components are installed on the OMT, their S-parameters are measured for calibration, with a network analyzer and measure return loss of each feed/OMT from coupler input (on diplexer side).Use R3 (see R3 description at the bottom of this document) with a polarized screen to check that the polarizations are flowing correctly end to end. (R3 target is provided by GSFC). Repeat for each of the 3 feed/OMT radiometer chains.ST19: Scat Subsystem Calibration and Test, Responsibility: Scatterometer, Instrument EngineeringRequirements Addressed: 644, Cal-3.2.1.6, Cal-3.2.1.8, Cal-3.2.1.9, Cal-3.3.2.1 through 3.3.2.11Collect calibration data per Calibration Requirements section of this document. Perform FOL test with ICDS, measure SSPA power over tempMeasure scat noise figure, gain, loopback level, linearity, clock stability, max input level

ST 21: Antenna Subsystem Calibration and Test, Responsibility: Antenna, Instrument System EngineeringRequirements Addressed:, Cal-3.2.1.3, Cal-3.2.1.4, Cal-3.3.1.1, Cal-3.3.1.3Collect calibration data per Calibration Requirements section of this document. Measure beam and sidelobe pattern, measure reflected power from the reflector, insertion loss and its stability, phase between channels and its stability, isolation and its stability.

ST4: OMT Performance Test, Responsible Subsystem: AntennaRequirements Addressed: , Cal-3.2.1.6, Cal-3.2.1.7, Cal-3.2.1.9, Cal-3.2.1.11, Cal-3.2.1.12, Cal-3.2.1.16, Cal-3.3.1.2.Measure loss, phase, and return loss through OMT assembly (without horn) as a function of temperature. Test data to be combined with analysis A3.

42 of 27


Calibration Approach (CVVD)

6.2 Scatterometer Measurement Error To validate that the scatterometer will achieve its science performance objectives, it is first necessary to determine how radiometrically stable the as-built scatterometer will be. This is done in a fashion similar to the radiometer where the measured performance of all the component elements are put into a model-based formulation. The loss vs. temperature curves are determined at the subsystem level (per the calibration requirements in Section 3, and the subsystem tests/analyses in Sections 4 and 5 of this document). These components and this modeling approach are illustrated in Figure 6-3. The loss vs. temperature curves are combined with the thermal model predictions for the physical temperature variations, and a net radiometric estimate of the calibration stability is produced. This model-based process is in turn validated by test at the system level in T/V using the FOL (fiber optic link) technique. Once the total expected radiometric stability of the scatterometer has been estimated, it is combined with the expected radiometric precision (or “Kp”) estimate of the as-built instrument. This combined number is the total relative error, which is then combined with the model function (relating backscatter error to roughness correction error) in order to compare with the allocation of 0.12 K.

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Calibration Approach

44 of 27


Transmit Path

ICDS ref. clk& ADC clk:16 MHz

Scat ChirpGen.(SCG)

STALO

PLMx120

SSPA_RFgate

960 MHz

1256 MHz

To ICDS

SSPA

SSPADC_gate

SSPAPwr supply

Scat Front End (SFE)

8 MHzFc=300 MHzBW=5 MHz

PLMX157

Scat Back End (SBE)

16 MHzx2

1H

TP

TP

PwrMon.

LB_gate

Beam_pol_Sel

Test load

Diplexer:LPF for ScatBPF for rad

couplerOMT/feed1

To radiometer

H

Limiter+LNA

Stepatten

NoiseDiode

TP

Fc=1260 MHzBW=5 MHz

Diplexer

V(removableTermination)

8 MHz digital(from ICDS)

BPF

To limit RFI

2H

3H

1V

2V

3V

IRM

Fc=1260 MHzBW=5 MHz

Fc=4 MHzBW=5 MHz

960 MHz

TP

TP

LPF

Scatterometer Block Diagram Transmit Path ExampleLoop-back calibration path, ()

Receiver Gain Reference ( is measured from this point forward.)

Variable attenuator,( during transmit)

Transmit Power Reference ()

Loop-Back Calibration Path ()

Transmit Path H1 ()

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Receive Path

ICDS ref. clk& ADC clk:16 MHz

Scat ChirpGen.(SCG)

STALO

PLMx120

SSPA_RFgate

960 MHz

1256 MHz

To ICDS

SSPA

SSPADC_gate

SSPAPwr supply


8 MHzFc=300 MHzBW=5 MHz

PLMX157

Scat Back End (SBE)

16 MHzx2

1H

TP

TP

PwrMon.

LB_gate

Beam_pol_Sel

Test load

Diplexer:LPF for ScatBPF for rad

couplerOMT/feed1

To radiometer

H

Limiter+LNA

Stepatten

NoiseDiode

TP

Fc=1260 MHzBW=5 MHz

Diplexer

V(removableTermination)


BPF

To limit RFI

2H

3H

1V

2V

3V

IRM

Fc=1260 MHzBW=5 MHz

Fc=4 MHzBW=5 MHz

960 MHz

TP

TP

LPF

Scatterometer Block Diagram Receive Path Example

Receiver Gain Reference ( is measured from this point forward.)

Receive Path H1 ()

Variable attenuator,( during receive)

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Scat Chirp

Gen.

(SCG)

STALO

PLMx120

SSPA_RFgate

960 MHz

1256 MHz

To ICDS

SSPA

SSPA

DC_gate

SSPAPwr supply


8 MHz Fc=300 MHz

BW=5 MHz

PLMX157

Scat Back End (SBE)

16 MHzx2

ICDS ref. clk

& ADC clk:

16 MHz

1H

TP

TPPwrMon.

LB_gate

Beam_pol_Sel

Test

load

Diplexer:

LPF for Scat

BPF for rad

couplerOMT/feed1

To

radiometer

H

Limiter

+LNA

Step

atten

NoiseDiode

TP

Fc=1260 MHz

BW=5 MHz

DPLX

V

To

radiometer

(removableTermination)


BPF

To limit RFI

2H

3H

1V

2V

3V

IRM

Fc=1260 MHz

BW=5 MHz

Fc=4 MHz

BW=5 MHz

960 MHz

TP

TP

LPF

Scat Chirp

Gen.

(SCG)

STALO

PLMx120

SSPA_RFgate

960 MHz

1256 MHz

To ICDS

SSPA

SSPA

DC_gate

SSPAPwr supply


8 MHz Fc=300 MHz

BW=5 MHz

PLMX157

Scat Back End (SBE)

16 MHzx2

ICDS ref. clk

& ADC clk:

16 MHz

1H

TP

TPPwrMon.

LB_gate

Beam_pol_Sel

Test

load

Diplexer:

LPF for Scat

BPF for rad

couplerOMT/feed1

To

radiometer

H

Limiter

+LNA

Step

atten

NoiseDiode

TP

Fc=1260 MHz

BW=5 MHz

DPLX

V

To

radiometer

(removableTermination)


BPF

To limit RFI

2H

3H

1V

2V

3V

IRM

Fc=1260 MHz

BW=5 MHz

Fc=4 MHz

BW=5 MHz

960 MHz

TP

TP

LPF

Scatterometer Subsystem functional block diagram

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Scatterometer Timing Diagram

sec

Antenna AntennaAntenna

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12

Antenna Antenna Antenna Antenna calcal calcalCND

Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam 1_VNoise only

Beam 1Tx H

Rcv_protect

One Aquarius Radiometer sub-cycle, 120 ms

Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

One Aquarius Scatterometer Sequence, 180 ms

•Scatterometer sequence repeats every 180 msec and is fixed (if in single beam mode, just stay on that beam)

•Radiometer OMT noise diode is always fired during scat noise only interval•Radiometer is blanked during every receive protect pulse•Radiometer sequence repeats every 120 msec

Beam 2Tx_H

Beam 2Tx_V

Beam 2Tx_V

Beam 2_VNoise only

Beam 2Tx H

Rx_V Rx_V Rx_HRx_H

Beam 2_HNoise only

sec0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24

Beam 3Tx_H

Beam 3Tx_V

Beam 3Tx_V

Beam 3_VNoise only

Beam 3Tx H

Rx_V Rx_V Rx_HRx_H

Beam 3_HNoise only

Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam1_VNoise only

Beam 1Tx H

Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

Avg’d togetherAvg’d over 10 subcycles

Avg’d over 10 subcycles


Avg’d over 2 subcyclesAvg’d together

H H H H

H H H H

sec


0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12


Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam 1_VNoise only

Beam 1Tx H

Rcv_protect


Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

One Aquarius Scatterometer Sequence, 180 ms

•Scatterometer sequence repeats every 180 msec and is fixed (if in single beam mode, just stay on that beam)

•Radiometer OMT noise diode is always fired during scat noise only interval•Radiometer is blanked during every receive protect pulse•Radiometer sequence repeats every 120 msec

Beam 2Tx_H

Beam 2Tx_V

Beam 2Tx_V

Beam 2_VNoise only

Beam 2Tx H

Rx_V Rx_V Rx_HRx_H

Beam 2_HNoise only

sec0.12 0.13 0.14 0.15 0.16 0.17 0.18 0.19 0.20 0.21 0.22 0.23 0.24

Beam 3Tx_H

Beam 3Tx_V

Beam 3Tx_V

Beam 3_VNoise only

Beam 3Tx H

Rx_V Rx_V Rx_HRx_H

Beam 3_HNoise only

Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam1_VNoise only

Beam 1Tx H

Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

Avg’d togetherAvg’d over 10 subcycles



Avg’d over 2 subcyclesAvg’d together

H H H H

H H H H


Level 1 Algorithm

Simon Yueh

49 of 27


L1 Processing Flow

• Two stages of processing will be used for Level 1 processing.– Heritage from SeaWind/QuikSCAT processing

• Stage 1 will initialize a cubic spline algorithm.– Looks forward and backward in time.

– Allows greater accuracy

– Less sensitive to unevenly spaced or missing data.

• Stage 2 will use the result of stage 1 processing as input for the geometric calculations.

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Level 1 Stage A Processing Flow

Module SA1: Interpolate the Ephemeris using a cubic spline algorithm. Save the result for use in stage B processing.

Ephemeris: TimeX,Y,Z positionX,Y,Z velocitySpacecraft Attitude

Module SA2: Write Noise only data out to a separate file for use in stage B processing

Radar data:

Module SA3: Write loop-back calibration data out to a separate file for use in stage B processing. Include time, loop-back measurement, etc.


Noise only file*

PtGr file*

Temperature file*

Module SA4: Convert temperature from data number to degree centigrade. Write temperature data out to a separate file for use in stage B processing. Include time and temperature(s).

file*: This may be implemented as storage in RAM if desired.

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Module SB3: For each value of Ps calculate the value of Xcal, using temperature telemetry if necessary.

Module SB2: Calculate Doppler Frequency Shift

Module SB1: For each value of Pe perform geometric calculations to locate each measurement on the earth (with latitude and longitude).

Level 1 Stage B Processing Flow

eP

calX


Module SB4: For each value of Ps estimate the best value for Ps. Calculate the SNR and Kpc.

Radar file

Temperature file*

PtGr file*

Noise only file*

Scatterometer Parameter file

eP

file*: This may be implemented as storage in RAM if desired.

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Module SB6: Calculate 0.

Module SB5: Look up Xint based on beam number and orbit location.

Level 1 Stage B Processing Flow (cont)

Module SB8: Set quality flags, land and ice* flags, etc.

Module SB9: Write stage 2 output file(s).

Module SB7: Calculate the polarization roll angle.

*Sea ice flag algorithm will be developed using polarization ratio


Level 2 Algorithm

Simon Yueh

54 of 27


Level 2 ATBD – Excess Surface Emission

• The brightness temperature of sea surfaces is influenced by sea surface roughness.– Tower and airborne measurements in 1970-2000s showed the

response of TB to wind and wave height.

• The ocean backscatter (σ0) measured by scatterometer is directly influenced by roughness.

• PALS measurements in 2000 and 2002 demonstrated the relationship between excess TB and σ0.

• The baseline scatterometer L2 algorithm will estimate the excess brightness temperature from the total σ0 (VV+HH+VH+HV).

• Implement ΔTB in the processor using a look-up table of beam#, incidence angle (θ), radiometer polarization, wind direction (φ), cell azimuth (), wave height (SWH).

0( , #, , , , , )B BT T beam polarization SWH

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Level 2 ATBD – Solar Reflection

• The solar radiation can be reflected into the main beam of the antenna during summer or winter solstice.– The induced antenna brightness temperature is proportional to the

bistatic scattering coefficients (γ) of sea surfaces.

– The impact is estimated to be less than a few tenths of Kelvin for solar flare.

• The Aquarius ocean backscatter (σ0) is a measure of radar backscattering coefficients and is highly correalted to the bistatic scattering coefficient γ.

• The plan is to estimate the reflected solar radiation due to solar flare from the backscatter measurement.– Develop an empirical relationship between σ0 and γ.

– Use solar flux measurements

– Estimate the reflected brightness temperature

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Level 2 Scatterometer Algorithm Flow

Module SC1: Apply quality flag filter (land, ice, etc.)Average 4 blocks of data (5.76 sec) and matchup with radiometer data

Level 1 output

Level 2 Output

Module SC2: Compute Tb correction due to excess emissivity and solar reflection

•Ancillary: Operational wind direction and wave field•Sun bistatic scattering geometry Module SC3:

Compute Tb correction due to solar reflection

57 of 27


Scatterometer Level 2 Algorithm Output

• Geolocated σ0 (VV, HH, VH, and HV) matchup with radiometer data packet for each 5.76 sec window.

• ΔTB for each antenna beam and polarization.

• Solar reflection ΔTB introduced by the bistatic scattering coefficient of surface roughness.

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Sigma0-Tb Model Development Approach

• Pre-launch– Use a two-scale scattering model tuned with PALS experimental data to

obtain σ0 and ΔTB pairs for each antenna beam and polarization

– Construct σ0-ΔTB model function.

• Post-launch

– Collocate L2A TB and ancillary (numerical model or buoy) SSS, SST

and winds.

– Calculate smooth surface Tbs from SSS and SST matchup.

– Calculate excess surface brightness temperature ΔTB = TB – Tbs.

– Bin ΔTB as a function σ0, SSS, SST, wind direction and wave height to develop the model function.

– Examine if the model function has any regional dependence.


Scatterometer Algorithm Tasks

60 of 27


Scatterometer Algorithm Tasks

61 of 27


Geometry

62 of 27


Ephemeris processing

• To include cubic-spline interpolation routines for ephemeris processing

• Need to finalize the definition of ephemeris data. We have codes to process data either way.– ECF x, y, and z will be more convenient for us

– MJ2K x, y, and z are ok for us, but require more codes for conversion

63 of 27


Attitude processing

• S/C attitude rotation for SeaWinds was assumed. Need to get confirmation from CONAE on the definition of pitch, roll, and yaw and sequence of rotations

• If Quaternion is to be used, we still need to know the sequence of rotations because we need to parameterize the Xint table as a function of attitude

• Need sample attitude data from CONAE

64 of 27


Misc. software update

• Update the earth flattenning ratio in the subroutine, initialize_constants; usno almanac flattening ratio is being used, not wgs84.

• Check the convergence criterion for the subroutine, compute_sc_nadir_components, and investigate alternate algorithm

• Include year, month and day as inputs into the subroutine, rotate2_system_due_to_procession

• Include Julian date to year, month and day conversion in the subroutine, reformat_julian_time

65 of 27


Radiometric Calibration

66 of 27


Develop Xint table

• Implement formulation for polarimetric radar equation

• Identify and evaluate candidate functional forms for Xint– Xint table should be insensitive to spacecraft altitude and can be accurately

parameterized as a function of latitude and attitude– Verify X_int integration algorithm and correct for off-boresight polarization

rotation

• Update antenna gain and pattern

67 of 27


Loss calibration

• Update the definition of front end loss tables to match the test configuration

• Include temperature dependence tables and correction routines for losses

68 of 27


Land and sea ice

69 of 27


Implement ice flag algorithm using external ancillary data

• Who is going to provide the sea ice map? What will be the format?

• Need sample ice map or ice edge data

70 of 27


L2 TB correction

71 of 27


Develop TB-sigma0-wind-wave model function table

• Develop TB-wind-wave model function table

• Develop sigma0-wind-wave model function table

72 of 27


Simulator

73 of 27


L1 Simulator

• Remove the sigma0 calibration bias from the current version of simulator

• Update geometry routines

• Update radiometric calibration routines

• Update sigma0 model functions

• Include Faraday rotation

• Update instrument simulator

74 of 27


L2 simulator

• Determine size of model function tables

• Develop prototype codes

75 of 27


Back-up Material

76 of 27


Scatterometer L1 Algorithm Overview

Pre-Launch Calibration Measurement

Spacecraft Ephemeris and Attitude

Aquarius Instrument

R

g

eP

nP

calP

intX

calX

sP

0

0 location

SNR

pcK

Noise

Radar Design Parameters

Temperatures

Correct Losses for Temperature

4

lbcL

calL

opL

TL

RL

pkG

Radar timing

h

77 of 27


ATBD Xcal

• Xcal is composed of constants and loss terms.• Components which contribute path loss and are sensitive to

temperature will be calibrated before launch as a function of temperature.

• A function of radiometric loss vs temperature will be incorporated into the processor. These may be implemented as a lookup table or a function of a least square fit.

22

34

pk

t r

cal lbc cal bp

calop T R bp p

P L L GX

L L L B

78 of 27


Level 1 ATBD (Calibration Equation) – Alternate Form

Define the following terms: 4

int 43

c r t

dB area

R g g hdAX

A R

223

3 44

pk

t r

cal lbc cal bp dBcal

op T R bp p c

P L L G AX

L L L B R

• This alternate form for Xint should be less sensitive to the orbit latitude and spacecraft altitude

• Xint is a function of latitude, roll, pitch and yaw of the spacecraft– Need s/c attitude data (quaternion or roll, pitch and yaw and sequence

of rotations)

79 of 27


Level 1 Geometry ATBD

• The Input will consist of the ephemeris (state vector), attitude (roll, yaw, and pitch), and time.

• The ephemeris and some other parameters will be interpolated using a cubic spline technique.

• Geometric Calculations– Compute the spacecraft altitude and location.

– Compute the latitude and longitude of the center of each beam for each echo.

– Compute the incidence angle, azimuth angle relative to north, and rotation angle for each beam.

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BEAM 1BEAM 3

BEAM 2BEAM 1

Averaged over 2 or 10 cyclesaveragedaveraged

Instrument Timing

sec


Aquarius Instrument Master Timing

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12


Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam 1_VNoise only

Beam 1Tx H

Rcv_protect


Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

One Aquarius Scatterometer Timing Cycle, 180 ms

One Aquarius science data block is 1.44 sec long and contains: 8 scatterometer cycles12 radiometer sub-cycles

When scat is in single beam mode, the sequence is preserved; the same beam is used in all 18 PRIs.The CND noise diode is synchronous with a V-pol noise-only scat measurement, cycling through each beam.

Beam 2Tx_H

Beam 2Tx_V

Beam 2Tx_V

Beam 2_VNoise only

Beam 2Tx H

Rx_V Rx_V Rx_HRx_H

Beam 2_HNoise only

sec0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.11 0.12

Beam 3Tx_H

Beam 3Tx_V

Beam 3Tx_V

Beam 3_VNoise only

Beam 3Tx H

Rx_V Rx_V Rx_HRx_H

Beam 3_HNoise only

Beam 1Tx_H

Beam 1Tx_V

Beam 1Tx_V

Beam1_VNoise only

Beam 1Tx H

Rx_V Rx_V Rx_HRx_H

Beam 1_HNoise only

cal = Dicke load and/or internal noise diode, or zero-offset

(each beam, every channel)

81 of 27


Level 1 ATBD (Radiometric Calibration)

3

22 20

4

4 1bp bp

pk

T R

e nt r bp

area

L LP P

g dAPG GR

Where

bpTL Transmit path Loss between the start of the cal-loop and the antenna.

bpRL Receive path Loss between the end of the cal-loop and the antenna.

tP Transmit Power.

rG Receiver Gain

pkbpG Peak Antenna Gain.

g Relative Antenna Gain Pattern R Distance from the radar antenna to the earth. Radar Wavelength 4 Constant

eP The echo power measured by Aquarius

nP The noise power measured by Aquarius

0 Normalized Radar Backscatter.

82 of 27


Geometry Modules

• Temporal interpolation of ephemeris• Compute spacecraft nadir components• Compute local coordinates• Compute rotations

– Compute attitude rotation matrix (roll, yaw, pitch)– Compute geocentric to geodetic rotation– Compute antenna pointing relative to spacecraft

• Compute antenna pointing vector• Convert local to rectangular system• Locate cell on earth• Compute cell latitude and longitude• Compute cell incidence angle• Compute cell azimuth (from north)• Compute Beam Rotation

83 of 27


Scatterometer Header

B2HH pwr 3 16

B3HV pwr 3 16

B3nV pwr 3 16

B3VV pwr 3 16

B3VH pwr 3 16

B3nH pwr 3 16

B3HH pwr 3 16

B1HV pwr 4 16

B1nV pwr 4 16

The general format of subcycle status words: - bit 7: 0 – at least 1 pwr accum. overflows in cycle, 1 none - bit 6: 1 if at least 1 RFI flag in cycle - bit 5: 0 for receive H, 1 for receive V - bit 4: 0 for xmit H, 1 for xmit V - bit 3-2: beam # (0-2) - bit 1: 1 for echo, 0 for noise - bit 0: 1 for receive, 0 for lpbk.

84 of 27


Scatterometer Science Data

field total # of bits

B1HV pwr 16B1nV pwr 16B1VV pwr 16B1VH pwr 16B1nH pwr 16B1HH pwr 16B2HV pwr 16B2nV pwr 16B2VV pwr 16B2VH pwr 16B2nH pwr 16B2HH pwr 16B3HV pwr 16B3nV pwr 16B3VV pwr 16B3VH pwr 16B3nH pwr 16B3HH pwr 16

Repeated 8 times in the block

85 of 27


Loop-Back Scatterometer Data

field sequence # total # of bits

B1HV pwr 1-8 16

B1nV pwr 1-8 16

B1VV pwr 1-8 16

B1VH pwr 1-8 16

B1nH pwr 1-8 16

B1HH pwr 1-8 16

B2HV pwr 1-8 16

B2nV pwr 1-8 16

B2VV pwr 1-8 16

B2VH pwr 1-8 16

B2nH pwr 1-8 16

B2HH pwr 1-8 16

B3HV pwr 1-8 16

B3nV pwr 1-8 16

B3VV pwr 1-8 16

B3VH pwr 1-8 16

B3nH pwr 1-8 16

B3HH pwr 1-8 16

B1HV DC 1-8 16

B1NV DC 1-8 16

86 of 27


Ephemeris Geometry Software Testing

• Three sample ephemeris files from CONAE were received.– Each file contains about 40 orbits of the earth.– They are in different formats, but they each contain information on the

same 40 orbits. – The sample ephemeris were delivered with 1 minute spacing.

• The three formats are:– Keplerian– State Vector (Time, X, Y, Z for position and velocity)– Geodetic (Time, latitude, longitude altitude)

• The orbits are consistent with flying with geodetic attitude• The sample ephemeris data are being used to develop and test the

geometry software.

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ATBD Polarimetric Inversion

3 41 1 1 1

2

(4 ) cs pr gr r gt pt

RM M M M M M

national aeronautics and space administration scatterometer algorithm simon yueh, adam freedman and...

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