National Aeronautics and Space Administration Scatterometer Algorithm Simon Yueh, Adam Freedman and Greg Neumann Jet Propulsion Laboratory Aquarius Science Algorithm Workshop March 2007, GSFC

2 of July, 2006 Aquarius Science Pre-CDR Outline Algorithm Overview (Day 1) –Requirements –ATBD –Algorithm flow overview –Development approach Simulator Status and Simulation (Day 1) Remaining Tasks and Plans (Day 2)

3 of July, 2006 Aquarius Science Pre-CDR 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)

4 of July, 2006 Aquarius Science Pre-CDR Level 1 ATBD (Calibration Loop Data)

5 of July, 2006 Aquarius Science Pre-CDR Level 1 ATBD (Calibration Equation) – Current Form Ps= signa+noise data, Pn=noise only data and Pcal= cal-loop data.

6 of July, 2006 Aquarius Science Pre-CDR ATBD Forward Polarimetric Radar Equation Mueller Matrix and Stokes Vector Formulation Scalar Radar Equation Polarimetric Radar Equation Mueller matrix for polarization roll Mueller matrix for antenna gain Mueller matrix for ocean scattering

7 of July, 2006 Aquarius Science Pre-CDR 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

8 of July, 2006 Aquarius Science Pre-CDR 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

9 of July, 2006 Aquarius Science Pre-CDR Level 1 Output Parameters for Each Block One block includes data from 1.44 sec window. About 12-15MB for each orbit of L1B data file

10 of July, 2006 Aquarius Science Pre-CDR 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)

11 of July, 2006 Aquarius Science Pre-CDR 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

National Aeronautics and Space Administration Aquarius Scatterometer Simulation and Data Inversion Software Design and Status Adam Freedman Simon Yueh Greg Neumann March 21-22, 2007 Aquarius Data Processing System Algorithm Implementation Workshop GSFC

13 of July, 2006 Aquarius Science Pre-CDR 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

14 of July, 2006 Aquarius Science Pre-CDR 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

15 of July, 2006 Aquarius Science Pre-CDR 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 time Compute x, v, at t in ECF Read orbit file, one record at a time Compute x, v, at t in ECF Compute S/P nadir location Compute S/P local frame orientation Compute S/P nadir location Compute S/P local frame orientation Instrument Simulator Compute Xcal_sim, LB power, noise power, DC offset Instrument Simulator Compute Xcal_sim, LB power, noise power, DC offset Integration Over Beam Pattern Compute Xint, beam-weighted sig-0, Mean sig-0 over 3-dB footprint Integration Over Beam Pattern Compute 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 files Antenna beam pattern files Complex Eco and Ecr, (theta,phi,beam#,H/V-pol) Antenna beam pattern files Complex 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 options Orbit ephemeris file S/P XYZ position vs time, either ECF or MJ2K Orbit ephemeris file S/P XYZ position vs time, either ECF or MJ2K S/P Attitude file S/P RPY vs time, or equivalent S/P Attitude file S/P RPY vs time, or equivalent Scatterometer HW data file Tx power, gains, losses, etc. Scatterometer HW data file Tx power, gains, losses, etc. Compute simulated measurement HV,nV,VV,VH,nH,HH,LB,DC vs t Compute simulated measurement HV,nV,VV,VH,nH,HH,LB,DC vs t Next orbit position Next beam

16 of July, 2006 Aquarius Science Pre-CDR Beam Integration Block Diagram Initialize wind field Loop though beam pattern, for each theta (elevation) and phi (azimuth) Within range of thetas (±15°,±20°) Loop though beam pattern, for each theta (elevation) and phi (azimuth) Within range of thetas (±15°,±20°) Compute two-way gain matrices Gh 2,Gv 2,Ghv,etc. for co- and cross-pol Compute two-way gain matrices Gh 2,Gv 2,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-weighted Gain (area*G 2 /range 4 ) Compute area and range-weighted Gain (area*G 2 /range 4 ) Apply range gate factor if full chirp not contained in Rx window Apply range gate factor if full chirp 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 field U and V components 0.5 deg spacing or better NSCAT or equiv wind field U 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-0 Sum sig-0 weighted gain Sum weighted gain Sum sig-0 in 3-dB region Sum area in 3-dB region Sum sig-0 weighted gain Sum weighted gain Sum sig-0 in 3-dB region Sum area in 3-dB region Exit and return integrated measurements Exit and return integrated measurements Completed integration

17 of July, 2006 Aquarius Science Pre-CDR 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

18 of July, 2006 Aquarius Science Pre-CDR Beam Patterns Beam 1 two-way gain patterns in dB Elevation range ±15°

19 of July, 2006 Aquarius Science Pre-CDR Wind Field NSCAT Wind Field 11/20/96 00 UT 0.5° resolution U and V, m/sec

20 of July, 2006 Aquarius Science Pre-CDR Ocean Backscatter Over Footprint Beam 1 Ocean Backscatter sigma-0 in dB Model function (NSCAT winds) Land sig-0 set to -10 dB Elevation range ±15°

21 of July, 2006 Aquarius Science Pre-CDR Ocean Backscatter Weighted by Beam Pattern Beam 1 Ocean sigma-0 weighted by beam pattern, range loss, receive window Elevation range ±15°

22 of July, 2006 Aquarius Science Pre-CDR Measurements Over an Orbit Simulated scatterometer measurements over about 3 orbits (HV barely visible above noise floor)

23 of July, 2006 Aquarius Science Pre-CDR Global Simulation Simulated Global Coverage over 7 days, spacecraft position at 1 minute intervals Ground tracks for each beam

24 of July, 2006 Aquarius Science Pre-CDR Modeled Received Power Over Earth

25 of July, 2006 Aquarius Science Pre-CDR 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 ~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

26 of July, 2006 Aquarius Science Pre-CDR 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

27 of July, 2006 Aquarius Science Pre-CDR 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

28 of July, 2006 Aquarius Science Pre-CDR Scatterometer Measurement Inversion Block Diagram For each measurement epoch, And for each beam For each measurement epoch, And for each beam Compute Xcal (SB3) Time, temperature telemetry, Max reflector gains, LB power Psig = Pecho - Pnoise - Pdc SNR = Psig / Pnoise Psig = Pecho - Pnoise - Pdc SNR = Psig / Pnoise Compute Kpc (SB4) Compute Xint (SB5) Compute Sig-0 Sig-0 = Psig - Xint - Xcal Compute Sig-0 Sig-0 = Psig - Xint - Xcal Write to output file Read from measurements file Time, echo power, LB power, DC offset, telemetry Read from measurements file Time, echo power, LB power, DC offset, telemetry Xint value computed from simulator Time, location, sigma-0, quality flags

29 of July, 2006 Aquarius Science Pre-CDR Estimated Ocean Surface Backscatter Over one orbit: Sigma-0 estimated from simulated measurements, vs. sigma-0 averaged over 3-dB footprint

30 of July, 2006 Aquarius Science Pre-CDR Estimated Sigma-0 and Error: Beam 1 VV Simulated global measurements over 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.

31 of July, 2006 Aquarius Science Pre-CDR Estimated Sigma-0 and Error: Beam 2 HV Simulated global measurements over 7 days, spacecraft position at 1 minute intervals (400 km spacing). 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.

32 of July, 2006 Aquarius Science Pre-CDR Estimated Sigma-0 and Error: Beam 3 HH Simulated global measurements over 7 days, spacecraft position at 1 minute intervals (400 km spacing). 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.

33 of July, 2006 Aquarius Science Pre-CDR 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

34 of July, 2006 Aquarius Science Pre-CDR Scatterometer L1a-to-L1b Processing Temporal 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 position X,Y,Z velocity Spacecraft Attitude Every 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). Ephemeris Cubic Spline Coefficient file* Noise only file* PtGr file* Temperature file* file*: This may be implemented as storage in RAM, if desired.

35 of July, 2006 Aquarius Science Pre-CDR Sample Data and Telemetry

36 of July, 2006 Aquarius Science Pre-CDR Sample DN-to-EU Telemetry Conversions SSPA RF Deck tempdeg C$POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3 SCG tempdeg C$POLY0 + ($*256*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*256*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*256*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3 SBE LNA tempdeg 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 tempdeg 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 tempdeg 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 tempdeg C$POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3 SFE loopback switch tempdeg C$POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3 SFE beam switch tempdeg C$POLY0 + ($*$GAIN_NORM + $OFFSET_NORM)*$POLY1 + (($*$GAIN_NORM + $OFFSET_NORM)**2)*$POLY2 + (($*$GAIN_NORM + $OFFSET_NORM)**3)*$POLY3 SFE Tx power monitorvolts$*5/65536 SFE 15N voltage monitorvolts$*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 Monvolts$*5/256 LVPS Converter Currentvolts$*5/256 SSPA output stage voltagevolts$*5/256*10 SSPA intermediate stage voltagevolts$*5/256*10 SSPA input stage voltagevolts$*5/256*5 SFE +5V monitorvolts$*5/256*2 SCG +5V monitorvolts$*5/256*2 SBE +5V monitorvolts$*5/256*2 SBE +12V monitor (non switched)volts$*5/256*4.8 CAL_RES1_RES360 CAL_RES2_RES460 CAL_RES3_RES640 CAL_RES4_RES550 GAIN_NORM($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 POLY POLY21.39E-05 POLY31.88E-08

National Aeronautics and Space Administration Pre-Launch Calibration Requirement Adam Freedman

38 of July, 2006 Aquarius Science Pre-CDR Scat Pre-Launch Calibration Requirements A 3.3 Scatterometer Measurement Calibration Antenna Subsystem Scatterometer Calibration All scatterometer calibration requirements apply at the scatterometer center frequency of 1.26 GHz 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 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 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.

39 of July, 2006 Aquarius Science Pre-CDR Scat Pre-Launch Calibration Requirements B Scatterometer Electronics Calibration 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 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 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 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.

40 of July, 2006 Aquarius Science Pre-CDR Scat Pre-Launch Calibration Requirements C 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 SSPA Transmit Power Monitor (TPM): Secondary Calibration: The SSPA transmit power monitor shall be calibrated to measure the transmit output power SSPA Transmit Power vs. Temperature: Secondary Calibration: The SSPA output power shall, as a goal, be determined as a function of temperature 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 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 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 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 July, 2006 Aquarius Science Pre-CDR Scat Pre-Launch Cal Planned Testing SA18: OMT/Feedhorn Loss and Stability Analysis Requirements Addressed: Cal , Cal , Cal , Cal , Cal Analysis Responsibility: Antenna Subsystem Analysis 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 Engineering Requirements Addressed: Cal , Cal Verify 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 Engineering Requirements Addressed: 644, Cal , Cal , Cal , Cal through Collect calibration data per Calibration Requirements section of this document. Perform FOL test with ICDS, measure SSPA power over temp Measure scat noise figure, gain, loopback level, linearity, clock stability, max input level ST 21: Antenna Subsystem Calibration and Test, Responsibility: Antenna, Instrument System Engineering Requirements Addressed:, Cal , Cal , Cal , Cal Collect 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: Antenna Requirements Addressed:, Cal , Cal , Cal , Cal , Cal , Cal , Cal 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 July, 2006 Aquarius Science Pre-CDR Calibration Approach (CVVD)

43 of July, 2006 Aquarius Science Pre-CDR Calibration Approach

44 of July, 2006 Aquarius Science Pre-CDR Transmit Path

45 of July, 2006 Aquarius Science Pre-CDR Receive Path

46 of July, 2006 Aquarius Science Pre-CDR Scatterometer Subsystem functional block diagram

47 of July, 2006 Aquarius Science Pre-CDR Scatterometer Timing Diagram

National Aeronautics and Space Administration Level 1 Algorithm Simon Yueh

49 of July, 2006 Aquarius Science Pre-CDR 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.

50 of July, 2006 Aquarius Science Pre-CDR 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: Time X,Y,Z position X,Y,Z velocity Spacecraft 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. Ephemeris Cubic Spline Coefficient file* 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.

51 of July, 2006 Aquarius Science Pre-CDR 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 Ephemeris Cubic Spline Coefficient file* 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 file*: This may be implemented as storage in RAM if desired.

52 of July, 2006 Aquarius Science Pre-CDR 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

National Aeronautics and Space Administration Level 2 Algorithm Simon Yueh

54 of July, 2006 Aquarius Science Pre-CDR Level 2 ATBD – Excess Surface Emission The brightness temperature of sea surfaces is influenced by sea surface roughness. –Tower and airborne measurements in s showed the response of T B to wind and wave height. The ocean backscatter (σ 0 ) measured by scatterometer is directly influenced by roughness. PALS measurements in 2000 and 2002 demonstrated the relationship between excess T B and σ 0. The baseline scatterometer L2 algorithm will estimate the excess brightness temperature from the total σ 0 (VV+HH+VH+HV). Implement ΔT B in the processor using a look-up table of beam#, incidence angle (θ), radiometer polarization, wind direction (φ), cell azimuth (  ), wave height (SWH).

55 of July, 2006 Aquarius Science Pre-CDR 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 (σ 0 ) 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 σ 0 and γ. –Use solar flux measurements –Estimate the reflected brightness temperature

56 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR Scatterometer Level 2 Algorithm Output Geolocated σ 0 (VV, HH, VH, and HV) matchup with radiometer data packet for each 5.76 sec window. ΔT B for each antenna beam and polarization. Solar reflection ΔT B introduced by the bistatic scattering coefficient of surface roughness.

58 of July, 2006 Aquarius Science Pre-CDR Sigma0-Tb Model Development Approach Pre-launch –Use a two-scale scattering model tuned with PALS experimental data to obtain σ 0 and ΔT B pairs for each antenna beam and polarization –Construct σ 0 -ΔT B model function. Post-launch –Collocate L2A T B and ancillary (numerical model or buoy) SSS, SST and winds. –Calculate smooth surface Tbs from SSS and SST matchup. –Calculate excess surface brightness temperature ΔT B = T B – Tbs. –Bin ΔT B as a function σ 0, SSS, SST, wind direction and wave height to develop the model function. –Examine if the model function has any regional dependence.

National Aeronautics and Space Administration Scatterometer Algorithm Tasks

60 of July, 2006 Aquarius Science Pre-CDR Scatterometer Algorithm Tasks

61 of July, 2006 Aquarius Science Pre-CDR Geometry

62 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR Radiometric Calibration

66 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR Land and sea ice

69 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR L2 TB correction

71 of July, 2006 Aquarius Science Pre-CDR Develop TB-sigma0-wind-wave model function table Develop TB-wind-wave model function table Develop sigma0-wind-wave model function table

72 of July, 2006 Aquarius Science Pre-CDR Simulator

73 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR L2 simulator Determine size of model function tables Develop prototype codes

75 of July, 2006 Aquarius Science Pre-CDR Back-up Material

76 of July, 2006 Aquarius Science Pre-CDR Scatterometer L1 Algorithm Overview

77 of July, 2006 Aquarius Science Pre-CDR 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.

78 of July, 2006 Aquarius Science Pre-CDR Level 1 ATBD (Calibration Equation) – Alternate Form 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 July, 2006 Aquarius Science Pre-CDR 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.

80 of July, 2006 Aquarius Science Pre-CDR BEAM 1 BEAM 3 BEAM 2 BEAM 1 Averaged over 2 or 10 cycles averaged Instrument Timing sec Antenna Aquarius Instrument Master Timing Antenna cal CND Beam 1 Tx_H Beam 1 Tx_V Beam 1 Tx_V Beam 1_V Noise only Beam 1 Tx H Rcv_protect One Aquarius Radiometer sub-cycle, 120 ms Rx_V Rx_H Beam 1_H Noise only One Aquarius Scatterometer Timing Cycle, 180 ms One Aquarius science data block is 1.44 sec long and contains: 8 scatterometer cycles 12 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 2 Tx_H Beam 2 Tx_V Beam 2 Tx_V Beam 2_V Noise only Beam 2 Tx H Rx_V Rx_H Beam 2_H Noise only sec Beam 3 Tx_H Beam 3 Tx_V Beam 3 Tx_V Beam 3_V Noise only Beam 3 Tx H Rx_V Rx_H Beam 3_H Noise only Beam 1 Tx_H Beam 1 Tx_V Beam 1 Tx_V Beam1_V Noise only Beam 1 Tx H Rx_V Rx_H Beam 1_H Noise only cal = Dicke load and/or internal noise diode, or zero-offset (each beam, every channel)

81 of July, 2006 Aquarius Science Pre-CDR Level 1 ATBD (Radiometric Calibration)

82 of July, 2006 Aquarius Science Pre-CDR 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 July, 2006 Aquarius Science Pre-CDR Scatterometer Header 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 July, 2006 Aquarius Science Pre-CDR Scatterometer Science Data Repeated 8 times in the block

85 of July, 2006 Aquarius Science Pre-CDR Loop-Back Scatterometer Data

86 of July, 2006 Aquarius Science Pre-CDR 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.

87 of July, 2006 Aquarius Science Pre-CDR ATBD Polarimetric Inversion