IWF/ÖAW GRAZ

Jason-2 Altimeter Calibration

Status Quo

Walter Hausleitner, Jörg Weingrill

Altimeter Calibration Workshop 2010

Graz, Austria

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Transponder Experiments

Transponder site on Gavdos, Greece

Jason-2 calibration –present statusproblems

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Transponder site

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Transponder instrument

Frequency / Bandwidth Centre Frequ. 13.7 GHz

Bandwidth: 600 MHz

Total gain: 77 dB

Intrument delay: 13.25 ns

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Ocean vs. point target response

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Point target response

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Calibration data availability 2009

Pass Cal Status Data

Date Cycle OK / fail S-IGDR SIMPACALCal. range

comm. Aux. Data

09 09 12 44 OK   YES YES  

09 09 22 45 fail YES YES    

09 10 01 46 fail YES YES    

09 10 11 47 OK   YES YES  

09 10 21 48 no CAL        

09 10 31 49 OK     YES  

09 11 10 50 OK YES YES YES  

09 11 20 51 fail YES      

09 11 30 52 no CAL YES      

09 12 10 53 no CAL YES      

09 12 20 54 no CAL YES      

09 12 30 55 no CAL YES     YES

09 01 09 56 no CAL YES     YES

09 01 19 57 no CAL YES     YES

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Calibration data availability 2010

Pass Cal Status Data

Date Cycle OK / fail S-IGDR SIMPACAL

CalibrationRange

command Aux. Data

10 01 28 58 fail YES     YES

10 02 08 59 no CAL YES     YES

10 02 17 60 fail YES     YES

10 02 27 61 no CAL YES     YES

10 03 09 62 OK YES YES   YES

10 03 19 63 fail YES     YES

10 03 29 64 OK YES YES   YES

10 04 08 65 fail YES     YES

10 04 18 66 fail YES     YES

10 04 28 67 no CAL YES      

10 05 08 68 OK YES YES    

10 05 17 69 fail YES      

10 05 27 70 OK YES YES    

10 06 06 71 OK YES      

10 06 16 72 fail YES      

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Data processing concept

Reproduce obs. corr.

Combine S-IGDR+Calibr.

Interp. TRP meas. corr.

Geometric Corr.

Precise range residual

Geophysical Corr.Atmospheric Corr.

S-IGDR data extraction

Calibration DataS-IGDR

Compute absolute times

Fit parabola to echo bins

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S-IGDR

Sensor Interim Geophysical Data Records (S-IGDRR)

NetCDF Files from podaac.jpl.nasa.gov1 Hz data + 20 Hz high-rate data

Waveforms

Latency: 2 days

Pass 018Descending Gavdos pass

Pass 018

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S-IGDR

S-IGDRRm data records used lat lat_20hz lon lon_20hz range_ku range_20hz_ku rad_wet_tropo_corr model_dry_tropo_corr iono_corr_alt_ku sea_state_bias_ku model_wet_tropo_corr

alt alt_20hz mean_sea_surface solid_earth_tide pole_tide inv_bar_corr hf_fluctuations_corr net_instr_corr_range_ku

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Jason-2 Calibration

S-IGDR error budget

From Jason-2 Products Handbook

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Calibration analysis concept

11 sec data gap

3 sec calibrationwaveforms

Computation of closest approach time from S-IGDR orbit

Identification of TRP echo bin for each elementary waveform

Parabola fit and determination of vertex

Tie vertex of parabola to closest orbit point for aligning the calibrations to the orbit

Derive absolute times for each TRP echo bin through the relative times given calibration interval and bin-size

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S-IGDR data interpolation

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Poseidon-2 elementary calibration

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TRP echo bin detection

Lagrange interpolation of TRP power response

Numerical differentiation and Gaussian curve fitting

Power dependent weighting for each bin

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Closest approach time/distance

Parabola fitting through TRP echo bins

Determination of fractional calibration number at parabola vertex

Aligning vertex with absolute time of closest approach

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Altimeter range commandDate 2009/11/10

Time 14:19:34

Date Exec. CAL2

Only known to integerseconds ?

Ho 4604232

LSB Ho .0073191518 m

NSPEC 3

NCAL 32

3.125 nsNS

PE

C *

0.0

5100

769

IWF/ÖAW GRAZ

Ambiguity of cal range

Altimeter range command 34 km

Ambiguity = (18/PRF)*c/2 PRF = 2058.513239 Hz

1310 km

Ambiguity + Calibration range 1344 km

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Altitude vs. Ku-band range

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Propagation and reflection effects

Source Uncorr. effect

Cycle 50Corr.

Wet

Troposph

0-30 cm 15 cm

Dry troposphere

230 cm 229.5 cm

Iono troposphere

0.2-20 cm 1.6 cm

Sea state bias

0-20 cm 8.8 cm

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Corrected range

m

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Sea surface height

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Geophysical corrections

Mean sea surface

Solid Earth tide

Geocentr. Ocean tide

Pole tide height

Inv. barom. height eff.

HF fluctuations of SST

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Geophysical corrections (cont’d)

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Interpolation effects

There is a significant difference between either

interpolating the individual corrections and sum up the interpolated corrections

Summing up the corrections and interpolate the sum of corrections

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Signal runtime corrections

r

Geoid

Ellipsoid

hS

Center of mass correctionAltimeter instrument delay

hT

href

SST

GPS Transponder/Altimetry

Dry troposphereWet troposphereIonosphere

Transponder delayOffset station markerSlant range correction

Solid Earth tidesPole tides

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TRP range residuals

r

Geoid

Ellipsoid

Calibration bin rangeAmbiguityAltimeter delayCoM CorrectionDry troposphereWet (water vapour)Ionosphere

TRP delay (electronic)TRP delay (geometric)Station marker eccentricitySlant range correction

TRP ell.heightSolid earth tides

Corrections

Effect Magnitude (m)

Orbital heightResidual

33738.0881310718.858 -5.173 0.471

- 3.972 -1.477 -0.824

251.169 -0.060

1344398.967 44.575

-2.297-0.116-0.016