Ocean Retracking Outputs

epoch_ocean_[x1]_[x2]
sigmac_ocean_[x1]_[x2]
sigmas_ocean_[x1]_[x2]
inverse_ms_slope_ocean_[x1]_[x2]
amplitude_ocean_[x1]_[x2]
max_power_ocean_[x1]_[x2]
thermal_noise_ocean_[x1]_[x2]
off_nadir_angle_wf_ocean_[x1]_[x2]
number_of_iterations_ocean_[x1]_[x2]
MQE_ocean_[x1]_[x2] where:
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

LRM mode: ocean re-tracking (ALT_RET_OCE_01 algorithm).
SAR mode: ocean/coastal re-tracking (ALT_RET_OCE_02 algorithm).
ALT_RET_OCE_01 algorithm performs the ocean re-tracking (called ocean-3 re-tracking from JASON heritage) on the waveforms. This algorithm estimates the altimetric parameters: epoch, composite Sigma, amplitude, square of the mispointing angle.The aim of the ocean-3 re-tracking algorithm is to make the measured waveform coincide with a return power model, according to weighted Least Square Estimators derived from Maximum Likelihood Estimators. Regarding mispointing, the return power model accounts for the second order terms.Moreover, within the Ku-band ocean-3 re-tracking, the square of the off-nadir angle is estimated together with the three standard altimetric parameters (epoch, composite sigma and amplitude).
The ALT_RET_OCE_02 algorithm performs the ocean/coastal zone re-tracking fitting the theoretical multi-looked waveform model to one 20 Hz Level-1B SAR waveform using the Levenberg-Marquardt method and retrieving geophysical variables as well fitting quality information.

Epoch: 10-15 secs
Composite Sigma: 1015 secs
RMS height of the specular points: 10-4 m
Inverse mean square slope: 10-6 (scale factor)
Amplitude: 10-6
FFT power units Maximum Received Power: 10-4 Watts
Thermal noise: 10-6 FFT power units
Square of the mispointing angle: 10-4 degrees
Number of iterations: count Mean Quadratic Error (MQE) between waveform and model: 10-4 count.

Reduced: none
Standard: number of iterations and MQE between waveform and model only
Enhanced: all

Epoch: LRM and SAR
Composite Sigma: LRM
RMS height of the specular points: SAR
Inverse mean square slope: SAR
Amplitude: LRM
Maximum Received Power: SAR
Thermal noise: LRM and SAR
Square of the mispointing angle: LRM and SAR
Number of iterations: LRM and SAR
Mean Quadratic Error (MQE) between waveform and model: LRM and SAR

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_RET_OCE_01 (LRM) and ALT_RET_OCE_02 (SAR) algorithms
20 Hz C-band: ALT_RET_OCE_01 (LRM) and ALT_RET_OCE_02 (SAR) algorithms

None

ESA's Global Land and Ocean Mission for GMES Operational Services

Ocean Sea Surface Height Anomaly

{ssha_[x1]_[x2]} where:
{[x1]}: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

The sea surface height (SSH) above the sea level is only computed for Ku-band measurements. The equation used to compute SSH is:
SSH anomaly =
Orb_Alt - (Alt_Range_Ku + Alt_Iono_Cor_Ku + Model_Dry_Tropo_Cor + Rad_Wet_Tropo_Cor + SSB_Ku + MSS + Solid_Earth_Tide + Geo_Ocean_Tide_1 + Geo_Pole_Tide + X) where:
Orb_Alt: altitude of satellite
Alt_Range_Ku: Ku-band corrected ocean altimeter range
Alt_Iono_Cor_Ku: altimeter ionospheric correction on Ku-band
Model_Dry_Tropo_Cor: model dry tropospheric correction
Rad_Wet_Tropo_Cor: radiometer wet tropospheric correction
SSB_Ku: sea state bias correction in Ku-band
MSS: mean sea surface
Solid_Earth_Tide: solid earth tide height
Geo_Ocean_Tide_1: geocentric ocean tide height solution
Geo_Pole_Tide: geocentric pole tide height
X: for NRT products inverted barometer height correction. For STC and NTC products, MOG2D (inverted barometer height correction + frequency fluctuations of the sea surface topography).

10-3 m

Reduced: 1 Hz Ku-band only
Standard: 1 Hz and 20 Hz Ku-band only
Enhanced: 1 Hz and 20 Hz Ku-band only

LRM and SAR

1 Hz Ku-band: ALT_PHY_RAN_02 and ALT_MAN_INT_01 algorithms
20 Hz Ku-band: ALT_PHY_RAN_02 and ALT_MAN_INT_01 algorithms
20 Hz C-band: none

None

ESA's Global Land and Ocean Mission for GMES Operational Services

Corrected Ocean Significant Wave Height

swh_ocean_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku -and or C-band

LRM mode: ocean re-tracking.
SAR mode: ocean/coastal re-tracking.
The GEN_MEC_CON_01 algorithm derives the significant wave height from composite Sigma.
The ALT_COR_SWH_01 algorithm adds the following corrections: modelled instrumental errors correction (mod_instr_cor_swh_[x1]_[x2]), system bias.
The ALT_COM_SWH_01 algorithm computes a compressed estimate of the re-tracked significant wave height from elementary estimates.
The ALT_COM_SWH_02 algorithm computes a compressed estimate of the re-tracked composite sigma from elementary estimates.

10-3 m

Reduced: 1 Hz Ku-band only
Standard: all
Enhanced: all

LRM and SAR

1 Hz Ku/C-bands: ALT_COR_SWH_01 algorithm
20 Hz Ku-band: ALT_COR_SWH_01 algorithm
20 Hz C-band: ALT_COR_SWH_01 algorithm

Ocean significant wave height validity flag (swh_ocean_qual_[x1]_[x2]). Flag indicating the use or not of the 20 Hz estimate of the ocean significant wave height in the computation of 1 Hz estimate.
RMS of the ocean significant wave height (swh_ocean_rms_[x1]_[x2]).
Number of valid points used to compute the ocean significant wave height (swh_ocean_numval_[x1]_[x2]).

ESA's Global Land and Ocean Mission for GMES Operational Services