Minimize Instrumental Corrections

Most instrumental corrections are computed at Level-1B processing and some are re-computed at Level-2 processing.

The altimeter range net instrumental correction is the sum of the following instrumental corrections:

  • USO drift correction
  • internal path delay correction
  • Doppler correction updated at Level-2 processing
  • distance from antenna to centre of gravity
  • modelled instrumental errors correction
  • system bias.

The backscatter coefficient net instrumental correction is the sum of the following instrumental corrections:

  • AGC instrumental correction
  • internal calibration correction
  • modelled instrumental errors correction
  • system bias.

The significant wave height net instrumental correction is the sum of the following instrumental corrections:

  • modelled instrumental errors correction
  • system bias. 
 
 

PARAMETER

Net Instrumental Corrections Applied to Backscatter Coefficient

NETCDF NAME

net_instr_cor_sig0_ [x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band

DESCRIPTION

The backscatter coefficient net instrumental corrections is the sum of the following instrumental corrections: AGC instrumental correction (agc_cor_[x1]_[x2]), internal calibration correction (internal_cor_sig0_ku_[x1]_[x2]), modelled instrumental errors correction (mod_instr_cor_sig0_[x1]_[x2]), system bias. The atmospheric attenuation correction (atm_cor_sig0_01_[x2]) is not included.
The ALT_COR_BAC_01 algorithm computes the net instrumental corrections. AGC and internal calibration corrections are computed at Level-1 processing. ALT_COR_GEN_01 (Ku-band) and ALT_COR_GEN_02 (C-band) algorithms compute the modelled instrumental errors correction.

UNITS

10-2 dB

DATA SET AVAILABILITY

Reduced: none
Standard: 20 Hz Ku and 20 Hz C-band only
Enhanced: 20 Hz Ku and 20 Hz C-band only

OPERATING MODE AVAILABILITY

LRM and SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_COR_BAC_01 algorithm
20 Hz C-band: ALT_COR_BAC_01 algorithm

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

None

PARAMETER DETAILED DESCRIPTION

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

Table 1. Backscatter coefficient

 
 

PARAMETER

Net Instrumental Corrections Applied to Altimeter Range

NETCDF NAME

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

DESCRIPTION

The altimeter range net instrumental correction is the sum of the following instrumental corrections:
*USO drift correction (uso_cor_[x1]_[x2])
*internal path delay correction (int_path_cor_[x1]_[x2])
*Doppler correction updated at Level-2 processing (dop_cor_[x1]_[x2])
*distance antenna centre of gravity (cog_cor_[x1]_[x2])
*modelled instrumental errors correction (mod_instr_cor_range_[x1]_[x2])
*system bias.
The ALT_COR_RAN_03 algorithm computes the net instrumental corrections. USO drift and internal path delay corrections are computed at Level-1 processing. The ALT_COR_RAN_01 algorithm computes the Doppler correction. The PLA_MAN_CGM_01 algorithm computes the distance antenna-centre of gravity correction. The ALT_COR_GEN_01 (Ku-band) and ALT_COR_GEN_02 (C-band) algorithms compute the modelled instrumental errors correction.

UNITS

10-4 m

DATA SET AVAILABILITY

Reduced: none
Standard: 20 Hz Ku and 20 Hz C-band only
Enhanced: 20 Hz Ku and 20 Hz C-band only

OPERATING MODE AVAILABILITY

LRM and SAR

DATA ORIGIN

1 Hz Ku/C-bands: none
20 Hz Ku-band: ALT_COR_RAN_03 algorithm
20 Hz C-band: ALT_COR_RAN_03 algorithm

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

Doppler correction computed at Level-1 processing (dop_cor_l1b_[x1]_[x2]).
Doppler correction corrected due to line of sight variations arising over sloping surfaces dop_slope_cor_[x1]_[x2].

PARAMETER DETAILED DESCRIPTION

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

Table 2. Altimeter range

 

 

PARAMETER

Net Instrumental Corrections Applied to Significant Wave Height

NETCDF NAME

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

DESCRIPTION

The GEN_COR_RAN_01 algorithm computes the dry tropospheric correction at measurement altitude from meteorological models. A dry tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for dry tropospheric range delays of the radar pulse.
The RAD_PHY_GEN_02 algorithm computes from the microwave radiometer brightness temperatures, the Ku-band backscattering coefficient, the Sea Surface Temperature (SST) and the lapse rate (decreasing rate of the atmosphere temperature with altitude). Wet tropospheric correction must be added (negative value) to the instrument range to correct this range measurement for wet tropospheric range delays of the radar pulse.

UNITS

10-3 m

DATA SET AVAILABILITY

Reduced: 1 Hz (dry tropospheric) and none (wet tropospheric)
Standard: 1 Hz only
Enhanced: 1 Hz only

OPERATING MODE AVAILABILITY

LRM and SAR

DATA ORIGIN

1 Hz Ku/C-bands: GEN_COR_RAN_01 and RAD_PHY_GEN_02 algorithms
20 Hz Ku-band: none
20 Hz C-band: none

ADDITIONAL INFORMATION

None

PARAMETERS RELATED

Composite web tropospheric correction (comp_wet_tropo_cor_[x1]_[x2]).
It is based on both radiometer and model corrections over areas where the radiometer wet troposphere correction is missing or supposed as invalid due to the proximity of emerged lands: coastal areas and/or radiometer gaps in open oceans.
Dry tropospheric correction at zero altitude (mod_dry_tropo_cor_zero_altitude_ [x1]_[x2]).
Wet tropospheric correction at both zero and measurement altitude (mod_wet_tropo_cor_zero_altitude_ [x1]_[x2] and mod_wet_tropo_cor_meas_altitude_ [x1]_[x2]).
Wet tropospheric correction computed from the MWR 23.8 GHz and 36.5 GHz brightness temperatures (interpolated at the SRAL time-tag) and from the Ku-band sigma0.

PARAMETER DETAILED DESCRIPTION

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

Table 3. Significant wave heights