2.9.3 Level 2 processing
The auxiliary files to be used solely for the
RA2/MWR L2 processing are the following:
RA2_IOC_AX (Model ionospheric coefficients file)
This file contains the values of the polynomial
coefficients to be used in the
computation of the ionospheric correction
from the Bent model in the FDGDR processing.
There are two sets of coefficients
in every record: the first set of
coefficients is related to the critical
frequency and the second set to the
ratio of maximum usable frequency to the
critical frequency. This file has to be updated
typically once a year, since these
coefficients cover one year (one
record per month). This file, used only for NRT
processing, has not been updated yet.
In the off line processing, the ionospheric
correction is computed using daily
TEC maps coming from a different
(nonPDS formatted) auxiliary file, that can be
distributed only by the AVISO
catalogue entity.
RA2_MSS_AX (Mean Sea Surface)
This file contains the values of the mean sea
surface heights.
The MSS model used for the calculation of the sea
heights has been updated since
launch. Currently the CLS01 model is used.
The values are recorded on a regular grid with 2
minutes resolution in longitude and
latitude. This file is used in the
FDGDR, IGDR and GDR processing.
RA2_SOL_AX (Solar activity data file)
The data in this file, containing the 12 month
running average of the sunspot
numbers (solar activity indexes), is
used to compute the Bent model ionospheric
correction in NRT. The solar
activity indexes neededfor the OFL DORIS iono
correction are extracted from a different
external file (daily DORIS TEC maps).
Predicted solar activity data is used for NRT
while measured data is used for the
off line processing. The data in this
file is updated approx. once per month by a
dedicated IECF function.
RA2_POL_AX (Pole location position data file)
The data contained in this file is related to the
position of the pole, needed to
calculate the geocentric pole tide
height. The predicted pole data is used for NRT
processing, while the analysed data
is used for off line. The polar
motion data in this file is updated twice per
week by a dedicated IECF function.
RA2_PLA_AX (Platform data file)
This file contains the center of mass correction
(i.e. distance between antenna phase
center and the center of gravity of
the satellite) that is applied during the (NRT
and off line) level 2 processing to the
retracked altimeter range. The CoM 
antenna phase center distance is obtained
only from the projection on the zaxis, since
the xaxis component is negligible.
The file is updated every time there
is a consumption of satellite fuel due to a
manoeuvre. In NRT this is done
automatically by a dedicated IECF function.
In OFL, the CoMantenna data, coming also from
the FOS file, is stored in a
different aux. file.
RA2_SOI_AX (Ocean/Ice 2 configuration system file)
This file contains the processing parameters
(constants, thresholds, tables) for
the ocean/ice2 processing. These
parameters are used for NRT and off line
processing.The file has been updated
during Commissioning Phase in the frame of
the Level 2 algorithms verification group activities.
RA2_ICT_AX (Ice1/ sea ice Configuration system
file)
This file contains the processing parameters
(constants, thresholds, tables) for
the ice 1/sea ice processing. These
parameters are used for off line processing. The
file has been updated during
Commissioning Phase in the frame of the
Level 2 algorithms verification group activities
RA2_SSB_AX (Sea State Bias table file)
This file contains the values of the sea state
bias corrections for the Ku and S
bands, to be used for NRT and off
line processing. It is a double input table
depending on significant waveheight
and windspeed. The SWH coverage is
from 0 t o12 m, with a resolution of 0.25 m,
while the coverage for windspeed is
from 0 to 25 m/s with a resolution
of 0.25 m/s.
This file has been updated with a new one that is
based on the analysis of ten cycles
(cycle 25 to 35), using residuals
relative to a mean sea surface and applying the
non parametric estimation technique
RA2_DIP_AX (Modified Dip Map file)
This file contains the values of the modified
magnetic dip used in the computation
of the ionospheric correction from
the Bent model in the NRT processing. The values
are recorded on a regular grid with
2 degrees resolution in longitude
and latitude.
RA2_SET_AX (Cartwright Amplitudes file)
This file contains the values of Cartwright
amplitudes of the tidal constituents
harmonic coefficients and amplitudes
which are used for the computation of the solid
earth tide height in the NRT and off
line processing. Each record
contains six harmonic coefficients and the
amplitude for each potential term of
the second and third order.
No update of this file has been done during
Commissioning Phase.
RA2_OT1_AX (Coefficient map for the ocean tide
calculation  solution 1)
This file contains the values of the harmonic
coefficients for the height of the
principal tide waves of the GOT00.2
model. They are used for the computation of the
nonequilibrium ocean tide height in the NRT and
off line processing. The values are
recorded on a regular grid with 0.5
deg resolution in longitude and latitude. Eight
values of the A1 harmonic
coefficients and eight values of the A2
harmonic coefficients are recorded at each grid point.
RA2_OT2_AX (Coefficient map for the ocean tide
calculation  solution 2)
This file contains the values of the harmonic
coefficients for the height of the
principal tide waves of FES2002 model
for NRT and FES2004 for Offline processing. They
are used for the computation of the
nonequilibrium ocean tide height.
The values are recorded on a regular grid with
0.25 deg resolution for NRT, and
0.125 deg for OFL, in latitude and
longitude. Eight values of the A1 harmonic
coefficients and eight values of the
A2 harmonic coefficients are
recorded at each grid point.
RA2_TLG_AX (Coefficients map for the tidal
loading calculation  solution 1)
This file contains the values of the harmonic
coefficients for the height
principal tide waves of the GOT00.2 model.
They are used for the computation of the height
of the tidal loading effect in the
NRT and off line processing. The
values are recorded on a regular grid with 0.5
deg resolution in latitude and
longitude. Eight values of the B1
harmonic coefficients and eight values of the B2
harmonic coefficients are recorded
at each grid point.
RA2_TLD_AX (Coefficients map for the tidal
loading calculation  solution 2)
This file contains the values of the harmonic
coefficients for the height
principal tide waves computed from the
Francis and Mazzega's method, using the
solution 2 ocean tide model as
input. They are used for the computation of
the height of the tidal loading effect in the
NRT and off line processing. The
values are recorded on a regular grid
with 0.25 deg resolution in latitude and
longitude. Eight values of the B1
harmonic coefficients and eight values of
the B2 harmonic coefficients are recorded at
each grid point.
RA2_GEO_AX (Geoid height map)
This file contains the values of the geoid
heights, EGM96, during NRT and off
line processing. The values are recorded
on a regular grid with 0.25 deg resolution in
latitude and longitude.
AUX_DEM_AX (Ocean depth/land elevation map)
This ENVISAT wide file contains the values of the
ocean depth or land elevation,
MACESS model to be used for the NRT
processing. The values are recorded on a regular
grid with a 5 minutes resolution in
longitude and latitude for NRT and
with a 2 minutes resolution in longitude and
latitude for off line processing.
RA2_SL1_AX (RA2 slope model for Greenland data file)
This file contains the Greenland slope data to be
used in the ice1/sea ice processing
in off line processing. The
horizontal sampling resolution for this model is
2.5 Km. Each record contains the x
and y range slope components.
RA2_SL2_AX (RA2 slope model for Antarctica data
file)
This file contains the Antarctica slope data to
be used in the ice1/sea ice
processing in off line processing. The
horizontal sampling resolution for this model is
5 Km. Each record contains the x and
y range slope components.
MWR_LSF_AX (Land/Sea mask map)
This file contains the values of the land/sea
flag to be used for the RA2/MWR
level 2 NRT and off line processing. The
values are recorded on a regular grid with 2
minutes resolution in latitude and
longitude. Each value is recorded at
each grid point with the following meaning: 0
(oceans or semienclosed seas), 1
(enclosed seas or lakes), 2
(continental ice) or 3 (land).
RA2_MET_AX (Altitude of meteorological grid points)
This file contains the altitude of meteorological
grid points to be used during the
NRT processing. This file contains
only one record corresponding to the 360X181
grid points of the meteorological
grid found in the predicted
meteorological data.
AUX_ECF_AX and AUX_ECA_AX (ECMWF forecast and
analysis meteorological data files)
The predicted ECMWF data provided by ECMWF are
relative to the prediction of the
wet and dry tropospheric corrections,
and the 10 m wind vectors. They are used in the
NRT processing to compute the wet
and dry tropospheric range
corrections and the sea state bias correction to
be applied on the altimeter
measurement. The ECMWF parameters used
during the processing are the relative humidity,
geopotential, temperature, mean sea level
pressure, and U and V components of
the 10 m wind vector. The first three
parameters are profiles (relative to 21 altitude
levels of the meteorological model)
while the three latter ones are
surface parameters. All of them are provided on
a global regular grid, with 1 deg
resolution in longitude and latitude.
The meteo data coming from MeteoFrance, that
uses as input the analysis ECMWF
products, is used for the off line processing.
