Time Tags, Locations and Surface Type

  • Table 1: The distance to the coast is computed using the theoretical distance to the shore table of the Sentinel-3 mission.
  • Table 2: The orbit parameters (latitude and longitude) are computed, interpolating them at the time of the measurement.
  • Table 3: The time-tags of the measurements are the UTC seconds elapsed since 1 January 2000.
  • Table 4: The altitude rate of the altimeter measurement is used to determine the closest grid point to the shore table.
  • Table 5: The altitude is computed, interpolating it at the time of measurement.
  • Table 6: The surface type can be set to open ocean or semi-enclosed seas, enclosed seas or lakes, continental ice or land.
Table 1. Distance to the coast
PARAMETER Distance to the coast
NETCDF NAME dist_coast_[x1]_[x2] where:
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION Distance to the coast at time time_[x1]_[x2]. The distance to the coast is computed using the theoretical distance to the shore table of the Sentinel-3 mission. The altitude rate of the altimeter measurement is used to determine the closes grid point to the shore table.
UNITS m
DATA SET AVAILABILITY Reduced: 1 Hz only
Standard: 20 Hz Ku-band only
Enhanced: 20 Hz Ku-band only
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: GEN_ENV_DIS_01
20 Hz Ku-band: GEN_ENV_DIS_01
20 Hz C-band: none
ADDITIONAL INFORMATION None
PARAMETERS RELATED None
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 2. Latitude and Longitude
PARAMETER Latitude and Longitude
NETCDF NAME lat_[x1]_[x2]
lon_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION Latitude position at time time_[x1]_[x2].
Longitude position at time time_[x1]_[x2].
This algorithm uses an ESA library called CFI Software Explorer Orbit that computes both latitude and longitude, interpolating them from the satellite orbit state vector positions file at the precise time of the input measurement.
UNITS 10-6 degrees
DATA SET AVAILABILITY Reduced: 1 Hz only
Standard: all
Enhanced: all
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: Orbit CFI algorithm
20 Hz Ku-band: Orbit CFI algorithm
20 Hz C-band: Orbit CFI algorithm
ADDITIONAL INFORMATION Positive latitude is North latitude, negative latitude is South latitude.
East longitude relative to the Greenwich meridian.
PARAMETERS RELATED None
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 3. Time tags
PARAMETER Time-Tag
NETCDF NAME time_[x1]_[x2] where:
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION

Time of the occurrence of the measurement. UTC time elapsed since January 1st 2000. This time has been:

  • converted from on-board time counters
  • referenced to the overflown surface
  • referenced to the middle of the tracking cycle
UNITS seconds
DATA SET AVAILABILITY seconds
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: ALT_MAN_TIM_01 algorithm
20 Hz Ku-band: SRAL Level-1B product
20 Hz C-band: SRAL Level-1B product
ADDITIONAL INFORMATION None
PARAMETERS RELATED
  1. UTC days and seconds in the day elapsed since January 1st 2000 (UTC_day_[x1]_[x2] and UTC_sec_[x1]_[x2])
  2. Time-tag of the 1 Hz measurement (UTC_time_1hz_[x1]_[x2])
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 4. Orbit
PARAMETER Orbital Altitude Rate
NETCDF NAME orb_alt_rate_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION The satellite altitude rate is the height rate of the satellite at time time_[x1]_[x2].
The reference surface for the orbital altitude rate is the combined mean sea surface/geoid surface.
The orbital altitude rate is used to compute the Doppler correction on the altimeter range. This algorithm uses an ESA library called CFI Software Explorer Orbit that computes altitude rate interpolating it from the satellite orbit state vector positions file at the precise time of the input measurement.
UNITS 10-2 m/s
DATA SET AVAILABILITY Reduced: none
Standard: all
Enhanced: all
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: Orbit CFI algorithm
20 Hz Ku-band: Orbit CFI algorithm
20 Hz C-band: Orbit CFI algorithm
ADDITIONAL INFORMATION None
PARAMETERS RELATED None
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 5. Altitude
PARAMETER Orbit altitude
NETCDF NAME alt_[x1]_[x2]
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION The satellite altitude is the height of the satellite above the reference ellipsoid at time time_[x1]_[x2]. This algorithm uses an ESA library called CFI Software Explorer Orbit that computes altitude interpolating them from the satellite orbit state vector positions file at the precise time of the input measurement.
UNITS 10-4 m. An offset of 700,000m to be added to the value read from the netCDF file.
DATA SET AVAILABILITY Reduced: 1 Hz only
Standard: all
Enhanced: all
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands:Orbit CFI algorithm
20 Hz Ku-band: Orbit CFI algorithm
20 Hz C-band: Orbit CFI algorithm
ADDITIONAL INFORMATION For further information about orbit CFI, CFI Website
PARAMETERS RELATED None
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services

 

Table 6. Surface type
PARAMETER Surface types
NETCDF NAME surf_type_[x1]_[x2] where:
[x1]: 1 Hz or 20 Hz data rates
[x2]: Ku-band or C-band
DESCRIPTION Surface type at time time_[x1]_[x2]. Surface type is computed using the land/sea mask of the Sentinel-3 mission. The latitude and longitude of the altimeter measurement are used to determine the nearest grid point in the land/sea mask file. The surface type is set to the surface type reported for this nearest grid point.
UNITS The possible surface types are:
open ocean or semi-enclosed seas (0b)
enclosed seas or lakes (1b)
continental ice (2b)
land (3b)
DATA SET AVAILABILITY Reduced: 1 Hz only
Standard: 1 Hz only
Enhanced: 1 Hz only
OPERATING MODE AVAILABILITY LRM and SAR
DATA ORIGIN 1 Hz Ku/C-bands: SRAL Level-1B product
20 Hz-Ku-band: SRAL Level-1B product
20 Hz C-band: SRAL Level-1B product
ADDITIONAL INFORMATION None
PARAMETERS RELATED Radiometer-derived surface type (rad_surf_type[x1]_[x2]): The algorithm that computes the radiometer-derived surface type is RAD_MAN_INT_03. This algorithm averages/interpolates the radiometer data at 7 Hz to the 1 Hz altimeter time tags.
PARAMETER DETAILED DESCRIPTION ESA's Global Land and Ocean Mission for GMES Operational Services