Skip to main content

Description

Provides L2 high resolution (HR) near real time (NRT; 3-hour latency) altimetry from the Poseidon-4 SAR altimeter on the Sentinel-6A Michael Freilich spacecraft. It contains Sea Surface Height (SSH), Sea Surface Height Anomalies (SSHA) and Significant Wave Height (SWH), along with 1 Hz Ku-band measurements processed from L1B altimetry including the range, orbital altitude, time, and water vapour. It also includes altimetry corrections, significant wave height and wind-speed from the AMR-C. This release is reduced to exclude the 20 Hz observations that are included in the standard product. The S6A NRT product is analogous to the Jason-3 OGDR product.

Product Summary

Platforms
Sentinel-6A
Instruments
Poseidon-4 Radar Altimeter ,
AMR-C ,
DORIS ,
GNSS RECEIVER
Spatial Extent

N: 66.15 S: -66.15 E: 180 W: -180

Geographic Region
GLOBAL ,
GLOBAL OCEAN
Coordinate System
CARTESIAN
Granule Spatial Representation
GEODETIC
Temporal Extent
2020-12-07
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C1968980549-POCLOUD
Data State
ACTIVE
Number of Files/Granules
264471
Processing Level
2
Science Keywords
Sea Surface Height ,
Significant Wave Height

Citation

Citation is critically important for dataset documentation and discovery. This dataset is openly shared, without restriction, in accordance with the EOSDIS Data Use and Citation Guidance.

Copy Citation

SENTINEL-6. (2021). Sentinel-6A MF/Jason-CS L2 P4 Altimeter High Resolution (HR) NRT Reduced Ocean Surface Topography [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/S6AP4-2HRNR Date Accessed: 2025-12-14

Documents

Variables

Variables are a set of physical properties whose values determine the characteristics or behavior of something. For example, temperature and pressure are variables of the atmosphere. Parameters and variables can be used interchangeably. Variable level attributes provide individual information for each variable.

The Name in this table is the variable name. Fill value indicates missing or undefined data points in a variable. Valid range is the range of values the variable can store. Scale factor is used to increase or decrease the size of an object and can be used to correct for distortion. For questions on a specific variable, please use the Earthdata Forum.

Name Description Units Data Type Fill Value Valid Range Scale Factor
/data_01/altitude Altitude of the satellite center of mass above the reference ellipsoid (WGS84). m int 2147483647 N/A 0.0001
/data_01/altitude_rate Instantaneous altitude rate of the satellite center of mass with respect to the reference ellipsoid (WGS84) m/s int 2147483647 N/A 0.0001
/data_01/altitude_rate_mean_sea_surface Instantaneous altitude rate of the satellite center of mass with respect to the mean sea surface m/s int 2147483647 N/A 0.0001
/data_01/angle_of_approach_to_coast Angle of approach to the closest coast. 0 is parallel to the coast with the land on the right. Positive values indicate the satellite is approaching the land. Negative values indicate the satellite is leaving the land. Values close to +/-180 degrees have the land on the left. degrees short 32767 N/A 0.01
/data_01/climato_use_flag Flag indicating whether the climatological values from meteorological model (backup solution) have been used or not to compute the atmospheric sigma0 correction (atm_cor_sig0). If not, radiometer data is used. N/A byte 127 N/A 1
/data_01/dac Combines the high frequency fluctuations of the sea surface topography due to high frequency air pressure and wind effect, and the low-frequency heights from inverted barometer effect [inv_bar_cor]. To be added as correction to range measurements for NTC/STC products. Not available for NRT products. m short 32767 N/A 0.0001
/data_01/delta_ellipsoid_tp_wgs84 Height difference between TOPEX ellipsoid and WGS84 ellipsoid. To convert heights in this product to be relative to the TOPEX ellipsoid, substract delta_ellipsoid_tp_wgs84. m int 2147483647 N/A 0.0001
/data_01/depth_or_elevation Ocean depth (bathymetry) is given as negative values; land elevation as positive values m short 32767 N/A 1
/data_01/distance_to_coast Distance to the closest coast m short 32767 N/A 100
/data_01/geoid Height of the geoid above the reference ellipsoid (WGS84) computed from the model with a correction to refer the value to the mean tide system i.e. includes the permanent tide (zero frequency). m int 2147483647 N/A 0.0001
/data_01/internal_tide Internal tide prediction from the HRET model. This only includes the so-called static harmonic components of the waves O1, K1, M2 and S2. m short 32767 N/A 0.0001
/data_01/inv_bar_cor Computed at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. To be added to range measurement to correct for the depression of the ocean surface caused by the local barometric pressure for NRT products (because the high frequency fluctuation [dac] is not available). Do not apply this correction for NTC/STC off line products (it is already included in the dynamic atmospheric correction [dac]) m short 32767 N/A 0.0001
/data_01/iono_cor_alt Ionospheric correction derived from the LR altimeter measurements and valid over ocean and lake surfaces only. A ionospheric correction must be added (negative value) to the instrument range measurement to correct it for the ionospheric delays of the radar pulse m short 32767 N/A 0.0001
/data_01/iono_cor_alt_filtered Smoothed ionospheric correction derived from the LR altimeter measurements and valid over ocean and lake surfaces only, using an iterative process based on median and Lanczos filtering. A ionospheric correction must be added (negative value) to the instrument range measurement to correct it for the ionospheric delays of the radar pulse m short 32767 N/A 0.0001
/data_01/ku/atm_cor_sig0 Two-way atmospheric attenuation to backscatter coefficient (sig0), based either on the radiometer (if available) or atmospheric model (otherwise). See climato_use_flag dB short 32767 N/A 0.01
/data_01/ku/index_first_20hz_measurement Level 2 record counter of the first 20 Hz elementary measurement used to derive the 1 Hz measurement 1 int 2147483647 N/A 1
/data_01/ku/iono_cor_gim GIM ionospheric correction, computed from GPS ionospheric data. A ionospheric correction must be added (negative value) to the instrument range measurement to correct it for the ionospheric delays of the radar pulse m short 32767 N/A 0.0001
/data_01/ku/model_instr_cor_range_ocean Modelled instrumental correction on the altimeter range, extracted from look-up tables. The correction is computed at 1-Hz then applied to 20-Hz estimates. m int 2147483647 N/A 0.0001
/data_01/ku/model_instr_cor_sig0_ocean Modelled instrumental correction on the backscatter coefficient, extracted from look-up tables. The correction is computed at 1-Hz then applied to 20-Hz estimates. dB short 32767 N/A 0.01
/data_01/ku/model_instr_cor_swh_ocean Modelled instrumental correction on the significant wave height, extracted from look-up tables. The correction is computed at 1-Hz then applied to 20-Hz estimates. m short 32767 N/A 0.001
/data_01/ku/net_instr_cor_range_ocean Sum of all Instrumental corrections on the altimeter range: USO drift (L1B range_cor_uso) + internal path delay (L1B range_cor_internal_delay_cal and range_cor_internal_delay_diff) + external path delay (L1B range_cor_external_group_delay) + distance antenna-COG (L1B range_cor_com) + Doppler correction (L2 range_cor_doppler) + modeled instrumental errors correction (L2 model_instr_cor_range_ocean) + system bias m int 2147483647 N/A 0.0001
/data_01/ku/net_instr_cor_sig0_ocean Sum of all Instrumental corrections on the backscatter coefficient: all calibrated instrument gains (L1B power_scaling_to_antenna) + modeled instrumental errors correction (L2 model_instr_cor_sig0_ocean) + system bias. The atmospheric attenuation correction is not included. dB short 32767 N/A 0.01
/data_01/ku/net_instr_cor_swh_ocean Sum of all Instrumental corrections on the significant wave height: modeled instrumental errors correction and system bias m short 32767 N/A 0.001
/data_01/ku/numtotal_20hz_measurement Total number of 20 Hz measurements in the 1 Hz time interval [time-0.5s, time+0.5s) 1 byte 127 N/A 1
/data_01/ku/ocean_geo_corrections Sum of meteorological and geophysical corrections to be applied to SSHA over ocean: altimeter ionospheric correction (iono_cor_alt_filtered) + model dry tropospheric correction at zero altitude (model_dry_tropo_cor_zero_altitude) + radiometer wet tropospheric correction (rad_wet_tropo) + sea state bias correction (sea_state_bias) + solid earth tide height (solid_earth_tide) + geocentric ocean tide height solution 2 (FES) (ocean_tide_sol2) + internal tide (internal_tide) + geocentric pole tide height (pole_tide) + dynamic atmospheric correction (dac for NTC/STC off line products, inv_bar_cor for NRT products) m int 2147483647 N/A 0.0001
/data_01/ku/rad_atm_cor_sig0_qual Quality flag for the radiometer two-way atmospheric correction to the operational band backscatter coefficient N/A byte 127 N/A 1
/data_01/ku/range_cor_doppler Doppler correction computed with respect to the mean sea surface / geoid. It is applied to the altimeter range m int 2147483647 N/A 0.0001
/data_01/ku/range_ocean Range computed from the ocean retracker. It includes all instrumental corrections from net_instr_cor_range_ocean m int 2147483647 N/A 0.0001
/data_01/ku/range_ocean_numval Number of valid 20 Hz measurements used to compute the 1 Hz measurement 1 byte 127 N/A 1
/data_01/ku/range_ocean_qual Validity flag indicating 'good' or 'bad' measurement of the ocean altimeter range N/A byte 127 N/A 1
/data_01/ku/range_ocean_rms Standard deviation of 20 Hz measurements. Compression of the 20 Hz measurements is preceded by a detection of outliers. Only valid 20 Hz values are used to compute this 1 Hz measurement. m short 32767 N/A 0.0001
/data_01/ku/sea_state_bias Sea state bias correction derived for: LR Ku-band, LR C-band and HR Ku-band. A sea state bias correction must be added (negative value) to the instrument range measurement to correct it for sea state bias delays of the radar pulse m short 32767 N/A 0.0001
/data_01/ku/sig0_ocean Backscatter coefficient computed from the ocean retracker. It includes all instrumental corrections from net_instr_cor_sig0_ocean and sig0_scaling_factor as well as the atmospheric attenuation correction. dB short 32767 N/A 0.01
/data_01/ku/sig0_ocean_numval Number of valid 20 Hz measurements used to compute the 1 Hz measurement 1 byte 127 N/A 1
/data_01/ku/sig0_ocean_qual Validity flag indicating 'good' or 'bad' ocean backscatter coefficient measurement N/A byte 127 N/A 1
/data_01/ku/sig0_ocean_rms Standard deviation of 20 Hz measurements. Compression of the 20 Hz measurements is preceded by a detection of outliers. Only valid 20 Hz values are used to compute this 1 Hz measurement. dB short 32767 N/A 0.01
/data_01/ku/ssha Sea surface height anomaly = altitude of satellite (altitude) - Ku band corrected ocean altimeter range (range_ocean) - geo corrections (ocean_geo_corrections) - mean sea surface (mean_sea_surface_sol1) m int 2147483647 N/A 0.0001
/data_01/ku/swh_ocean SWH computed from the ocean retracker. It includes all instrumental corrections from net_instr_cor_swh_ocean m short 32767 N/A 0.001
/data_01/ku/swh_ocean_numval Number of valid 20 Hz measurements used to compute the 1 Hz measurement 1 byte 127 N/A 1
/data_01/ku/swh_ocean_qual Validity flag indicating 'good' or 'bad' ocean significant wave height measurement N/A byte 127 N/A 1
/data_01/ku/swh_ocean_rms Standard deviation of 20 Hz measurements. Compression of the 20 Hz measurements is preceded by a detection of outliers. Only valid 20 Hz values are used to compute this 1 Hz measurement. m short 32767 N/A 0.001
/data_01/l2_record_counter This is the Level 2 record counter. Starting from 0 for each Level 2 product 1 int 2147483647 N/A 1
/data_01/latitude Latitude of measurement [-90, +90]. Positive latitude is North latitude, negative latitude is South latitude degrees_north int 2147483647 N/A 1.0E-6
/data_01/load_tide_sol1 This value has already been added to the corresponding ocean tide height value recorded in the product (ocean_tide_sol1) m short 32767 N/A 0.0001
/data_01/load_tide_sol2 This value contains the total load tide height (short-period and long-period) for the geocentric ocean tide (solution 2). To get only the pure ocean tide height (solution 2), do: ocean_tide_sol2 + ocean_tide_non_eq - load_tide_sol2. This value has already been added to the corresponding ocean tide height value recorded in the product (ocean_tide_sol2) m short 32767 N/A 0.0001
/data_01/longitude Longitude of measurement [0, 360). East longitude relative to Greenwich meridian degrees_east int 2147483647 N/A 1.0E-6
/data_01/manoeuvre_flag Manoeuvre flags contained within the NAVATT file N/A byte 127 N/A 1
/data_01/mean_dynamic_topography Mean dynamic topography above geoid m short 32767 N/A 0.0001
/data_01/mean_dynamic_topography_acc Mean dynamic topography (above geoid) accuracy m short 32767 N/A 0.0001
/data_01/mean_dynamic_topography_qual Interpolation flag (good or bad) for the mean dynamic topography N/A byte 127 N/A 1
You're viewing 50 of 111