N: 66.15 S: -66.15 E: 180 W: -180
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 and 20 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 standard product release provides the geophysical parameters at both 1 and 20 Hz. The S6A NRT product is analogous to the Jason-3 OGDR product.
Product Summary
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Variables
The table below lists the variables contained within a single granule for this dataset. Variables often contain observed or derived geophysical measurements collected from a variety of sources, including remote sensing instruments on satellite and airborne platforms, field campaigns, in situ measurements, and model outputs. The terms variable, parameter, scientific data set, layer, and band have been used across NASA’s Earth science disciplines; however, variable is the designated nomenclature in NASA’s Common Metadata Repository (CMR). Variable metadata attributes such as Name, Description, Units, Data Type, Fill Value, Valid Range, and Scale Factor allow users to efficiently process and analyze the data. The full range of attributes may not be applicable to all variables. Additional information on variable attributes is typically available in the data, user guide, and/or other product documentation.
For questions on a specific variable, please use the Earthdata Forum.
| Name Sort descending | Description | Units | Data Type | Fill Value | Valid Range | Scale Factor | Offset |
|---|---|---|---|---|---|---|---|
| /data_20/ku/ocean_tide_sol1 | Solution 1 corresponds to GOT model. Includes the corresponding loading tide (load_tide_sol1) and equilibrium long-period ocean tide height (ocean_tide_eq). The permanent tide (zero frequency) is not included in this parameter because it is included in the geoid and mean sea surface (geoid, mean_sea_surface_sol1, mean_sea_surface_sol2) | m | short | 32767 | N/A | 0.0001 | N/A |
| /data_20/ku/ocean_tide_sol1_qual | Interpolation flag for the ocean tide solution 1 (GOT). Number of interpolated points (4 for good) | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/ocean_tide_sol2 | Solution 2 corresponds to FES model. Includes the corresponding loading tide (load_tide_sol2) and equilibrium long-period ocean tide height (ocean_tide_eq). The permanent tide (zero frequency) is not included in this parameter because it is included in the geoid and mean sea surface (geoid, mean_sea_surface_sol1, mean_sea_surface_sol2) | m | short | 32767 | N/A | 0.0001 | N/A |
| /data_20/ku/ocean_tide_sol2_qual | Interpolation flag for the ocean tide solution 2 (FES). Number of interpolated points (4 for good) | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/p4_mode_flag | Flag containing the mode identifier from the P4 instrument source packets | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/peakiness | Peakiness of the waveform (Laxon's derivation). It is the ratio of the maximum power in the waveform and the average of the waveform power to the right hand-side of the expected waveform leading edge location | 1 | short | 32767 | N/A | 0.01 | N/A |
| /data_20/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 | N/A |
| /data_20/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 | 1300000 |
| /data_20/ku/range_ocean_qual | Flag indicating the use or not of the 20 Hz ocean altimeter range estimate in the computation of the 1 Hz estimate (map of compression) | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/range_ocog | Corrected OCOG altimeter range. This includes the instrumental corrections in tracker_range_calibrated. | m | int | 2147483647 | N/A | 0.0001 | 1300000 |
| /data_20/ku/range_oversampling_factor | The instrument samples the waveforms with a 395 MHz clock, providing a nominal_sampling = c / 395e6 / 2 = ~0.379m (with c=speed of light). In addition, the ground processor can apply an oversampling factor, providing a waveform_sampling = nominal_sampling / range_oversampling_factor. Note that the altimeter range resolution is fixed and given by the chirp bandwidth of 320 MHz: c / 320e6 / 2 = ~0.468m | 1 | byte | 127 | N/A | 1 | N/A |
| /data_20/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 | N/A |
| /data_20/ku/sig0_ocean_qual | Flag indicating the use or not of the 20 Hz estimate of the off-nadir angle, derived from the waveform ocean retracking, in the computation of the 1 Hz estimate (map of compression) | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/sig0_ocog | Backscatter coefficient computed from OCOG retracking. It includes all calibrated instrument gains from L1B power_scaling_to_antenna plus geometry and antenna gain from sig0_scaling_factor | dB | short | 32767 | N/A | 0.01 | N/A |
| /data_20/ku/sig0_scaling_factor | The scaling factor in order to retrieve sigma-0 from L1B waveform. It includes the antenna gains and all the geometry factors satellite-surface, according to the radar equation. It is not applied to the L1B waveforms. | dB | short | 32767 | N/A | 0.01 | N/A |
| /data_20/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 | N/A |
| /data_20/ku/surface_classification_flag | 7-state surface type classification from MODIS and GlobCover | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/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 | N/A |
| /data_20/ku/swh_ocean_qual | Flag indicating the use or not of the 20 Hz estimate of the ocean significant waveheight in the computation of the 1 Hz estimate (map of compression) | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/telemetry_type_flag | Telemetry packet type: LRM, RAW or RMC. A Level 2 product can include combinations of SAR RAW and RMC telemetry packets. | N/A | byte | 127 | N/A | 1 | N/A |
| /data_20/ku/time | It contains the seconds since 1 Jan 2000 00:00:00. Time is in UTC. Time refers to the instant the L1B waveform (which is a combination of echoes for both LR and HR) touches the surface. Whenever a leap second occurs, the attribute leap_second will be set to the appropriate value | seconds since 2000-01-01 00:00:00.0 | double | N/A | N/A | 1 | N/A |
| /data_20/ku/time_tai | Time of measurement in seconds in the TAI time scale since 1 Jan 2000 00:00:00 TAI. This time scale contains no leap seconds. The difference (in seconds) with time in UTC is given by the attribute [time:tai_utc_difference]. | seconds since 2000-01-01 00:00:00.0 | double | N/A | N/A | 1 | N/A |
| /data_20/ku/tracker_range_calibrated | This is the 1-way distance from the satellite's center of mass to the middle of the range window (sample 128, counting from 0). It includes the following range calibrations: (a) range_cor_internal_delay_cal, (b) range_cor_internal_delay_diff, (c) range_cor_external_group_delay, (d) range_cor_com. Note: the actual altimeter clock (variable 'altimeter_clock_ku') has been used to compute the altimeter range | m | int | 2147483647 | N/A | 0.0001 | 1300000 |
| /data_20/ku/variable_digital_gain | Variable component of the gain produced by the digital processing unit | dB | short | 32767 | N/A | 0.01 | N/A |
| /data_20/ku/waveform_qual | This flag indicates the quality of the waveform. If not OK, it is not used in further processing. | N/A | byte | 127 | N/A | 1 | N/A |