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Description

Provides L1A high resolution (HR) short time critical (STC; 36-hour latency) altimetry intermediate outputs from the Poseidon-4 SAR altimeter on the Sentinel-6A Michael Freilich spacecraft, which are geo-located bursts of Ku-band echoes (at ~140 Hz) with all instrument calibrations applied and full rate complex waveforms for delay/Doppler or HR processing. The S6A STC product is analogous to the Jason-3 IGDR product.

Product Summary

Platforms
Sentinel-6A
Instruments
Poseidon-4 Radar Altimeter ,
AMR-C ,
DORIS ,
GNSS RECEIVER ,
GNSS-RO RECEIVER ,
Star Tracker
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
C1968979558-POCLOUD
Data State
ACTIVE
Number of Files/Granules
46013
Processing Level
1A
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 L1A P4 Altimeter High Resolution (HR) STC Intermediate Outputs with Instrument Calibrations [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/S6AP4-1AHST 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_140/ku/altimeter_clock This is the actual altimeter clock. The altimeter clock is based upon the USO clock. The nominal USO clock is 10MHz, while the nominal altimeter clock is 395 MHz. The actual USO clock is provided regularly as a drift information: based on the USO drift, the actual altimeter clock is computed, assuming a linear dependency Hz int -2147483647 N/A 1.0E-6
/data_140/ku/altimeter_power_drift This is a measure of the instrument power drift. It is mainly composed of a temperature-dependent harmonic variation along the orbit and a long-term decay. It is regularly measured from CAL1 impulse response with respect to a reference at the beginning of the mission. dB short -32767 N/A 0.01
/data_140/ku/altitude Altitude of the satellite center of mass above the reference ellipsoid (WGS-84). m int -2147483647 N/A 0.0001
/data_140/ku/altitude_rate Instantaneous altitude rate at the center of mass with respect to the reference ellipsoid (WGS-84) m/s int -2147483647 N/A 0.0001
/data_140/ku/attenuation_calibrated The ISPs contain the ATT command applied within a radar cycle. The actual ATT value, which slightly differs from the nominal one, is extracted from a look-up table. This variable provides the extracted an applied ATT value. dB short -32767 N/A 0.01
/data_140/ku/burst_counter The L1A record counter, starting from 0 for each product 1 int -2147483647 N/A 1
/data_140/ku/cai This is the Coarse Altitude Instruction (CAI) of the burst. The CAI can potentially change within each pulse in a burst. The L1A processor has the (configurable) capability of removing the CAI variation within the burst and replace it with the altitude rate estimated per orbit. The L1A product gives the CAI of the first Ku pulse within the burst. Note: T0 = 1/altimeter_clock_ku_ku T0*4 int -2147483647 N/A 1
/data_140/ku/cal1_power Max/total power of the instrument PTR from CAL1 measurement. It can be either the max or the total power following configuration specifications. The configuration choice is provided in the variable processing_configuration_flag. It has been corrected for: (a) calibrated attenuator correction, (b) variable digital gain, (c) residual CAL1 fixed digital gain. dB short -32767 N/A 0.01
/data_140/ku/fai This is the Fine Altitude Instruction (FAI) of the burst. The CAI can potentially change within each pulse in a burst. The L1A processor has the (configurable) capability of removing the FAI variation within the burst and replace it with the altitude rate estimated per orbit. The L1A product gives the FAI of the first Ku pulse within the burst. Note: T0 = 1/altimeter_clock_ku_ku T0/16/64 short -32767 N/A 1
/data_140/ku/i_samples The in-phase component of each L1A waveform. Each waveform is a fully calibrated, pulse limited complex echo. Echoes are phase coherent, which makes the SAR processing possible. Each pulse within the burst is: (a) given in the frequency domain, (b) power calibrated with 'power_scaling_to_antenna', (c) calibrated with CAL2 mask (when correction switched on). All pulses within a burst are: (d) aligned in range, with the altitude rate being removed by the altimeter or by the L1A Processor, (e) calibrated with CAL1 pulse-to-pulse amplitude and phase correction (when correction switched on). A final scaling, given in the variable 'iq_scale_factor', is applied in order to best fit the i-component into 1 byte. 1 byte -128 N/A 1
/data_140/ku/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_140/ku/longitude Longitude of measurement [0, 360). East longitude relative to Greenwich meridian degrees_east int -2147483647 N/A 1.0E-6
/data_140/ku/manoeuvre_flag Flags contained within the NAVATT file N/A byte -1 0 to 1 1
/data_140/ku/mcd_flags This variable provides information about errors collected along the processing. If set to one, then error has occurred. N/A short -1 0 to 1023 1
/data_140/ku/off_nadir_pitch_angle_pf Pitch angle with respect to the nadir pointing, measured by the STRs and post-processed by AOCS or by ground facility. The attribute 'add_offset' contains the estimated pitch bias. Note: nominal pointing is at satellite nadir (antenna perpendicular to ellipsoid) and corresponds to: pitch = 0 degrees int -2147483647 N/A 1.0E-7
/data_140/ku/off_nadir_roll_angle_pf Roll angle with respect to the nadir pointing, measured by the STRs and post-processed by Attitude and Orbit Control System(AOCS) or by ground facility. The attribute 'add_offset' contains the estimated roll bias. Note: nominal pointing is at satellite nadir (antenna perpendicular to ellipsoid) and corresponds to: roll = 0 degrees int -2147483647 N/A 1.0E-7
/data_140/ku/off_nadir_yaw_angle_pf Yaw angle with respect to the nadir pointing, measured by the STRs and post-processed by AOCS or by ground facility. The attribute 'add_offset' contains the estimated yaw bias. Note: nominal pointing is at satellite nadir (antenna perpendicular to ellipsoid) and corresponds to: yaw = 0 degrees int -2147483647 N/A 1.0E-7
/data_140/ku/orbit_type_flag Orbit type used for the product generation N/A byte -1 0 to 8 1
/data_140/ku/p4_instrument_configuration_flags It contains flags from ISPs related to P4 configuration and tracking. N/A byte -1 0 to 63 1
/data_140/ku/p4_mode_flag Flag containing the P4 mode identifier from the P4 Instrument Source Packets N/A byte -1 5 to 19 1
/data_140/ku/power_scaling_to_antenna The overall instrument gain, including: (a) attenuator_calibrated, (b) variable_digital_gain, (c) cal1_power, (d) g_scaling, (e) antenna_gain. This variable is applied to the L1A waveforms as power scaling once applied the L1A waveform power results in the ratio of received power vs transmitter power. dB short -32767 N/A 0.01
/data_140/ku/ptr_main_lobe_width Width of tha CAL1 waveform main lobe at -3dB m int -2147483647 N/A 1.0E-6
/data_140/ku/q_samples The quadrature component of each L1A waveform. Each waveform is a fully calibrated, pulse limited complex echo. Echoes are phase coherent, which makes the SAR processing possible. Each pulse within the burst is: (a) given in the frequency domain, (b) power calibrated with 'power_scaling_to_antenna', (c) calibrated with CAL2 mask (when correction switched on). All pulses within a burst are: (d) aligned in range, with the altitude rate being removed by the altimeter or by the L1A Processor, (e) calibrated with CAL1 pulse-to-pulse amplitude and phase correction (when correction switched on). A final scaling, given in the variable 'iq_scale_factor', is applied in order to best fit the q-component into 1 byte. 1 byte -128 N/A 1
/data_140/ku/range_cor_com It is the (1-way) distance in the z-component between the center of mass and the antenna reference point. m short -32767 N/A 0.0001
/data_140/ku/range_cor_doppler It is the (1-way) Doppler range correction due to satellite altitude rate m short -32767 N/A 0.0001
/data_140/ku/range_cor_internal_delay_att The 1-way range correction due to potential delays introduced by the attenuator. m short -32767 N/A 0.0001
/data_140/ku/range_cor_internal_delay_cal The internal path delay is periodically measured on flight. The delay introduced by the attenuator is provided in a separate variable within this product: 'range_cor_internal_delay_att' m short -32767 N/A 0.0001
/data_140/ku/range_cor_uso It is the USO Drift (1-way) range correction. The USO drift is applied directly to the clock. m short -32767 N/A 1.0E-5
/data_140/ku/snr_instr_estimation instrument estimated SNR from Telemetry, converted from engineering to physical unit. The SNR is estimated on tracking waveform (N-2) dB short -32767 N/A 0.01
/data_140/ku/surface_classification_flag 7-state surface type classification from MODIS and GlobCover N/A byte -1 0 to 6 1
/data_140/ku/telemetry_type_flag Telemetry packet type can be: null, LRM, RAW or RMC. The generation of L1A data is only done for HR data, therefore this variable can only be RAW or RMC for L1A. A L1A product may include a combination of RAW and RMC telemetry packets N/A byte -1 0 to 3 1
/data_140/ku/time Time refers to the instant the (theoretical) middle of the burst reaches the surface. [tai_utc_difference] is the difference between TAI and UTC reference time (seconds) for the first measurement of the data set. [leap_second] is the UTC time at which a leap second occurs in the data set, if any. After this UTC time, the [tai_utc_difference] is increased by 1 second seconds since 2000-01-01 00:00:00 double N/A N/A 1
/data_140/ku/time_tai Time refers to the instant the (theoretical) middle of the burst reaches the surface. [tai_utc_difference] is the difference between TAI and UTC reference time (seconds) for the first measurement of the data set. [leap_second] is the UTC time at which a leap second occurs in the data set, if any. After this UTC time, the [tai_utc_difference] is increased by 1 second seconds since 2000-01-01 00:00:00 double N/A N/A 1
/data_140/ku/tm_ambiguity_rank The Pulse Ambiguity Rank, taken from ISP, it is the number of pulses that are transmitted between the transmission and the reception of each pulse. It is constant by design 1 byte -128 N/A 1
/data_140/ku/tm_burst_num Each radar cycle contains 7 bursts: this is the burst counter within the radar cycle, from 1 to 7. NOTE: the L1A contains full radar cycles (groups of 7 bursts), which makes the dimension time multiple of 7. 1 byte -128 N/A 1
/data_140/ku/tm_cor2 The COR2 (altitude rate estimation) value, copied from ISP. The altimeter estimates one COR2 value per radar cycle. It is used in combination with the H0 to compute the CAI and FAI instructions. NOTE: T0 = 1/altimeter_clock_ku. T0/16/64 int -2147483647 N/A 1
/data_140/ku/tm_h0 The H0 (initial altitude instruction) value, copied from ISP. The altimeter provides one H0 value per radar cycle. It is used in combination with the COR2 to compute the CAI and FAI instructions. NOTE: T0 = 1/altimeter_clock_ku T0/4 int -2147483647 N/A 1
/data_140/ku/tm_nimp It is the number of pulses in one radar cycle taken from ISP. It is constant by design. 1 short -32767 N/A 1
/data_140/ku/tm_pri The Pulse Repetition Interval (PRI) is constant within all received pulses in a radar cycle, but it can change within consecutive radar cycles. It is provided in counters of (T0*8) by the altimeter, with T0 = 1/altimeter_clock_ku T0*4 short -32767 N/A 1
/data_140/ku/tm_source_sequence_counter This is the instrument record counter, copied from ISP. Each L1A record (dimension time) corresponds to 1 single Instrument Source Packet (HR RAW or HR RMC) 1 short -32767 N/A 1
/data_140/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 samples/2 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
/data_140/ku/tracker_range_calibrated_diode This is the 1-way distance from the satellite's center of mass to the middle of the range window derived from the DIODE+DEM (sample samples/2 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
/data_140/ku/variable_digital_gain Variable component of the gain produced by the digital processing unit dB short -32767 N/A 0.01
/data_140/ku/velocity_vector velocity vector at the center of mass in ITRF. The 3 components are given according to the 'space_3d' dimension: [1] x, [2] y, [3] z m/s int -2147483647 N/A 0.0001
/global/ku/antenna_gain Maximum antenna gain measured during instrument on ground characterization dB int -2147483647 N/A 1.0E-6
/global/ku/burst_phase_array_cor Burst Phase correction to be applied to the SAR Ku waveforms. It is obtained by averaging the Burst Phase along a configurable time window to reduce noise. rad int -2147483647 N/A 1.0E-6
/global/ku/burst_power_array_cor Burst power correction to be applied to the SAR Ku waveforms. It is obtained by averaging the Burst Phase along a configurable time window to reduce noise. dB int -2147483647 N/A 1.0E-6
/global/ku/cal2_correction CAL2 to be applied to the science data. It is obtained by averaging CAL2 along a configurable time window to reduce noise. 1 double N/A N/A 1
/global/ku/g_scaling Ratio of losses between the tracking and calibration intrument paths measured during instrument on ground characterization dB int -2147483647 N/A 1.0E-6
/global/ku/processing_configuration_flags This variable provides information about the L1 configuration switches active during the generation of this product: - uso_correction_activated: real USO clock correction applied to the data - cal1_correction_activated: CAL1 correction applied to the data - cal1_power_cor_max: CAL1 max power applied to the data. Otherwise, relative power applied. - cal2_correction_activated: CAL2 correction applied to the data. By design this should be not applied. - cal1_delay_cor_max. N/A byte -1 0 to 15 1
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