Skip to main content

Description

The TOPEX/POSEIDON Geophysical Data Record (GDR) contains global coverage altimeter data. The objective of the TOPEX/POSEIDON mission, launched in August 1992, is to determine ocean topography with a sea surface height measurement precision of 3 cm and a sealevel measurement accuracy of 13 cm. The dataset contains measurements from two altimeters, a NASA dual frequency (Ku and C band) instrument similar to the Geosat altimeter, and a French space agency (CNES) instrument which is a proof-of-concept solid-state altimeter (Ku band). It also contains Sea Surface Height (SSH), significant wave height, ionospheric correction, tides and other geophysical corrections. It is emphasized that this product is considered research data because of the form and content of the data. The data consist entirely of files comprising headers and data records which contain over a hundred parameters for each second. It is swath data and there are no images. Analysis software is the responsibility of the user. Calculation of sea surface height anomalies from the altimeter range and environmental corrections is the responsibility of the user. The data are arranged in 10 day cycles that are separated into 254 passes, each about 56 minutes.

Version Description

Reprocessed Geophysical Data Record (GDR) Version F

Product Summary

Platforms
TOPEX/POSEIDON
Instruments
ALT (TOPEX) ,
TMR
Projects
TOPEX/POSEIDON
Spatial Extent

N: 66 S: -66 E: 180 W: -180

Coordinate System
GEODETIC
Granule Spatial Representation
GEODETIC
Temporal Extent
1992-10-13 to 2005-10-04
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C2599212091-POCLOUD
Data State
COMPLETE
Number of Files/Granules
117669
Processing Level
2
Published
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

TOPEX/POSEIDON. (2023). TOPEX/POSEIDON Geophysical Data Record Version F [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/TPXPS-GDRF1 Date Accessed: 2026-06-04

Documents

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 Description Units Data Type Fill Value Valid Range Scale Factor Offset
rad_tb_21_qual Quality flag for 21 GHz equalized brightness temperature. N/A byte 127 0 to 1 1 N/A
rad_tb_37 Equalized brightness temperature measurement at 37 GHz. Value is smoothed (along-track averaging has been performed). K int 2147483647 N/A 0.01 N/A
rad_tb_37_qual Quality flag for 37 GHz equalized brightness temperature. N/A byte 127 0 to 1 1 N/A
rad_tmb_18 Main beam brightness temperature measurement at 18 GHz. Value is unsmoothed (along-track averaging has not been performed). K int 2147483647 N/A 0.01 N/A
rad_tmb_18_qual Quality flag for 18 GHz main beam brightness temperature. N/A byte 127 0 to 1 1 N/A
rad_tmb_21 Main beam brightness temperature measurement at 21 GHz. Value is unsmoothed (along-track averaging has not been performed). K int 2147483647 N/A 0.01 N/A
rad_tmb_21_qual Quality flag for 21 GHz main beam brightness temperature. N/A byte 127 0 to 1 1 N/A
rad_tmb_37 Main beam brightness temperature measurement at 37 GHz. Value is unsmoothed (along-track averaging has not been performed). K int 2147483647 N/A 0.01 N/A
rad_tmb_37_qual Quality flag for 37 GHz main beam brightness temperature. N/A byte 127 0 to 1 1 N/A
rad_water_vapor Integrated water vapor content. kg/m^2 short 32767 0 to 32766 0.1 N/A
rad_water_vapor_qual Quality flag for radiometer water vapor content. N/A byte 127 0 to 1 1 N/A
rad_wet_tropo_cor Value must be added to altimeter range to correct for delay due to the wet troposphere. m short 32767 N/A 0.0001 N/A
rad_wet_tropo_cor_qual Quality flag for radiometer wet troposphere correction. N/A byte 127 0 to 1 1 N/A
rad_wind_speed Sea surface wind speed. m/s short 32767 0 to 32766 0.01 N/A
rad_wind_speed_qual Quality flag for radiometer wind speed. N/A byte 127 0 to 1 1 N/A
rain_flag The rain flag indicates where differences between Ku- and C-band backscatter coefficient indicate a likelihood of rain. A bias of 2.44 dB and 1.34 dB is added to sig0_ku_mle3 and sig0_c, respectively, before applying rain flag algorithm that is based upon Jason-2 MLE-3 data. N/A byte 127 N/A 1 N/A
range_20hz_c 20 Hz C-band MLE3 range. Net instrument range correction (net_instr_cor_range_c) has been added. m int 2147483647 N/A 0.0001 1300000
range_20hz_ku 20 Hz Ku-band MLE4 range. Net instrument range correction (net_instr_cor_range_ku) has been added. m int 2147483647 N/A 0.0001 1300000
range_20hz_ku_mle3 20 Hz Ku-band MLE3 range. Net instrument range correction (net_instr_cor_range_ku_mle3) has been added. m int 2147483647 N/A 0.0001 1300000
range_c 1 Hz C-band MLE3 range. Net instrument range correction (net_instr_cor_range_c) has been added. m int 2147483647 N/A 0.0001 1300000
range_cor_doppler_c Doppler correction to C-band range. Computed using orbit altitude rate (altitude_rate_mean_sea_surface). m int 2147483647 N/A 0.0001 N/A
range_cor_doppler_ku Doppler correction to Ku-band range. Computed using orbit altitude rate (altitude_rate_mean_sea_surface). m int 2147483647 N/A 0.0001 N/A
range_c_qual Quality flag for 1 Hz C-band MLE3 range. N/A byte 127 N/A 1 N/A
range_ku 1 Hz Ku-band MLE4 range. Net instrument correction (net_instr_cor_range_ku) has been added. m int 2147483647 N/A 0.0001 1300000
range_ku_mle3 1 Hz Ku-band MLE3 range. Net instrument correction (net_instr_cor_range_ku_mle3) has been added. m int 2147483647 N/A 0.0001 1300000
range_ku_mle3_qual Quality flag for 1 Hz Ku-band MLE3 range. N/A byte 127 N/A 1 N/A
range_ku_qual Quality flag for 1 Hz Ku-band MLE4 range. N/A byte 127 N/A 1 N/A
range_numval_c Number of 20 Hz C-band MLE3 range measurements (range_20hz_c) used to generate 1 Hz range. count byte 127 0 to 20 1 N/A
range_numval_ku Number of 20 Hz Ku-band MLE4 range measurements (range_20hz_ku) used to generate 1 Hz range. count byte 127 0 to 20 1 N/A
range_numval_ku_mle3 Number of 20 Hz Ku-band MLE3 range measurements (range_20hz_ku_mle3) used to generate 1 Hz range. count byte 127 0 to 20 1 N/A
range_rms_c RMS of 20 Hz C-band MLE3 range measurements. Only valid 20 Hz measurements are used to compute this element. m short 32767 N/A 0.0001 N/A
range_rms_ku RMS of 20 Hz Ku-band MLE4 range measurements. Only valid 20 Hz measurements are used to compute this element. m short 32767 N/A 0.0001 N/A
range_rms_ku_mle3 RMS of 20 Hz Ku-band MLE3 range measurements. Only valid 20 Hz measurements are used to compute this element. m short 32767 N/A 0.0001 N/A
range_used_20hz_c Map of valid points from range_20hz_c used to compute 1-Hz C-band MLE3 range, range_c. N/A byte 127 N/A 1 N/A
range_used_20hz_ku Map of valid points from range_20hz_ku used to compute 1-Hz Ku-band MLE4 range, range_ku. N/A byte 127 N/A 1 N/A
range_used_20hz_ku_mle3 Map of valid points from range_20hz_ku_mle3 used to compute 1-Hz Ku-band MLE3 range, range_ku_mle3. N/A byte 127 N/A 1 N/A
sea_state_bias_c Computed using wind speed (wind_speed_alt) and significant waveheight (swh_ku). A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. Applicable to C-band MLE3 ranges. m short 32767 N/A 0.0001 N/A
sea_state_bias_c_3d Sea state bias computed from 3D model with mean wave period (mean_wave_period_t02) as third input. A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. m short 32767 N/A 0.0001 N/A
sea_state_bias_ku Computed using wind speed (wind_speed_alt) and significant waveheight (swh_ku). A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. Applicable to Ku-band MLE4 ranges. m short 32767 N/A 0.0001 N/A
sea_state_bias_ku_3d Sea state bias computed from 3D model with mean wave period (mean_wave_period_t02) as third input. A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. m short 32767 N/A 0.0001 N/A
sea_state_bias_ku_mle3 Computed using wind speed (wind_speed_alt_mle3) and significant waveheight (swh_ku_mle3). A sea state bias correction must be added (negative value) to the instrument range to correct this range measurement for sea state delays of the radar pulse. This element should not be used over land. Applicable to Ku-band MLE3 ranges. m short 32767 N/A 0.0001 N/A
sig0_20hz_c Sum of C-band AGC, MLE-3 retracked C-band echoes amplitude correction (including C-band point target response correction, given in net_instr_cor_sig0_c), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_c), and constant C-band bias to align with the original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_20hz_ku Sum of Ku-band AGC, MLE-4 retracked Ku-band echoes amplitude correction (including Ku-band point target response correction, given in net_instr_cor_sig0_ku), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_ku), and constant Ku-band bias to align with original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_20hz_ku_mle3 Sum of Ku-band AGC, MLE-3 retracked Ku-band echoes amplitude correction (including Ku-band point target response correction, given in net_instr_cor_sig0_ku_mle3), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_ku), and constant Ku-band bias to align with original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_c Sum of C-band AGC, MLE-3 retracked C-band echoes amplitude correction (including C-band point target response correction, given in net_instr_cor_sig0_c), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_c), and constant C-band bias to align with the original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_c_qual Quality flag for 1 Hz C-band MLE3 backscatter coefficient. N/A byte 127 N/A 1 N/A
sig0_ku Sum of Ku-band AGC, MLE-4 retracked Ku-band echoes amplitude correction (including Ku-band point target response correction, given in net_instr_cor_sig0_ku), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_ku), and constant Ku-band bias to align with original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_ku_mle3 Sum of Ku-band AGC, MLE-3 retracked Ku-band echoes amplitude correction (including Ku-band point target response correction, given in net_instr_cor_sig0_ku_mle3), amplitude correction to account for satellite altitude, atmospheric attenuation (rad_atm_cor_sig0_ku), and constant Ku-band bias to align with original geophysical data record from side B. dB short 32767 N/A 0.01 N/A
sig0_ku_mle3_qual Quality flag for 1 Hz Ku-band MLE3 backscatter coefficient. N/A byte 127 N/A 1 N/A
sig0_ku_qual Quality flag for 1 Hz Ku-band MLE4 backscatter coefficient. N/A byte 127 N/A 1 N/A
You're viewing 150 of 189