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Description

The Sensory Geophysical Data Record (SGDR) files contain full accuracy altimeter data, with a high precision orbit (accuracy ~1.5 cm). The instruments on Jason-1 make direct observations of the following quantities: altimeter range, significant wave height, ocean radar backscatter cross-section (a measure of wind speed), ionospheric electron content (derived by a simple formula), tropospheric water content, mean sea surface, and position relative to the GPS satellite constellation. The SGDR contain all relevant corrections needed to calculate the sea surface height. It also contains the 20Hz waveforms that are required for retracking. The SGDR is an expert level product, if you do not require the waveforms then the GDR/GPN or GPR will be more suited for your needs.

Product Summary

Platforms
JASON-1
Instruments
TRSR ,
DORIS ,
JASON-1 Microwave Radiometer ,
POSEIDON-2
Spatial Extent

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

Location
GLOBAL
Coordinate System
CARTESIAN
Granule Spatial Representation
CARTESIAN
Temporal Extent
2002-01-14 to 2012-03-03
Data Partner
Physical Oceanography Distributed Active Archive Center, Jet Propulsion Laboratory, NASA (NASA/JPL/PODAAC)
Concept ID
C1940472420-POCLOUD
Data State
COMPLETE
Number of Files/Granules
92126
Processing Level
2
Published
Updated
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

JASON-1. (2015). Jason-1 SGDR version E NetCDF [Data set]. NASA Physical Oceanography Distributed Active Archive Center. https://doi.org/10.5067/J1GPS-NC00E Date Accessed: 2026-05-12

Documents

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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 Description Units Data Type Fill Value Valid Range Scale Factor Offset
ta_340 34.0 GHz antenna temperature K short 32767 N/A 0.01 N/A
tb_187 Brightness temperatures are unsmoothed (along-track averaging has not been performed on the brightness temperatures) K short 32767 N/A 0.01 N/A
tb_187_smoothed Brightness temperatures are along-track averaged K short 32767 N/A 0.01 N/A
tb_238 Brightness temperatures are unsmoothed (along-track averaging has not been performed on the brightness temperatures) K short 32767 N/A 0.01 N/A
tb_238_smoothed Brightness temperatures are along-track averaged K short 32767 N/A 0.01 N/A
tb_340 Brightness temperatures are unsmoothed (along-track averaging has not been performed on the brightness temperatures) K short 32767 N/A 0.01 N/A
tb_340_smoothed Brightness temperatures are along-track averaged K short 32767 N/A 0.01 N/A
time [tai_utc_difference] is the difference between TAI - UTC (i.e., leap 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. time variable is corrected from datation bias. See Jason-1 User handbook. seconds since 2000-01-01 00:00:00.0 double N/A N/A 1 N/A
time_20hz [tai_utc_difference] is the difference between TAI - UTC (i.e., leap 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. time_20hz variable is corrected from datation bias. See Jason-1 User handbook. seconds since 2000-01-01 00:00:00.0 double 1.844674407371E+19 N/A 1 N/A
tracker_20hz_c C-band operating tracker. This includes the Distance antenna-COG (cog_corr), USO drift correction (uso_corr) and internal path correction (internal_path_delay_corr_c). But not the Doppler correction (doppler_corr_c), modeled instrumental errors correction (modeled_instr_corr_range_c) and system bias m float 1.0E+30 N/A 1 N/A
tracker_20hz_ku Ku-band operating tracker (\'Diode+DEM\' or \'Median\' or \'Split-Gate\' tracker). This includes the Distance antenna-COG (cog_corr), USO drift correction (uso_corr) and internal path correction (internal_path_delay_corr_ku). But not the Doppler correction (doppler_corr_ku), modeled instrumental errors correction (modeled_instr_corr_range_ku) and system bias m float 1.0E+30 N/A 1 N/A
uso_corr Correction of the USO frequency drift on the altimeter range m int 2147483647 N/A 0.0001 N/A
waveforms_20hz_c Waveforms are not corrected for the Low Pass Filter effects count short 32767 N/A 1 N/A
waveforms_20hz_ku Waveforms are not corrected for the Low Pass Filter effects count short 32767 N/A 1 N/A
wind_speed_alt Should not be used over land. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wind_speed_model_u Computed at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wind_speed_model_u_era Courtesy of ECMWF. Computed at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wind_speed_model_v Computed at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wind_speed_model_v_era Courtesy of ECMWF. Computed at the altimeter time-tag from the interpolation of 2 meteorological fields that surround the altimeter time-tag. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wind_speed_rad Should not be used over land. See Jason-1 User Handbook m/s short 32767 N/A 0.01 N/A
wvf_ind Set to be compliant with the CF-1.1 convention count byte N/A N/A 1 N/A
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