Source/Sensor: CNES Solid State Altimeter 

Coverage: January 15, 2002 (Cycle 1) - current data, global oceans, -66 deg to +66 deg latitude 

Abstract: The Jason-1 Along Track Gridded Sea Surface Height Anomaly (J1ATG_SSHA_V2) product is generated from the Jason-1 Sea Surface Height Anomaly (J1SSHA) product, Reference 1. There are 127 orbits per cycle and each orbit has a period of 112 minutes. The ground track of the orbits are about 315 km apart at the equator. Along track measurements are approximately 1 sec and 6 km apart. 

Each orbit is composed of 2 passes, one ascending from -66 deg to +66 deg latitude and the other descending from +66 deg to - 66 deg. The passes are organized this way to avoid data boundaries in the middle of the oceans. All odd-numbered passes are ascending and all even-numbered passes are descending. There are a maximum of 254 passes per cycle. 

It is organized as 1 file per cycle and contains a header record followed by 254 records of SSHA parameters. Each file record represents a pass file of the cycle and the SSHA parameters correspond to measurement values taken from the Jason-1 Sea Surface Height Anomaly (J1SSHA) product. The times and SSHA values from the J1SSHA products are gridded along the satellite ground track. Each SSHA value in the ATG was derived using a set of cubic spline coefficients with reference latitudes and longitudes as the independent variable. Thus, these interpreted SSHA values are tied to a fixed set of reference latitudes and longitudes. Also, before interpretation, the ionospheric correction used in the SSHA was replaced by a smoothed value by averaging 8 iono values before and after the given iono. The 8 iono values correspond to approximately 50 km along track on either side of the given location of the iono data point. 

It is swath data and no images are provided with this product. 

The Sea Surface Height Anomaly, the only parameter in this product, represents the difference between the best estimate of the sea surface height and a mean sea surface. The sea surface height used was corrected for atmospheric effects (ionosphere, wet and dry troposphere), effects due to surface conditions (electromagnetic bias), and other contributions (ocean tides, pole tide, and inverse barometer). 

Refer to Reference 2 for a description of this product. 

This product is compatible with the TOPEX/POSEIDON Along Track Gridded Sea Surface Height Anomaly (TPATG_SSHA_V2) product, also available from PO.DAAC. These two products, the TPATG_SSHA_V2 and J1ATG_SSHA_V2, can be read by the same read software. 

Data Set Volume: The data on the PO.DAAC ftp site are gzipped and the volume is approximately 643 KBytes per cycle. Unzipped volume is approximately 1.5 MBytes per cycle. 

Anonymous FTP Site: podaac.jpl.nasa.gov Directory: pub/sea_surface_height/jason/j1_atg 





Smallest order: 1 pass file via ftp 

Std. product: ftp 

Formats: Unix byte order, binary data with ASCII header.




Smallest order: 1 pass file 

Std. product: ftp 

Formats: Unix byte order, binary data with ASCII header on passfiles.