Source/Sensor: CNES POSEIDON solid-state altimeter

Coverage: January 15, 2002 (Cycle 1) - currently in process, global oceans, -66 deg to +66 deg latitude

Abstract: The Jason-1 Sea Surface Height Anomaly product is generated from the Jason-1 Geophysical Data Record (J1 GDR). 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.

It is organized as 10 day repeat cycles containing a maximum of 254 pass files per cycle, the same as the J1 GDR. There is a one to one correspondence between the SSHA and J1 GDR cycles and pass files. Each pass file of the SSHA consists of header records followed by data records containing 11 parameters: time of record in days and milliseconds, latitude, longitude, sea surface height anomaly, significant wave height, inverse barometer, sigma0, total electron content of the atmosphere, ocean depth, and mean sea surface. It is swath data and no images are provided with this product.

The Sea Surface Height Anomaly, the principal 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). Because some users may want to provide their own values for the mean sea surface and inverse barometer effect, the values used in calculating this SSHA are included in the data product.

Calculation of the sea surface height anomaly is derived from Jason-1 GDR parameters using a set of editing criteria which are described in Reference 1.

This product is compatible with the TOPEX/POSEIDON Sea Surface Height Anomaly (TPSSHA) product (Reference 2), also available from PO.DAAC. These two products, the TPSSHA and J1SSHA, have the same number of header records, data records, and data sizes. They can both 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 12 MBytes per cycle. Unzipped volume is approximately 16 MBytes per cycle. Each passfile is approximately 62 Kbytes unzipped.

Anonymous FTP Site: podaac.jpl.nasa.gov

Directory: pub/sea_surface_height/jason/j1_ssha

Smallest order: 1 pass file

Std. product: ftp

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