Mission
Jason-1 is an altimetric mission that measures significant wave height, mean sea surface, sigma0 (which can be converted to wind speed), and all the parameters needed to calculate sea surface height anomalies. It launched December 7, 2001 and began collecting data January 15, 2002 ( cycle 1). As of December 2007, Jason-1 has an orbit accuracy of ~2.5 cm and measures sea surface height with an accuracy of ~3.9 cm. A list of the Jason-1 cycles by date is available at: http://podaac.jpl.nasa.gov/DATA_CATALOG/j1_cyclelist.txt

Announcements

Jason-1 was returned to nominal science operations on Friday, 25 September 2009, at around 17h30 UTC.
Thanks to the close cooperation and intensive efforts by the CNES and JPL Operations Teams, the anomaly that caused the safe hold is now well understood.  Science Cycles 283 and 284 were impacted by this safe hold.  Nominal science operations resumed prior to the start of Science Cycle 285, which began at 07:18 UTC on 26 September 2009.  There will be no permanent impact on the Project's ability to meet all Level-1 science requirements as a result of this safe hold.

If you have any questions please direct them to podaac@podaac.jpl.nasa.gov

Error in GDR-C Cycle 32
GDR-C Cycle 32 has been temporarily removed due to an error found, which effected the dry troposphere, inverse barometer and other parameters required in calculating Sea Surface Height and Anomalies. If you have already downloaded cycle 32 please delete it. Cycle 32 will be reprocessed and once completed it will be posted back in this directory. Sorry for the inconvenience.

If you have any questions please direct them to podaac@podaac.jpl.nasa.govUpdated JMR Replacement Product:
An update to the October 2008 release of the Jason Microwave Radiometer (JMR) replacement product is now available at:
ftp://podaac.jpl.nasa.gov/sea_surface_height/jason/jmr_replacement

The JMR data provided on the Jason-1 Version C GDRs use JMR calibration coefficients that were derived from repeat cycles 1-227 of the Jason-1 mission. The Version C GDRs do not account for any JMR calibration shifts that may have occurred after cycle 227, e.g. after the cycle 242 safehold event. A preliminary recalibration of the JMR data during cycles 228-259 has been performed by Shannon Brown at JPL, and is provided in this update to the JMR replacement product. This update is primarily aimed towards improving cross-calibration of the Jason-1 and OSTM/Jason-2 missions.

The JMR replacement product currently available at PODAAC should be used as
follows:

1) For cycles 1-212, the product replaces JMR parameters on the Version B Jason-1 GDRs to reflect measurements provided on the Version C Jason-1 GDRs. There are no changes to the October 2008 release of the JMR replacement product for these cycles.

2) For cycles 213-227, no replacement product is provided since the Version C GDRs for these cycles were already (or soon to be) available at the time of the October 2008 release.

3) For cycles 228-259, the product replaces JMR parameters on the Version C GDRs to reflect a recent preliminary recalibration of the JMR performed by Shannon Brown at JPL. This update is aimed towards improving the JMR calibration during the remainder of the time where Jason-1 was on its original ground track, but especially during the phase when Jason-1 and OSTM/Jason-2 were flying on the same ground track.

Please refer questions or comments to Shailen Desai.

Temporary fix until entire Jason-1 mission is reprocessed to version C:
Users are advised to note the following primary differences between the version B and version C Jason-1 GDRs.
1) Use of ITRF2005 reference frame and time variable gravity in precise orbits.
2) In improved sea state bias model that is consistent with the MLE4 retracked altimeter data.
3) Updated altimeter instrument corrections.
4) Recalibrated JMR measurements using data from cycles 1-227. Details on the impact of these changes are provided in version 4.1 of the Jason-1 user handbook
(ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr_c/doc/Handbook_Jason_v4-1.pdf).

Given the schedule for reprocessing version C GDRs, the OST science team is providing users with an interim means to correct the version B Jason-1 GDRs for these primary changes, as follows:
1) GDR-C precise orbit ephemerids are provided as sp1 files on the following ftp server.
ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c_aux_files/poe
2) The sea state bias model used on the version C GDRs is provided on the following ftp server:
ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c_aux_files
3) Tables of the altimeter instrument corrections used on the version C GDRs are provides on the following ftp server: ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c_aux_files
4) A JMR replacement product that adopts the JMR calibration parameters used to generate the version C GDRs is available on the following ftp server: ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/jmr_replacement

Spatial resolution
Jason-1 surveys from 66.15° to -66.15°. The along track resolution is 5.8 km. A table showing the equator crossing for each pass is available at: ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr_c/doc/Handbook_Jason_v4-1.pdf

Picot, N., K. Case, S. Desai and P. Vincent, 2006, “AVISO and PODAAC User Handbook.
IGDR and GDR Jason Products”, SMM-MU-M5-OP-13184-CN (AVISO), JPL D-21352 (PODAAC). ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr_c/doc/Handbook_Jason_v4-1.pdf

Berwin, Robert. W, "PO.DAAC Jason-1 Sea Surface Height Anomaly Product User's Reference Manual"
ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/j1_ssha/doc/j1ssha_manual_v2.html

Berwin, Robert. W. "PO.DAAC Along-Track Gridded Sea Surface Height Anomaly for TOPEX/Poseidon and Jason-1, User's Reference Manual" ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/j1_atg/doc/along_track_gridded_manual_v2.html

The satellite also performed a series of maneuvers to ensure orbital accuracy.  A list of maneuvers is available at http://podaac.jpl.nasa.gov/DATA_CATALOG /j1_maneuver.txt

Various conditions, such as heavy rain or ice, may affect input titleimetric measurements.  Known environmental and geophysical problems are flagged to allow researchers to easily evaluate these measurements.  A description of the Jason-1 flags is available in the Jason-1 IGDR and GDR ftp://podaac.jpl.nasa.gov/pub/sea_surface_height/jason/gdr_c/doc/Handbook_Jason_v4-1.pdf

Frequently Asked Questions
http://podaac.jpl.nasa.gov/FAQ/index.html#altimetry

Q: What are the differences between Jason-1 GDR-b and GDR-c?
A: The GDR-c has a different file naming convention and has improved corrections.
- The file extension .NASA and .CNES are not added to the GDR-c file names
- There are two new parameters, pseudo_datation_bias_corr_ku and mdt
- Better orbit, sea stat bias, ionospheric range, inverse barometer, and tidal corrections
- Improved rain and ice flags
For more details please refer to the handbook.

Citations/References
Menard, Y. and B. Haines, 2001. “Jason-1 CALVAL Plan”, JPL Ref: TP2-J0-PL-974-CN (PO.DAAC).
http://podaac.jpl.nasa.gov/jason/documents/calval4.0.pdf

Vincent, P., M.Ablain, J.Donrandeu, S.Desai, and K.Case.  “Jason-1 Calval results”.
http://www.aviso.oceanobs.com/en/newsstand/newsletter/newsletter10/index.html

Chambers, D.P., J. C. Roes, T.J. Urban.  2003.  Calibration and verification of Jason-1 using along-track residual with TOPEX.  Marine Geodesy.  Vol. 26, no. 3-4, pg. 305-317.

MacMillan, D., Y. Bock, P. Fang, B. Beckely, C. Ma.  Calibration of the TOPEX and Jason-1 Altimeter microwave radiometers using VLBI and GPS derived tropospheric delays. http://sealevel.jpl.nasa.gov/science/invest-macmillan.html