• Monomission data : updates
• May 2013: Jason-1 GDR production delay until mid-July
• October 2012: Jason-1 geodetic mission and Jason-2 GDR-D standards applied in monomission CorSSH and SLA products
• July 2012: release of the Jason-2 GDRs version "D"
• July 2012: Information about the new altimetric standard version "D" in Jason-2
• May 2012: New geodetic orbit for Jason-1
• February 2011: start of Envisat reprocessing in version 2.1
• June 2010: New reprocessed CorSSH and SLA monomission products
• October 2009: new ftp site to download monomission products
• January 2009: Jason-1's orbit has been shifted
• December 2008: Jason-1 GDR-C standards applied on monomission CorSSH and SLA
• October 2008: Version C Jason-1 GDR
• August 2008: Envisat CorSSH and SLA modifications
• July 2008: Jason-1 CorSSH and SLA modifications
• April 26, 2007: Jason-1 CorSSH and SLA products
• September 8, 2006: Envisat CorSSH and SLA products
• August 9, 2006: Jason-1 CorSSH and SLA products
• October 24, 2005: Envisat GDR and IGDR products
• October 21, 2005: Jason-1 GDR and IGDR products

Jason-1 is on its new geodetic orbit since May 2012. The cycle 500 is the first cycle of this geodetic mission and the CorSSH products are now delivered. No SLA is delivered after cycle 374 since the orbit is non repetitive.

For Jason-2, monomission CorSSH and SLA are now using the version D of Jason-2 Geophysical Data Records (GDRs) standards starting from cycle 146. Previous cycles are still in version C, and will be reprocessed in the future.

All information available in the CorSSH and SLA user Handbook

Jason-2 OGDRs, IGDRs and GDRs will switch to a new altimetric standard (version "D") this summer. A reprocessing campaign will process the four first years of mission to provide an homogeneous GDR dataset.

Read more

Following the on-board anomaly on March 3rd, the Cnes-Nasa Joint Steering Group directed the Jason-1 Project to move the satellite to a geodetic orbit.

Maneuvers

The target orbit was 12+297/406 with a mean altitude at the Equator of 1323.4 km.
Jason-1 maneuver operations were started on April 23^rd with this baseline, and the first operations to lower the orbit were performed on April 25^th.
After an initial series of 4 maneuvers were completed, they encountered a serious new propulsion anomaly which resulted in the unexpected overconsumption of hydrazine.
A 5^th maneuver was designed in order to correct orbital eccentricity. At the time of this new anomaly, Jason-1 was -12.0 km below the reference altimetric orbit with 600m remaining to reach the -12.6 km goal, however there were very few grams of fuel remaining in the tank to continue orbit lowering.

Final orbit

After checking the current orbit carefully, the operational team determined that a geodetic mission was still possible. It was also decided to preserve all remaining fuel for future station keeping maneuvers which is mandatory in a geodetic orbit. Core payloads were switched ON on May 4^th and after some POSEIDON2 radar (PRF) adjustments the mission was resumed on May 7^th at 15:12:48 UTC.

Below are the characteristics of the new orbit which will be maintained, as before, within +/- 1km control box at the Equator:

Products

For this new phase of the Jason-1 mission, the cycle numbering will restart at 500. Off-line products will be produced once a day for the IGDR and every 11 days for the GDR's.

Since February 2011, the reprocessing of Envisat data in version 2.1 has begun and will continue during all the year 2011. It concerns cycles 10 to 92.

See the validation reports (in pdf)

The changes and comparisons between version 2.1 (IPF V6.04 and CMA V9.3_05) and the previous version (IPF V5.06 and CMA V9.2_03) have been analysed by: Ollivier A, J.F. Legeais, N. Granier, Y. Faugere, F-PAC Calval Team: "CalVal status on the Envisat V2.1 reprocessing impact on main altimetric parameters"

Mofications were applied on CorSSH and SLA monomission products with new standards for corrections and/or models and processing of ERS-1 data. Major changes are:

• T/P: new non parametric Sea State bias solution from N.Tran et al. (2010) with up-to-date standards (e.g. : DAC or wind algorithm) and orbit solution.
• T/P: new orbit solution, kindly provided by GSFC.
• Jason-1: GDR-C used from 2009 reprocessing.
• ENVISAT: new non parametric SSB solution from S.Labroue.
• ENVISAT: GDR-C orbits used (from cycle 15).
• GFO: new orbit solution, kindly provided by GSFC. As the new solution is not allways available, the <dfn>GDR</dfn> orbit is also used with empirical coherency restoration in between.
• GFO: new non parametric Sea State bias solution from N. Tran et al. (2010) with up-to-date standards and orbit solution (computed after orbit error minimization on calibrated reference missions)
• ERS: minimization of brightness temperature drift before wet tropo computation (NN)
• All missions: GDR-C or better standards applied whenever necessary (GOT4v7, High Resolution DAC correction...)
• All missions: new mean profiles computed in coherency with the new standards and algorithms. New algorithms were applied to correct for time-averaging period discrepancies (e.g.: T/P = Jason-1) or ocean variability. The new mean profiles are still referenced over 1993-1999 for the sake of coherency, but they integrate a precious information from the most recent missions and datasets.
• All missions: minor upgrades of the editing process and complete re-editing based on new standards and corrections.

The handbook has been updated to follow all changes.

We are changing our ftp site to provide you with a better service. From now on monomission products (SLA monomission and CorSSH) are delivered on a new ftp site.

The new ftp address is: ftp.aviso.oceanobs.com . This one replace the old one (ftp.cls.fr).

The anonymous access, the directory paths and the file nomenclature don't change : ftp://ftp.aviso.oceanobs.com/pub/oceano/AVISO/SSH/monomission/

After more than 7 years of service on the nominal ground track, the Jason-1 satellite began several maneuvers to be moved to a new ground track on January 26, 2009 after the end of repeat cycle 259. Several maneuvers shifted Jason-1 on its new orbit  on mid-February. Nominal production of all data products in the new orbit resumed on 14-Feb-2009 at 20:51 UTC.  Nominal science data delivery will continue for the remainder of Science Cycle 262.  The first complete science cycle in the new Jason-1 orbit (Cycle 263) will begin at 04:18 UTC on 20-Feb-2009.

Jason-1 assumes a new orbit midway between its original ground tracks but with a time lag of approximately 5 days with OSTM/Jason-2.The OSTM/Jason-2 satellite will continue the long term climate data record on the primary Topex/Jason-1/OSTM-Jason-2 ground tracks.  

Jason-1 monomission CorSSH and SLA are now using the new version C Jason-1 Geophysical Data Records (GDRs) standards, starting from cycle 233. Previous cycles are still in version B, and will be reprocessed in the future, following Jason-1 GDRs reprocessing.

New version C Jason-1 Geophysical Data Records (GDRs). Currently, cycles 213-232, and 240 are available on the Aviso and Podaac ftp servers:

• AVISO: ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c/ 
• PODAAC: ftp://podaac.jpl.nasa.gov/sea_surface_height/jason/gdr_c/

Early versions of some cycles (e.g. 220-239) of the version C GDRs were released in July, but have since been  reprocessed with modified precise orbit ephemerides. Users are advised to download those cycles again, and to only use version C GDRs that have file generation times of August 12, 2008 onwards.  All version C Jason-1 GDRs for all cycles will be available by the middle of 2009.

Users are advised to note the following primary differences between the version B and version C Jason-1 GDRs:

• Use of ITRF2005 reference frame and time variable gravity in precise orbits. 
• In improved sea state bias model that is consistent with the MLE4 retracked altimeter data.
• Updated altimeter instrument corrections.
• Recalibrated JMR measurements using data from cycles 1-227.

Given the schedule for reprocessing version C GDRs, we are providing users with an interim means to correct the version B Jason-1 GDRs for these primary changes, as follows:

• GDR-C precise orbit ephemerides are provided as sp1 files on the following ftp server.    ftp://avisoftp.cnes.fr/AVISO/pub/jason-1/gdr_c_aux_files/poe/
• 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/
• 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/ 
• 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/

An updated user handbook is provided:

• SMM-MU-M5-OP-13184-CN, Edition 4.1, October 2008 
  Aviso and PoDaac User Handbook - IGDR and GDR Jason-1 Products, pdf version (2 Mo)

Mofications were applied on Envisat CorSSH and monomission SLA to follow Jason-1 standards, starting from cycle 65. Changes are:

• Mog2D high resolution replaces Mog2D
• Wet tropospheric correction is now a composite of radiometer correction (further than 50 km from the coast) and model correction (between 10 and 50 km), with smoothing at the frontier.
• change in ERS mean profile, including now coastal effects
• GIM correction replaces the dual-frequency ionospheric correction

The handbook has been updated to follow all changes.

Mofications were applied on CorSSH and monomission SLA to follow Jason-1 GDR-C standards. Changes are:

• Mog2D high resolution replaces Mog2D
• Wet tropospheric correction is now a composite of radiometer correction (further than 50 km from the coast) and model correction (between 10 and 50 km), with smoothing at the frontier.
• changes in validation process (including a new ice flag, effects from Mog2D High Resolution, looser criteria near the coasts...)
• change in T/P mean profile, including now coastal effects

The handbook has been updated to follow all changes.

Jason-1 CorSSH and SLA "Ref" products were reprocessed:

• sea state bias (SSB) is issued from non parametric method already available in the GDRs 'b' from cycle 001 to 021 (Labroue, S., P. Gaspar, J. Dorandeu, F. Mertz, OZ. Zanifé, 2006, Overview of the Improvements Made on the Empirical Determination of the Sea State Bias Correction, 15 years of progress in radar altimetry Symposium, Venice, Italy, 2006)
• a new ice flag, similar as for ERS, is now applied.

Attention: cycles 32, 60, 89, 90 et 91 are not validated yet and not delivered on the server.

Envisat CorSSH and SLA products were reprocessed, modifications are the same as for Jason-1; please refer to previous information published on August 9, 2006.

Jason-1 CorSSH and SLA products were reprocessed, hereafter the modifications:

• Sea State Bias correction is the one provided in the GDRs 'b' and is homogeneous all along the time period.
• With the new version of GDRs (cycle 136) IB correction based on a cartesian grid (cycle 1 to 135) was, by mistake, replaced by an IB correction based.

Implementation of a new Envisat operational production chain; starting dates for the new processing chain are as follows:

• IGDR products (near real time products): October, 24th 2005
• GDR products (off line products): September, 20th 2005 (i.e. from cycle 41).

Improvements concern MOE/POE orbit computation chains and new algorithms.
More details about those improvements are available on ESA web site.

Implementation of a new Jason-1 operational production chain; starting dates for the new processing chain are as follows:

• IGDR products (near real time products): October, 24th 2005 (i.e. first day of cycle 140)
• GDR products (off line products): September, 14th 2005 (i.e. from cycle 136).

This new version will be identified with the letter "b", therefore GDR Jason-1 products will be named "JA1_GDR_2Pb" from the start of the new chain.

Main features:

New MOE and POE orbit computation chains :

Both chains will use the latest GRACE geoid model developed by the LEGOS group (EIGEN-CG03C). The POE chain also takes into account GPS data (MOE orbits are computed with Doris data solely). See Choi et al., 2004.

New JMR characterization file :

A new calibration file has been developed to correct for jumps in the JMR path delays and to minimize yaw state effects (Brown et al., 2004).

New MLE4 retracking algorithm :

Based on a second-order altimeter echo model, MLE4 simultaneously retrieves the 4 parameters that can be inverted from the altimeter waveforms: epoch, SWH, Sigma0 and mispointing angle. This algorithm is more robust for large off-nadir angles, (up to 0.5°, as encountered in August-September 2005). See Amarouche et al. 2004.

Instrumental tables (fields # 31-32, 47-48 and 61-62):

New instrumental correction tables have been established, based on MLE4 algorithm (Thibaut et al., 2004).

Vandemark/Gourrion wind algorithm (fields # 85-88):

A specific empirical wind-speed model has been tailored to Jason-1 data by Collard et al. (2004). This represents an update from the previous version of the altimeter wind estimate (the previous algorithm was fitted on TOPEX data).

SSB table (fields # 38-40):

Sea-State bias table has been recomputed accounting for the impact of the geophysical parameters used (Labroue et al., 2003). Note that this SSB table was derived from altimeter data that we computed from the MLE3 retracking algorithm.

Tidal models (fields # 77-78 and 81-82):

The two tide models (FES and GOT) have been updated to their latest versions (respectively FES2004 and GOT00.2). As before, both geocentric ocean tide fields (fields #77 and #78) also include the load tides from the respective models (also provided separately in fields #81 and #82), and the equilibrium long-period ocean tide (also provided separately in field #79). These two fields (#77 and #78) now also include the S1 oceanic response to atmospheric pressure based on the model from Ray and Egbert (2004). The FES2004 model now also includes the M4 ocean tide. Note that the load tide fields (fields #81 and #82) only include the load tides from the GOT00.2 and FES2004 models, and do not contain the load tides from the S1, M4, or equilibrium long-period ocean tides.

Non Equilibrium Long Period Tides (fields # 80):

Previously set to default value, this field is now calculated based on the predictions of the Mf, Mm, Mtm, Msqm tides from the FES2004 model. This field is provided as a correction to the equilibrium long-period ocean tide. To apply this correction, it should be added to fields 77, 78, or 79, depending on which ocean tide field is being used.

MSS (field # 70):

CLS01 MSS model solution has been implemented (Hernandez, 2002).

Non-tidal High Frequency correction (field # 75) :

The correction is calculated from the Mog2D ocean model, and is only available in GDR products. Note that the IB correction is still taken from ECMWF atmospheric pressure products. This field is provided as a correction to the inverse barometer. To apply this correction, it should be added to field #74.

S1/S2 management (fields # 33 and 74) :

S1 and S2 ocean tide effects have been removed from the inverse barometer correction (field #74) and from the non-tidal high frequency correction (field #75) as both ocean tides are now included in the ocean tide models. Note also that explicit models for the S1 and S2 atmospheric tides have been added into the dry tropospheric correction.

Rain Flag (field # 93):

A new table provided by Tournadre (2004) is used in ground processing for rain_flag determination.