Les produits CorSSH et SLA "Ref" de la mission Jason-1 ont été retraités:

• le biais d'état de mer (SSB) est estimé via une méthode non paramétrée, présent sur les GDR version 'b' Jason-1 des cycles 001 à 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).
• un flag glace de type ERS remplace le flag glace des produits.

Attention cependant: les cycles 32, 60, 89, 90 et 91 ne sont pas encore valides et n'ont donc pas été relivrés sur le serveur.

Les produits CorSSH et SLA de la mission Envisat ont été retraités. Pour plus de details, se référer aux retraitement effectués sur Jason-1 (09 août 2006).

Les produits CorSSH et SLA de la mission Jason-1 ont été retraités. Voici ce qui a évolué dans ces produits :

• La correction de biais d'état de mer est homogène sur toute la période (il s'agit de celle présente dans les GDR version 'b').
• Suite au changement de version des GDRs (cycle 136), la correction IB issue des grilles cartésiennes (utilisée sur les cycles 1 à 135) avait été remplacée par une correction IB calculée à partir des grilles gaussiennes, laquelle contient une anomalie près des côtes. C'est maintenant réparé, et la correction combiné MOG2D + baromètre inverse (grille cartésienne) est homogène sur toute la période.

Des nouveautés dans la chaîne de traitement des données Envisat: ces modifications prennent effet à compter du

• 24 Octobre 2005 pour les IGDR (produits temps quasi-réel)
• 20 septembre (i.e 1er jour du cyle 41) pour les GDR

Ces modifications concernent les calculs d'orbite MOE/POE et les évolutions des algorithmes de corrections utilisés pour la génération des produits.
Voir les détails de la nouvelle chaîne de traitement (site internet de l'ESA).

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.