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6.2 Evolution of the IPF

As part of the continuous effort made by the QWG for the improvement of the quality of the GOMOS products, several successive IPF versions have been already developed. A new IPF version bases on the most recent version of the prototype GOPR, once the implementation of configuration changes proposed by the QWG in the prototype is validated. Those changes are then implemented in the IPF baseline. After verification and validation, the new IPF is then activated for operational processing.

The whole evolution cycle of the algorithm includes the following steps:

o      specification of the algorithm inputs from the assessment of the current IPF performance;

o      implementation in the prototype and validation;

o      implementation in the IPF baseline and verification;

o      delivery of the IPF and activation

It may take between one and two years for the cycle to be completely achieved.

The most recent version of the IPF (5.00) has been activated in August 2006. All products between July 2002 and August 2006 have been reprocessed (second reprocessing activities) with the version of the prototype corresponding to the IPF currently in operation (version 5.00), so that all consolidated products made available to the user are coherent. Datasets from a first reprocessing performed with a previous version of the prototype are also still available (measurements for 2003 and for the period between March and December 2004). Some of the Level2 changes implemented in IPF 5.00 are presented and compared to the configuration of GOPR used for the first reprocessing in Table B. 2 . Level1b changes in IPF 5.00 had implied mostly the implementation of new corrections or the modifications of already existing ones; they are given in Table B. 3 .



GOPR (1st reprocessing)

IPF 5.00

Aerosol law


a + bl + cl2


GOMOS cross-sections for all species

ORPHAL cross-section for O3 (only)

Air retrieval

Air is retrieved

Air is fixed to ECMWF

Additional errors

No additional errors

Additional errors for O3, NO3 and aerosols

Flagging strategy

Negative values are systematically flagged

Negative values are not systematically flagged


Improvement of the HRTP algorithm

Table B. 60444301'> 2 : Description of the Level2 configuration of the prototype version used for the first reprocessing and of IPF 5.00 (this list is non-exhaustive).

Level1b changes in IPF 5.00 compared to GOPR (1st reprocessing)

Modification of the FP unfolding algorithm

Background correction of SPB in full dark limb applied

Modification of the flat-field correction implementation

Use of corrected reflectivity LUT

Updated wavelength assignment for SPA1, SPA2, SPB1

Correction of the star spectra from reflectivity variations

Table B. 60444368'> 3 : Description of the Level1b changes implemented in IPF 5.00 (compared to the prototype version used for the first reprocessing); this list is non-exhaustive.