Three atmospheric chemistry sensors are on-board ENVISAT, launched on March 2002. Since then, the instruments and the processors have been accurately monitored in order to detect as early as possible any issue that could impact the quality of the data products. In this paper we show how the quality monitoring has evolved since the beginning of the mission and how the monitoring baseline and environment was adjusted to mission events like instrument anomalies and/or degradations and data processor issues and how the users benefit from this.

The ENVISAT atmospheric chemistry instruments GOMOS, MIPAS and SCIAMACHY provide to the user community three separated, but complementary datasets of the most interesting trace gases, spanning a time interval of about seven years. With the project of extending the ENVISAT lifetime up to the end of 2013, the users will have the unique opportunity to investigate seasonal trend and long term evolution of several atmospheric phenomena over a time range of eleven years. This paper summarizes the activities performed in the frame of the data processing and quality assessment applied to the ENVISAT Atmospheric Chemistry instruments.

An important part of the quality assessment is the Geophysical Validation. At the ACVT Validation workshop held in Frascati, Italy, from 3-7 May 2004, scientists and engineers presented analyses of the exhaustive series of tests that have been run on each of ENVISAT atmospheric chemistry sensors since the spacecraft was launched in March 2002. On the basis of workshop results it was decided that most of the data products provided by the ENVISAT atmospheric chemistry instruments are ready for operational delivery.

In addition to ESA and its industrial partners in the Envisat consortium, many other companies and research institutes have contributed to the calibration and validation programme under ESA contract as expert support laboratories (ESLs). A major contribution has also been made by the Principal Investigators of approved proposals submitted to ESA in response to a worldwide Announcement of Opportunity for the Exploitation of the Envisat Data Products in 1998. Working teams have been formed in which the different participants worked side by side to achieve the objectives of the calibration and validation programme.

Three atmospheric-chemistry sensors form part of the ENVISAT payload that has been placed into orbit in March 2002. This paper presents reviews the end-toend performance of the GOMOS, MIPAS and SCIAMACHY observation systems and will discuss the product quality control assessment of these instruments. An important part of the quality assessment is the Geophysical Validation. At the ACVT Validation workshop held in Frascati, Italy, from 4-7 December 2006, scientists and engineers presented analyses of the exhaustive series of tests that have been run on each of ENVISAT atmospheric chemistry sensors since the spacecraft was launched in March 2002.