User requirements for monitoring the evolution of stratospheric ozone at high vertical resolution ‘Operoz’: Operational ozone observations using limb geometry Final Report

I Introduction
The ESA study ‘User requirements for monitoring the evolution of stratospheric ozone at high vertical resolution has been executed in the time period October 2014 to February 2015. The project has been referred to as the ‘Operoz’ project where ‘Operoz’ is an acronym for ‘Operational ozone observations using limb geometry’.
II Purpose and Scope of the Study
The purpose of the Operoz study has been threefold:
(i) To establish the user requirements for an operational mission targeting ozone profiles at high vertical resolution,
(ii) To identify the observational gaps with respect to these user requirements taking into account planned operational missions and observational ground networks, and
(iii) To perform a reality check on the observational requirements based on proven concepts and present-day knowledge of potentially available measurement techniques and to identify options for a small to medium size satellite mission.
Background information on operational ozone monitoring needs has been assembled and user requirements have been derived. The mission objectives call for operational, i.e. sustained long-term monitoring from space of ozone profiles (and possibly related observables) in the stratosphere in limb geometry at high vertical resolution. A small set of mission extensions has been defined and has been prioritized into desirable and other useful mission extensions. All mission extensions would significantly enhance the mission objectives of the minimum mission and would contribute fulfilling more than just mandatory user requirements.
Secondly, based on the mission objectives defined specific observational requirements have been defined in terms of satellite Level-2 products and auxiliary requirements. Observational requirements are provided for a minimum mission that would add significant value to the existing and planned suite of observations, as well as a set for the identified set of desirable mission extensions.
Thirdly, a detailed preliminary assessment has been made of available measurement techniques to fulfil the observational requirements for both the minimum mission and the desirable mission extensions. The capabilities of existing instrumentation have been assessed and for each of the different classes of space instrumentation relevant for an ozone monitoring mission, a reality check has been performed on the observational requirements. Finally, conclusions have been drawn and some general recommendations have been formulated.
During the study it has been appreciated that, next to stratospheric ozone (loosely referred to as the ‘ozone layer’), also other important societal and science applications could be identified which potentially call for augmenting the operational monitoring of the atmosphere with high vertical resolution in the middle atmosphere using limb geometry. Identified applications specifically include numerical weather prediction, climate change, impact of large volcanic eruptions and (future) geo-engineering. Even though some of the observational requirements presented in this study are potentially relevant for these other applications, the definition of mission objectives and the prioritization for operational limb monitoring for other applications – i.e. other than targeting the ‘Ozone Layer’, has been considered out of the scope of the rather concise Operoz project.