CO2M level-2 NO₂ science support

The CO2M mission will include observations of nitrogen dioxide (NO₂) to determine the extension of emission plumes. These observations will be on a high spatial resolution of 2x2 km². Also, other aspects of the CO2M NO₂ observations will differ from previous missions, including the overpass time and the optional glint mode over the ocean. The aim of this study is to develop the algorithms that derive the NO₂ tropospheric column (NO₂ TTC) from the CO2M observations. These algorithms will contain heritage from previous satellite missions but will also include new innovations specifically developed for CO2M.

Contractually it is arranged as a sub-task of the CO2M level-1 scientific support service.

Objectives

The objectives of the study are to:

• derive the specific needs and potentials for the NO₂ TTC processing, according to instrument design and mission objectives;
• establish the error budget of the NO₂ TTC product for CO2M;
• develop the Algorithm Theoretical Basis Document (ATBD) for the CO2M NO₂ TTC level-2 data product.

Overview

This study will assess the potential impact of the unique features of the CO2M mission on the NO₂ TTC algorithms. Features to be addressed include:

• The objective of the NO₂ observations is to support greenhouse gas observations.
• High spatial resolution.
• Narrower satellite swath in comparison to NO₂ heritage missions (coverage extended by multiple CO2M platforms).
• High spectral resolution and high spectral oversampling.
• Overpass time around mid-day which differs from previous LEO missions observing NO₂.
• The CO2M mission provides aerosol and cloud mapping instruments.
• CO2M mission is expected to measure in glint mode over the ocean.

The study will provide the ATBD for the NO₂ TTC level-2 product. Heritage from previous algorithm developments (Sentinel 5P, Sentinel-4, Sentinel-5, GEMS and TEMPO) will be taken into account. The ATBD will focus on the baseline algorithm components, but will also describe possible future enhancements of the algorithm.

To support the ATBD development, simulation and retrieval algorithm breadboard software will be set-up. Also, a methodology for reporting the error budget will be developed. Where possible, the ATBD developments will be aligned with activities performed by ESA and activities performed in other EUMETSAT studies for CO2M.