G2.30   Lack of uncertainty quantification for Pandora O3 measurements

Gap detailed description

Pandora is a relatively new UV-VIS instrument for measuring total O3 and also O3 profiles in a similar way as MAX-DOAS instruments. So far only a few studies exist which describe the measurement uncertainties or measurement validation (see e.g. Herman et al. 2015, Tzortziou et al, 2012). This yields low confidence that the measurement uncertainties are currently either fully documented or rigorously quantified. For example, systematic uncertainty in Pandora direct-sun measurements are limited by temperature effects not corrected in current operational baselines. The neglect of temperature effects (related to the O3 spectroscopy in the Huggins bands) leads to seasonally dependent systematic biases, of various amplitudes depending on the latitude of the site. This gap is partially addressed within GAIA-CLIM.

Activities within GAIA-CLIM related to this gap

A literature review will be written on the uncertainties related to total ozone retrievals using the Pandora instrument. Based on this and additional information obtained during the CINDI-2 campaign and analysis of Pandora O3 observations at Helsinki, preliminary studies related to selected types of uncertainties will be done. We expect that the outcomes of the CINDI-2 campaign in September 2016 will provide input for this gap (http://www.tropomi.eu/science/cindi-2). Several Pandora instruments as well as MAX-DOAS instruments will participate in the campaign. Exercises and studies performed during this campaign will provide the community with relevant datasets and information about how to proceed most effectively.

Gap remedy(s)

Remedy #1

Specific remedy proposed

A literature review together in consultation with the Pandora community will be undertaken to gain better quantification of the measurement uncertainties. This literature review will be supported by findings from the CINDI-2 campaign and Pandora/Helsinki analysis, taking into account the limited funding available within GAIA-CLIM for this effort.

Measurable outcome of success

To reduce the total uncertainty of the final O3 data product and to understand the uncertainty budget.

Achievable outcomes

Technological / organizational viability: medium.

Indicative cost estimate: low (<1 million).


Given that the Pandora instruments will form the backbone of a new measurement network (PANDONIA) run in close collaboration with NDACC, any better understanding of and reduction in the measurement uncertainties will contribute to the homogenisation of the O3 data products available within these networks.


The gap will not be fully solved within the GAIA-CLIM project timeframe.

Gap risks to non-resolution

Identified future risk / impact

Probability of occurrence if gap not remedied

Downstream impacts on ability to deliver high quality services to science / industry / society

Potential systematic errors may limit satellite validation if not taken into account in the validation.

Relevance varies depending on the geographical positions if the effect is not taken into account in the satellite validation.

Potential source of systematic errors that are correlated in time and space.


Work package: