In-Flight Retrieval of SCIAMACHY Instrument Spectral Response Function

Mourad Hamidouche,Günter Lichtenberg

doi:10.3390/rs10030401

Mourad Hamidouche, Günter Lichtenberg

Open Access

https://doi.org/10.3390/rs10030401

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Journal: Remote Sensing	Publication Date: Mar 5, 2018
Citations: 5	License type: CC BY 4.0

Affiliation: German Aerospace Center

Abstract

The instrument Spectral Response Function (ISRF) has a strong impact on spectral calibration and the atmospheric trace gases retrievals. An accurate knowledge or a fine characterization of the ISRF shape and its FWHM (Full width at half maximum) as well as its temporal behavior is therefore crucial. Designing a strategy for the characterization of the ISRF both on ground and in-flight is critical for future missions, such as the spectral imagers in the Copernicus program. We developed an algorithm to retrieve the instrument ISRF in-flight. Our method uses solar measurements taken in-flight by the instrument to fit a parameterized ISRF from on ground based calibration, and then retrieves the shape and FWHM of the actual in-flight ISRF. With such a strategy, one would be able to derive and monitor the ISRF during the commissioning and operation of spectrometer imager missions. We applied our method to retrieve the SCIAMACHY instrument ISRF in its different channels. We compared the retrieved ones with the on ground estimated ones. Besides some peculiarities found in SCIAMACHY channel 8, the ISRF results in other channels were relatively consistent and stable over time in most cases.

Highlights

One of the key components that is needed to perform spectral calibration and to proces Level 1 and Level 2 data is the instrument spectral response function (ISRF) which is sometimes referred to as a slit function
We developed a model that used SCIAMACHY solar measurements to obtain its ISRF on a daily basis over its lifetime
The ISRF is parameterized by a mathematical function that we modeled for each tested channel

Summary

Introduction

One of the key components that is needed to perform spectral calibration and to proces Level 1 and Level 2 data is the instrument spectral response function (ISRF) which is sometimes referred to as a slit function. As a matter of fact, one of the origins of the instrument introduced errors is insufficient knowledge of the ISRF during the mission. It is one of the most important parameters for level 2 retrieval. Some studies have investigated the ISRF impact on data retrievals and calibration for different instruments in-flight, like GOME-2 (e.g., [2,3]). Another study [4] reported that the retrieved in-flight ISRF in the UV improved the level 1 data in the period of 2003–2011

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Conclusion