Introduction to the calibration ringing effect in satellite hyperspectral atmospheric spectrometry

TL;DR

This paper explains the calibration ringing error in satellite hyperspectral spectrometry, its theoretical basis, and its impact on measurement accuracy, emphasizing its importance for future instrument calibration.

Contribution

It provides a detailed theoretical analysis of the calibration ringing effect and assesses its impact on radiometric measurements in Fourier transform spectrometers used for atmospheric sensing.

Findings

Calibration ringing error is intrinsic to Fourier transform spectrometers.

This error can significantly affect radiometric accuracy in new-generation instruments.

Ignoring this effect in early instruments was acceptable, but it must be considered in future designs.

Abstract

Atmospheric remote spectrometry from space has become in the last 20 years a key component of the Earth monitoring system: their large coverage and deci-kelvin stability have demonstrated their usefulness for weather prediction, atmospheric composition monitoring as well as climate monitoring. It is thus critical to investigate the possible sources of errors associated to this technique. One of them is the so-called "calibration ringing error" that appears in Fourier transform spectrometers at the radiometric calibration step when the instrument transmission varies at the scale of the spectral resolution and is not accounted by the data users. This paper exposes the theoretical basis of this particular type of radiometric uncertainty. Its sensitivity to instrumental parameters as well as the impact on the radiometrically calibrated measurements is assessed in the context of atmospheric infrared sounding using Fourier transform spectrometers. It is shown that this error is an intrinsic feature of such instruments that could safely be ignored in early-generation instruments but will have to be taken into account in the new generation ones as it can yield a significant degradation of the radiometric error budget.