Characterization and correction of stray light in TROPOMI-SWIR

Paul J. J. Tol, Tim A. van Kempen, Richard M. van Hees, Matthijs Krijger, Sidney Cadot, Ralph Snel, Stefan T. Persijn, Ilse Aben, Ruud W. M. Hoogeveen

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

The shortwave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this purpose, calibrated radiance measurements are needed that are minimally contaminated by instrumental stray light. Therefore, a method has been developed and applied in an on-ground calibration campaign to characterize stray light in detail using a monochromatic quasi-point light source. The dynamic range of the signal was extended to more than 7 orders of magnitude by performing measurements with different exposure times, saturating detector pixels at the longer exposure times. Analysis of the stray light indicates about 4.4 % of the detected light is correctable stray light. An algorithm was then devised and implemented in the operational data processor to correct in-flight SWIR observations in near-real time, based on Van Cittert deconvolution. The stray light is approximated by a far-field kernel independent of position and wavelength and an additional kernel representing the main reflection. Applying this correction significantly reduces the stray-light signal, for example in a simulated dark forest scene close to bright clouds by a factor of about 10. Simulations indicate that this reduces the stray-light error sufficiently for accurate gas-column retrievals. In addition, the instrument contains five SWIR diode lasers that enable long-term, in-flight monitoring of the stray-light distribution.
Original languageEnglish
Pages (from-to)4493-4507
JournalAtmospheric Measurement Techniques
Volume11
Issue number7
DOIs
Publication statusPublished - 27 Jul 2018

Cite this

Tol, P. J. J., van Kempen, T. A., van Hees, R. M., Krijger, M., Cadot, S., Snel, R., ... Hoogeveen, R. W. M. (2018). Characterization and correction of stray light in TROPOMI-SWIR. Atmospheric Measurement Techniques, 11(7), 4493-4507. https://doi.org/10.5194/amt-11-4493-2018
Tol, Paul J. J. ; van Kempen, Tim A. ; van Hees, Richard M. ; Krijger, Matthijs ; Cadot, Sidney ; Snel, Ralph ; Persijn, Stefan T. ; Aben, Ilse ; Hoogeveen, Ruud W. M. / Characterization and correction of stray light in TROPOMI-SWIR. In: Atmospheric Measurement Techniques. 2018 ; Vol. 11, No. 7. pp. 4493-4507.
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Tol, PJJ, van Kempen, TA, van Hees, RM, Krijger, M, Cadot, S, Snel, R, Persijn, ST, Aben, I & Hoogeveen, RWM 2018, 'Characterization and correction of stray light in TROPOMI-SWIR' Atmospheric Measurement Techniques, vol. 11, no. 7, pp. 4493-4507. https://doi.org/10.5194/amt-11-4493-2018

Characterization and correction of stray light in TROPOMI-SWIR. / Tol, Paul J. J.; van Kempen, Tim A.; van Hees, Richard M.; Krijger, Matthijs; Cadot, Sidney; Snel, Ralph; Persijn, Stefan T.; Aben, Ilse; Hoogeveen, Ruud W. M.

In: Atmospheric Measurement Techniques, Vol. 11, No. 7, 27.07.2018, p. 4493-4507.

Research output: Contribution to JournalArticleAcademicpeer-review

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T1 - Characterization and correction of stray light in TROPOMI-SWIR

AU - Tol, Paul J. J.

AU - van Kempen, Tim A.

AU - van Hees, Richard M.

AU - Krijger, Matthijs

AU - Cadot, Sidney

AU - Snel, Ralph

AU - Persijn, Stefan T.

AU - Aben, Ilse

AU - Hoogeveen, Ruud W. M.

PY - 2018/7/27

Y1 - 2018/7/27

N2 - The shortwave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this purpose, calibrated radiance measurements are needed that are minimally contaminated by instrumental stray light. Therefore, a method has been developed and applied in an on-ground calibration campaign to characterize stray light in detail using a monochromatic quasi-point light source. The dynamic range of the signal was extended to more than 7 orders of magnitude by performing measurements with different exposure times, saturating detector pixels at the longer exposure times. Analysis of the stray light indicates about 4.4 % of the detected light is correctable stray light. An algorithm was then devised and implemented in the operational data processor to correct in-flight SWIR observations in near-real time, based on Van Cittert deconvolution. The stray light is approximated by a far-field kernel independent of position and wavelength and an additional kernel representing the main reflection. Applying this correction significantly reduces the stray-light signal, for example in a simulated dark forest scene close to bright clouds by a factor of about 10. Simulations indicate that this reduces the stray-light error sufficiently for accurate gas-column retrievals. In addition, the instrument contains five SWIR diode lasers that enable long-term, in-flight monitoring of the stray-light distribution.

AB - The shortwave infrared (SWIR) spectrometer module of the Tropospheric Monitoring Instrument (TROPOMI), on board the ESA Copernicus Sentinel-5 Precursor satellite, is used to measure atmospheric CO and methane columns. For this purpose, calibrated radiance measurements are needed that are minimally contaminated by instrumental stray light. Therefore, a method has been developed and applied in an on-ground calibration campaign to characterize stray light in detail using a monochromatic quasi-point light source. The dynamic range of the signal was extended to more than 7 orders of magnitude by performing measurements with different exposure times, saturating detector pixels at the longer exposure times. Analysis of the stray light indicates about 4.4 % of the detected light is correctable stray light. An algorithm was then devised and implemented in the operational data processor to correct in-flight SWIR observations in near-real time, based on Van Cittert deconvolution. The stray light is approximated by a far-field kernel independent of position and wavelength and an additional kernel representing the main reflection. Applying this correction significantly reduces the stray-light signal, for example in a simulated dark forest scene close to bright clouds by a factor of about 10. Simulations indicate that this reduces the stray-light error sufficiently for accurate gas-column retrievals. In addition, the instrument contains five SWIR diode lasers that enable long-term, in-flight monitoring of the stray-light distribution.

U2 - 10.5194/amt-11-4493-2018

DO - 10.5194/amt-11-4493-2018

M3 - Article

VL - 11

SP - 4493

EP - 4507

JO - Atmospheric Measurement Techniques

JF - Atmospheric Measurement Techniques

SN - 1867-1381

IS - 7

ER -

Tol PJJ, van Kempen TA, van Hees RM, Krijger M, Cadot S, Snel R et al. Characterization and correction of stray light in TROPOMI-SWIR. Atmospheric Measurement Techniques. 2018 Jul 27;11(7):4493-4507. https://doi.org/10.5194/amt-11-4493-2018