Warning message

Member access has been temporarily disabled. Please try again later.
The GLOPAC website is undergoing a major upgrade that began Friday, October 11th at 5:00 PM PDT. The new upgraded site will be available no later than Monday, October 21st. Until that time, the current site will be visible but logins are disabled.

 

Disclaimer: This material is being kept online for historical purposes. Though accurate at the time of publication, it is no longer being updated. The page may contain broken links or outdated information, and parts may not function in current web browsers. Visit https://espo.nasa.gov for information about our current projects.

 

Characterization of the OCO-2 instrument line shape functions using on-orbit...

Sun, K., X. Liu, C. Nowlan, Z. Cai, K. Chance, C. Frankenberg, R. A. M. Lee, R. Pollock, R. Rosenberg, and D. Crisp (2017), Characterization of the OCO-2 instrument line shape functions using on-orbit solar measurements, Atmos. Meas. Tech., 10, 939-953, doi:10.5194/amt-10-939-2017.
Abstract: 

Accurately characterizing the instrument line shape (ILS) of the Orbiting Carbon Observatory-2 (OCO-2) is challenging and highly important due to its high spectral resolution and requirement for retrieval accuracy (0.25 %) compared to previous spaceborne grating spectrometers. Onorbit ILS functions for all three bands of the OCO-2 instrument have been derived using its frequent solar measurements and high-resolution solar reference spectra. The solar reference spectrum generated from the 2016 version of the Total Carbon Column Observing Network (TCCON) solar line list shows significant improvements in the fitting residual compared to the solar reference spectrum currently used in the version 7 Level 2 algorithm in the O2 A band. The analytical functions used to represent the ILS of previous grating spectrometers are found to be inadequate for the OCO-2 ILS. Particularly, the hybrid Gaussian and super-Gaussian functions may introduce spurious variations, up to 5 % of the ILS width, depending on the spectral sampling position, when there is a spectral undersampling. Fitting a homogeneous stretch of the preflight ILS together with the relative widening of the wings of the ILS is insensitive to the sampling grid position and accurately captures the variation of ILS in the O2 A band between decontamination events. These temporal changes of ILS may explain the spurious signals observed in the solar-induced fluorescence retrieval in barren areas.

PDF of Publication: 
Download from publisher's website.
Mission: 
Orbiting Carbon Observatory-2 (OCO-2)