## 1 Introduction  
Satellite retrievals of the atmospheric dry-air column-average mole fraction of CO\({}_{2}\) (XCO\({}_{2}\)) based on hyperspectral measurements in appropriate near (NIR) and short wave infrared (SWIR) O\({}_{2}\) and CO\({}_{2}\) absorption bands can help to answer pressing questions about the carbon cycle (e.g., [1]). However, the precision and even more the accuracy requirements for applications like surface flux inversion or emission monitoring are demanding (e.g., [2; 3; 4]). As an example, large scale biases of a few tenths of a ppm can already hamper an inversion with mass-conserving global inversion models [2; 3]. The Scanning Imaging Absorption Spectrometer for Atmospheric Chatrography (SCIAMACHY, [5; 6]) became operational in 2002 and its radiance measurements allowed to start the time series of NIR/SWIR XCO\({}_{2}\) retrievals. With an overlap of about three years, the Greenhouse Gases Observing Satellite (GOSAT, [7]) allowed complementation and continuation of this time series in 2009. The Orbiting Carbon Observatory-2 (OCO-2) was launched in 2014 also aiming at continuing and improving XCO\({}_{2}\) observations from space. As part of the A-train satellite constellation, OCO-2 flies in a sun-synchronous orbit crossing the equator at 13:36 local time. It measures one polarization direction of the solar backscattered radiance in three independent wavelength bands: the O\({}_{2}\)-A band at around 760 nm (band1) with a spectral resolution of about 0.042 nm and a spectral sampling of about 0.015 nm, the weak CO\({}_{2}\) band at around 1610 nm (band2) with a spectral resolution of about 0.080 nm and a spectral sampling of about 0.031 nm, and the strong CO\({}_{2}\) band at around 2060 nm (band3) with a spectral resolution of about 0.103 nm and a spectral sampling of about 0.040 nm. OCO-2 is operated in a near-push-broom fashion and has eight footprints across track and an integration time of 0.333 s. The instrument's spatial resolution at ground is 1.29 km across track and 2.25 km along track. More information on the OCO-2 instrument can be obtained from the publications of [PERSON] et al. [8; 9]. Several XCO\({}_{2}\) retrieval algorithms exist for the SCIAMACHY and GOSAT observations covering the whole mission periods (e.g., [10; 11; 12; 13; 14; 15; 16; 17; 18]). Because of the sparse ground based validation sites, the analyses of an ensemble of independently developed algorithms can give important insights in the quality of the retrievals, especially, remote from the validation sites [19] and strengthen the geophysical interpretation of the data [20]. Nevertheless, so far only the operational NASA algorithm exists for OCO-2 [21; 22] covering the whole mission period. One reason for this is that many of the existing algorithms require computationally expensive multiple scattering radiate transfer (RT) calculations and the data rate of OCO-2 is about two orders of magnitude larger than for GOSAT. In part 1 of this publication [23], the Fast atmOspheric traCe gAs retrievaL (FOCAL) has been introduced. It approximates multiple scattering effects with an analytic solution of the scalar RT problem of an isotropic scattering layer and a Lambertian surface. This enhances the computational efficiency by orders of magnitude making it possible to process the whole OCO-2 data stream on few CPU cores in real time and will allow also the analyses of future satellite missions which will provide at least an order of magnitude more data. In part 1, [PERSON] et al. [23] tested various retrieval setups with simulated OCO-2 measurements and concluded that their _3-Scat_ setup is a promising candidate for further studies with measured OCO-2 data. The _3-Scat_ retrieval setup fits the OCO-2 measured radiance simultaneously in four fit windows: SIF (\(\sim\)758.26-759.24 nm), O\({}_{2}\) (\(\sim\)757.65-772.56 nm), wCO\({}_{2}\) (\(\sim\)1595.0-1620.6 nm), and sCO\({}_{2}\) (\(\sim\)2047.3-2080.9 nm).