OCO-3 Level 2 geolocated XCO2 retrievals results, physical model, Forward Processing V11 (OCO3_L2_Standard) at GES DISC

Version 11 is the current version of the data set. Older versions will no longer be available and are superseded by Version 11.

The Orbiting Carbon Observatory -3 (OCO-3) was deployed to the International Space Station in May, 2019. It is technically a single instrument, almost identical to OCO-2.

The Orbiting Carbon Observatory is the first NASA mission designed to collect space-based measurements of atmospheric carbon dioxide with the precision, resolution, and coverage needed to characterize the processes controlling its buildup in the atmosphere.

OCO-3 incorporates three high-resolution spectrometers that make coincident measurements of reflected sunlight in the near-infrared CO2 near 1.61 and 2.06 micrometers and in molecular oxygen (O2) A-Band at 0.76 micrometers. The three spectrometers have different characteristics and are calibrated independently.

Oxygen-A Band cloud screening algorithm is one of the primary cloud screening tools implemented in the operational OCO processing pipeline. The algorithm was introduced and applied to early GOSAT data with further analysis performed on OCO-2 simulations.

The OCO ABO2 algorithm employs a fast Bayesian retrieval to estimate surface pressure and surface albedo from high resolution spectra of the molecular oxygen (O2) A-band, near 0.765 µm. The radiative transfer forward model (FM) assumes a clear-sky condition, i.e. Rayleigh scattering only, such that differences between the modeled and measured radiances are apparent when the measurement scene contains cloud or aerosol.

本数据集当前版本为版本11，所有旧版本均已停止提供服务，并由版本11全面替代。

轨道碳观测站3号（Orbiting Carbon Observatory-3, OCO-3）于2019年5月被部署至国际空间站（International Space Station）。从技术属性来看，其为一套独立载荷，与OCO-2几乎完全一致。

轨道碳观测站项目是美国国家航空航天局（National Aeronautics and Space Administration, NASA）发起的首个任务，旨在以精准度、分辨率与覆盖范围获取天基大气二氧化碳测量数据，从而刻画控制大气中二氧化碳累积的相关过程。

OCO-3搭载三台高分辨率光谱仪，可同步测量近红外波段中对应二氧化碳吸收峰1.61与2.06微米处，以及分子氧（O₂）A波段（0.76微米）处的反射太阳光。三台光谱仪特性各不相同，且各自独立完成标定。

氧A波段云检测算法是在轨运行的OCO数据处理流程中的核心云检测工具之一。该算法最初被提出并应用于早期温室气体观测卫星（Greenhouse Gases Observing Satellite, GOSAT）的观测数据，后续还针对OCO-2模拟数据开展了进一步分析。

OCO ABO2算法采用快速贝叶斯反演方法，基于0.765微米附近的分子氧A波段高分辨率光谱，估算地表气压与地表反照率。该辐射传输正演模型（radiative transfer forward model, FM）假设场景为晴空条件，即仅考虑瑞利散射，因此当测量场景中存在云或气溶胶时，模拟辐射与实测辐射之间的差异将清晰可见。