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ACOS GOSAT/TANSO-FTS Level 2 Full Physics Standard Product V9r (ACOS_L2S) at GES DISC

Metadata Updated: December 7, 2023

Version 9r is the current version of the data set. Older versions will no longer be available and are superseded by Version 9r.

This data set is currently provided by the OCO (Orbiting Carbon Observatory) Project. In expectation of the OCO-2 launch, the algorithm was developed by the Atmospheric CO2 Observations from Space (ACOS) Task as a preparatory project, using GOSAT TANSO-FTS spectra. After the OCO-2 launch, "ACOS" data are still produced and improved, using approaches applied to the OCO-2 spectra.

The "ACOS" data set contains Carbon Dioxide (CO2) column averaged dry air mole fraction for all soundings for which retrieval was attempted. These are the highest-level products made available by the OCO Project, using TANSO-FTS spectral radiances, and algorithm build version 7.3.

The GOSAT team at JAXA produces GOSAT TANSO-FTS Level 1B (L1B) data products for internal use and for distribution to collaborative partners, such as ESA and NASA. These calibrated products are augmented by the OCO Project with additional geolocation information and further corrections. Thus produced Level 1B products (with calibrated radiances and geolocation) are the input to the "ACOS" Level 2 production process.

Even though the GES DISC is not publicly distributing Level 1B ACOS products, it should be known that changes in this version are affecting both Level 1B and Level 2 data. An important enhancement in Level1B will address the degradation in the number of quality-passed soundings.

Elimination of many systematic biases, and better agreement with TCCON (Total Carbon Column Observing Network), is expected in Level 2 retrievals. The key changes to the L2 algorithm include scaling the O2-A band spectroscopy (reducing XCO2 bias by 4 or 5 ppm); using interpolation with the instrument lineshape [ ILS ] (reducing XCO2 bias by 1.5 ppm); and fitting a zero level offset to the A-band. Users have to also carefully familiarize themselves with the disclaimer in the new documentation.

An important element to note are the updates on data screening. Although a Master Quality Flag is provided in the data product, further analysis of a larger set of data has allowed the science team to provide an updated set of screening criteria. These are listed in the data user's guide, and are recommended instead of the Master Quality Flag.

Lastly, users should continue to carefully observe and weigh information from three important flags:

  "sounding_qual_flag" - quality of input data provided to the retrieval processing

  "outcome_flag" - retrieval quality based upon certain internal thresholds (not thoroughly evaluated)

Access & Use Information

Public: This dataset is intended for public access and use. License: No license information was provided. If this work was prepared by an officer or employee of the United States government as part of that person's official duties it is considered a U.S. Government Work.

Downloads & Resources


Metadata Created Date November 12, 2020
Metadata Updated Date December 7, 2023

Metadata Source

Harvested from NASA Data.json

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Additional Metadata

Resource Type Dataset
Metadata Created Date November 12, 2020
Metadata Updated Date December 7, 2023
Identifier C1633158704-GES_DISC
Data First Published 2019-10-02
Language en-US
Data Last Modified 2016-04-14
Category OCO, geospatial
Public Access Level public
Bureau Code 026:00
Metadata Context
Metadata Catalog ID
Schema Version
Catalog Describedby
Citation OCO-2 Science Team/Michael Gunson, Annmarie Eldering. 2019-10-04. ACOS_L2S. Version 9r. ACOS GOSAT/TANSO-FTS Level 2 Full Physics Standard Product V9r. Greenbelt, MD, USA. ACOS_L2S_9r. Archived by National Aeronautics and Space Administration, U.S. Government, Goddard Earth Sciences Data and Information Services Center (GES DISC). Digital Science Data.
Creator OCO-2 Science Team/Michael Gunson, Annmarie Eldering
Data Presentation Form Digital Science Data
Graphic Preview File
Harvest Object Id 592d97f0-17ec-47a9-b5e1-c59844cabeea
Harvest Source Id 58f92550-7a01-4f00-b1b2-8dc953bd598f
Harvest Source Title NASA Data.json
Issue Identification ACOS_L2S_9r
Homepage URL
Metadata Type geospatial
Old Spatial -180.0 -90.0 180.0 90.0
Program Code 026:001
Release Place Greenbelt, MD, USA
Series Name ACOS_L2S
Source Datajson Identifier True
Source Hash 06a6cf4249a87881226bb0b795ee508b64f41a16face7ae46cf0dcea1916bd54
Source Schema Version 1.1
Temporal 2009-04-20T00:00:00Z/2022-01-17T00:00:00Z

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