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<p>The Thermal And Near infrared Sensor for carbon Observation – Fourier Transform Spectrometer (TANSO-FTS) on the Japanese Greenhouse gases Observing SATellite (GOSAT) has been returning data since April 2009. The version 9 (v9) Atmospheric Carbon Observations from Space (ACOS) Level 2 Full Physics (L2FP) retrieval algorithm <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx43">Kiel et al.</a>, <a href="#bib1.bibx43">2019</a>)</span> was used to derive estimates of carbon dioxide (CO<span class="inline-formula">₂</span>) dry air mole fraction (XCO<span class="inline-formula">₂</span>) from the TANSO-FTS measurements collected over its first 11 years of operation. The bias correction and quality filtering of the L2FP XCO<span class="inline-formula">₂</span> product were evaluated using estimates derived from the Total Carbon Column Observing Network (TCCON) as well as values simulated from a suite of global atmospheric inversion systems (models) which do not assimilate satellite-derived CO<span class="inline-formula">₂</span>. In addition, the v9 ACOS GOSAT XCO<span class="inline-formula">₂</span> results were compared with collocated XCO<span class="inline-formula">₂</span> estimates derived from NASA's Orbiting Carbon Observatory-2 (OCO-2), using the version 10 (v10) ACOS L2FP algorithm.</p> <p>These tests indicate that the v9 ACOS GOSAT XCO<span class="inline-formula">₂</span> product has improved throughput, scatter, and bias, when compared to the earlier v7.3 ACOS GOSAT product, which extended through mid 2016. Of the 37 million soundings collected by GOSAT through June 2020, approximately 20 % were selected for processing by the v9 L2FP algorithm after screening for clouds and other artifacts. After post-processing, 5.4 % of the soundings (<span class="inline-formula">2×10⁶</span> out of <span class="inline-formula">37×10⁶</span>) were assigned a “good” XCO<span class="inline-formula">₂</span> quality flag, as compared to 3.9 % in v7.3 (<span class="inline-formula">&lt;1</span> <span class="inline-formula">×10⁶</span> out of <span class="inline-formula">24×10⁶</span>). After quality filtering and bias correction, the differences in XCO<span class="inline-formula">₂</span> between ACOS GOSAT v9 and both TCCON and models have a scatter (1<span class="inline-formula"><i>σ</i></span>) of approximately 1 ppm for ocean-glint observations and 1 to 1.5 ppm for land observations. Global mean biases against TCCON and models are less than approximately 0.2 ppm. Seasonal mean biases relative to the v10 OCO-2 XCO<span class="inline-formula">₂</span> product are of the order of 0.1 ppm for observations over land. However, for ocean-glint observations, seasonal mean biases relative to OCO-2 range from 0.2 to 0.6 ppm, with substantial variation in time and latitude.</p> <p>The ACOS GOSAT v9 XCO<span class="inline-formula">₂</span> data are available on the NASA Goddard Earth Science Data and Information Services Center (GES-DISC) in both the per-orbit full format (<a href="https://doi.org/10.5067/OSGTIL9OV0PN">https://doi.org/10.5067/OSGTIL9OV0PN</a>, <span class="cit" id="xref_altparen.2"><a href="#bib1.bibx61">OCO-2 Science Team et al.</a>, <a href="#bib1.bibx61">2019</a><a href="#bib1.bibx61">b</a></span>) and in the per-day lite format (<a href="https://doi.org/10.5067/VWSABTO7ZII4">https://doi.org/10.5067/VWSABTO7ZII4</a>, <span class="cit" id="xref_altparen.3"><a href="#bib1.bibx60">OCO-2 Science Team et al.</a>, <a href="#bib1.bibx60">2019</a><a href="#bib1.bibx60">a</a></span>). In addition, a new set of monthly super-lite files, containing only the most essential variables for each satellite observation, has been generated to provide entry level users with a light-weight satellite product for initial exploration (CaltechDATA, <a href="https://doi.org/10.22002/D1.2178">https://doi.org/10.22002/D1.2178</a>, <span class="cit" id="xref_altparen.4"><a href="#bib1.bibx22">Eldering</a>, <a href="#bib1.bibx22">2021</a></span>). The v9 ACOS Data User's Guide (DUG) describes best-use practices for the GOSAT data <span class="cit" id="xref_paren.5">(<a href="#bib1.bibx63">O'Dell et al.</a>, <a href="#bib1.bibx63">2020</a>)</span>. The GOSAT v9 data set should be especially useful for studies of carbon cycle phenomena that span a full decade or more and may serve as a useful complement to the shorter OCO-2 v10 data set, which begins in September 2014.</p>