GOSAT (GOSAT-2·GOSAT-GW)¶

Greenhouse gases Observing SATellite series (GOSAT 'IBUKI', GOSAT-2 'IBUKI-2', GOSAT-GW 'IBUKI GW') — column-averaged XCO2 and XCH4 from TANSO-FTS, FTS-2 and TANSO-3

Available

At a glance¶

Note on period: GOSAT (launched 2009-01-23) L2 data begin with April 2009 observations (both JAXA EORC and NASA ACOS start on 2009-04-18). GOSAT-2 (launched 2018-10-29) FTS-2 SWIR L2 starts with 2019-03-01 observations; by version, V02.20 covers 2019-03-01 to 2024-02-29, V02.21 covers 2024-03-01 onward, and V02.30 (general release 2026-08) covers 2019-03-01 onward. NASA ACOS GOSAT Lite v11.0 starts on 2009-04-18; the collection abstract says it runs to 2025-03-26, but on 2026-10-13 CMR held files through 2026-07-31. GOSAT-GW TANSO-3 made its first observations in August 2025; L1B has been public since 2026-07-23, and L2 is planned for spring 2027. Instrument anomalies and manoeuvres cause gaps of days to weeks (see notices).

Overview¶

The GOSAT series comprises Japan's dedicated greenhouse-gas satellites, run by the Ministry of the Environment, NIES and JAXA. GOSAT (IBUKI), launched in 2009, was the first spacecraft to measure column-averaged CO2 and methane (CH4) from space; GOSAT-2 (IBUKI-2), launched in 2018, continued the record and added CO; and GOSAT-GW, launched in 2025, carries the imaging spectrometer TANSO-3, which also observes NO2. NIES distributes L2 XCO2 and XCH4 (shortwave-infrared retrievals from reflected sunlight) as well as L3 monthly maps and L4 fluxes and 3-D concentrations, and NASA separately provides ACOS XCO2 retrieved from the same GOSAT spectra. The record, running since 2009, is widely used for global greenhouse-gas growth rates and methane emission inversions.

What changes with the successor¶

GOSAT (TANSO-FTS) → GOSAT-2 (TANSO-FTS-2)¶

Transition: 2018-10

GOSAT-2 keeps GOSAT's measurement approach (Fourier-transform spectroscopy of reflected sunlight) and adds carbon monoxide (CO) retrievals and Intelligent Pointing to steer around clouds. Both satellites still observe together, so their overlap can be used to check continuity (NIES published a consistency study in September 2023).

Sources: GOSAT-2 Spacecraft & Instruments (NIES) · Imasu et al. (2023) GOSAT-2 mission overview · GOSAT-2 FTS-2 SWIR L2 SWFP V02.30 Release Note

GOSAT-2 (TANSO-FTS-2) → GOSAT-GW (TANSO-3) Planned¶

Transition: 2027

GOSAT-GW replaces the point-sampling Fourier-transform spectrometer with TANSO-3, an imaging spectrometer that maps CO2, CH4 and NO2 together across a wide swath. It launched on 29 June 2025 and L1B has been public since July 2026, but general release of XCO2, XCH4 and NO2 L2 is planned for spring 2027, so this transition is marked as planned.

Sources: GOSAT-GW News (NIES) · NIES press release — initial analysis of TANSO-3 focus-mode data (2026-01-08) · GOSAT-GW (TANSO-3) Data Policy (revised 2026-06-22)

Available variables¶

GOSAT-2 names and units follow the product format description of the 'GOSAT-2 TANSO-FTS-2 SWIR L2 Column-averaged Dry-air Mole Fraction Product' (V02.30, March 2026; HDF5, daily files). Variable names in GOSAT (NIES V03.05) L2 and L3 files could not be confirmed (archive data2.gosat.nies.go.jp under maintenance on 2026-10-14) and are not listed. ACOS Lite names follow the GES DISC 'ACOS B11 L2 Lite Data User's Guide'; GOSAT-GW names follow the pre-release L2 format descriptions (Version C, 2025).

instantaneous mean accumulated maximum minimum static — instantaneous: value at the time stamp · mean/accumulated/maximum/minimum: over the indicated interval · static: does not change with time

GOSAT-2 FTS-2 SWIR L2 column-averaged mole fractions (SWFP V02.30, daily HDF5)¶

GOSAT TANSO-FTS SWIR L2 (NIES, V03.05 etc.)¶

GOSAT L3 monthly maps¶

GOSAT-GW TANSO-3 L2 (general release planned for spring 2027)¶

The full variable list is in the official documentation.

How to get the data¶

• GOSAT Data Archive Service (GDAS, NIES) — GOSAT — Web search and ordering (user registration required)
  • The source for GOSAT L1B–L4 standard products. Register first through user authentication on the 'product & service' page. On 2026-10-13 the site showed only an 'under maintenance' page, so current versions and the registration flow could not be confirmed.
• GOSAT-2 Product Archive (NIES) — Web ordering (cart → zip download) / SFTP batch acquisition
  • General User registration: agree to the terms of use and personal-data policy, enter a profile, and click the confirmation link in the e-mail within seven days. When an order is ready you get an e-mail and download a zip from the order page; order history is kept for 90 days. Authorized Users (e.g. Research Announcement investigators) e-mail an application form to gosat-2_desk@nies.go.jp. Format descriptions and release notes for each version are on the Documents page.
• GOSAT-GW TANSO-3 Product Archive (NIES) — Browser or command-line search; download after user registration (HDF5)
  • L1B (V101.101) has been public since 2026-07-23. New L1B delivery pauses from 2026-10-19 until around 2027-02; general L2 release is planned for spring 2027.
• NASA GES DISC — ACOS_L2_Lite_FP v11.0 (GOSAT XCO2) — HTTPS / earthaccess / Earthdata Search (Earthdata Login)
  • Daily bias-corrected XCO2 produced at Colorado State University from GOSAT spectra (JAXA L1B v300300 and v300301) with the same ACOS algorithm used for OCO-2. Starts 2009-04-18 (files through 2026-07-31 as of 2026-10-13).
• JAXA EORC GOSAT site — Operation status and notices; daily partial-column GHGs, monthly GHG maps, GHG trend viewer
  • Observation suspensions and resumptions for GOSAT and GOSAT-2 are posted here first.

Example code¶

(1) Downloads NASA ACOS GOSAT Lite v11.0 with earthaccess and lists its variables; (2) selects 'Good'-quality XCO2 from a GOSAT-2 SWFP daily file (HDF5) obtained from the GOSAT-2 Product Archive. GOSAT-2 files are named GOSAT2TFTS2YYYYMMDD_02SWFPV0230...h5; the name below is a placeholder.

import earthaccess, xarray as xr, h5py, numpy as np

# (1) NASA ACOS GOSAT XCO2 (2009-04-18 onward)
earthaccess.login()  # free NASA Earthdata account
res = earthaccess.search_data(short_name="ACOS_L2_Lite_FP", version="11.0",
                              temporal=("2020-07-01", "2020-07-31"),
                              bounding_box=(120, 30, 135, 45))
files = earthaccess.download(res, "acos_gosat")
print(xr.open_dataset(files[0]).data_vars)   # check variable names and units

# (2) GOSAT-2 FTS-2 SWIR L2 SWFP (file from the Product Archive)
with h5py.File("GOSAT2TFTS2_example_02SWFPV0230.h5", "r") as f:
    xco2 = f["RetrievalResult/xco2"][:]               # ppm, missing = -999
    qf   = f["RetrievalResult/xco2_quality_flag"][:]   # 0 Good, 1 Fair, 2 Poor, 3 NG
    lat  = f["SoundingGeometry/latitude"][:]
    lon  = f["SoundingGeometry/longitude"][:]
good = (qf == 0) & (xco2 > 0)
print(good.sum(), np.mean(xco2[good]))

Practical tips¶

• For GOSAT-2 SWFP, use only 'Good' (0) quality soundings. The fill value is -999.0.
• GOSAT-2 XCH4 is stored in ppm, not ppb. Multiply by 1000 when comparing with products in ppb (e.g. TROPOMI).
• GOSAT-2 Band 1 sensitivity degraded exponentially after launch and then recovered by about 10% in 2024–2026; V02.30 does not correct this, so Xgas after 2024 carries a time-varying positive bias. State this in any trend or growth-rate analysis after 2024.
• The GOSAT-2 V02.21 release note (revised July 2026) gives empirical bias-correction formulas and coefficients for XCO2, XCH4 and XCO derived against TCCON (GGG2020). The format description lists no bias-corrected variable, so apply the formulas from the release note of your version yourself if needed.
• NIES GOSAT L2 and NASA ACOS GOSAT are separate products from the same spectra with different algorithms. Do not mix them in one time series, and state which one you used.
• GOSAT and GOSAT-2 have gaps of days to weeks from anomalies and manoeuvres (e.g. GOSAT FTS 2025-12-18 to 2026-02-04). Check the number of observing days when building monthly means.
• Do not omit the credit line: 'JAXA/NIES/MOE' for GOSAT and GOSAT-2, 'NIES/MOE' for GOSAT-GW (TANSO-3).

Notices and change history¶

References for your paper¶

Dataset citation¶

NASA ACOS GOSAT Lite XCO2 v11.0 (GES DISC) — DOI 10.5067/UAY6VJYTS8OD

@misc{acos_gosat_lite_v110,
  author    = {O'Dell, Chris and Taylor, Tommy},
  title     = {{ACOS} {GOSAT/TANSO-FTS} Level 2 bias-corrected {XCO2} and other select fields from the full-physics retrieval aggregated as daily files v11.0},
  year      = {2026},
  publisher = {Goddard Earth Sciences Data and Information Services Center (GES DISC)},
  address   = {Greenbelt, MD, USA},
  doi       = {10.5067/UAY6VJYTS8OD}
}

Reference papers¶

First GOSAT XCO2 and XCH4 retrievals (SOLA) — DOI 10.2151/sola.2009-041

@article{yokota2009gosat,
  author  = {Yokota, T. and Yoshida, Y. and Eguchi, N. and Ota, Y. and Tanaka, T. and Watanabe, H. and Maksyutov, S.},
  title   = {Global Concentrations of {CO2} and {CH4} Retrieved from {GOSAT}: First Preliminary Results},
  journal = {SOLA},
  volume  = {5},
  pages   = {160--163},
  year    = {2009},
  doi     = {10.2151/sola.2009-041}
}

GOSAT-2 mission overview (PEPS) — DOI 10.1186/s40645-023-00562-2

@article{imasu2023gosat2,
  author  = {Imasu, Ryoichi and Matsunaga, Tsuneo and Nakajima, Masakatsu and Yoshida, Yukio and Shiomi, Kei and Morino, Isamu and others},
  title   = {Greenhouse gases Observing {SATellite} 2 ({GOSAT-2}): mission overview},
  journal = {Progress in Earth and Planetary Science},
  volume  = {10},
  pages   = {33},
  year    = {2023},
  doi     = {10.1186/s40645-023-00562-2}
}

Acknowledgements¶

NIES GOSAT and GOSAT-2 products have no dataset DOIs (checked 2026-10-13). As the data policy requires, credit "JAXA/NIES/MOE" (or Japan Aerospace Exploration Agency / National Institute for Environmental Studies / Ministry of the Environment) in publications, and "NIES/MOE" for GOSAT-GW TANSO-3 data, and state the product name and version (e.g. FTS-2 SWIR L2 SWFP V02.30). If you use NASA ACOS GOSAT, cite the GES DISC DOI above.

Information on the datasets used in this study was compiled with the help of the Korean Climate Data Navigator (KCDN) (Sim, 2026; https://doi.org/10.5281/zenodo.23300923).

Links¶

• GOSAT Project (NIES)
• GOSAT-2 Project (NIES)
• GOSAT-GW Project (NIES)
• JAXA EORC GOSAT (operation status and notices)
• GOSAT-2 Product Archive documents (format descriptions and release notes)
• GOSAT-2 Product Archive User's Manual
• GOSAT/GOSAT-2 and GOSAT-GW data policies (NIES)
• JAXA GOSAT-2 satellite page
• GOSAT whole-atmosphere monthly mean CO2 (NIES)