GOCI-II (GEO-KOMPSAT-2B)¶

Geostationary Ocean Color Imager II (GOCI-II) on GEO-KOMPSAT-2B — hourly ocean colour around Korea and daily full-disk observations

Available

At a glance¶

Note on period: GEO-KOMPSAT-2B was launched in February 2020, and the NOSC history page lists October 2020 as the start of the GEO-KOMPSAT-2B service (in-orbit testing ran through September 2020). KIOST reports that Level 1 data have been public since October 2020 and the 26 Level 2 products since January 2021. The planned mission lifetime is 10 years (2020 to 2029).

Overview¶

GOCI-II succeeds GOCI on COMS (Chollian-1), the world's first geostationary ocean colour sensor (2010–2021), and was launched on GEO-KOMPSAT-2B in February 2020. It images the seas around Korea every hour in daylight (10 times a day) at 250 m and adds a once-daily Full Disk observation that GOCI did not have. The number of bands rose from 8 to 12 (380–865 nm). NOSC distributes L2 products in NetCDF, from basic ocean colour (remote-sensing reflectance, chlorophyll, suspended matter, coloured dissolved organic matter) to red tide, floating algae, sea fog, surface currents, low-salinity water, aerosol and land products. The same satellite also carries the GEMS air-quality spectrometer.

Available variables¶

Product names and codes are those listed in the NOSC download menus and Open API guide; the code is the product identifier at the end of an L2 file name (e.g. …_LA_Chl.nc). The NetCDF variable names and units inside the files are given in "GOCI-II Level-2 OCR data format (v04, 2025-02-28)" on the NOSC technical documents board; we could not read that document, so they are not listed here. Other products include sea ice (SI), primary production (PP), fishing ground information (FGI) and land products (land surface reflectance SRL, broadband and narrowband land albedo LSAB/LSAN, vegetation index VI, land cover LCC).

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

Atmospheric correction and optical properties (L2, per acquisition)¶

Basic ocean colour (L2, per acquisition)¶

Ocean products (L2, per acquisition)¶

Atmospheric products (L2, per acquisition)¶

The full variable list is in the official documentation.

How to get the data¶

• NOSC — GOCI-II LA Downloads — Web search and download (level, product, date, slot; NetCDF and JPG) No login needed
  • No registration or login is needed. Dates can be chosen in KST or UTC, and you pick individual slots (S000–S011) or the mosaic. NetCDF downloads work only on a PC. The Korean page also offers NOSC application products (sea surface temperature, Sargassum horneri daily and hourly).
• NOSC — GOCI-II FD Downloads — Web search and download (L1B, L2) No login needed
  • FD L2 products are mainly ocean colour products (atmospheric correction, IOP, Kd, Secchi depth, chlorophyll, suspended matter, CDOM, floating algae).
• NOSC Web Directory — Folder browsing and download (level, product groups AC, IOP, AERO, OC, OCEAN, LAND; LA/FD; NetCDF/JPG) No login needed
  • Recommended by the NOSC FAQ, together with OPeNDAP, for bulk downloads.
• NOSC OPeNDAP — OPeNDAP (search page https://www.nosc.go.kr/program/opendapSearch.do, up to 90 days per search)
  • A user manual (PDF and video, 2026-06-04) and the bulk-download tool noscCollector (2024-06-21) are on the NOSC general documents board. Automated access to the server listing failed on 2026-10-14, so whether it requires a login was not confirmed.
• NOSC OPEN API — REST (JSON, XML) — metadata, satellite image and satellite NetCDF information APIs
  • After agreeing to the terms and submitting a request (usage type, affiliation, service URL, purpose), NOSC approves it and issues a service key. Calls are limited to 20,000 a day, and a lost key must be requested again. The NetCDF information API (openapi/GK2BNcMedia/search.do) returns file paths and names for given startDate, endDate and slot (0–11, or 13 for the whole Korean area).

Example code¶

Inspects the group and variable structure of one L2 NetCDF file downloaded from NOSC. Check the variable names against the "GOCI-II Level-2 OCR data format" document. The file name is the example from the NOSC Open API guide; replace it with your own.

# pip install netCDF4 xarray
import netCDF4
import xarray as xr

fname = "GK2B_GOCI2_L2_20211221_001530_LA_S002_AC.nc"   # replace with your file

# 1) List groups and variables (L2 files may be organised in groups)
with netCDF4.Dataset(fname) as nc:
    print(nc.ncattrs())                       # global attributes such as observation time
    for gname, g in nc.groups.items():
        print(gname, list(g.variables))

# 2) Open the group you need with xarray, using a group name found above
# ds = xr.open_dataset(fname, group="<group name>")
# print(ds)

Practical tips¶

• File names use UTC. The 08:15 KST acquisition carries the previous UTC date (23:15 UTC), so a daily composite for a Korean calendar day spans two UTC dates.
• On 2025-02-28 NOSC announced that past L2 products had been reprocessed and re-released (with atmospheric correction v31, IOP v20 and data format v04 documents). Fetch again any L2 time series built from earlier downloads.
• An updated atmospheric correction was implemented in the ground segment in October 2023 (KIOST, IOCS 2023), and an explanatory document on the improved remote-sensing reflectance was posted on 2024-04-15. Check the processing information in your files so that versions are not mixed across periods.
• Station keeping happens on Tuesdays and Thursdays at varying times, removing that acquisition (NOSC FAQ). Daily means that assume all 10 acquisitions can be biased because the missing hour changes from day to day.
• Around the equinoxes NOSC posts solar interference notices. In those periods and on days with safe-mode notices (e.g. 2022-09-04, 2023-12-11), data are missing or were withheld from the service.
• NASA OBPG (OceanColor) and NASA CMR hold no GOCI-II data (checked 2026-10-14; the OBPG Level-2 listing includes only the earlier GOCI). Get GOCI-II from NOSC.
• To join GOCI (2011–2021) with GOCI-II, note that GOCI comes from NASA OBPG and GOCI-II from NOSC with different processing. Compare the two over the overlap period (2020-10 to 2021-03) first.
• GEMS on the same satellite (NIER) also observes East Asia hourly in daylight. KIOST has evaluated using GEMS and GK-2A total ozone in GOCI-II atmospheric correction (Lee et al., 2025, Korean Journal of Remote Sensing 41(6)).

Notices and change history¶

References for your paper¶

Reference papers¶

One year of GOCI-II (in Korean) — DOI 10.7780/kjrs.2021.37.5.2.1

@article{choi2021goci2,
  author  = {Choi, Jong-kuk and Park, Myung-sook and Han, Kyung-soo and Kim, Hyun-cheol and Im, Jungho},
  title   = {One Year of {GOCI-II} Launch: Present and Future},
  journal = {Korean Journal of Remote Sensing},
  volume  = {37},
  number  = {5-2},
  pages   = {1229--1234},
  year    = {2021},
  doi     = {10.7780/kjrs.2021.37.5.2.1}
}

Improved GOCI-II water vapour absorption correction (atmospheric correction) — DOI 10.3390/rs15082124

@article{lee2023goci2wv,
  author  = {Lee, Kyeong-Sang and Park, Myung-Sook and Choi, Jong-Kuk and Ahn, Jae-Hyun},
  title   = {Improvement of {GOCI-II} Water Vapor Absorption Correction through Fusion with {GK-2A/AMI} Data},
  journal = {Remote Sensing},
  volume  = {15},
  number  = {8},
  pages   = {2124},
  year    = {2023},
  doi     = {10.3390/rs15082124}
}

GOCI and GOCI-II sea surface salinity continuity in the East China Sea — DOI 10.3390/rs16122111

@article{jang2024gocisss,
  author  = {Jang, Eunna and Choi, Jong-Kuk and Ahn, Jae-Hyun},
  title   = {Continuity and Enhancements in Sea Surface Salinity Estimation in the {East China Sea} Using {GOCI} and {GOCI-II}: Challenges and Further Developments},
  journal = {Remote Sensing},
  volume  = {16},
  number  = {12},
  pages   = {2111},
  year    = {2024},
  doi     = {10.3390/rs16122111}
}

Acknowledgements¶

We found no dataset DOI or recommended citation for GOCI-II data on the NOSC website. Credit the source as "National Ocean Satellite Center (NOSC), KHOA — GEO-KOMPSAT-2B GOCI-II", and state the product code, level, coverage (LA/FD) and download date (before or after the reprocessing). Pages displaying Open API results must credit the KHOA OPEN API.

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¶

• NOSC website (English)
• GK-2B GOCI-II (coverage and bands)
• GOCI-II Products (file naming)
• Technical documents (ATBDs)
• Operational notices (English)
• NOSC FAQ (Korean; acquisitions per day, update timing, bulk downloads)
• OPEN API developer guide (Korean)
• General documents (OPeNDAP manual, noscCollector; Korean)
• WMO OSCAR — GOCI-II
• This site — predecessor GOCI (COMS)
• This site — GEMS on the same satellite
• This site — GK-2A (GEO-KOMPSAT-2A meteorological satellite)