Geostationary Ocean Color Imager (GOCI), a payload of the Communication, Ocean and Meteorology Satellite
(COMS), is the world's first ocean color observation satellite in geostationary orbit. It was launched at Kourou Space
Center in French Guiana in June 2010. The detector array in GOCI is custom CMOS Image sensor about 2 Mega-pixels,
featuring rectangular pixel size to compensate for the Earth oblique projection.
This satellite is being operated on geostationary orbit about 36,500km far from the earth; hence it can be more influenced
by sun activities than the other on low Earth orbit. Especially, the detector is sensitive of heat and it may give rise to
increasing the defective pixels. In this paper, radiometric performance variations have been analyzed through the time
series analysis, using the offset parameters and detector temperature estimated in GOCI radiometric model. It is essential
to monitor the overall sensitivity of GOCI sensor, and it will helpful to the radiometric calibration.
In the result, we notified there was no great variation in time series of offset parameters after operating the GOCI in July
2010, but we monitored an anomaly by an operational event. One of them related to thermal electron showed slightly
increasing trend and the diurnal variation by the sun energy. Although sun interferences are occurred sometimes, any
significant anomaly isn't found. With these results of characterization, we find that GOCI has been carrying out stably in
the aspect of radiometric performance, and expect that it will be kept during the mission life.
The world's first space-borne ocean color observation geostationary satellite was launched on June 27, 2010. Systems
and Korea Ocean Satellite Center was established for receiving, processing and distributing images captured
Geostationary Ocean Color Imager (GOCI) since 2005. Trials test of the systems had been conducted continuously for
stabilized operation since 2009. Systems in KOSC were set up to operate from receiving image to distributing data
nonstop. Because this means that stabilized operation of each system and relation of them is important, it is crucial to
figure out problem when anomaly occurred and analyze effect on each system. Also it is very significant to figure out
additional unexpected problem during in-orbit test period, analyze it and then propose solutions to it, because operation
of geostationary satellite for ocean is the first in the world.
In conclusion, we artificially make emergencies and propose solutions responding to them before lunching satellite. Also
we analyze anomalies which are occurred during in-orbit test period, then seek solutions responding them for setting up
stabilized operation. The results drawing from the paper will good source to KOSC which operate system of GOCI and
agencies concerned for 7 years from now.
The data processing software system of Geostationary Ocean Color Imager (GOCI) is composed of the image preprocessing
system (IMPS) and the GOCI data processing system (GDPS). IMPS generate GOCI level 1B from raw
satellite data and GDPS is the post-processing system to generate GOCI level 2.
IMPS have a radiometric correction module as IRCM and a geometric correction module named as INRSM. The former
is focused on equipment's mechanical noise reduction and radiometric accuracy and the latter image navigation and
image registration accuracy by landmark matching method and image mosaic method.
GDPS have the atmospheric correction algorithms, as the spectral shape matching method (SSMM) and the sun glint
correction algorithm (SGCA), and BRDF algorithm to solve bi-directional problem. Several Case-II water analytical
algorithms, like chlorophyll concentration, suspended sediment and dissolved organic matter, are contained in GDPS.
Also, GDPS will generate the value added product like water quality, fishery ground information, water current vector,
During in-orbit test period planned six months after successful launch of satellite, IMPS and GDPS will be verified with
respect to those requirements and algorithms and functionality and accuracy by pre-defined test procedure like test,
inspection, demonstration. And then those configuration parameters will be modified and the algorithm descriptions will
be updated. In this paper, we will present the preliminary analyzed results of data processing system test and update
planning during in-orbit test.
The World's first Ocean Color Observation Satellite, the GOCI (Geostationary Ocean Color Imager) equipped with is
scheduled to be launched on Communication, Ocean and Meteorological Satellite (COMS) in November 2009. Korea
Ocean Research & Development Institute (KORDI) has developed GOCI Data Processing System (GDPS) which
produces ocean environment analysis data such as chlorophyll concentration, TSS, CDOM, Red-Tide, water current
vector, etc. In order to retrieve water-leaving radiance more precisely, atmospheric and BRDF (Bi-Directional
Reflectance Distribution Function) correction algorithms optimized for the environment of the GOCI coverage area and
COMS satellite orbit characteristics have been developed and implemented into the GDPS. GOCI operational
atmospheric correction algorithm has a capability to retrieve water-leaving radiance in the presence of aerosols with high
optical thickness (i.e. Asian Dust). At-sensor radiance which is affected by relative change of the Sun and satellite
position is corrected by the GOCI BRDF Correction algorithm. GOCI L2 data which is the product of the GDPS is
provided with 8 VNIR band images with 4967 x 5185 pixel resolution on the GOCI coverage area. As GOCI main
operation center, Korea Ocean Satellite Center (KOSC) has been established by KORDI. Main operational functions of
KOSC are the acquisition, processing, and storage of the GOCI data and distribution service of ocean satellite standard
products generated from the GOCI data. Operational systems of KOSC are GDAS(GOCI Data Acquisition System),
IMPS(Image Pre-processing System), GDPS, DMS(Data Management System), and GDDS(GOCI Data Distribution
System). After the launch, KOSC has a plan to provide the GOCI data for the real time ocean environment and marine
bio-physical phenomena variability monitoring.
The instrument level ground test of the Geostationary Ocean Color Imager(GOCI) has been completed and integrated
onto the Communication, Ocean and Meteorological Satellite(COMS) which is scheduled for launch in late 2009.
In order to monitor the short-term biophysical phenomena with better temporal and spatial resolution, The GOCI has
developed with eight VNIR bands, 500m GSD, and 2500km×2500km coverage centered at 36°N and 130°E. The GOCI
planned to observe the full coverage region by every hour in daytime, and provide 8 images in daytime during single day.
The GOCI ground test campaign for characterization and calibration has been performed by Korea Aerospace Research
Institute(KARI), Korea and EADS Astrium, France. Korea Ocean Research & Development Institute(KORDI) has
verified that test results satisfy all the GOCI performance requirements(Ex. MTF, SNR, Polarization, etc.) requested by
The GOCI has been sufficiently characterized under both of ambient and thermal-vacuum environments in order to
develop the on-orbit radiometric calibration algorithm. GOCI radiometric model has been finalized with 3rd order
polynomial. Because solar calibration is the on-orbit radiometric calibration method of the GOCI, Solar Diffuser made
of fused silica and Diffuser Aging Monitoring Device(DAMD) are implemented as on-board calibration system.
Diffusion factor of the Solar Diffuser and DAMD with respect to the solar incident angle, wavelength, and pixel location
has been successfully characterized. Diffuser aging factor has been calculated for the compensation of the diffuser
degradation by space environment. Diffusion factor of Solar Diffuser and DAMD, and diffuser aging factor
characterized during prelaunch ground test are implemented into the GOCI radiometric calibration S/W developed by