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26/05/2014
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26/05/2014 1
David Blondeau-Patissier
Remote Sensing Group
Purple 12, office 2.26
26 May 2014
Geostationary satellites:
the future of ocean colour remote
sensing at a regional scale
Geo-stationary Ocean Color Imager (GOCI), Korea Ocean Satellite Center (KOSC)
1) Sun-synchronous ocean colour satellites
a. Basic definition and coverage
b. Detecting Chlorophyll-a in East China Sea
2) Geostationary ocean colour satellites
a. GOCI, a Korean pioneer
b. Detecting change in tidal currents,
chlorophyll-a and suspended sediment
3) Conclusion
Content
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Near-polar sun-synchronous orbits:
The old fashion way
Credits : NASA Ocean Biology Processing Group (OBPG)
http://oceancolor.gsfc.nasa.gov/DOCS/SeaDAS/seadas
_training.html
• Near-polar orbits = Orbital plane
crosses the poles and is situated at
high inclination to the Earth's rotation
• low-altitude (700 Km) imaging
• global daily coverage
• Sun-synchronous orbits cross the
equator at the same local time
• Pass over any given latitude at almost
the same local time during each orbital
pass
• Pixel resolution: 1 km ~ 0.3 Km
Swath: 2,330 km 4
Credits : NASA Ocean Biology Processing Group (OBPG)
http://oceancolor.gsfc.nasa.gov/DOCS/SeaDAS/seadas
_training.html
Near-polar sun-synchronous orbits:
MODIS (NASA) Coverage of the Earth in 1 day
MODIS: Moderate Resolution Imaging Spectroradiometer
Source:
Oceanography of Skeletonema costatum harmful algal blooms in the East China Sea using MODIS and QuickSCAT satellite data, Li Shen ;
Huiping Xu ; Xulin Guo ; Ping Wu, J. Appl. Remote Sens. 6(1), 063529 (May 21, 2012).
Chlorophyll-a
4 June 2004 5 June 2004 6 June 2004 7 June 2004 8 June 2004
MODIS (NASA)
Example of daily Chlorophyll-a concentrations
The world’s first geostationary satellite for ocean
colour - GOCI
• Agency: KORDI (Korea)
• On-board COMS satellite
• Launched : 26 June 2010
• Altitude: 36,000 km
• Repeat cycle: 8 images/ day
• Swath: 2,500 km
• Resolution: 500 m
• Hyperspectral : 8 bands
GOCI: Geostationary Ocean Colour Imager
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“Geostationary ocean colour will not be available for at
least another decade”
(IOCCG, 1998)
2010: GOCI has been successfully launched
First image: 13 Jul 2010
“This new way of observing the oceans is likely to generate
unforeseen discoveries or entirely new
ways of processing ocean-colour data.“
(IOCCG, 2012)
The world’s first geostationary satellite for ocean
colour - GOCI
GOCI: example of application
Hourly monitoring of Suspended SedimentEffect of tidal currents in a coastal areas:
• Up to several m/s
• Strong effect on mixing
• Strong effect on sediment load
• Timescale: diurnal
Source: J-H Ryu, KOSC, "GOCI status and GOCI-II plan"
GOCI: example of application
Typhoon and tidal effects
Tides
Typhoon
Sources: Wikipedia; J-H Ryu, KOSC, "GOCI status and GOCI-II plan"
GOCI-II
Taking over the world….
GOCI-II:
• Project has started in 2012
• Launch scheduled in 2018
Challenges and opportunities
Source: Ruddick et al. (2014), Challenges and opportunities for geostationary ocean colour remote sensing of regional seas: A review of recent results, RSE, 146, 63-76.
Sun-synchronous (MODIS, MERIS etc) Geostationary (GOCI)
Launch 1999/2002 - 2010
Temporal resolution Daily to 1 image every 3 days Hourly
Temporal coverage 1.30PM LST equator crossing 8 images per day
Spatial resolution 1 km (up to 300 m with MERIS) 500 m
Spectral resolution 16 bands (visible + NIR) 8 bands (visible + NIR)
Swath ~ 2,000 Km ~ 2,000 Km
Advantages • global applications of near-daily
acquisition of data for the entire earth
from a single sensor
• Well established (for 10+ years,
algorithms are well developed)
• more spectral bands
• Greatly increased temporal
resolution
• Can resolve fast processes
relating to diurnal variability of
biological processes/ tidal …
Challenges • Clouds = still number one problem
• Can’t resolve tidal processes in dynamic
coastal environments ….
• Limited spectral resolution
• No none of the Short Wave
Infrared band necessary for
turbid water atmospheric
corrections…
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Geostationary satellites: the future of ocean
colour remote sensing at a regional scale
David Blondeau-Patissier
Remote Sensing Group
Purple 12, office 2.26
Source: J-H Ryu, KOSC, "GOCI status and GOCI-II plan"
Hyperspectral Ocean colour sensors :
Example of HICO
HICO: Hyperspectral Imager for the Coastal Ocean
• Agency: Office of Naval Research
• On-board International Space Station
• Launched : 18 September 2009
• Altitude: ~ 350 km
• Repeat cycle: limited
• Swath: 50 km
• Resolution: 100 - 500 m
• Hyperspectral : >80 bands, 380 – 900nm
The International Space Station
From “The Hyperspectral Imager for the Coastal Ocean (HICO): Sensor and Data Processing Overview”, by Curtiss O. Davis,
Oregon State University (USA)
Hyperspectral Ocean colour sensors :
Example of HICO – Key Largo, Florida Keys
Chlorophyll-a Attenuation Backscattering
Search Criteria
Time Period: Entire mission (daytime)Sensors: HICO(ISS)
Area of Interest: region bounded by 12.0S and 13.0S and 130.0E and 131.0E
Number of swaths: 21 swaths
Hyperspectral Ocean colour sensors :
Example of HICO – Darwin