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Remote
sensing of ocean colour from space began in 1978 with the successful launch
of
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NASA's
Coastal Zone Color Scanner (CZCS). Despite the fact that CZCS was an experimental
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mission
intended to last only one year, the sensor continued to generate a valuable
time-series
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of
data over selected test sites until early 1986. Ten years passed before
othere sources of
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ocean-colour
data became available with the launch of MOS, OCTS
and POLDER in 1996,
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and SeaWiFS in 1997. Several new
ocean-colour sensors have recently been launched and still
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more
are planned for the near future by various space agencies.
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There
are two types of orbits for Earth observation satellites, polar orbiting and geostationary.
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Polar-orbiting
satellites typically operate at an altitude of around 800 km, with a
revisit time of
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2-3
days, whereas geostationary satellites operate in time scales of hours,
which could
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theoretically
provide data on the diurnal variation in phytoplankton abundance and
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productivity.
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