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Landsat
Orbit
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The Landsat satellites have repetitive,
circular, sun-synchronous, near-polar orbits,
providing full coverage between 81°N
and 81°S. The sensors always scan the
ground at satellite nadir. The sun-synchronous
orbit means that all acquisitions over
a given area occur at the same time, giving
consistent shadows for the time of year.
The equatorial crossing time during descending
passes (ascending passes are at night)
is, for all Landsat Missions, between 9:30
and 10:00 local time.
A Landsat track is 183km wide. The repeat
cycle for Landsat 4,5 & 7 is 16 days. Landsat
7 was launched on April 15, 1999, and orbits
8 days behind Landsat 5.
Sensors
Landsats 1—3 carried the Return Beam
Vidicon (RBV) camera and the Multispectral
Scanner (MSS). The second generation of
Landsat satellites, beginning in 1982 with
Landsat 4, carries a Thematic Mapper (TM)
in addition to the MSS. Landsat 7 is equipped
with an Enhanced Thematic Mapper, ETM+.
ETM+ brings a number of advantages over
its predecessor, with a Panchromatic band
with 15 metres resolution intrinsically
registered with the multispectral bands,
while the resolution of the thermal infrared
has improved to 60m. There is an on-board
Solid State Recorder (SSR) with 378 Gb
(500 full scenes) of data capacity. |
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