Answer:
In
1992, the U.S. Congress authorized the procurement,
launch and operation of a new Landsat satellite. This
new system, Landsat 7, was launched in April, 1999. It
is latest in a series of earth observation satellites
dating back to 1972. The thirty year record of data
acquired by the Landsat satellites constitutes the
longest continuous record of the earth's continental
surfaces. Preservation of the existing record and
continuation of the Landsat capability were identified
in the law as critical to land surface monitoring and
global change research. Landsat 7 has a unique and
essential role in the realm of earth observing
satellites in orbit. No other system matches Landsat's
combination of synoptic coverage, high spatial
resolution, spectral range and radiometric
calibration. In addition, the Landsat Project is
committed to providing Landsat digital data to the
user community in greater quantities, more quickly and
at lower cost than at any previous time in the history
of the Project. The earth observing instrument on
Landsat 7, the Enhanced Thematic Mapper Plus (ETM+),
replicates the capabilities of the highly successful
Thematic Mapper instruments on Landsat 4 and 5. The
ETM+ also includes new features that make it a more
versatile and efficient instrument for global change
studies, land cover monitoring and assessment, and
large area mapping than its design forebears. The
primary new features on Landsat 7 are:
-
a panchromatic band with 15m spatial resolution
-
on board, full aperture, 5% absolute radiometric
calibration
-
a thermal IR channel with 60m spatial resolution
