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
