-------- Original Message --------
Subject:        Landsat Longevity Update
Date:   Fri, 3 Apr 2009 11:22:21 -0500
From:   John C Fouke <[log in to unmask]>
To:



Below is a statement from EROS about the longevity of Landsats 5 and 7,
and the anticipated launch of Landsat 8, although obviously these dates
are speculative in nature because of all the variables.

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It is extremely difficult to predict when the useful life of an aging
earth-observing satellite will end.  At any time, a failure could occur
within its imaging instrument, such as having its scanning mirror fail to
move properly; the satellite's data transmitters could fail, which would
keep image data from reaching a ground receiving terminal; its
flight-control gyroscopes could fail, etc.  To date, the satellite and
sensor subsystems on Landsat 5 and Landsat 7 have shown remarkable
endurance even though both satellites are well beyond their
engineering-design lifetimes.

If no major subsystem shows signs of failure, then a satellite's
orbit-positioning fuel reserve becomes the logical source for projecting
the mission's end of life.  To that end, the projected dates for end of
life of Landsat 5 and Landsat 7 are re-computed periodically -- based on
actual vs. projected fuel usage and assuming no subsystem fails.  Current
USGS fuel-use projections show both satellites operating up to and
somewhat beyond the launch of the Landsat Data Continuity Mission
(LDCM/Landsat 8), currently scheduled for December 2012.