CHAPTER 7 SECTIONS > Overview | Scan-correlated Shift | Memory Effect | Coherent Noise
Dropped Lines | Inoperable Detectors | Banding | Striping
Analyses performed on Landsat 5 data over the years has revealed the
existence of imperfections or image artifacts caused by the instrument's
electronics, dead or dying detectors, and downlink errors. As a decendant
of the Thematic Mapper, the ETM+ generates data with similar characteristics.
In the past, these effects were ignored or artificially removed using
cosmetic algorithms such as histogram equalization during radiometric
processing. A proactive approach is in place for Landsat 7. The goal of
the ground system is to remove image artifacts prior to radiometric processing.
Remnant artifacts, if they exist, are subsequently removed in a post-processing
step using cosmetic algorithms.
The known ETM+ image artifacts are scan correlated shift, memory effect,
modulation transfer function, and coherent noise. Dropped lines and inoperable
detectors also exist as a result of decommutating errors and detector
failure. Remnant artifacts which may exist include banding and striping.
A discussion of each of these effects and characterization methodologies
follows. Eliminating their presence from data products is addressed in
a later chapter on Level 1 processing.