Landsat Missions
Figure 1. Night Data, Band 1 Detector 9 Click to view larger image. |
Figure 2. Water Imagery, Band 1 Detector 9 Click to view larger image. |
Figure 3. Terrain Imagery, Band 1 Detector 9 Click to view larger image. |
Figure 4. Night Data, Band 8 Detector 14 Click to view larger image. |
Detector Ringing is an artifact that affects a few detectors on Landsat 7 ETM+. This anomaly appears as alternating bright and dark pixels that appear suddenly and with no obvious cause. The intensity of the ringing gradually diminishes until the detector returns to normal operation. The initial magnitude of a ringing event may be 200 DN or more. Because this value adds to any underlying imagery, this artifact almost always saturates the detector data at 0 or 255, or both.
We have found a relationship between the Detector Ringing events and the appearance of anomalous coherent noise. While using the Side A electronics, only three detectors have exhibited ringing behavior: Band 1 detectors 9 and 11, and Band 8 detector 14. These detectors also have the largest magnitude anomalous coherent noise.
The current theory to explain this relationship is that charge buildup on the spacecraft leads to a dialectric breakdown event that allows noise current to enter the circuitry. The dialectric breakdown event creates a Detector Ringing artifact, and the noise current is the source of the anomalous coherent noise. This theory is supported by the observation that ringing artifacts are more frequently found at the beginning of subinterval collections. Moreover, the artifacts occur slightly more often in data over polar regions where the charged particle environment of the satellite is strongest. Ringing events have occurred less frequently since the failure of the Scan Line Corrector in 2003, but they are still sometimes observed.
Detector Ringing artifacts are uncorrectable, but they are not expected to cause any lasting damage to the detectors involved. They have been rare on Landsat 7 ETM+. An examination of the Image Assessment System (IAS) trending database estimates that one percent of all Landsat imagery contains ringing artifacts.
See Also – Coherent Noise, Coherent Noise Storm, Detector Failure
U.S. Department of the Interior |
U.S. Geological Survey
URL: http://landsat.usgs.gov
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Page Last Modified: May 13, 2008
