Landsat Missions

Scan Mirror Pulse

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Known Issues

Landsat data are systematic, geometric, radiometric, and terrain corrected to provide the highest quality data to the user communities. Occasionally, anomalies occur and artifacts are discovered that require research and monitoring. The Landsat Calibration and Validation (Cal/Val) team investigates and tracks anomalous data.

A number of known issues regarding Landsat data are listed on this page. Updates to this list are not only made when new anomalies and artifacts are discovered, but also when investigations require changes to already existing issues.

If you discover data artifacts that are not listed here, please contact us.

Known Issues Home, Banding, Coherent Noise, Coherent Noise Storm, Data Loss, Detector Failure, Detector Ringing, Detector Striping, Gimbaled X-band Antenna (GXA) Anomaly, IC Intrusion, Impulse Noise (IN), Lower Truncation Acquisitions, Memory Effect (ME), Optical Leak, Oversaturation, Scan Correlated Shift (SCS), Scan Mirror Pulse, Shutter Synchronization Anomalies, Single Event Upset (SEU), Thermal Infrared Sensor Select Mechanism Anomaly

Scan Mirror Pulse

Example of Scan Mirror Pulse Anomaly in Landsat MSS scene.

Figure 1. Example of Scan Mirror Pulse Anomaly in Landsat MSS scene.

Operational Landsat 5 Multispectral Scanner (MSS) imaging continued until 1999, though downlinking over the United States halted in 1992. In January 1999, the MSS sensor was turned off due to an anomaly in the sensor scanning mechanism. In addition, in 1995 MSS Band 4 was switched off due to low voltage levels.

The MSS Scan Mirror Monitor transmits pulses to the on-board computer at the start of scan, at the mid-scan point, and at the end of scan. When functioning normally, the mid-scan pulse does not preempt imagery at the mid-scan point, and the start-of-scan indicator and end-of-scan marker (which do appear in the raw imagery) are removed during ground processing.

The scanning anomaly first noticed in mid-January of 1999 remained after the Landsat 5 MSS sensor was turned back on in 2012. An investigation showed that the mid-scan marker could not be turned off without also turning off all other pulse markers. Without the start-of-scan and end-of-scan markers, MSS data cannot be successfully processed to higher level products at this time. Thus, the decision was made to acquire L5 MSS data with all three scan mirror pulses.

This results in a normal looking scene except for the pulse at the mid-scan point (4 pixels of black and 4 pixels of white per line per band in the raw imagery). This is in all bands, and will appear as an eight pixel stripe down the center of the scene.

Location of scan marker in the image.

Figure 2. Location of scan marker in the image.

Close-up of scan marker

Figure 3. Close-up of scan marker.

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Landsat represents the world's longest continuously acquired collection of space-based moderate-resolution land remote sensing data. Four decades of imagery provides a unique resource for those who work in agriculture, geology, forestry, regional planning, education, mapping, and global change research. Landsat images are also invaluable for emergency response and disaster relief.

 

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Page Last Modified: 10/18/18 11:39 am
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