Landsat Multi-Spectral Scanner (MSS)
Landsat (MSS) Information
There have been many research projects here at CALMIT which have been foccussed upon studying wetlands here in Nebraska, particularly in the Western Sandhills region. Nearly all of these projects have made use of data from the Landsat series of satellites. Most of the data that has been gathered came from the sensor onboard the Landsat satellite called the Multi-Spectral Scanner, or MSS. The MSS was in operation from August of 1972 until September 1992.
It gathered image data in four bands, reflected green light, reflected red light, and two reflective near-infrared (NIR) bands; the latter two have been referred to as NIR1 and NIR2.The size of the smallest picture element of the MSS images is about 80 meters. This would mean than object would have to be about 240 feet long and about 240 feet wide before the sensor on the satellite could "see" it.
|Band Number||Color in Spectrum||Wavelength, nanometers|
|1||Green||500 - 600|
|2||Red||600 - 700|
|3||NIR1||700 - 800|
|4||NIR2||800 - 1100|
In 1992, the last MSS sensor in use (in Landsat 5) was shutdown in order to conserve Landsat 5's onboard resources which allowed the Thematic Mapper (TM) sensor to continue its normal operation.
Even though the MSS is no longer functioning, the data that it acquired is still being used in current research efforts here at CALMIT. What follows below is a time-series of images that were acquired of an area in the Western Nebraska Sandhills during the 1983 growing season.
Landsat (MSS) Interpretation
The images are shown as standard color infrared images. In this type of image, the bands NIR2, Red, and Green (4,2, and 1) are represented as red, green and blue layers on the picture. This is the image that you would see if you would be looking at a color infrared photograph.
In these images, red tones are associated with vegetation. You can see that there is quite a bit of vegetation around the wetlands as well as some vegetation that is present as crops that are being irrigated by center-pivot irrigation systems. The center pivots are easy to spot because of their very round shape.
Can you see any changes in the fields being irrigated by the center-pivot systems over the course of the growing season? What activities are being represented by these changes?
There is a sparse cover of grass that is covering most of the area, but it doesn't show up as red because it just isn't thick enough. The wetland vegetation shows up very well because it is thick and lush enough. You can see how the extent of the vegetation varies with the availability of water and you can also see how the vigor of the wetland vegetation changes over the growing season. In the latter case, the wetland vegetation is largely dormant until around May when the plants have started to receive enough solar radiation for photosynthesis to really begin in earnest. Additionally, its about this time that the temperatures are warming up enough to facilitate the growth processes.
< There are some features that may be a little difficult to identify. For example, the white features on the April 2, 1983 image aren't clouds, as one might expect, but they are snow. Snow is highly reflective in all of the MSS bands so the combination of all of the three bands makes the snow appear white, just as you would see in a regular color photograph. This could create a problem when you are trying to make a distinction between snow and clouds, which also appear as white features. There are several complicated methods that can be used to identify which white features are clouds and which is snow. One of the simplest is that clouds will project black shadows whereas snow will not. The June 21, 1983 image has some clouds in the upper-right corner of it.
During this time of the year, the sun appears to us on the ground as being in the eastern sky. If that is true, then what compass direction do the shadows that are being cast by the clouds point toward?
If these were images of New Zealand (which is at approximately 40 degrees south latitude) during its summertime, what compass direction would the shadows cast by the clouds point toward?
|March 1, 1983||April 2, 1983||May 4, 1983||June 21, 1983|
|July 7, 1983||August 8, 1983||September 25, 1983||October 27, 1983|