What is Landsat?

The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey (USGS). In 1972, the launch of ERTS-1 (Earth Resources Technology Satellite, later renamed Landsat 1) started the era of a series of satellites that have since continuously acquired space-based land remote sensing data.

The latest satellite in the Landsat series, the Landsat Data Continuity Mission (LDCM), was launched on February 11, 2013. Now renamed Landsat 8, the data acquired by the satellite continues to expand the archive for users worldwide. Thanks to Landsat, today we have a better understanding of things as diverse as coral reefs, tropical deforestation, and Antarctica’s glaciers.

(Source: https://landsat.usgs.gov/about_project_descriptions.php)

The 30 m spatial resolution and 185 km swath of Landsat imagery fills an important scientific niche because the orbit swaths are wide enough for global coverage every season of the year, yet the images are detailed enough to characterize human-scale processes such as urban growth, agricultural irrigation, and deforestation. The video below shows the importance of the Landsat satellites in our understanding of change in land cover over time.

(Source: https://landsat.gsfc.nasa.gov/?page_id=2295)

With Landsat 8, the public can view real-time imagery. To view recent Landsat 8 imagery visit: 

EarthNow! Landsat Image Viewer

(the site may take a moment to load. The plugin Java(TM) is required to view this) 

How do scientists use Landsat Imagery to study the world using Landsat imagery? 

 Below are two pictures of the Chesapeake Bay that focuses over Baltimore, Maryland and Washington D.C.

The picture on the left is in the same colors of how your eyes would normally see an image. We see things in the visible part of the electromagnetic spectrum. This is called a "true color" image. This image was made using the red, green, and blue bands from Landsat (see the table below).  The picture on the right was taken at the same exact time, but scientists have assigned different bands (the infrared band) to the image that our eyes might not normally see. This image is called a “false color” image. Notice that nearly everything in the true color image what was a shade of green is a shade of red in the false color image.  The reason why scientists would do this is because we can see where the healthiest vegetation is located.  The brighter the red, the healthier the vegetation. 

When Landsat transmits data back to Earth, scientists have an option to view 7 different bands, which are 7 different wavelength ranges of light. By knowing what each band can show us, scientists will put different band combinations together in order to see different things.  Below is a chart that shows the 7 bands of Landsat, the wavelength ranges, and what each band “sees” best.

(Source: https://compositor.gsfc.nasa.gov/index.html)

Landsat 4-5 Thematic Mapper (TM) and
Landsat 7 Enhanced Thematic Mapper Plus (ETM+)

Source: https://landsat.usgs.gov/best_spectral_bands_to_use.php

Review:

1. What is the purpose of the Landsat Satellites?

2. What is the difference between a true color and false color image?

3. Bonus! What band would help you determine the difference between a forest with mostly oak and maple trees and a forest of mostly pine and cedar trees?