Landsat

Landsat Satellite System

Overview/History

Landsat was the first program to launch Earth monitoring satellites into orbit. This began in 1972 when Landsat 1, formerly known as the Earth Resources Technology Satellite, was launched with the purpose of studying and monitoring the Earth’s landmasses. Landsat is a joint program of NASA and the USGS that has been helping all of humanity understand how the Earth has been changing for nearly forty years.

Since 1972, seven Landsat satellites have been launched, with six of them successfully reaching their desired orbit. Landsat 6 was the only Landsat satellite that wasn’t able to reach its orbit due to mechanical problems in 1993. Currently, Landsat 5 and Landsat 7 are the only Landsat satellites still in use. In January of 2013, however, the Landsat Data Continuity Mission is scheduled to launch with the goal of maintaining the continuity of the Landsat data record.

Spatial/Spectral/Time Resolution

Landsat 7 sensors have 185km swath and a moderate spatial-resolution (30 m), which means its images do not allow you to see smaller objects such as individual houses, but you can see roads and other larger man-made objects. Having a moderate spatial-resolution is effective because it allows an image to have global coverage while still being able to see human-scale processes and events such as urban growth or deforestation. Landsat 7 orbits the Earth around fourteen times per day at an altitude of 705km.

Pros

The orbit swaths are wide enough for global coverage every season of the year. The images are detailed enough to be able to analyze a diverse range of things such as coral reefs, Antarctic glaciers, and tropical deforestation. Landsat images are also detailed enough to make maps showing fault lines and environmental change. Also, Landsat has more multispectral bands than other commercial satellites and the data is free.

Cons

Landsat images do not have enough resolution to show smaller objects on earth such as individual houses in much detail. Data can be complicated and can require a lot time to be processed, sometimes taking as long as sixteen days. One organization mentioned the unsure future of Landsat as a con.

Examples of Use

The use of Landsat images is very diverse. An example I found is from an article on NASA’s website involving irrigation in Idaho. Farmers in Idaho use Landsat data to map evapotranspiration in order to ensure they are effectively utilizing every drop of water. Agriculture is huge in Idaho and water is very scarce because it does not rain very often. "It is the consistent relationship between surface temperature and heat transfer to the air that allows researchers to calculate evapotranspiration for every pixel in a satellite image." To be able to calculate how much available energy was heating the ground air allows them to estimate how much was being used for evapotranspiration. Using the spatial resolution (a 30 meter pixel) from a Landsat image allows farmers to know how much water was being used in each field. Other examples of use include cancer research and atmospheric modeling studies.