Landsat: 5 decades of imagery and data

Landsat’s legacy

The latest in NASA’s series of Landsat satellites – Landsat 9 – launched this week, on September 27. It’ll continue what’s now a 50-year record of Landsat images and data, showing Earth changes, acquired from Earth-orbit. So far, there are 9 million space images of our home planet’s landscapes and coastlines in the Landsat series. All are free to scientists to analyze and understand. Landsat is NASA’s workhorse satellite series. Aloft since 1972, these satellites have provided the longest-running continuous record of what’s happening on Earth.

The Landsat series began on July 23, 1972, when NASA and the U.S. Geological Survey (USGS) launched the Earth Resources Technology Satellite (ERTS-1) into orbit. They later renamed it Landsat 1. It was the first Earth-observing satellite launched with the idea of monitoring Earth’s surface.

Since then, there has always been at least one Landsat satellite in orbit, looking towards Earth. These satellites continuously and consistently collect global imagery. They’ve created a historical archive unmatched in quality, detail, coverage, and length. The images let researchers monitor important trends such as agricultural productivity, forest extent and health, water quality, coral reef habitat health, and glacier dynamics. They show humanity’s spread. After all, there are more than twice as many people on Earth now as there were when the Landsat program began in 1972. All along, Landsat’s goal has been to give land managers and policymakers tools for making wise decision about Earth resources.

In December 2020, speaking with Alok Patel of PBS’s NOVA Now podcast, NASA project scientist Jeff Masek said:

When you grow up in an area, you don’t really notice the changes that occur over years and decades. But when you run the movie in fast motion, suddenly we see all these changes: urbanization and changes in forest management, areas where agricultural irrigation suddenly goes into desert environments.

The launch of Landsat 9

The latest satellite in the Landsat series, Landsat 9, launched this week on Monday, September 27, 2021. It’s the ninth in the Landsat program and will work in tandem with Landsat 8 to collect images, able to cover the entire planet every eight days. The satellite duo will help track urban sprawl, forest cover, and the retreat of glaciers, among other features and phenomena. Technology marches on, and so Landsat 9 is outfitted with two unique instruments expected to provide better imaging than ever before.

The Operational Land Imager 2, or OLI-2, has an image swath 115 miles wide (185 km) with enough resolution to distinguish land cover features like urban centers, farms, and forests. Each pixel in these images represents an area about 98 feet (30 m) across. At this resolution, individual houses aren’t distinguishable, but researchers can see large human-made objects such as highways.

The second instrument is the Thermal Infrared Sensor 2, also known as TIRS-2. It will measure land surface temperature in two thermal infrared bands, using quantum physics principles to measure infrared energy emissions.

Putting Landsat to use

NASA was in charge of building and launching Landsat 9, though the U.S. Geological Survey (USGS) will operate the satellite and process its data. All Landsat images and the embedded data are free and publicly available. It’s resulted in more than 100 million downloads since it was made public in 2008.

Thomas Zurbuchen, associate administrator for science at NASA, said in a statement:

Landsat 9 will be our new eyes in the sky when it comes to observing our changing planet. Working in tandem with the other Landsat satellites, as well as our European Space Agency partners who operate the Sentinel-2 satellites, we are getting a more comprehensive look at Earth than ever before. With these satellites working together in orbit, we’ll have observations of any given place on our planet every two days. This is incredibly important for tracking things like crop growth and helping decision-makers monitor the overall health of Earth and its natural resources.

Watch this video for a Landsat road trip through time.

Bottom line: The Landsat program provides the longest continuous space-based record of Earth’s land in existence. Every day, Landsat satellites provide essential information to help land managers and policy makers make wise decisions about our resources and our environment.

Source: NASA

Via Space.com