In a September 21, 1966 press release, Secretary of the Interior Stewart Udall announced that the DOI was launching "Project EROS (Earth Resources Observation Satellites)." Udall's vision was to observe the Earth for the benefit of all.
The Landsat Missions are currently comprised of eight Earth-observing operational satellites that carry remote sensors to collect data and image our planet as a part of the U.S. Geological Survey (USGS) National Land Imaging (NLI) Program. Landsat data is processed and hosted at the USGS’s Earth Resources Observation and Science (EROS) Center in Sioux Falls, South Dakota.
Beginning in the 1960s, the remote sensing and science community worked to realize these missions for the benefit of humankind. Geography, geology, hydrology, and other natural resource management fields have all benefited from the holistic view of the Earth.
In a September 1966 press release, then Secretary of the Interior Stewart Udall, announced that the Department of the Interior (DOI) was launching "Project EROS (Earth Resources Observation Satellites)" to collect invaluable information about Earth through remote sensing satellite observation. Udall's vision was to observe the Earth for the benefit of all. Secretary Udall boldly revealed that National Aeronautics and Space Administration (NASA) and the DOI would collaborate on Earth-observing space technology to monitor the planet’s natural resources. He stated "the program will provide us with the opportunity to collect valuable resource data and use it to improve the quality of our environment."
The DOI, NASA, and the U.S. Department of Agriculture (USDA) then embarked on an ambitious effort to develop and launch the first civilian Earth observation satellite. These revolutionary satellites would be set in a heliosynchronous, near-polar orbit, completing several revolutions around the Earth every day to capture the land surface of the planet. The heliosynchronous, near-polar orbit means the satellite passes near the North and South pole consistently as it revolves around the Earth. This type of orbit allows a Landsat spacecraft to pass over the equator at a different longitude on each revolution, resulting in the spacecraft completing a full image of our planet after 251 orbits, about 16 days.
The interagency effort achieved their goal on July 23, 1972, with the launch of the Earth Resources Technology Satellite (ERTS-1), later renamed Landsat 1. Project EROS led to numerous international collaborations focusing on science and technology including a fundamental one on how to operate Landsat.
At the time, nations around the world utilized the Landsat data, but there was no conventional labeling system for scenes developed. To catalog Landsat imagery collected over Canada, the Canada Centre for Remote Sensing (CCRS) set up a series of grid paths across their country drawn parallel to latitude lines. The USGS later adopted this schema extending the reference to the entire surface of the planet. This grid reference system became known as the Worldwide Reference System (WRS-1). After the expansion, WRS-1 descending had a total of 251 paths and 119 rows where each intersection of a path and a row denotes the nominal center of a Landsat scene. Today, we use Worldwide Reference System-2 (WRS-2), an extension of the WRS-1 notation system. WRS-2 descending has 233 paths and 124 rows for a sixteen-day ground coverage cycle. Landsat 1 through 3 used WRS-1, and Landsat 4 through 9 uses WRS-2. Each day, Landsat 8 and 9 together capture 28 swaths, or paths, cumulating to a full image of Earth every 8 days.
Each commissioned satellite carried the storied heritage of the program. The launches of Landsat 2, Landsat 3, and Landsat 4 followed in 1975, 1978, and 1982, respectively. When Landsat 5 launched in 1984, no one could have predicted that the satellite would deliver high quality, global data of Earth’s land surfaces for 28 years and 10 months. This officially set a new Guinness World Record for "longest-operating Earth observation satellite." Landsat 6 failed to achieve orbit in 1993. As a result of the lost mission, the satellite is not included in successful Landsat counts. The remainder of Landsat satellites have proved successful launches and data collection: Landsat 7 in 1999, Landsat 8 in 2013, and Landsat 9 in September 2021. All Landsat satellites have launched from Vandenberg Air Force Base (as of May 2021, known as Vandenberg Space Force Base).
The next mission, Landsat Next, is planned for launch in 2030. Landsat Next will be a constellation of three observatories sent into orbit on the same launch vehicle, will provide improved temporal revisit on a new World Reference System, return data in a total of 26 spectral bands and will collect on average about 20 times more data than Landsat 9.
The enduring legacy of Project EROS continues with the Landsat program to this day. The information gathered by multiple Earth observation satellites, such as Landsat, now serves as a common, reliable record for environmental change around the world. Indeed, in the last half century, the record of Earth observation from space has become the indispensable foundation of almost all deliberations about the state of the planet. Secretary Udall’s vision has fundamentally remade how we see and understand our planet.
