Landsat

Overview

Landsat is the Land Remote Sensing Satellite Program managed by the U.S. Geological Survey (USGS). The Landsat Satellite series began in 1972 to gather information about land surface features of the planet. These satellites collect remotely sensed imagery of the Earth’s surface at moderate resolution.

Landsat 1 was launched in 1972 as the Earth Resources Technology Satellite. It transmitted data until 1977. Landsat 2 was launched in 1975 and transmitted data until 1977. Landsat 3 was launched in 1978 and returned MultiSpectral Scanner (MSS) data until 1982, when NASA launched Landsat 4.

Landsat 5, launched in 1984, and Landsat 7, launched in 1999, are still in orbit and have continued to supply images and data for the many users of the information, but they are operating beyond their designed life and may fail at any time. In November 2011, imaging from Landsat 5 was suspended due to technical difficulties.

Landsat has been used in a wide variety of applications, including climate research, natural resources management, commercial and municipal land development, public safety, homeland security and natural disaster management. Despite its wide use, efforts in the past to commercialize Landsat operations have not been successful. Most of the users of the data are other government agencies. For that reason, funding a replacement for the failing Landsat orbiters has been a federal responsibility.

Landsat stakeholders include (1) investigators in geophysical and atmospheric sciences; (2) decision makers and program managers at NASA, USGS, and other federal agencies, including land management agencies; (3) international government and military decision makers; (4) for-profit enhanced Landsat products distributors; and (5) consumers of commercial land surface imagery and environmental data.

Despite its long history, the Landsat satellite series has never been considered a truly operational capability. All Landsat satellites have been justified, built, and flown as experimental, scientific research systems with no assurance of the long-term continuity of the data.

For close to 30 years, the policy of the federal government has been to encourage commercialization of space capabilities and systems including Landsat. Despite previous attempts to commercialize moderate-resolution data-collection in the United States, a viable commercial option has not yet emerged even though the products are used widely by governments, government support contractors, universities, private for-profit, and nonprofit organizations.

Some of the challenges that have inhibited commercialization include: lack of expected market growth, higher costs for Landsat products (to help cover investment costs and profit expected by the private sector), failure to realize operating costs savings, inhibited applications of the data, and reduced data use by the end-users resulting from these cost factors.

Unique aspects of Landsat

The U.S. Landsat satellite series is unique and unparalleled in the world. Since 1972, Landsat satellites have provided data for both U.S. and global needs, and these data are essential for meeting the needs of many levels of government, including Federal, State, local, and tribal jurisdictions. Such data are critical in national and global agricultural assessments performed by the U.S. Department of Agriculture and provide essential data for U.S. international agencies. For example, the U.S. Agency for International Development's Famine Early Warning System Network currently uses Landsat imagery for food security applications for numerous nations in Africa, the Middle East, and Central Asia. In addition, numerous U.S. and international land cover programs rely on Landsat data for human health and ecological planning. Landsat data are also used for U.S. national and homeland security operations.

Three characteristics make the existing U.S. moderate-resolution land imaging system unique:

• Landsat is the only moderate-resolution satellite that provides global cloud-free coverage of the entire Earth’s land surface on a seasonal basis.
• The radiometric, spectral, and geometric quality of Landsat’s imagery is unparalleled and its coverage across several key spectral bands is unique among the world’s satellites.
• The 35-year-old U.S. Landsat archive, managed by the U.S. Geological Survey, is a unique repository of satellite imagery, allowing accurate comparisons of natural and human-induced changes on the Earth’s surface over several decades.

How Landsat works

Landsat sensors record reflected and emitted energy from Earth in various wavelengths of the electromagnetic spectrum. Today, Landsats 5 and 7 "see" and record blue, green, and red light in the visible spectrum as well as near-infrared, mid-infrared, and thermal-infrared light that human eyes cannot perceive (although we can feel the thermal-infrared as heat). Landsat records this information digitally and it is transmitted to ground stations, where it is processed, and stored in a data archive.

Landsat is designed to provide "relatively high" resolution images of the Earth (thus its designation as a moderate-resolution satellite) and "relatively frequent" coverage of the whole Earth (thus its typical classification as a research satellite dedicated to climate science), so it falls in between high- and low-resolution imaging systems. As such, Landsat is designed to satisfy a broad range of requirements in both the operational sciences and basic science. Nonetheless, Landsat properly belongs to the operational science community given the breadth of its uses for civil and security applications.

History of Landsat

The year Landsat 5 was launched Congress decided that land satellites could be privatized (Land Remote Sensing Commercialization Act of 1984). NOAA, the agency in charge of all Landsat operations, was instructed to find a commercial vendor for Landsat data. NOAA selected Earth Observation Satellite Company (EOSAT).

The contract gave EOSAT the responsibility for archiving, collecting and distributing current Landsat data as well as the responsibility for building, launching and operating the following two Landsat satellites (with government subsidies).

Commercialization proved troublesome, EOSAT had limited commercial freedom due to provisions of the 1984 law. Given these constraints, NOAA and then EOSAT raised image prices from $650 to $3700 to $4400 and restricted redistribution. While the U.S. monopoly of Landsat-like data made this 600% increase feasible, the practice priced out many data users. (As a result, many data users migrated to the free low-resolution land data being captured by meteorological satellites.) In 1986, a French Landsat-like satellite launch broke the U.S. monopoly.

During the EOSAT commercialization era, Landsat coverage standards languished. Many observations from 1984 to 1999 were missed because there was no obvious and immediate buyer. With commercial data marketing, it makes sense to only collect data for which there is an established customer, whereas a true scientific mission collects as much global data as possible for future scientific study. Landsat 4 and 5 system calibration and characterization lapsed during this period as well.

By 1989, with two aging satellites and no operational budget, NOAA directed EOSAT to turn off the satellites (no government agency was willing to commit augmentation funding for continued satellite operations and data users were unwilling to make the hefty investments in computer processing hardware if future data collection was uncertain). The program was only saved by a strong protest from Congress and foreign and domestic data users, and an intervention by the Vice-President.

Given this outcry and the unexpected outcome of privatization, Congress passed the Land Remote Sensing Policy Act of 1992, which instructed Landsat Program Management to build a government-owned Landsat 7. Two years after the launch of Landsat 7, Space Imaging (formerly EOSAT) returned operational responsibility for Landsat 4 and Landsat 5 back to the U.S. Government.

On July 1, 200l when operational control was officially returned to the federal government, Space Imaging also relinquished their commercial right to Landsat data, enabling the USGS to sell all Landsat 4 and Landsat 5 data in accordance with the USGS pricing policy.

NASA and the USGS jointly operate Landsat today. The two agencies are developing a follow-on initiative known as the Landsat Data Continuity Mission (LDCM). The LDCM spacecraft (LDCM 1 or Landsat 8), with its instrument payload, was planned for launch in December 2012, but is now scheduled for January 15, 2013, at the earliest. NASA advanced the project to its final pre-launch development phase November 8, 2011, proceeding to final assembly and testing of the integrated satellite system and the launch of the satellite. With LDCM 1 proceeding to launch, interest is shifting to follow-up missions.

Sources

• A Plan for a U.S. National Land Imaging Program, at 2.
• Landsat and the Data Continuity Mission, Summary, 1, 2.

External resources

• NASA, Landsat History (full-text).
• NASA, Landsat Then and Now (full-text).
• NASA, The Landsat Program, Landsat News, The Numbers Behind Landsat (full-text).