space
Reference:

Landsat: Four Decades of Images and Data

Landsat is an ongoing series of satellites that conduct Earth observations. The satellites have been used to track urban sprawl, monitor the effects of climate change, and see how deforestation affects the surrounding landscape. The program has run continuously since 1972, so scientists have four decades of information in hand to track changes in land use over time.

Over the years, the Landsat program has been shifted to different government agencies and went through an aborted attempt to commercialize it in the late 1980s and early 1990s. At one point, a government agency was prepared to shut the satellites off. The program, however, continues functioning today under government management, with Landsat 7 still working in orbit and Landsat 8 is set to launch in February 2013.

Seeking more Earth information

Early human spaceflight missions, according to NASA, provided the impetus for a satellite that would constantly look at the Earth. In the 1960s, there was little information available for weather prediction or land use. This made it difficult for scientists to obtain information about how the world works, and how people use resources.

Some of the Mercury, Gemini and early Apollo missions included Earth photography. In 1965, the then-director of the U.S. Geological Survey proposed a long-term satellite mission to improve the data.  On a website about Landsat's history, NASA wrote that the proposal carried much controversy.

"It met with intense opposition from the Bureau of Budget and those who argued high-altitude aircraft would be the fiscally responsible choice for Earth remote sensing," NASA stated.

"The Department of Defense feared that a civilian program such as Landsat would compromise the secrecy of their reconnaissance missions. Additionally, there were ... geopolitical concerns about photographing foreign countries without permission."

The first Landsat satellite - ERTS-1.
The first Landsat satellite - ERTS-1. It launched on July 23, 1972.
Credit: NASA
The first fully operational Landsat image taken on July 25, 1972, inaugurating a 40-year run when the first satellite was known as the Earth Resources Technology Satellite, or ERTS.
The first fully operational Landsat image taken on July 25, 1972, inaugurating a 40-year run when the first satellite was known as the Earth Resources Technology Satellite, or ERTS.
Credit: NASA’s Earth Observatory

Landsat 1 – then known as the Earth Resources Technology Satellite – launched successfully on July 23, 1972.

Notably, it was equipped with a special sensor called a multispectral scanner, which allowed images of Earth in four different types of wavelengths – green, red, and two bands of infrared. This is important as vegetation, water and other parts of the Earth tend to "show up" best in different bands of light.

Landsat 1's success spawned a series of other Earth-sensing satellites that were similar in construction and capabilities. Landsat 2 followed just 2.5 years later, on Jan. 22, 1975. Then Landsat 3 made it into orbit on March 5, 1978 – just two months after Landsat 1 ceased functioning.

Commercialization and near-death

As the satellites steadily made their way into space, program changes were brewing. President Jimmy Carter issued Presidential Directive 54 in 1979 transferring operations of Landsat, which were then under NASA, to the National Oceanic and Atmospheric Administration.

The shift, according to NASA, was to make Landsat an operational program rather than one of pure research. Carter further directed that Congress assist NOAA with shifting the program to the private sector.

"Our goal is the eventual operation by the private sector of our civil land remote sensing activities," Carter stated in the directive. Congress would receive money in fiscal year 1981 to start the transition.

Four years later, in 1985, American companies Hughes Aircraft and RCA began a joint venture (called Earth Observation Satellite Company, or EOSAT) to take over operations. By this time, Landsats 4 and 5 were in orbit.

But moving the satellites to a commercial operation was "troublesome," according to a NASA website. The act transferring responsibility to EOSAT only allowed the entity certain ways of raising money.

"Given these constraints, NOAA and then EOSAT raised image prices from $650 to $3,700 to $4,400 and restricted redistribution. While the U.S. monopoly of Landsat-like data made this 600 percent increase feasible, the practice priced out many data users," NASA stated.

Some users migrated to lower-resolution images, NASA added, and by 1986 France had put its own competing system above Earth – SPOT, a French acronym for "System for Earth Observation." Low data usage, old satellites and uncertainty in government funding continued for years, until in 1989 NOAA told EOSAT to turn off Landsats 4 and 5.

"The program was only saved by a strong protest from Congress and foreign and domestic data users, and an intervention by the vice president (Dan Quayle)," NASA wrote on the website.

Timeline showing lifespans of the Landsat satellites.
Timeline showing lifespans of the Landsat satellites.
Credit: NASA

New Landsat flying in 2013

Congress restricted NOAA's budget for Landsat in 1990 and 1991, with the idea being that users of Landsat data would pick up part of the tab. (Notably, NOAA did not request funds for operating the satellites.) The measure didn't work as well as hoped. So in 1992, Congress passed the Land Remote Sensing Policy Act to start construction of Landsat 7 with government funding.

Landsat 6, unfortunately, failed during launch in 1993, accelerating the need for a new satellite. Users feared there could be a gap in coverage because the predecessor satellites were so old, but by the time Landsat 7 launched in 1999, Landsat 5 was still operational – and in fact, was still working as of early 2013. NASA planned to retire the 29-year-old satellitein the first few months of the year.

Compared to the first Landsat, Landsat 7 can take pictures in far more spectral bands, and it can transmit data faster to Earth. The U.S. Geological Survey made all of the satellite's data free to users in 2008, accelerating the use of the pictures. The move also made the information more accessible to developing countries.

More recently, the satellite's advanced age is drawing concern from critics worried about the viability of the aging Earth observation infrastructure.

In 1998, the U.S. Geological Survey began operating the satellites after they were transferred from NOAA. Space Imaging (formerly EOSAT) transferred management to the department in 2001.

Landsat 7 continues operating today, although the satellite suffered a partial hardware failure that reduces the size of some of its images. NASA plans to launch the next satellite, called the Landsat Data Continuity Mission, on Feb. 11, 2013, from the Vandenberg Air Force Base in California.

NASA plans to put the satellite into a polar orbit, which allows it to image all areas of Earth. It will circle the globe 14 times a day, taking pictures from about 438 miles (705 kilometers) above the surface. Every 16 days, the satellite will return to the same spot above Earth.

— Elizabeth Howell, SPACE.com Contributor

landsat 8
An artist's concept of Landsat 8, the Landsat Data Continuity Mission.
Credit: NASA

Related:

More from Space.com