Landsat program
The Landsat program is the longest-running enterprise that has acquired satellite imagery of Earth. It is a joint NASA / USGS program. On 23 July 1972, the Earth Resources Technology Satellite was launched. This was eventually renamed to Landsat 1 in 1975. The most recent, Landsat 9, was launched on 27 September 2021.
The instruments on the Landsat satellites have acquired millions of images. The images, archived in the United States and at Landsat receiving stations around the world, are a unique resource for global change research and applications in agriculture, cartography, geology, forestry, regional planning, surveillance, and education, and can be viewed through the U.S. Geological Survey "EarthExplorer" website. Landsat 7 data has eight spectral bands with spatial resolutions ranging from ; the temporal resolution is 16 days. Landsat images are usually divided into scenes for easy downloading. Each Landsat scene is about 115 miles long and 115 miles wide.
History
In 1965, William T. Pecora, the then director of the United States Geological Survey, proposed the idea of a remote sensing satellite program to gather facts about our planet's natural resources. Pecora stated that the program was "conceived in 1966 largely as a direct result of the demonstrated utility of the Mercury and Gemini orbital photography to Earth resource studies."While weather satellites had been monitoring Earth's atmosphere since 1960 and were largely considered useful, there was no appreciation of terrain data from space until the mid-1960s. So, when Landsat 1 was proposed, it met with intense opposition from the Bureau of Budget and those who argued that high-altitude aircraft would be the fiscally responsible choice for Earth remote sensing. Concurrently, the Department of Defense feared that a civilian program such as Landsat would compromise the secrecy of its reconnaissance missions. Additionally, there were geopolitical concerns about photographing foreign countries without permission. In 1965, NASA began methodical investigations of Earth remote sensing using instruments mounted on planes.
In 1966, the USGS convinced the Secretary of the Interior, Stewart Udall, to announce that the Department of the Interior would proceed with its Earth-observing satellite program. This savvy political stunt coerced NASA into expediting the building of Landsat. However, budgetary constraints and sensor disagreements between application agencies again stymied the satellite construction process. Finally, by 1970, NASA had a green light to build a satellite. Remarkably, Landsat 1 was launched within only two years, heralding a new age of remote sensing of land from space.
The Hughes Aircraft Company from the Santa Barbara Research Center initiated, designed, and fabricated the first three Multispectral Scanners in 1969. The first MSS prototype, designed by Virginia Norwood, was completed within nine months, in the fall of 1970. It was tested by scanning Half Dome at Yosemite National Park. Norwood was called "The Mother of Landsat" for this design work.
Working at NASA's Goddard Space Flight Center, Valerie L. Thomas managed the development of early Landsat image processing software systems and became the resident expert on the Computer Compatible Tapes, or CCTs, that were used to store early Landsat imagery. Thomas was one of the image processing specialists who facilitated the ambitious 'Large Area Crop Inventory Experiment', known as LACIE — a project that showed for the first time that global crop monitoring could be done through remote sensing with Landsat satellite imagery.
The program was initially called the Earth Resources Technology Satellites Program, which was used from 1966 to 1975. In 1975, the name was changed to Landsat. In 1979, Jimmy Carter's Presidential Directive 54 transferred Landsat operations from NASA to the National Oceanic and Atmospheric Administration, recommended development of a long-term operational system with four additional satellites beyond Landsat 3, and recommended transition to private sector operation of Landsat. This occurred in 1985 when the Earth Observation Satellite Company, a partnership of Hughes Aircraft Company and RCA, was selected by NOAA to operate the Landsat system with a ten-year contract. EOSAT operated Landsat 4 and Landsat 5, had exclusive rights to market Landsat data, and was to build Landsats 6 and 7.
In 1989, this transition had not been fully completed when NOAA's funding for the Landsat program was due to run out, and NOAA directed that Landsat 4 and Landsat 5 be shut down.
The head of the newly formed National Space Council, Vice President Dan Quayle, noted the situation and arranged emergency funding that allowed the program to continue with the data archives intact.
Again in 1990 and 1991, Congress provided only half of the year's funding to NOAA, requesting that agencies that used Landsat data provide the funding for the other six months of the upcoming year.
In 1992, various efforts were made to procure funding for follow-on Landsats and continued operations, but by the end of the year, EOSAT ceased processing Landsat data. Landsat 6 was finally launched on 5 October 1993, but was lost in a launch failure. Processing of Landsat 4 and 5 data was resumed by EOSAT in 1994. NASA finally launched Landsat 7 on 15 April 1999.
Congress recognized the value of the Landsat program in October 1992 when it passed the Land Remote Sensing Policy Act, authorizing the procurement of Landsat 7 and assuring the continued availability of Landsat digital data and images, at the lowest possible cost, to traditional and new users of the data.
Satellite chronology
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bar:Landsat9 from:09/27/2021 till:06/04/2025 color:green
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Spatial and spectral resolution
Landsat 1 through 5 carried the Landsat Multispectral Scanner. Landsat 4 and 5 carried both the MSS and Thematic Mapper instruments. Landsat 7 uses the Enhanced Thematic Mapper Plus scanner. Landsat 8 uses two instruments, the Operational Land Imager for optical bands and the Thermal Infrared Sensor for thermal bands. The band designations, bandpasses, and pixel sizes for the Landsat instruments are:| Landsat 1–3 MSS | Landsat 4–5 MSS | Wavelength | Resolution |
| Band 4 – Green | Band 1 – Green | 0.5 – 0.6 | 60* |
| Band 5 – Red | Band 2 – Red | 0.6 – 0.7 | 60* |
| Band 6 – Near Infrared | Band 3 – NIR | 0.7 – 0.8 | 60* |
| Band 7 – NIR | Band 4 – NIR | 0.8 – 1.1 | 60* |
| Bands | Wavelength | Resolution |
| Band 1 – Blue | 0.45 – 0.52 | 30 |
| Band 2 – Green | 0.52 – 0.60 | 30 |
| Band 3 – Red | 0.63 – 0.69 | 30 |
| Band 4 – NIR | 0.76 – 0.90 | 30 |
| Band 5 – Shortwave Infrared 1 | 1.55 – 1.75 | 30 |
| Band 6 – Thermal | 10.40 – 12.50 | 120* |
| Band 7 – SWIR 2 | 2.08 – 2.35 | 30 |
| Bands | Wavelength | Resolution |
| Band 1 – Blue | 0.45 – 0.52 | 30 |
| Band 2 – Green | 0.52 – 0.60 | 30 |
| Band 3 – Red | 0.63 – 0.69 | 30 |
| Band 4 – NIR | 0.77 – 0.90 | 30 |
| Band 5 – SWIR 1 | 1.55 – 1.75 | 30 |
| Band 6 – Thermal | 10.40 – 12.50 | 60* |
| Band 7 – SWIR 2 | 2.09 – 2.35 | 30 |
| Band 8 – Panchromatic | 0.52 – 0.90 | 15 |
| Bands | Wavelength | Resolution |
| Band 1 - Ultra Blue | 0.435 – 0.451 | 30 |
| Band 2 - Blue | 0.452 – 0.512 | 30 |
| Band 3 - Green | 0.533 – 0.590 | 30 |
| Band 4 – Red | 0.636 – 0.673 | 30 |
| Band 5 – NIR | 0.851 – 0.879 | 30 |
| Band 6 – SWIR 1 | 1.566 – 1.651 | 30 |
| Band 7 – SWIR 2 | 2.107 – 2.294 | 30 |
| Band 8 – Panchromatic | 0.503 – 0.676 | 15 |
| Band 9 – Cirrus | 1.363 – 1.384 | 30 |
| Band 10 – Thermal 1 | 10.60 – 11.19 | 100* |
| Band 11 – Thermal 2 | 11.50 – 12.51 | 100* |
An advantage of Landsat imagery, and remote sensing in general, is that it provides data at a synoptic global level that is impossible to replicate with in situ measurements. However, there are tradeoffs between the local detail of the measurements and the spatial scale of the measured area. Landsat imagery is coarse in spatial resolution compared to other remote sensing methods, such as imagery from airplanes. Landsat's spatial resolution is relatively high compared to other satellites, yet its revisit time is relatively less frequent.