View source for Astronomy:Landsat program

{{Short description|American network of Earth-observing satellites for international research purposes}}
[[Image:Landsat7photo.jpg|thumb|upright|right|Landsat 7, launched in 1999, is the 7th of 9 satellites in the Landsat program.]]
{{multipleimage
| direction         = horizontal
| image1            = Large Kolkata Landsat.jpg
| caption1          = A false-color satellite image of [[Place:Kolkata|Kolkata]], India, from [[Engineering:Landsat 7|Landsat 7]] in 2004, showing rivers, vegetated areas, and developed areas
| image2            = Island of Hawai'i - Landsat mosaic.jpg
| caption2          = A land cover map of the big island of Hawaii using 1999–2001 data from [[Engineering:Landsat 7|Landsat 7]], showing black lava flows from [[Earth:Mauna Loa|Mauna Loa]], grayish dormant [[Earth:Mauna Kea|Mauna Kea]], a plume of smoke from active Kilauea, dark green tropical forests, and light green agricultural areas.
}}

The '''Landsat program''' is the longest-running enterprise for acquisition of [[Astronomy:Satellite imagery|satellite imagery]] of [[Astronomy:Earth|Earth]]. It is a joint [[Organization:National Aeronautics and Space Administration|NASA]] / USGS program. On 23 July 1972, the '''[[Engineering:Landsat 1|Earth Resources Technology Satellite]]''' was launched. This was eventually renamed to Landsat 1 in 1975.<ref>{{cite book |last=Short|first=N.M.|title=The LANDSAT Tutorial Workbook: Basics of Satellite Remote Sensing|id=1078|date=1982 |location=Washington DC |publisher=NASA|hdl=2060/19830002188}} {{PD-notice}}</ref> The most recent, [[Engineering:Landsat 9|Landsat 9]], was launched on 27 September 2021.

The instruments on the Landsat satellites have acquired millions of images. The images, archived in the {{wipe|United States}} and at Landsat receiving stations around the world, are a unique resource for global change research and applications in [[Earth:Agriculture|agriculture]], [[Earth:Cartography|cartography]], [[Earth:Geology|geology]], forestry, [[Engineering:Regional planning|regional planning]], surveillance and education, and can be viewed through the U.S. Geological Survey (USGS) "EarthExplorer" website. [[Engineering:Landsat 7|Landsat 7]] data has eight [[Physics:Spectral bands|spectral bands]] with [[Image resolution#Spatial resolution|spatial resolutions]] ranging from {{cvt|15|to|60|m}}; the [[Engineering:Temporal resolution|temporal resolution]] is 16 days.<ref>[http://landsat.gsfc.nasa.gov/about/L7_td.html The Landsat Program – Technical Details] {{webarchive|url=https://web.archive.org/web/20100501135128/http://landsat.gsfc.nasa.gov/about/L7_td.html |publisher=NASA|date=2010-05-01}} {{PD-notice}}</ref> Landsat images are usually divided into scenes for easy downloading. Each Landsat scene is about 115 miles long and 115 miles wide (or 100 nautical miles long and 100 nautical miles wide, or 185 kilometers long and 185 kilometers wide).

== History ==
[[File:Virginia Norwood VT-Storm-Radar-web.png|thumb|upright=1.0|right|Virginia Norwood, "The Mother of Landsat", designed the multispectral scanner.]]
[[File:Landsat 40th.ogv|thumb|upright=1.0|right|Interview with Jim Irons – Landsat 8 Project Scientist – NASA Goddard Space Flight Center]]
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 the natural resources of our planet. 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 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 their 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 (DOI) was going to proceed with its own Earth-observing satellite program. This savvy political stunt coerced NASA to expedite the building of Landsat. But budgetary constraints and sensor disagreements between application agencies (notably the Department of Agriculture and DOI) again stymied the satellite construction process. Finally, by 1970 NASA had a green light to build a satellite. Remarkably, within only two years, Landsat 1 was launched, heralding a new age of remote sensing of land from space.<ref name="Landsat History">{{cite news|title=Landsat History|agency=NASA|url=https://landsat.gsfc.nasa.gov/about/history|access-date=2021-07-05}}</ref>

The [[Company:Hughes Aircraft Company|Hughes Aircraft Company]] from Santa Barbara Research Center initiated, designed, and fabricated the first three [[Engineering:Multispectral Scanner|Multispectral Scanner]]s (MSS) 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. For this design work Norwood was called "The Mother of Landsat".<ref name="Pennisi">{{cite journal |last1=Pennisi |first1=Elizabeth |title=Meet the Landsat pioneer who fought to revolutionize Earth observation |journal=Science |date=10 September 2021 |volume=373 |issue=6561 |page=1292 |doi=10.1126/science.acx9080|s2cid=239215521 }}</ref>

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 with Landsat satellite imagery.<ref>[https://landsat.gsfc.nasa.gov/a-face-behind-landsat-images-meet-dr-valerie-l-thomas/ NASA Landsat Science, A Face Behind Landsat Images: Meet Dr. Valerie L. Thomas] {{PD-notice}}</ref>

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, President of the United States [[Biography:Jimmy Carter|Jimmy Carter]]'s Presidential Directive 54<ref name="jimmycarterlibrary.gov">{{cite web|title=Presidential Directive 54|url=https://www.jimmycarterlibrary.gov/documents/pddirectives/pd54.pdf |website=jimmycarterlibrary.gov|publisher=Jimmy Carter Library|access-date=April 18, 2017|date=November 16, 1979|archive-url=https://web.archive.org/web/20170130202926/https://www.jimmycarterlibrary.gov/documents/pddirectives/pd54.pdf|archive-date=January 30, 2017}} {{PD-notice}}</ref><ref name="Folger">{{cite web|last1=Folger |first1=Peter|title=Landsat: Overview and Issues for Congress|url=https://fas.org/sgp/crs/misc/R40594.pdf|website=fas.org|publisher=Congressional Research Service|access-date=April 18, 2017|date=October 27, 2014}} {{PD-notice}}</ref> transferred Landsat operations from [[Organization:NASA|NASA]] to [[Organization:National Oceanic and Atmospheric Administration|National Oceanic and Atmospheric Administration]] (NOAA), 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 (EOSAT), a partnership of [[Company:Hughes Aircraft Company|Hughes Aircraft Company]] and [[Company:RCA|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 (NOAA had not requested any funding, and U.S. Congress had appropriated only six months of funding for the fiscal year)<ref name="Space Economics">{{cite book|last1=Greenberg|first1=Joel S.|last2=Hertzfeld|first2=Henry|title=Space Economics|publisher=AIAA (American Institute of Aeronautics & Astronautics)|year=1992|page=372|isbn=978-1-56347-042-4}}</ref> and NOAA directed that Landsat 4 and Landsat 5 be shut down.<ref name="fundsrunout">{{cite news|title=The government, saying it ran out of money, pulled the plug on two environmental satellites|agency=United Press International (UPI)|date=1989-03-02|author=Vincent del Giudice|url=https://www.upi.com/Archives/1989/03/02/The-government-saying-it-ran-out-of-money-pulled/6994604818000/|access-date=2023-03-13}}</ref>

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.<ref name="Space Economics"/><ref name="fundsrunout"/><ref>{{cite news|title=Quayle backs satellite program|agency=Associated Press|newspaper=Sun Journal (Lewiston)|date=1989-03-07 |url=https://news.google.com/newspapers?id=7L0gAAAAIBAJ&dq=satellite%20quayle&pg=1441%2C798034|access-date=2010-05-19}}</ref><ref>{{cite news|title=U.S. Halts Plan to Turn Off the Landsat Satellites|first=John Noble|last=Wilford|newspaper=The New York Times|date=1989-03-17|url=https://www.nytimes.com/1989/03/17/us/us-halts-plan-to-turn-off-the-landsat-satellites.html?pagewanted=1|access-date=2010-05-19}}</ref>

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.<ref name="Space Economics"/>

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.

The value of the Landsat program was recognized by Congress in October 1992 when it passed the Land Remote Sensing Policy Act (Public Law 102-555) 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 ==
{| class="wikitable sortable" style="width:100%;text-align:center;"
|-
! Instrument !! Picture !! Launched !! Terminated !! Duration !! Notes
|-
| [[Engineering:Landsat 1|Landsat 1]] || [[File:Sketch of ERTS-1 renamed Landsat1.jpg|100px|Landsat 1]] || 23 July 1972 || 6 January 1978 || {{Age in years, months and days|1972|06|23|1978|01|06}} || Originally named Earth Resources Technology Satellite 1. Landsat 1 carried two vital instruments: a camera built by the Radio Corporation of America (RCA) known as the Return Beam Vidicon (RBV); and the Multi spectral Scanner (MSS) built by the [[Company:Hughes Aircraft Company|Hughes Aircraft Company]].
|-
| [[Engineering:Landsat 2|Landsat 2]] || [[File:Landsat-1.jpg|100px|Landsat 2]] || 22 January 1975 || 25 February 1982 || {{Age in years, months and days|1975|01|22|1982|02|25}} || Nearly identical copy of Landsat 1. Payload consisting of a Return Beam Vidicon (RBV) and a Multi spectral Scanner (MSS). The specifications of these instruments were identical to Landsat 1.
|-
| [[Engineering:Landsat 3|Landsat 3]] || [[File:Landsat3.jpg|100px|Landsat 3]] || 5 March 1978 || 31 March 1983 || {{Age in years, months and days|1978|03|05|1983|03|31}} || Nearly identical copy of Landsat 1 and Landsat 2. Payload consisting of a Return Beam Vidicon (RBV) as well as a Multi spectral Scanner (MSS). Included with the MSS was a short-lived thermal band. MSS data was considered more scientifically applicable than the RBV which was rarely used for engineering evaluation purposes.  
|-
| [[Engineering:Landsat 4|Landsat 4]] || [[File:Landsat5.jpg|100px|Landsat 4]] || 16 July 1982 || 14 December 1993 || {{Age in years, months and days|1982|07|16|1993|12|14}} || Landsat 4 carried an updated Multi Spectral Scanner (MSS) used on previous Landsat missions, as well as a Thematic Mapper.
|-
| [[Engineering:Landsat 5|Landsat 5]] || [[File:Landsat5.jpg|100px|Landsat 5]] || 1 March 1984 || 5 June 2013 <ref>{{cite web|url=http://landsat.gsfc.nasa.gov/?p=5596|title=Historic Landsat 5 Mission Ends - Landsat Science|date=26 June 2013}}</ref> || {{Age in years, months and days|1984|03|01|2013|06|05}} || Nearly identical copy of Landsat 4. Longest Earth-observing satellite mission in history. Designed and built at the same time as Landsat 4, this satellite carried the same payload consisting of a Multi Spectral Scanner (MSS) as well as a Thematic Mapper.
|-
| [[Engineering:Landsat 6|Landsat 6]] || [[File:Landsat-6.jpg|100px|Landsat 6]] || 5 October 1993 || 5 October 1993 || 0 days || Failed to reach orbit. Landsat 6 was an upgraded version of its predecessors. Carrying the same Multi spectral Scanner (MSS) but also carrying an Enhanced Thematic Mapper, which added a 15m resolution panchromatic band.
|-
| [[Engineering:Landsat 7|Landsat 7]] || [[File:Landsat7photo.jpg|100px|Landsat 7]] || 15 April 1999 || 6 April 2022 || {{Age in years, months and days|year=1999|month=4|day=15}} || Operating with scan line corrector disabled since May 2003.<ref>{{cite web|url=http://landsat.gsfc.nasa.gov/|title=Landsat Science}} {{PD-notice}}</ref> The main component on Landsat 7 was the Enhanced Thematic Mapper Plus (ETM+). Still consisting of the 15m-resolution panchromatic band, but also includes a full aperture calibration. This allows for 5% absolute [[Physics:Radiometric calibration|radiometric calibration]].<ref>{{cite web|url=https://landsat.gsfc.nasa.gov/landsat-7-2/|archive-url=https://web.archive.org/web/20161108221655/http://landsat.gsfc.nasa.gov/landsat-7-2/|archive-date=2016-11-08|title=Landsat 7 - Landsat Science|website=landsat.gsfc.nasa.gov|access-date=2017-03-19}} {{PD-notice}}</ref>
|-
| [[Engineering:Landsat 8|Landsat 8]] || [[File:Landsat Data Continuity Mission Observatory testing.jpg|100px|Landsat 8]] || 11 February 2013 || active || {{Age in years, months and days|year=2013|month=2|day=11}} || Originally named Landsat Data Continuity Mission from launch until 30 May 2013, when NASA operations were turned over to United States Geological Survey (USGS).<ref name=Turnover>{{cite web|title=Landsat 8 Data Now Available!|url=http://landsat.usgs.gov/LDCM_Landsat8.php|publisher=USGS|access-date=May 30, 2013|archive-url=https://web.archive.org/web/20130605224029/http://landsat.usgs.gov/LDCM_Landsat8.php|archive-date=June 5, 2013}} {{PD-notice}}</ref> Landsat 8 has two sensors with its payload, the [[Engineering:Operational Land Imager|Operational Land Imager]] (OLI) and the Thermal InfraRed Sensor (TIRS).<ref>{{cite web|url=https://landsat.gsfc.nasa.gov/landsat-8/|archive-url=https://web.archive.org/web/20161106124438/http://landsat.gsfc.nasa.gov/landsat-8/|archive-date=2016-11-06|title=Landsat 8 - Landsat Science|website=landsat.gsfc.nasa.gov |publisher=NASA|access-date=2017-03-19}} {{PD-notice}}</ref>
|-
| [[Engineering:Landsat 9|Landsat 9]] || [[File:Landsat 9 processing.jpg|100px|Landsat_9_processing]] || 27 September 2021  ||  active || {{Age in years, months and days|year=2021|month=9|day=27}} || Landsat 9 is a rebuild of its predecessor Landsat 8.<ref name="SFN20200907b">{{cite web|url=https://www.nasa.gov/press-release/media-invited-to-virtual-briefing-on-launch-of-nasa-usgs-landsat-9|title=Virtual Briefing on Launch of NASA, USGS Landsat 9|publisher=NASA.gov|date=27 August 2021|access-date=27 September 2021}}</ref><ref name="NASA-L9">{{cite web|url=http://landsat.gsfc.nasa.gov/landsat-9/|archive-url=https://web.archive.org/web/20161109202110/http://landsat.gsfc.nasa.gov/landsat-9/|archive-date=9 November 2016|title=Landsat 9 |publisher=NASA Landsat Science|access-date=21 December 2016}} {{PD-notice}}</ref>
|}

;Timeline
<timeline>
ImageSize = width:450 height:auto barincrement:21
PlotArea = left:70 bottom:30 top:10 right:10
TimeAxis = orientation:horizontal format:yyyy
Colors = 
   id:canvas value:gray(0.97)
   id:grid1 value:gray(0.8)
   id:grid2 value:gray(0.6)
BackgroundColors = canvas:canvas
DateFormat = mm/dd/yyyy
Period = from:01/01/1972 till:01/01/2022
AlignBars = justify
ScaleMajor = increment:2 start:1973 unit:year grid:grid1
ScaleMinor = increment:1 start:1974 unit:year
BarData =
   bar:Landsat1    text:"Landsat 1"
   bar:Landsat2    text:"Landsat 2"
   bar:Landsat3    text:"Landsat 3"
   bar:Landsat4    text:"Landsat 4"
   bar:Landsat5    text:"Landsat 5"
   bar:Landsat6    text:"Landsat 6"
   bar:Landsat7    text:"Landsat 7"
   bar:Landsat8    text:"Landsat 8"
   bar:Landsat9    text:"Landsat 9"
PlotData =
  align:left anchor:from fontsize:M width:13 shift:(4,-6) textcolor:black
  bar:Landsat1     from:07/23/1972 till:01/06/1978 color:blue
  bar:Landsat2     from:01/22/1975 till:02/25/1982 color:blue
  bar:Landsat3     from:03/05/1978 till:03/31/1983 color:blue
  bar:Landsat4     from:07/16/1982 till:12/14/1993 color:orange
  bar:Landsat5     from:03/01/1984 till:06/05/2013 color:orange
  bar:Landsat6     from:10/05/1993 till:10/05/1993 color:black
  bar:Landsat7     from:04/15/1999 till:05/31/2003 color:red
  bar:Landsat7     from:05/31/2003 till:end color:coral
  bar:Landsat8     from:02/11/2013 till:end color:green
  bar:Landsat9     from:09/27/2021 till:end color:green

</timeline>

== Spatial and spectral resolution ==
Landsat 1 through 5 carried the Landsat [[Engineering:Multispectral Scanner|Multispectral Scanner]] (MSS). Landsat 4 and 5 carried both the MSS and [[Engineering:Thematic Mapper|Thematic Mapper]] (TM) instruments. Landsat 7 uses the [[Engineering:Landsat 7|Enhanced Thematic Mapper Plus]] (ETM+) scanner. Landsat 8 uses two instruments, the [[Engineering:Operational Land Imager|Operational Land Imager]] (OLI) for optical bands and the Thermal Infrared Sensor (TIRS) for thermal bands. The band designations, bandpasses, and pixel sizes for the Landsat instruments are:<ref>{{cite web|url=https://landsat.usgs.gov/what-are-band-designations-landsat-satellites|title=What are the band designations for the Landsat satellites? {{!}} Landsat Missions|website=landsat.usgs.gov|access-date=2019-01-29|archive-url=https://web.archive.org/web/20170122043515/https://landsat.usgs.gov/what-are-band-designations-landsat-satellites|archive-date=2017-01-22}} {{PD-notice}}</ref>
{| class="wikitable"
|+Landsat 1–5 Multispectral Scanner (MSS)
!Landsat 1–3 MSS
!Landsat 4–5 MSS
!Wavelength (micrometers)
!Resolution (meters)
|-
|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 (NIR)
|Band 3 – NIR
|0.7 – 0.8
|60*
|-
|Band 7 – NIR
|Band 4 – NIR
|0.8 – 1.1
|60*
|}
<nowiki>*</nowiki> Original MSS pixel size was 79 x 57 meters; production systems now resample the data to 60 meters.
{| class="wikitable"
|+Landsat 4–5 Thematic Mapper (TM)
!Bands
!Wavelength (micrometers)
!Resolution (meters)
|-
|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 (SWIR) 1
|1.55 – 1.75
|30
|-
|Band 6 – Thermal
|10.40 – 12.50
|120* (30)
|-
|Band 7 – SWIR 2
|2.08 – 2.35
|30
|}
<nowiki>*</nowiki> TM Band 6 was acquired at 120-meter resolution, but products are resampled to 30-meter pixels.
{| class="wikitable"
|+Landsat 7 Enhanced Thematic Mapper Plus (ETM+)
!Bands
!Wavelength (micrometers)
!Resolution (meters)
|-
|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* (30)
|-
|Band 7 – SWIR 2
|2.09 – 2.35
|30
|-
|Band 8 – Panchromatic
|0.52 – 0.90
|15
|}
<nowiki>*</nowiki> ETM+ Band 6 is acquired at 60-meter resolution, but products are resampled to 30-meter pixels.

[[File:The spectral band placement for each sensor of Landsat.jpg|thumb|upright=2|The spectral band placement for each sensor of Landsat]]

{| class="wikitable"
|+Landsat 8 Operational Land Imager (OLI) and Thermal Infrared Sensor (TIRS)<ref>{{Cite journal|last1=Barsi|first1=Julia A.|last2=Lee|first2=Kenton|last3=Kvaran|first3=Geir|last4=Markham|first4=Brian L.|last5=Pedelty|first5=Jeffrey A.|date=October 2014|title=The Spectral Response of the Landsat-8 Operational Land Imager|journal=Remote Sensing|volume=6|issue=10|pages=10232–10251|doi=10.3390/rs61010232|bibcode=2014RemS....610232B|doi-access=free}}</ref>
!Bands
!Wavelength (micrometers)
!Resolution (meters)
|-
|Band 1 - Ultra Blue (coastal/aerosol)
|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* (30)
|-
|Band 11 – Thermal 2
|11.50 – 12.51
|100* (30)
|}
<nowiki>*</nowiki> TIRS bands are acquired at 100 meter resolution, but are resampled to 30 meter in delivered data product.

An advantage of Landsat imagery, and [[Earth:Remote sensing|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 (radiometric resolution, number of spectral bands) and the spatial scale of the area being measured. Landsat imagery is coarse in spatial resolution compared to using other remote sensing methods, such as imagery from airplanes. Compared to other satellites, Landsat's spatial resolution is relatively high, yet revisit time is relatively less frequent.

== MultiSpectral Scanner (MSS) ==
The [[Astronomy:Landsat program|Landsat program]] incorporated the [[Engineering:Multispectral Scanner|Multispectral Scanner]] (MSS) from its first mission up to its fifth. The MSS, gave the United States an advantage in satellite imaging, facilitating the launch of Landsat ahead of the French SPOT satellite.

The MSS was unique in its design. Rather than a static camera, it employed a moving mirror, capturing Earth's images in four distinct spectral bands. This capability allowed the MSS to record variations in sunlight reflected from the Earth. Notably, Landsat 3's MSS was further advanced, with an added capability to detect heat radiation.<ref name="nasa-mss">{{cite web |title=The Multispectral Scanner |url=http://landsat.gsfc.nasa.gov/about/mss.html |url-status=dead |archive-url=https://web.archive.org/web/20070126235924/http://landsat.gsfc.nasa.gov/about/mss.html |archive-date=2007-01-26 |publisher=[[Organization:NASA|NASA]] }}</ref>

One of the prominent features of the MSS was its consistent imaging. Each captured frame represented an area on the Earth's surface approximately 83 meters in length and 68 meters in width. Additionally, the system was designed to ensure a continuous image sweep across a swath equivalent to 185 km on the Earth's surface. The MSS's design also emphasized precision; by precisely timing the mirror's movements, it ensured that consecutive images did not overlap.<ref name="nasa-mss"/>

However, by the 1980s, the cost dynamics shifted. Accessing Landsat's imagery became substantially more expensive, making the French SPOT satellite's images a more cost-effective alternative for many users. The rise in Landsat's prices can be attributed to U.S. policy shifts, initiated under President Carter's leadership and finalized during President Reagan's administration.<ref name="Folger"/><ref>{{cite web|url=http://www.the-scientist.com/?articles.view/articleNo/17221/title/Failure-Of-Landsat-6-Leaves-Many-Researchers-In-Limbo/|title=Failure Of Landsat 6 Leaves Many Researchers In Limbo|publisher=The Scientist (magazine)}}</ref>

== Uses of Landsat imagery ==
[[File:Happy Launch Anniversary, Landsat 8 (12463694884).jpg|thumb|One year after launch, Landsat 8 imagery had over one million file downloads by data users.]]
Landsat data provides information that allows scientists to predict the distribution of species, as well as detecting both naturally occurring and human-generated changes over a greater scale than traditional data from field work. The different spectral bands used on satellites in the Landsat program provide many applications, ranging from ecology to geopolitical matters. Land cover determination is a common use of Landsat imagery around the world.<ref>{{cite journal |last1=Cohen |first1=Warren B. |last2=Goward |first2=Samuel N. |title=Landsat's Role in Ecological Applications of Remote Sensing |journal=BioScience |date=2004 |volume=54 |issue=6 |pages=535–545 |doi=10.1641/0006-3568(2004)054[0535:LRIEAO]2.0.CO;2 |s2cid=86219373 |url=https://andrewsforest.oregonstate.edu/sites/default/files/lter/pubs/pdf/pub3748.pdf}}</ref>

Landsat imagery provides one of the longest uninterrupted time series available from any single remote sensing program, spanning from 1972 to present.<ref name="Hemati Hasanlou Mahdianpari Mohammadimanesh p=2869">{{cite journal | last1=Hemati | first1=MohammadAli | last2=Hasanlou | first2=Mahdi | last3=Mahdianpari | first3=Masoud | last4=Mohammadimanesh | first4=Fariba | title=A Systematic Review of Landsat Data for Change Detection Applications: 50 Years of Monitoring the Earth | journal=Remote Sensing | publisher=MDPI AG | volume=13 | issue=15 | date=22 July 2021 | issn=2072-4292 | doi=10.3390/rs13152869 | page=2869| bibcode=2021RemS...13.2869H | doi-access=free }}</ref> Looking to the future, the successful launch of [[Engineering:Landsat 9|Landsat-9]] in 2021 shows that this time series will be continued forward.<ref name="Landsat9">{{cite web | title=Landsat 9 Reaches Orbit, Makes Ground Contact to Continue Legacy | website=USGS.gov | url=https://www.usgs.gov/center-news/landsat-9-reaches-orbit-makes-ground-contact-continue-legacy?qt-news_science_products=1#qt-news_science_products | access-date=14 October 2021}}</ref>

[[File:Garden City Kansas irrigation-Landsat7-segment2.jpg|thumb|A false-color image of [[Earth:Irrigation|irrigated]] fields near Garden City, Kansas, taken by the Landsat 7 satellite.]]
In 2015, the Landsat Advisory Group of the National Geospatial Advisory Committee reported that the top 16 applications of Landsat imagery produced savings of approximately 350 million to over 436 million dollars each year for federal and state governments, NGO's, and the private sector. That estimate did not include further savings from other uses beyond the top sixteen categories.<ref name="USGS.gov">{{cite web | title=Landsat Seen as Stunning Return on Public Investment | website=USGS.gov | url=https://www.usgs.gov/news/landsat-seen-stunning-return-public-investment | access-date=14 October 2021}}</ref> The top 16 categories for Landsat imagery use, listed in order of estimated annual savings for users, are: 
# U.S. Department of Agriculture risk management
# U.S. Government mapping
# Agricultural water use monitoring
# Global security monitoring
# Support for fire management
# Detection of forest fragmentation
# Detection of forest change
# World agriculture supply and demand estimates
# Vineyard management and water conservation
# Flood mitigation mapping
# Agricultural commodities mapping
# Waterfowl habitat mapping and monitoring
# Coastal change analysis
# Forest health monitoring
# National Geospatial-Intelligence Agency global shoreline mapping
# Wildfire risk assessment <ref name="USGS.gov"/>

Further uses of Landsat imagery include, but are not limited to: fisheries, forestry, shrinking inland water bodies, fire damage, glacier retreat, urban development, and discovery of new species. A few specific examples are explained below.

=== Natural resources management ===
[[File:NASA's Landsat Satellite Looks for a Cloud-Free View (8778994889).jpg|thumb|Landsat image of the Aral Sea in 2013.]]
[[File:Fire and the Future of Yellowstone - NASA Earth Observatory.jpg|thumb|Landsat images of burned land in Yellowstone National Park in 1989 and 2011.]]
[[File:World of Change Columbia Glacier, Alaska (7215814492).png|thumb|[[Engineering:Landsat 5|Landsat-5]] false color images of the Columbia Glacier, Alaska in 1986 and 2011.]]
[[File:Vancouver Landsat.jpg|thumb|Landsat false color image highlighting developed areas in pink in Vancouver, British Columbia, Canada.]]

==== Fisheries ====
In 1975, one potential application for the new satellite-generated imagery was to find high yield fishery areas. Through the Landsat Menhaden and Thread Investigation, some satellite data of the eastern portion of the Mississippi sound and another area off the coast of the Louisiana coast data was run through classification [[Algorithm|algorithm]]s to rate the areas as high and low probability fishing zones, these algorithms yielded a classification that was proven with [[Biology:In situ|in situ]] measurements – to be over 80% accurate and found that water color, as seen from space, and turbidity significantly correlate with the distribution of [[Biology:Menhaden|menhaden]] – while surface temperature and salinity do not appear to be significant factors. Water color – measured with the multispectral scanners four spectral bands, was used to infer [[Biology:Chlorophyll|Chlorophyll]], [[Biology:Turbidity|turbidity]], and possibly fish distribution.<ref>{{cite web|url=http://spo.nmfs.noaa.gov/mfr391/mfr3913.pdf|title=Finding Fish With Satellites|last=Kemmerer|first=Andrew|date=March 2017 |publisher=NOAA}} {{PD-notice}}</ref>

==== Forestry ====
An ecological study used 16 [[Earth:Orthophoto|ortho-rectified]] Landsat images to generate a land cover map of Mozambique's [[Earth:Mangrove|mangrove]] forest. The main objective was to measure the mangrove cover and above ground [[Biology:Biomass|biomass]] on this zone that until now could only be estimated, the cover was found with 93% accuracy to be 2909 square kilometers (27% lower than previous estimates). Additionally, the study helped confirm that geological setting has a greater influence on biomass distribution than latitude alone - the mangrove area is spread across 16° of latitude but it the biomass volume of it was affected more strongly by geographic conditions.<ref>{{cite journal|title=Landscape-scale extent, height, biomass, and carbon estimation of Mozambique's mangrove forest with Landsat ETM+ and Shuttle Radar Topography Mission elevation data|journal=Journal of Geophysical Research: Biogeosciences|volume=113|last=Fatoyinbo|first=Temilola|date=March 2017|pages=n/a|doi=10.1029/2007JG000551|doi-access=free}}</ref>

=== Climate change and environmental disasters ===
==== Shrinking of the Aral Sea ====
The shrinking of the Aral Sea has been described as "One of the planet's worst environmental disasters". Landsat imagery has been used as a record to quantify the amount of water loss and the changes to the shoreline. Satellite visual images have a greater impact on people than just words, and this shows the importance of Landsat imagery and satellite images in general.<ref>{{cite magazine |url=https://www.wired.com/2012/07/landsat-40-significant-images/|title=Landsat's Most Historically Significant Images of Earth From Space|last=Mason|first=Betsy|date=March 2017|magazine=Wired}}</ref>

==== Fires in Yellowstone National Park ====
The Yellowstone fires of 1988 were the worst in the recorded history of the national park. They lasted from 14 June to 11 September 1988, when rain and snow helped halt the spread of the fires. The area affected by the fire was estimated to be 3,213 square kilometers – 36% of the park. Landsat imagery was used for the area estimation, and it also helped determine the reasons why the fire spread so quickly. Historic drought and a significant number of lightning strikes were some of the factors that created conditions for the massive fire, but anthropogenic actions amplified the disaster. On images generated previous to the fire, there is an evident difference between lands that display preservation practices and the lands that display clear cut activities for timber production. These two type of lands reacted differently to the stress of fires, and it is believed that that was an important factor on the behavior of the wildfire. Landsat imagery, and satellite imagery in general, have contributed to understanding fire science; fire danger, wildfire behavior and the effects of wildfire on certain areas. It has helped understanding of how different features and vegetation fuel fires, change temperature, and affect the spreading speed.<ref name="Zhao Meng Huang Zhao p=898">{{cite journal | last1=Zhao | first1=Feng | last2=Meng | first2=Ran | last3=Huang | first3=Chengquan | last4=Zhao | first4=Maosheng | last5=Zhao | first5=Feng | last6=Gong | first6=Peng | last7=Yu | first7=Le | last8=Zhu | first8=Zhiliang | title=Long-Term Post-Disturbance Forest Recovery in the Greater Yellowstone Ecosystem Analyzed Using Landsat Time Series Stack | journal=Remote Sensing | publisher=MDPI AG | volume=8 | issue=11 | date=29 October 2016 | issn=2072-4292 | doi=10.3390/rs8110898 | page=898| bibcode=2016RemS....8..898Z | doi-access=free | hdl=1903/31531 | hdl-access=free }}</ref><ref name="USGS_fires">{{cite web | title=EarthView–Fire and Rebirth: Landsat Tells Yellowstone's Story | website=USGS.gov | url=https://www.usgs.gov/news/earthview-fire-and-rebirth-landsat-tells-yellowstones-story | access-date=15 October 2021}}</ref>

==== Glacier retreat ====
The serial nature of Landsat missions and the fact that is the longest-running satellite program gives it a unique perspective to generate information of Earth. Glacier retreat in a big scale can be traced back to previous Landsat missions, and this information can be used to generate climate change knowledge. The Columbia glacier retreat for example, can be observed in false-composite images since [[Engineering:Landsat 4|Landsat 4]] in 1986.<ref name="Landslides Monitoring">{{citation|editor-last=Ray, Ram|title=Landslides - Investigation and Monitoring|publisher=IntechOpen|publication-date=19 November 2020|isbn=978-1-78985-824-2}}</ref>

====Urban development====
Landsat imagery gives a time-lapse like series of images of development. Human development specifically, can be measured by the size a city grows over time. Further than just population estimates and energy consumption, Landsat imagery gives an insight of the type of urban development, and study aspects of social and political change through visible change. In Beijing for example, a series of ring roads started to develop in 1980s following the economic reform of 1970, and the change in development rate and construction rate was accelerated in these time periods.<ref name="Landslides Monitoring"/>

===Ecology===
==== Discovery of new species ====
In 2005, Landsat imagery assisted in the discovery of new species. Conservation scientist Julian Bayliss wanted to find areas that could potentially become conservation forests using Landsat generated satellite images. Bayliss saw a patch in Mozambique that until then had no detailed information. On a reconnaissance trip, he found great diversity of wildlife as well as three new species of butterflies and a new snake species. Following his discovery, he continued to study this forest and was able to map and determine the forest extent.<ref>{{cite web|url=https://landsat.gsfc.nasa.gov/landsat-imagery-leads-to-discovery-of-new-species/|archive-url=https://web.archive.org/web/20170430083925/https://landsat.gsfc.nasa.gov/landsat-imagery-leads-to-discovery-of-new-species/|archive-date=2017-04-30|title=Landsat Imagery Leads to Discovery of New Species - Landsat Science|publisher=NASA}} {{PD-notice}}</ref>

== Recent and future Landsat satellites ==
[[File:L8and9-to-LandsatNext-BandComparison.png|thumb|Landsat 8/9 and Landsat Next spectral band comparison]]

[[Engineering:Landsat 8|Landsat 8]] launched on 11 February 2013. It was launched on an [[Engineering:Atlas V|Atlas V]] 401 from {{wipe|Vandenberg Air Force Base}} by the [[Company:Launch Services Program|Launch Services Program]]. It will continue to obtain valuable data and imagery to be used in agriculture, education, business, science, and government. The new satellite was assembled in Arizona by [[Company:Orbital Sciences Corporation|Orbital Sciences Corporation]].

[[Engineering:Landsat 9|Landsat 9]] launched on September 27, 2021. During FY2014 financial planning "appropriators chided NASA for unrealistic expectations that a Landsat 9 would cost US$1 billion, and capped spending at US$650 million" according to a report by the [[Social:Congressional Research Service|Congressional Research Service]]. United States Senate appropriators advised NASA to plan for a launch no later than 2020.<ref name="Folger"/> In April 2015, NASA and the USGS announced that work on Landsat 9 had commenced, with funding allocated for the satellite in the president's FY2016 budget, for a planned launch in 2023.<ref name="nasa.gov">{{cite web|url=http://www.nasa.gov/press/2015/april/nasa-usgs-begin-work-on-landsat-9-to-continue-land-imaging-legacy/|title=NASA, USGS Begin Work on Landsat 9|first=Karen |last=Northon|date=16 April 2015}}</ref> Funding for the development of a low-cost thermal infrared (TIR) free-flying satellite for launch in 2019 was also proposed, to ensure data continuity by flying in formation with Landsat 8.<ref name="nasa.gov"/>

In the future, there may also be more collaboration between Landsat satellites and other satellites with similar spatial and spectral resolution, such as the [[Organization:European Space Agency|ESA]]'s Sentinel-2 constellation.<ref name="Wulder Loveland Roy Crawford 2019 pp. 127–147">{{cite journal | last1=Wulder | first1=Michael A. | last2=Loveland | first2=Thomas R. | last3=Roy | first3=David P. | last4=Crawford | first4=Christopher J. | last5=Masek | first5=Jeffrey G. | last6=Woodcock | first6=Curtis E. | last7=Allen | first7=Richard G. | last8=Anderson | first8=Martha C. | last9=Belward | first9=Alan S. | last10=Cohen | first10=Warren B. | last11=Dwyer | first11=John | last12=Erb | first12=Angela | last13=Gao | first13=Feng | last14=Griffiths | first14=Patrick | last15=Helder | first15=Dennis | last16=Hermosilla | first16=Txomin | last17=Hipple | first17=James D. | last18=Hostert | first18=Patrick | last19=Hughes | first19=M. Joseph | last20=Huntington | first20=Justin | last21=Johnson | first21=David M. | last22=Kennedy | first22=Robert | last23=Kilic | first23=Ayse | last24=Li | first24=Zhan | last25=Lymburner | first25=Leo | last26=McCorkel | first26=Joel | last27=Pahlevan | first27=Nima | last28=Scambos | first28=Theodore A. | last29=Schaaf | first29=Crystal | last30=Schott | first30=John R. | last31=Sheng | first31=Yongwei | last32=Storey | first32=James | last33=Vermote | first33=Eric | last34=Vogelmann | first34=James | last35=White | first35=Joanne C. | last36=Wynne | first36=Randolph H. | last37=Zhu | first37=Zhe | title=Current status of Landsat program, science, and applications | journal=Remote Sensing of Environment | publisher=Elsevier BV | volume=225 | year=2019 | issn=0034-4257 | doi=10.1016/j.rse.2019.02.015 | pages=127–147| bibcode=2019RSEnv.225..127W | s2cid=134722096 | hdl=10919/88790 | hdl-access=free }}</ref>

Landsat NeXt is planned to be launched in 2029. NeXt will measure 25 spectral bands; current Landsat's 8 and 9 can measure only 11.<ref>{{cite web |title=Landsat NeXt {{!}} Landsat Science |url=https://landsat.gsfc.nasa.gov/satellites/landsat-next/ |publisher=NASA |access-date=11 March 2022 |date=30 November 2021}}</ref>
{{-}}

== Gallery ==
<gallery mode="packed">
Overview of the Thermal Infrared Sensor.ogv| Overview of the Thermal Infrared Sensor (TIRS), one of the instruments on Landsat 8.
Timelapse of TIRS for LDCM.ogv|A timelapse of the Thermal Infrared Sensor (TIRS) instrument for Landsat 8 being cleaned, bagged, and packed to ship to Orbital Sciences Corp, where TIRS will be integrated with the spacecraft.
Florida Everglades Landsat 5 Band Remix (high res).ogv|Animation showing how different LDCM bands can be combined to obtain different information over the Florida Everglades.
Landsat 8 LDCM Liftoff 5min.png|Screenshot capture from NASA TV showing the Atlas V during the launch of Landsat 8.
</gallery>

== See also ==
* [[Astronomy:Earth observation satellite|Earth observation satellite]]
* [[Geographic information system]]
* [[Earth:Orthophoto|Orthophoto]], corrected for uniform scale like a map
* [[Earth:Remote sensing|Remote sensing]]

== References ==
{{Reflist}}

== External links ==

* [http://landsat.usgs.gov/ Landsat USGS homepage]
* [http://landsat.gsfc.nasa.gov/ Landsat NASA homepage]
* {{gutenberg author| id=U.S._Landsat_Pathfinder | name= Landsat}}
* Landsat imagery from [http://glovis.usgs.gov/ GLOVIS] and [https://web.archive.org/web/20100529122657/http://ftp.glcf.umd.edu/index.shtml Global Land Cover Facility]
* Landsat mosaic imagery from the [https://web.archive.org/web/20110928032327/http://landsat.usgs.gov/WELD.php WELD] project.



[[Category:Landsat program| ]]
[[Category:NASA programs]]
[[Category:Satellite imagery]]

{{Sourceattribution|Landsat program}}