{{Short description|American earth observation satellite (1972–1978)}} {{redirect|LS-1||LS1 (disambiguation){{!}}LS1}}
{{good article}} {{Infobox spaceflight | name = Landsat 1 | image = Landsat 1.jpg | image_caption = Landsat 1 in flight configuration with solar panels deployed after tests at the G.E. Valley Forge Plant.
| mission_type = Earth imaging | operator = [[NASA]] | COSPAR_ID = 1972-058A | SATCAT = 06126<ref name=nssdc /> | mission_duration = {{time interval|23 Jul 1972|6 Jan 1978}} | manufacturer = [[GE Aerospace (1960s)|GE Aerospace]] | dry_mass = | launch_mass = {{cvt|1800|kg|lb}} | launch_date = 23 July 1972, 18:06 UTC | launch_rocket = [[Delta 0100|Delta 900]] | launch_site = [[Vandenberg Air Force Base|Vandenberg]] [[Vandenberg AFB Space Launch Complex 2|SLC-2W]] | disposal_type = Decommissioned | deactivated = 6 January 1978 | decay_date = | orbit_epoch = August 26, 1972<ref>{{cite web|url=http://planet4589.org/space/log/satcat.txt|title=Satellite Catalog|first=Jonathan|last=McDowell|work=Jonathan's Space Page|access-date=June 16, 2013}}</ref> | orbit_reference = [[geocentric orbit|Geocentric]] | orbit_regime = [[Sun-synchronous orbit|Sun-synchronous]] | orbit_periapsis = {{cvt|902|km|mi}} | orbit_apoapsis = {{cvt|917|km|mi}} | orbit_semimajor = {{cvt|7280|km|mi}} | orbit_inclination = 99.1 degrees | orbit_period = 117.04 minutes | apsis = gee
| programme = '''[[Landsat program]]''' | previous_mission = | next_mission = [[Landsat 2]] }}
'''Landsat 1''' ('''LS-1'''), formerly named '''Earth Resources Technology Satellite''' '''ERTS-A''' or '''ERTS-1''', was the first [[satellite]] of the United States' [[Landsat program]]. It was a modified version of the [[Nimbus 4]] meteorological satellite and was launched on July 23, 1972, by a [[Delta 0100|Delta 0900]] rocket from [[Vandenberg Air Force Base]] in California.
It was the first satellite to carry a [[Multispectral Scanner]].
The near-[[polar orbit]]ing spacecraft served as a stabilized, Earth-oriented platform for obtaining information on [[agricultural]] and [[forestry]] resources, [[geology]] and [[Natural resource|mineral resources]], [[hydrology]] and [[water resources]], geography, [[cartography]], environmental [[pollution]], [[oceanography]] and [[marine resources]], and [[Meteorology|meteorological]] phenomena.
==Background== [[File:Sketch of ERTS-1 renamed Landsat1.jpg|thumb|Sketch of Landsat 1. Designed for weather satellites of the time, Landsat 1 was noticeably similar to the [[Nimbus program|Nimbus]] satellites.<ref name="irons">{{cite web|last1=Irons|first1=James R.|last2=Taylor|first2=Michael P.|last3=Rocchio|first3=Laura|title=Landsat1|url=http://landsat.gsfc.nasa.gov/?p=3172|website=Landsat Science|publisher=NASA|access-date=March 25, 2016}}</ref>]] The multi-agency Earth Resources Satellites Program was begun in 1966 by the [[United States Department of the Interior|Department of the Interior]]. The goal of the program was to gather data from the Earth via [[remote sensing]] techniques. The following year a feasibility study was performed for the Earth Resources Technology Satellite (later named the Landsat 1). The [[Bureau of Budget and Planning|Bureau of Budget]] (BOB) did not grant funding to build the satellite, but provided $2 million to continue the feasibility studies.<ref name="nasa1" />
==Satellite design== ===Development=== Definition studies for two [[Earth observation satellite]]s began in 1967. The satellites were named Earth Resources Technology Satellite and were individually known as ERTS-A and ERTS-B.{{sfn|Wells|Whiteley|Karegeannes|1976|p=43}}
In 1970, [[General Electric]] was selected as the prime contractor for ERTS-A.<ref name="nasa1" /> It was manufactured by GE's Space Division in [[Valley Forge, Pennsylvania|Valley Forge]].<ref name="about">{{cite web|url=https://landsat.usgs.gov/landsat-1-history|title=Landsat 1 History|access-date=May 11, 2017|publisher=USGS|archive-date=February 5, 2017|archive-url=https://web.archive.org/web/20170205002004/https://landsat.usgs.gov/landsat-1-history|url-status=dead}}</ref>
===Operation=== The spacecraft was {{convert|3|m|ft|sp=us}} tall with a {{convert|1.5|m|ft|abbr=on}} diameter. Two [[Solar panels on spacecraft|solar panel arrays]] that were {{convert|4|m|ft|abbr=on}} long each, with single axis articulation, generated power for the spacecraft. ERTS-A had a liftoff weight of {{convert|953|kg|lb}}.<ref name="about" />
The main spacecraft propulsion was three [[hydrazine]] thrusters. An [[Spacecraft attitude determination and control|attitude control]] system permitted the spacecraft's orientation to be maintained within plus or minus 0.7 degrees in all three axes.<ref name="about" />
Spacecraft communications included a command subsystem operating at 154.2 and 2106.4 MHz and a [[pulse-code modulation]] (PCM) [[Narrowband|narrow-band]] [[telemetry]] subsystem, operating at 2287.5 and 137.86 MHz, for spacecraft housekeeping, attitude, and sensor performance data. Video data from the three-camera Return Beam [[Video camera tube#Vidicon|Vidicon]] (RBV) system was transmitted in both real-time and tape recorder modes at 2265.5 MHz, while information from the [[multispectral scanner]] (MSS) was constrained to a 20 [[Hertz|MHz]] radio-frequency bandwidth at 2229.5 MHz.<ref name=nssdc>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1972-058A|title=Landsat 1|access-date=July 2, 2017|publisher=NASA Space Science Data Coordinated Archive}}</ref>
The satellite also carried two [[Wideband|wide-band]] [[video tape recorder]]s (WBVTR) capable of storing up to 30 minutes of scanner or camera data, giving the spacecraft's sensors a near-global coverage capability.<ref name="about" />
The satellite was equipped with a [[data collection system]] (DCS) to collect information from remote, individually-equipped [[Ground station|ground stations]] and to relay the data to central acquisition stations. Due to the orbit of the satellite, data could be obtained at a minimum of every 12 hours. No data processing or signal [[multiplexing]] occurred on the satellite.<ref>{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/experiment/display.action?id=1972-058A-03|title=Data Collection System|publisher=NASA Space Science Data Coordinated Archive|access-date=May 17, 2017}}</ref> The design of the DCS came from the [[Nimbus 3]] platform, then known as the interrogation, recording, and location system (IRLS).<ref name="eo">{{cite web|url=https://directory.eoportal.org/web/eoportal/satellite-missions/l/landsat-1-3|title=Landsat-1 to Landsat-3|publisher=eoPortal Directory|access-date=May 19, 2017}}</ref>
===Sensors=== ERTS-A had two sensors to achieve its primary objectives: the return beam (RBV) and the MSS.<ref name="irons" />
The RBV was manufactured by the Radio Corporation of America ([[RCA Corporation|RCA]]). The RBV obtained [[visible light]] and [[near infrared]] photographic images of Earth. At launch, the RBV was considered the primary sensor.<ref name="irons" />
The MSS was designed by [[Virginia T. Norwood|Virginia Norwood]] at [[Hughes Aircraft Company]], which also manufactured it. Norwood is called "The Mother of Landsat."<ref name="Pennisi">{{cite journal |last1=Pennisi |first1=Elizabeth |author-link=Elizabeth Pennisi |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> The sensor was initially considered an experimental sensor, and was the secondary sensor, until scientists reviewed the data that was beamed back to Earth. After the data was reviewed, the MSS was considered the primary sensor. The MSS was a four-channel [[Radio scanner|scanner]] that obtained [[radiometric]] images of Earth.<ref name="irons" />
==Mission== [[File:Landsat 1 launch.jpg|thumb|upright=.75|ERTS-A in a Delta 0900 on the pad]]
===Launch=== ERTS-A was launched July 23, 1972, on a Delta 0900 out of Vandenberg Air Force Base in California.<ref name="about"/><ref>{{cite web |url=https://history.nasa.gov/SP-4012/vol3/table1.33.htm |title=Chronology of Thor-Delta Development and Operations |publisher=NASA|archive-url=https://web.archive.org/web/20041118074722/https://history.nasa.gov/SP-4012/vol3/table1.33.htm|archive-date=November 18, 2004|access-date=June 12, 2019}}</ref> The spacecraft was placed in a [[sun-synchronous orbit]], with an altitude between 907 and 915 km. The spacecraft was placed in an orbit with an [[Orbital inclination|inclination]] of 99 degrees which orbited the Earth every 103 minutes.<ref name="eo" /> It was the first satellite launched with the sole purpose of studying and monitoring the planet.<ref name="irons" /><ref>{{cite web|url=https://www.usgs.gov/land-resources/nli/landsat/landsat-1|title=Landsat 1|publisher=USGS|access-date=June 12, 2019}}</ref>
Upon reaching orbit, it was renamed to ERTS-1. On January 14, 1975, eight days before ERTS-B was to launch, NASA announced that ERTS-1 was renamed Landsat 1 and ERTS-B would be Landsat 2 after launch.{{sfn|Wells|Whiteley|Karegeannes|1976|p=43}}
===Operations=== Landsat 1's tape recorders malfunctioned in January 1978, and the satellite was taken out of service.<ref>{{cite web|url=http://www.astronautix.com/l/landsat1-2-3.html|archive-url=https://web.archive.org/web/20161228020505/http://astronautix.com/l/landsat1-2-3.html|url-status=dead|archive-date=December 28, 2016|title=Landsat 1-2-3|publisher=Astronautix|access-date=May 22, 2017}}</ref>
==Results== [[File:ERTS-1 San Francisco (ARC-1972-AC78-1116).jpg|thumb|San Francisco Bay Area as imaged by ERTS-1]] From launch until 1974, Landsat 1 transmitted over 100,000 images, which covered more than 75% of the Earth's surface.<ref name="nasa1">{{cite web|url=https://geo.arc.nasa.gov/sge/landsat/lpchron.html|title=Landsat Program Chronology|access-date=May 15, 2017|publisher=NASA|url-status=dead|archive-url=https://web.archive.org/web/20161202113747/https://geo.arc.nasa.gov/sge/landsat/lpchron.html|archive-date=December 2, 2016}}</ref> The majority of these images were taken with the multispectral scanner. On 5 August 1972 the return beam vidicon failed after taking only 1690 images.<ref name="eo" />
In 1976, Landsat 1 discovered a tiny uninhabited island 20 kilometers off the eastern coast of Canada. This island was thereafter designated [[Landsat Island]] after the satellite.<ref>{{cite web|url=http://landsat.gsfc.nasa.gov/news/news-archive/dyk_0001.html|title=Landsat Island |publisher=[[NASA]]|date=April 19, 2006|access-date=May 29, 2012|archive-url=https://web.archive.org/web/20090320122145/https://landsat.gsfc.nasa.gov/news/news-archive/dyk_0001.html|archive-date=March 20, 2009|url-status=dead}}</ref>
The MSS provided more than 300,000 images over the lifespan of the satellite. NASA oversaw 300 researchers that evaluated the data that Landsat 1 transmitted back to Earth.<ref name="irons" />
Landsat 1 images were used in the first study of the [[normalized difference vegetation index]] (NDVI), now an ubiquitous measure of global plant greenness.<ref>{{Cite journal|url=https://ntrs.nasa.gov/citations/19740022614|title=Monitoring vegetation systems in the Great Plains with ERTS|first1=J. W.|last1=Rouse|first2=R. H.|last2=Haas|first3=J. A.|last3=Schell|first4=D. W.|last4=Deering|date=January 1, 1974|journal=NASA. Goddard Space Flight Center 3d ERTS-1 Symp., Vol. 1, Sect. A|accessdate=June 23, 2023|via=ntrs.nasa.gov}}</ref>
== Notes == {{reflist}}
== References ==
*{{cite book|last1=Wells|first1=Helen T.|last2=Whiteley|first2=Susan H.|last3=Karegeannes|url=https://history.nasa.gov/SP-4402.pdf|id=SP-4402|title=Origins of NASA Names|first3=Carrie|series=NASA History Series|publisher=NASA|year=1976|location=Washington, D.C.}}
==External links== {{Portal|Spaceflight}} *{{Commonscatinline}} *[https://catalog.archives.gov/id/649405 NASA film, Earth Resources Technology Satellite (ERTS), at the National Archives]
{{Landsat program}}
{{Orbital launches in 1972}}
[[Category:Landsat program]] [[Category:Spacecraft launched in 1972]] [[Category:Spacecraft launched by Delta rockets]]