Landsat 1 (LS-1), formerly named ERTS-A and ERTS-1, was the first satellite of the United States'
Landsat program
The Landsat program is the longest-running enterprise for acquisition of satellite imagery of Earth. It is a joint NASA / United States Geological Survey, USGS program. On 23 July 1972, the Landsat 1, Earth Resources Technology Satellite was l ...
. It was a modified version of the Nimbus 4
meteorological
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...
satellite
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
and was launched on July 23, 1972, by a
Delta 900 rocket from
Vandenberg Air Force Base Vandenberg may refer to:
* Vandenberg (surname), including a list of people with the name
* USS General Harry Taylor (AP-145), USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in K ...
in
California
California is a U.S. state, state in the Western United States, located along the West Coast of the United States, Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the List of states and territori ...
.
It was the first satellite to carry a
Multispectral Scanner The Multispectral Scanner (MSS) is one of the Earth's observing sensors introduced in the Landsat program. A Multispectral Scanner was placed aboard each of the first five Landsat satellites. : "The Multispectral Scanner System", NASA Official: Dar ...
.
The near-
polar orbit
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of about ...
ing spacecraft served as a stabilized, Earth-oriented platform for obtaining information on agricultural and forestry resources, geology and mineral resources, hydrology and water resources, geography, cartography, environmental pollution, oceanography and marine resources, and meteorological phenomena.
Background
The multi-agency Earth Resources Satellites Program was begun in 1966 by the 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. The Bureau of Budget (BOB) did not grant funding to build the satellite, but provided $2 million to continue the feasibility studies.
Satellite design
Development
Definition studies for two Earth observation satellites began in 1967. The satellites were named Earth Resources Technology Satellite and were individually known as ERTS-A and ERTS-B.
In 1970,
General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable energ ...
was selected as the prime contractor for ERTS-A.
It was manufactured by GE's Space Division in
Valley Forge, Pennsylvania
The Village of Valley Forge is an unincorporated settlement located on the west side of Valley Forge National Historical Park at the confluence of Valley Creek and the Schuylkill River in Pennsylvania. The remaining village is in Schuylkill Tow ...
.
Operation
The spacecraft was tall with a diameter. Two solar panel arrays that were long each, with single axis articulation, generated power for the spacecraft. ERTS-A had a liftoff weight of .
The main spacecraft propulsion was three hydrazine thrusters. An attitude control system permitted the spacecraft's orientation to be maintained within plus or minus 0.7 degrees in all three axes.
Spacecraft communications included a command subsystem operating at 154.2 and 2106.4 MHz and a PCM 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 RBV system was transmitted in both real-time and tape recorder modes at 2265.5 MHz, while information from the MSS was constrained to a 20 MHz radio-frequency bandwidth at 2229.5 MHz.
The satellite also carried two wide-band
video tape
Videotape is magnetic tape used for storing video and usually sound in addition. Information stored can be in the form of either an analog or digital signal. Videotape is used in both video tape recorders (VTRs) and, more commonly, videocassette ...
recorders (WBVTR) capable of storing up to 30 minutes of scanner or camera data, giving the spacecraft's sensors a near-global coverage capability.
The satellite was also equipped with a data collection system (DCS) to collect information from remote, individually equipped 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. The design of the DCS came from the Nimbus-3 platform, then known as the interrogation, recording, and location system (IRLS).
Sensors
ERTS-A had two sensors to achieve its primary objectives: the return beam
vidicon
Video camera tubes were devices based on the cathode ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
(RBV) and the multispectral scanner (MSS).
The RBV was manufactured by the Radio Corporation of America (RCA). The RBV obtained
visible light
Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...
and
near infrared
Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
photographic images of Earth. At launch, the RBV was considered the primary sensor.
The MSS was designed by
Virginia Norwood at Hughes Aircraft Company, which also manufactured it. Norwood is called "The Mother of Landsat."
The sensor was 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 scanner that obtained radiometric images of Earth.
Mission
Launch
ERTS-A was launched July 23, 1972, on a Delta 0900 out of
Vandenberg Air Force Base Vandenberg may refer to:
* Vandenberg (surname), including a list of people with the name
* USS General Harry Taylor (AP-145), USNS ''General Hoyt S. Vandenberg'' (T-AGM-10), transport ship in the United States Navy, sank as an artificial reef in K ...
in California.
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 inclination of 99 degrees which orbited the Earth every 103 minutes.
It was the first satellite launched with the sole purpose of studying and monitoring the planet.
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.
Operations
Landsat 1's tape recorders malfunctioned in January 1978, and the satellite was taken out of service.
Results
![ERTS-1 San Francisco (ARC-1972-AC78-1116) (cropped)](https://upload.wikimedia.org/wikipedia/commons/f/f3/ERTS-1_San_Francisco_%28ARC-1972-AC78-1116%29_%28cropped%29.jpg)
From launch until 1974, Landsat 1 transmitted over 100,000 images, which covered more than 75% of the Earth's surface.
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.
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.
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.
Landsat 1 images were used in the first study of the
normalized difference vegetation index
The normalized difference vegetation index (NDVI) is a simple graphical indicator that can be used to analyze remote sensing measurements, often from a space platform, assessing whether or not the target being observed contains live green veget ...
(NDVI), now an ubiquitous measure of global plant greenness.
[Rouse, J.W, Haas, R.H., Scheel, J.A., and Deering, D.W. (1974) 'Monitoring Vegetation Systems in the Great Plains with ERTS.' ''Proceedings, 3rd Earth Resource Technology Satellite (ERTS) Symposium'', vol. 1, p. 48-62. https://ntrs.nasa.gov/citations/19740022614]
Notes
References
*
External links
NASA film, Earth Resources Technology Satellite (ERTS), at the National Archives
{{Orbital launches in 1972
Landsat program
Spacecraft launched in 1972
Spacecraft launched by Delta rockets