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Landsat program
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Landsat 7, launched in 1999, is the most recent addition to the Landsat program.
The Landsat program is the longest running enterprise for acquisition of imagery of
Earth from space. The first Landsat satellite was launched in 1972; the most recent,
Landsat 7, was launched on April 15, 1999. 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, education and national security. Landsat 7 data has eight spectral
bands with spatial resolutions ranging from 15 to 60 meters.
Contents
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1 History
2 Satellite chronology
3 Technical details
4 Future
5 References
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6 See also
7 External links
[edit] History
Hughes Santa Barbara Research Center initiated design and fabrication of the first three
MSS Multi-Spectral-Scanners in the same year man landed on the moon, 1969. The first
prototype MSS was completed within nine months by fall of 1970 when it was tested by
scanning Half Dome at Yosemite National Park.
The initial centerline for the primary layout of the MSS was drawn by Jim Kodak, the
opto-mechanical design engineer who designed the Pioneer spacecraft optical camera, the
first instrument to leave the solar system.
The program was called the Earth Resources Observation Satellites Program when it was
initiated in 1966, but the name was changed to Landsat in 1975. In 1979, Presidential
Directive 54 under President of the United States Jimmy Carter transferred Landsat
operations from NASA to NOAA, recommended development of 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 Hughes Aircraft and RCA, was selected by
NOAA to operate the Landsat system under a ten year contract. EOSAT operated
Landsats 4 and 5, had exclusive rights to market Landsat data, and was to build Landsats
6 and 7.
A simulated-color satellite image of Kolkata taken on NASA's Landsat 7 satellite.
In 1989, this transition had not been fully completed when NOAA's funding for the
Landsat program ran out and NOAA directed that Landsats 4 and 5 be shut down, but an
act of the United States Congress provided emergency funding for the rest of the year.
Funding ran out again in 1990 and once again Congress provided emergency funding to
NOAA for six more months of operations, requesting that agencies that used Landsat data
provide the funding for the other six months of the upcoming year. The same funding
problem and solution was repeated in 1991. In 1992, various efforts were made to finally
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 October
5, 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 April 15, 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.
[edit] Satellite chronology
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Landsat 1 (originally named Earth Resources Technology Satellite 1) - launched
July 23, 1972, terminated operations in 1978
Landsat 2 - launched January 22, 1975, terminated in 1981
Landsat 3 - launched March 5, 1978, terminated 1983
Landsat 4 - launched July 16, 1982, terminated 1993
Landsat 5 - launched March 1, 1984, still functioning. [1] [2]
Landsat 6 - launched October 5, 1993, failed to reach orbit
Landsat 7 - launched April 15, 1999, still functioning, but with faulty scan line
corrector (May 2003) [3]
[edit] Technical details
The Multi-Spectral-Scanner had a 9" fused silica dinner-plate mirror epoxy bonded to
three invar tangent bars mounted to base of a Ni/ Au brazed Invar frame in a serreuire
truss that was arranged with four "Hobbs-Links" (conceived by Dr. Gregg Hobbs)
crossing at mid truss. This construct ensured the secondary mirror would simply oscilate
about the primary optic axis to maintain focus despite vibration inherent from the 14-inch
Be scan mirror. This engineering solution allowed the US to develop LANDSAT at least
five years ahead of French SPOT which first used CCD arrays to stare without need for a
scanner.
The MSS FPA, or Focal Plane Array consisted of 24 square optical fibers extruded down
to .0002"square fiber tips in a 4x6 array to be scanned across the Nimbus spacecraft path
in a +/-6 degree scan as the satellite was in a 10:30 polar orbit, hence it had to be
launched from Vandenburg AFB. The fiber optic bundle was embedded in a fiber optic
plate to be terminated at a relay optic device that transmitted fiber end signal on into six
photodiodes and 18 photomultiplier tubes that were arrayed across a 0.30-inch thick
aluminum tool plate, with sensor weight balanced vs the 9-inch telescope on opposite
side. This main plate was assembled on a frame, then attached to the silver-loaded
magnesium housing with helicoil fasteners.
Key to MSS success was the scan monitor mounted on the underbelly of the Mg housing.
It consisted of a diode source & sensor mounted at ends of four flat mirrors that were
tilted so that it took 14 bounces for a beam to reflect length of the three mirrors from
source to sender striking Be scan mirror seven times as it reflected seven times off the flat
mirrors. It only sensed three positions, both ends of scan & the mid scan, but that was all
that was required to determine where MSS was pointed and electronics scanning could be
calibrated to display a map.
[edit] Future
The Landsat Data Continuity Mission, scheduled to be launched in 2011, will be the next
satellite in the Landsat series.[4]
[edit] References
1.
2.
3.
4.
^ http://www.universetoday.com/am/publish/landsat_5_20_years.html?432004
^ http://earth.esa.int/showcase/landsat/
^ http://landsat.gsfc.nasa.gov/
^ http://www.usgs.gov/newsroom/article.asp?ID=1676
[edit] See also
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Remote sensing
[edit] External links
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Landsat NASA homepage
Landsat.org Home Page
Works by Landsat at Project Gutenberg
o Landsat picture of Washington, D. C.
(Commercial) Landsat imagery
Atlogis Maps and Atlogis Meta-Maps: Online-Viewer for Landsat 5 and Landsat
7 Natural Color Mosaic from Atlogis. Meta-Maps includes Google, MSN and
Yahoo Maps.
Landsat imagery for circa 1975, 1990 and 2000 visualised in Google Earth
(required GE installed)
v•d•e
The Landsat Program
Landsat 1 · Landsat 2 · Landsat 3 · Landsat 4 · Landsat 5 · Landsat 6 ·
Landsat 7 · LDCM
Retrieved from "http://en.wikipedia.org/wiki/Landsat_program"
Categories: Earth observation satellites | National Oceanic and Atmospheric
Administration
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