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Encyclopedia > Landsat 7
Landsat 7
Landsat 7 being prepared for launch.
Launch
Date April 15, 1999
Vehicle Delta II
Site Vandenberg AFB
Orbit Characteristics
Reference system WRS-2
Type Sun-synchronous, near-polar
Altitude 705 km (438 mi)
Inclination 98.2°
Repeat cycle 16 days
Swath width 185 km (115 mi)
Equatorial crossing time 10:00 AM +/- 15 minutes


Landsat 7 is the latest satellite of the Landsat program. It was launched on April 15th, 1999. The primary goal of Landsat 7 is to refresh the global archive of satellite photos, providing up-to-date and cloud free images. Although the Landsat Program is managed by NASA, data from Landsat 7 is collected and distributed by the USGS. The NASA World Wind project allows 3D images from Landsat 7 and other sources to be freely navigated and viewed from any angle. Landsat 7 Photo This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... By analogy with the geosynchronous orbit, a heliosynchronous orbit is a heliocentric orbit of radius 24. ... Landsat 7, launched in 1999, is the most recent addition to the Landsat program. ... is the 105th day of the year (106th in leap years) in the Gregorian calendar. ... Year 1999 (MCMXCIX) was a common year starting on Friday (link will display full 1999 Gregorian calendar). ... The National Aeronautics and Space Administration (NASA) is an agency of the United States government, responsible for the nations public space program. ... The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Animation showing atmosphere and shading effects in v1. ...

Contents

Satellite specifications

Landsat 7 was designed to last for five years, and has the capacity to collect and transmit up to 532 images per day. It is in a polar, sun-synchronous orbit, meaning it scans across the entire earth's surface. With an altitude of 705 kilometres +/- 5 kilometres, it takes 232 orbits, or 15 days, to do so. The satellite weighs 1973 kg, is 4.04 m long, and 2.74 m in diameter. Unlike its predecessors, Landsat 7 has a solid state memory of 378 gigabits (roughly 100 images). The main instrument on board Landsat 7 is the Enhanced Thematic Mapper Plus (ETM+). Landsat 7 Schematic This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... By analogy with the geosynchronous orbit, a heliosynchronous orbit is a heliocentric orbit of radius 24. ...


Main features

  • A panchromatic band with 15m spatial resolution
  • Full aperture, 5% absolute radiometric calibration
  • A thermal infrared channel with 60 m spatial resolution

In telecommunication and physics, radiometry is the science of radiation measurement. ... Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ...

Scan Line Corrector failure

The effect of the SLC on ETM+ scans.
The effect of the SLC on ETM+ scans.

On May 31, 2003 the Scan Line Corrector (SLC) in the ETM+ instrument failed. The SLC consists of a pair of small mirrors that rotate about an axis in tandem with the motion of the main ETM+ scan mirror. The purpose of the SLC is to compensate for the forward motion (along-track) of the spacecraft so that the resulting scans are aligned parallel to each other. Without the effects of the SLC, the instrument images the Earth in a "zig-zag" fashion, resulting in some areas that are imaged twice and others that are not imaged at all. The net effect is that approximately one-fourth of the data in a Landsat 7 scene is missing when acquired without a functional SLC. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... is the 151st day of the year (152nd in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...


Following the SLC failure, an Anomaly Response Team (ART) was assembled, consisting of representatives from the USGS, NASA, and Hughes Santa Barbara Remote Sensing (the manufacturer of the ETM+ instrument). The team assembled a list of possible failure scenarios, most of which pointed at a mechanical problem with the SLC itself. Since there is no backup SLC, a mechanical failure would indicate that the problem was permanent. However, the team was unable to rule out the possibility of an electrical failure, though such a possibility was deemed remote. Nevertheless, on September 3, 2003, USGS director Charles G. Groat authorized the Landsat project to reconfigure the ETM+ instrument and various other subsystems on board Landsat 7 to use the spacecraft's redundant ("Side-B") electrical harness. The United States Geological Survey (USGS) is a scientific agency of the United States government. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States government, responsible for the nations public space program. ... is the 246th day of the year (247th in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ...


With this authorization, the USGS flight operations team at the NASA Goddard Space Flight Center uploaded a series of commands to the spacecraft, instructing it to operate using the redundant electrical harness. This operation was successful, and on September 5, 2003, the ETM+ instrument was turned on and acquired data that was sent to the Landsat ground system at EROS outside of Sioux Falls, South Dakota. It was immediately apparent that the migration to the Side-B electrical harness had not fixed the problem with the SLC. Following this, the instrument was reconfigured to use its primary electrical harness. The subsequent conclusion of the ART was that the SLC problem was mechanical and permament in nature. Aerial view of Goddard Space Flight Center. ... is the 248th day of the year (249th in leap years) in the Gregorian calendar. ... Year 2003 (MMIII) was a common year starting on Wednesday of the Gregorian calendar. ... The Center for Earth Resources Observation and Science (EROS) is a United States Geological Survey data management, systems development, and research field center. ... Sioux Falls (IPA: [su fɑlz]) is the largest city in the U.S. state of South Dakota, and the county seat of Minnehaha County. ...


Landsat 7 continues to acquire data in this mode. Data products are available with the missing data optionally filled in using other Landsat 7 data selected by the user. To continue the Landsat legacy, studies are underway to fly an equivalent scientific sensor on a new satellite towards the end of this decade.


Satellite imagery

A false color IR image of Washington DC, taken by Landsat 7.
A false color IR image of Washington DC, taken by Landsat 7.

In August of 1998, NASA contracted EarthSat to produce Landsat GeoCover (Geocover 2000 in NASA World Wind) - a positionally accurate orthorectified Landsat Thematic Mapper and Multispectral Scanner imagery covering the majority of the Earth's land mass. The contract was part of the NASA Scientific Data Purchase which was administrated through NASA's John C. Stennis Space Center. GeoCover was later enhanced to EarthSat NaturalVue, a simulated natural color Landsat 7 derived circa year 2000, orthorectified, mosaicked and color balanced digital image dataset. Other commercial simulated true color 15-meter global imagery products built from the NASA Landsat 7 imagery include TerraColor from Earthstar Geographics, TruEarth (found in Google Earth and Google Maps) from TerraMetrics, BrightEarth from ComputaMaps, Landsat 7 simulated Natural Color from Atlogis and a product of i-cubed used in World Wind. False infrared-colour, pans-sharpened Landsat 7 image of Washington DC (15m Resolution) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... False infrared-colour, pans-sharpened Landsat 7 image of Washington DC (15m Resolution) This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... A false color image showing the Chesapeake Bay and the city of Baltimore. ... The National Aeronautics and Space Administration (NASA) is an agency of the United States government, responsible for the nations public space program. ... Earth Satellite Corporation (EarthSat) was an early pioneer in the commercial utilization of the Earth observation satellite. ... Animation showing atmosphere and shading effects in v1. ... One of the Earth observing sensors introduced in the Landsat program. ... One of the Earth observing sensors introduced in the Landsat program. ... The John C. Stennis Space Center (or SSC), located in Hancock County, Mississippi at the Mississippi/Louisiana border, is NASAs largest rocket engine test facility. ... 2000 (MM) was a leap year starting on Saturday of the Gregorian calendar. ... Google Earth is a virtual globe program that was originally called Earth Viewer and was created by Keyhole, Inc. ... Screenshot of Google Maps showing a route from Toronto to Ottawa on the 400-Series highways. ... Screenshot of World Wind showing USGS Urban Ortho-Imagery of Huntington Beach, Los Angeles World Wind is a virtual globe developed by NASA for use on personal computers running Microsoft Windows. ...


Largest parts of the earth surface displayed on web mapping services like Google Maps/Google Earth, MSN Maps or Yahoo Maps are based on enhanced and color balanced Landsat 7 imagery. Web mapping is the process of designing, implementing, generating and delivering maps on the World Wide Web. ...


See also

Google Earth, a highly detailed virtual globe that comes with simple atmosphere and star dome NASA World Wind, an open source virtual globe with stars and advanced atmosphere & sunlight effects Microsoft Virtual Earth 3D within Windows Live Local site NASA World Wind showing near-real-time NASA JPL Terra MODIS... Animation showing atmosphere and shading effects in v1. ... Google Earth is a virtual globe program that was originally called Earth Viewer and was created by Keyhole, Inc. ...

External links



Landsat 7 Patch This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... The Boeing Company (NYSE: BA, TYO: 7661 ) is a major aerospace and defense corporation, originally founded by William Boeing. ...

v  d  e
      The Landsat Program
Landsat 5 spacecraft

Landsat 1 · Landsat 2 · Landsat 3 · Landsat 4 · Landsat 5 · Landsat 6 · Landsat 7 · LDCM Landsat 7, launched in 1999, is the most recent addition to the Landsat program. ... Image File history File links Landsat5 Artists Rendering (NASA PD) File links The following pages link to this file: Landsat 5 Landsat 4 ... Landsat 1, originally named Earth Resources Technology Satellite 1, was a modified version of the Nimbus 4 meteorological satellite. ... Landsat 2 is the second satellite of the Landsat program. ... Landsat 3 undergoing final launch preparations Landsat 3 is the third satellite of the Landsat program. ... An artists impression of Landsat 5, indentical in design to Landsat 4. ... Landsat 5 is the fifth satellite of the Landsat program. ... Landsat 6 was designed to continue the Landsat program, and was equipped with an upgraded set of instruments. ...

Landsat 7 mission patch

  Results from FactBites:
 
Landsat program - Wikipedia, the free encyclopedia (555 words)
The first Landsat satellite was launched in 1972; the most recent, Landsat 7, was launched on April 15, 1999.
Landsat 6 was finally launched on October 5, 1993, but was lost in a launch failure.
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 availabilty of Landsat digital data and images, at the lowest possible cost, to traditional and new users of the data.
Landsat 7 - definition of Landsat 7 in Encyclopedia (301 words)
The primary goal of Landsat 7 is to refresh the global archive of satellite photos, providing up-to-date and cloud free images.
Although the Landsat Program is managed by NASA, data from Landsat 7 is collected and distributed by the USGS.
Landsat 7 was designed to last for five years, and has the capacity to collect and transmit up to 532 images per day.
  More results at FactBites »

 
 

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