Landsat 7

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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 Mission Patch.

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.

Contents

[edit] Satellite specifications

Landsat 7 Schematic.

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+).

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

[edit] Main features

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

[edit] Scan Line Corrector failure

On May 31, 2003 the Scan Line Corrector (SLC) in this instrument failed. The effect of this is that the raster scanning of the image is angled rather than parallel, causing narrow bands of each image not to be acquired. 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.

[edit] Satellite imagery

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 and TruEarth (found in Google Earth and Google Maps) from TerraMetrics.

[edit] See also

[edit] External links


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Landsat 5 spacecraft

Landsat 1 · Landsat 2 · Landsat 3 · Landsat 4 · Landsat 5 · Landsat 6 · Landsat 7 · LDCM

 Landsat 7 mission patch
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