Landsat 7

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

1 Satellite specifications
2 Main features
3 Scan Line Corrector failure
4 Satellite imagery
5 See also
6 External links

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. 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.

Main features

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

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.

Satellite imagery

In August of 1998, NASA contracted EarthSat to produce Landsat GeoCover - 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 found in Google Earth and Google Maps. Other commercial simulated true color 15-meter global imagery products built from the NASA Landsat 7 imagery include [TerraColor] from Earthstar Geographics and [TruEarth] from TerraMetrics.

External links

[NASA's Landsat 7 Website]
[The USGS' Landsat Website]
[NASA's WorldWind Project] World Wind lets you zoom from satellite altitude into any place on Earth. Leveraging Landsat satellite imagery and Shuttle Radar Topography Mission data, World Wind lets you experience Earth terrain in visually rich 3D.
[NASA Applied Sciences Directorate] website for free viewing/download of Landsat GeoCover band 742 mosaics
[University of Maryland Global Land Cover Facility] for free viewing/download of individual Landsat images, GeoCover mosaics, and other earth imagery data
[EarthSat's NaturalVue 2000: Global natural color satellite imagery coverage (resolution 15 m), based on Landsat 7 data acquired between 1999 and 2001]
[TerraColor.Net] - TerraColor 15m imagery website
[ResMap] - Free on-line viewing of the full resolution TerraColor imagery
[TruEarth] 15m imagery website