One of the best known series of earth observation satellites is Landsat. First launched as the Earth Resource Technology Satellite in July 1972, it was later renamed Landsat 1. This satellite was followed by Landsat 2 through 5. Landsat 6 never reached orbit after launch in 1993. Landsat-7 began operations in 1999 and is now producing great imagery of our planet..

Landsat 7 is expected to have a 5 year mission life. The satellite orbits at an altitude of approximately 438 miles. It repeats its coverage of the earth every 16 days. The on-board sensors capture an image area of about 115 miles x 115 miles.

Most of the Landast imagery from the past ten years were from satellites 4 and 5. Two types of image data from these satellites are available: MultiSpectral Scanner (MSS) and Thematic Mapper (TM). Landsat 7 uses a new Enhanced Thematic Mapper Plus (ETM+). One of its new features is a panchromatic band (Band 8) with 15 meter resolution. Low cost sample datasets from Landsat 7 are available from the U.S.G.S. EROS Data Center.

You won't spot your house in a Landsat image, but cities, farms, major roads, airports, rivers, and lakes are visible. Search the NASA Visible Earth Collection using the keyword "Landsat" so see a wide variety of samples produced by government researchers.

A very comphehensive refrence to the Landsat 7 satellite system is the Landsat 7 Science Data Users Handbook

If your looking to see what a particular region looks like from space try the Earth Explorer search engine. It allows you to search for imagery using a map, place names, or coordinates. Earth Explorer will let you view available Landsat images. You can search for Enhanced Thematic Mapper Data (Landsat 7), Thematic Mapper Data (Landsat 4,5), or MultiSpectral Scanner (Landsat 1-5). My opinion is that the best data and browse imagery are from Landsat 7. The Landsat 7 browse images have a resolution of 825 by 750 pixels. The browse images will let you preview the scene to check cloud coverage and quality. If you see a scene you like, the digital data can be purchased on-line.

There are many other very low resolution "browse" images from Landsat available over the Internet. The Smithsonian Air and Space Museum Web Site has some low resolution images of certain U.S cities. Unfortunately, these have been JPEG compressed to a high degree and the quality is low.

NASA has placed a few 512 by 512 pixel subsets of 30 meter TM data on the web that are nice for experimentation.

For very fast searches try the "ImageNet Imagery" database at earth-info.

The U.S. Government does distribute certain high resolution Landsat MSS satellite images as part of the Landsat Pathfinder Program. A CD-ROM of data costs only $10. The data is part of a project called: North American Landscape Characterization. There are hundreds of scenes avialable to cover all areas of the continental United States. You have to do your own image processing of the raw data, but if you have the interest and equipment, you can produce some striking images of the earth from space. I have written a short document that describes my experiences obtaining and enhancing the NALC Landsat data.

If you are looking for low cost Landsat TM data of the Southwestern United States try Landsat4u. Their web site indicates that they sell public domain Landsat TM imagery on CD for $19.95 per scene.