This map of the Arctic Circle is overlaid by a network of lines and circles representing orbital flight paths and ‘nominal scene centres’ (the middle point of the image taken) for the Landsat

satellites 1, 2 and 3 launched between 1972 and 1978. On the reverse is the same map showing the same information for Landsat 4, launched in 1982. Landsat satellites take what is called remote sensing images from space  (remote sensing being a way of capturing an image of or studying  an area or object without any physical contact). The manned Apollo programme experimented with remote sensing before an unmanned satellite, called Earth Resources Technology Satellite, was launched in 1972. This was soon renamed Landsat and we are now up to Landsat 8, launched in 2013. These satellites have captured millions of images, and these are made available at the U.S. Geological Survey ‘Earthexplorer’ site (https://earthexplorer.usgs.gov/). Text on the map explains how the system works. Landsat uses a grid called the Worldwide Reference System, a lattice of 251 paths (the thick lines) and 119 rows (the circles) which intersect at geographic locations and it is at these points that the image centres. Red marks indicate levels of cloud cover.

With different ranges of dates and images available Landsat has proved a valuable resource for the study of climate change, agricultural development and change in natural development.

To balance things out here’s the Landsat map for the bottom of the World

Index to Landsat Worldwide Reference System (WRS), 1:10,000,000. Published by the United States Geological Survey and the National Oceanic and Atmospheric Administration 1981-82. B1 (99a)