Nasa has launched the latest mission in a 50-year unbroken line of satellites that monitor the Earth’s surface. Landsat 9 lifted off atop a United Launch Alliance Atlas V rocket from Vandenberg’s space launch complex 3E at 19.12 BST (14.12 EDT) on 27 September. The Landsat programme is a joint project between Nasa and the US Geological Survey. It continuously collects images of the Earth’s surface to monitor agricultural productivity, forest health, water quality, coral reefs and glaciers. The first Landsat satellite was launched in 1972. The decades-long history of images helps scientists understand changes in land use and natural changes brought about by climate change. In conjunction with Landsat 8, which is still in orbit, Landsat 9 will be able to capture the entire surface of the Earth every eight days. Landsat 9 carries two instruments, an optical camera and an infrared sensor. Together they will measure the light and heat that is either reflected or emitted from the Earth’s surface. From its operating orbit of 705km, Landsat 9’s image pixels will cover an area about 30 metres across. This is small enough to allow scientists to identify most crop fields in the US.