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Earth Live

posted May 11, 2012, 11:55 PM by Abel Mendez   [ updated Jun 4, 2012, 8:40 PM ]
We are working in a project to put online current daily global satellite images of Earth in true-color (colors as seen by the human eye). Unfortunately, satellites that have a full globe view of Earth (geostationary) take images that are good for land-weather analysis but not for a traditional color image. Weather reports use images that are based on mosaics from low-orbit superimposed with weather layers from geostationary satellites. In fact, we have more full-globe true-color images of Mars than Earth. The best color images of Earth are from planetary missions (NASA Visible Earth is a composition). With so many low-orbit satellites there is little need for a global color picture unless you are studying large or global land-weather patterns, and this does not requires color.

Here we are testing the reproduction of true-color images from the Meteosat-9 geostationary satellite. Meteosat has a global view of Earth over the Europe-Africa region. It takes images every 15 minutes in eleven channels (filters), mostly in the infrared, with two in the visible green and red spectrum. We combined these two visible channels with another two in the infrared to create a blue channel (not easy). The result is a near true-color full-globe image every 24 hours at 12 UTC (8 AM EDT) (Figure 1).

Figure 1. Animated full-globe color images of Earth from May 7-11, 2012 at 12 UTC (8 AM EDT) derived from the Meteosat satellite. You can download a high resolution static version (14 megapixels) here. CREDIT: PHL @ UPR Arecibo and the NERC Satellite Receiving Station, Dundee University, Scotland. All images are copyright of EUMETSAT.

We are still working in calibrating the colors to match more closely a true-color image, and this is the most difficult part. Color views from the Americas side will be more challenging because the GOES-E satellite have only one visible light channel. We will also try to use images from Meteosat-7 or Electro-L to cover the Asia region, MTSAT to cover the Japan-Australia region, and GOES-W for the pacific.

We expect that the final product will consist of five full-globe color images of Earth each day. We can do it almost real-time as each image is taken every 15 to 30 minutes but we are interested in the whole illuminated side and this only happens at particular times for each satellite. As far as we know this is the only project to create such "live" true-color global images of Earth. There are others from low-orbit (check here a live view from Landsat and soon by UrtheCast). This is part of a project to study how clouds patterns affect the surface characterization of habitable exoplanets.