Why do I receive more than one near real time alert in any given satellite overpass period?
The MODIS sensor is on board two polar orbiting satellites, Terra and Aqua. Each satellite makes two overpasses over the globe, 2 day time and 2 night time overpasses, equaling to a total of 4 overpasses of the MODIS sensor in a 24 hour period. The sensor images the earth in 2330 km swaths. If you subscribed to a large area, like the USA, you will receive multiple near real time email alerts for a given overpass (e.g. Terra daytime overpass) as it takes several swaths to cover the whole of the US. To determine where and when the overpass is going to occur, you may refer to the Terra and Aqua Orbit Tracks from the following websites. Terra: http://www.ssec.wisc.edu/datacenter/terra/GLOBAL.html Aqua: http://www.ssec.wisc.edu/datacenter/aqua/GLOBAL.html The maps show a series of white lines with tic marks showing what time the satellite will pass over a certain location on the Earth. The white lines represent the center of the swath and the tic marks and time show at what time in UTC the
