SPOT 4[edit]
SPOT 4 launched March 24, 1998 and stopped functioning July, 2013. In 2013, CNES lowered the altitude of SPOT 4 by 2.5 km to put it on a phased orbit with a five-day repeat cycle. On this orbit, SPOT4 was programmed to acquire a time-lapse series of images over 42 sites with a five days revisit period from February to end of May 2013. The data set it produced is aimed at helping future users of the Sentinel-2 mission to learn working with time-lapse series. The time-lapse series provided by SPOT4 (Take5) have the same repetitiveness as those that will be delivered by the Sentinel-2 satellites, starting in 2015 and 2016.