This animation will be regularly updated to show the orbits of the current earth observing fleet.
This most recent version, published in March 2017, includes the CYGNSS constellation and DSCOVR at L1. Visit the original page here.
Previous versions from recent years include:
entry 4274 a February 2015 version including SMAP
entry 3996 a spring 2014 version including GPM
entry 4070 a May 2013 version which added Landsat-8
entry 3892 a Dec 2011 version which added Suomi NPP and Aquarius
entry 3725 a version from June 2010