They had a lot of the right instruments in the right place. Graph of position (3 meters!): http://ivsopar.obspm.fr/earth/tigo Description of the TIGO package: http://cddis.gsfc.nasa.gov/lw12/docs/Riepl_Tigo.pdf Letter from the director: http://www.expres-eu.org/Chile_06032010.html -- These are my opinions, not necessarily my employer's. I hate spam.