earth_satellite.gif source=NASA notes=see http://www.harmsy.freeuk.com/images/earth2.jpeg, http://cac-science8.wikispaces.com/ nasa copyright rules here http://www.nasa.gov/audience/formedia/features/MP_Photo_Guidelines.html
moon.png source=public domain notes=http://astro.unl.edu/misc/moonpics/moon08_th.jpg public domain license at http://astro.unl.edu/misc/moonpics
space-station.png source=nasa notes=http://www.nasa.gov/images/content/323090main_s119e009793_hires.jpg linked from http://www.nasa.gov/mission_pages/station/multimedia/iss_sts119_images.html
sun.png source=NASA notes=http://www.eos.unh.edu/images/newsl_0309/sun_lg.jpg