BEFORE the space age, knowledge of the space particulateenvironment was based upon the Earth-bound study of the zodiacal light, meteors, comets, asteroids, and meteorites. Since then, severalmethodshavebeendevelopedtocollectparticledatafromspace itself. 1 The simplest of these methods is to expose a surface to the spaceenvironment, returnittoEarth, andexamineitforimpacts. Micrometeoroid impacts at very high velocities produce characteristic craters in the samples. These craters can be analyzed to obtain information about the particles that caused them. The fi rst microcraters found on experiments specifi cally designed for satellites were recovered from the Gemini2 and Skylab missions. 3 Other recovered surfaces with microcraters were Apollo windows, 4 the Surveyor III camera, 5 and lunar rocks. 6 These samples helped to establish the natural particle ux, or number of particles impacting a certain area over a given time.