Attempts to Measure Micrometeoroid Flux on the OGO 2 and

The micrometeoroid experiments on the OGO 2 and OGO 4 satellites are described. The aim of the OGO 2 experiment was to measure the velocities, masses, and orbits of dust particles in the earth's dust cloud. No orbits were determined, and it is questionable whether any micrometeoroids of mass >10−12 g impacted on the sensors during the 1300 hours in which good data were obtained. The OGO 4 experiment was modified in an attempt to measure a flux obviously much smaller than previously anticipated. No micrometeoroids capable of penetrating 4000 A of Al have impacted on ionization sensors of total effective area 5 cm2 ster during 3000 hour exposure. Thus, we find that the flux of micrometeoroids >10−12 g in the neighborhood of the earth is less than 2×10−3 particles/m2 sec 2π ster.