GEO debris and interplanetary dust: fluxes and charging behavior
  In September 1996, a dust/debris detector: GORID was launched into the geostationary (GEO) region as a piggyback instrument on the Russian Express-2 telecommunications spacecraft. The instrument began its normal operation in April 1997 and ended its mission in July 2002. The goal of this work was to use GORID's particle data to identify and separate the space debris to interplanetary dust particles (IDPs) in GEO, to more finely determine the instrument's measurement characteristics and to derive impact fluxes. While the physical characteristics of the GORID impacts alone are insufficient for a reliable distinction between debris and interplanetary dust, the temporal behavior of the impacts are strong enough indicators to separate the populations based on clustering. Non-cluster events are predominantly interplanetary, while cluster events are debris. The GORID mean flux distributions (at mass thresholds which are impact speed dependent) for IDPs, corrected for dead time, are 1.35x10^{-4} m^{-2} s^{-1} using a mean detection rate: 0.54 d^{-1}, and for space debris are 6.1x10^{-4} m^{-2} s^{-1} using a mean detection rate: 2.5 d^{-1}. Beta-meteoroids were not detected. Clusters could be a closely-packed debris cloud or a particle breaking up due to electrostatic fragmentation after high charging. 
Amara L. Graps (INAF-IFSI, Italy), Simon F. Green, Neil McBride   (PSSRI, The Open University, U.K.), J.A.M. McDonnell (Unis...