Cosmic Dust
A cosmic dust detector, consisting of a 22- by 22-cm aluminum impact plate which was coated on both sides with a nonconducting material and which had a crystal acoustical transducer bonded to one side, was used to continually monitor dust-particle flux and mass distritution from earth proximity through the Mars encounter. The impact plate and dielectric-aluminum film combination constituted a penetration detector in the form of a capacitor. The experiment was also intended to observe the degree of dust-particle concentration near earth and near Mars, the rate of change of the dust-particle flux density with respect to distance from earth, and the perturbation effects of large planetary bodies on the dynamic behavior of the dust particles. The instrument was mounted above the main spacecraft bus, with the case just inside the thermal shield to protect it from the sun. The sensor protruded through an opening in the thermal shield. The instrument memory consisted of two 8-bit binary data-analysis registers and a microphone accumulator which recorded the number of microphone events observed by the instrument. Experiment data were received concerning particle momentum, the incoming particle direction, particle impacts below the microphone threshold, and microphone event accumulations. Measurements revealed a dust concentration near earth with a mass distribution somewhat different from that of interplanetary space. In-flight calibration was performed once a day on command from the ground. No instrument degradation was detected.