Interplanetary dust

Dust detection methods and the Radio Dust Analyzer

For the planetary and interplanetary medium, some techniques have been developed to measure dust characteristics. 

One of them is the dust detector which provides in situ measurements of the mass and the velocity vector of the dust grains. Another are the plasma wave and radio science experiments on board of several interplanetary spacecraft, detecting broad-band noise, in the ring planes of the outer giant planets and in tails of comets. This noise is believed to be caused by small dust grains bombarding the body of the spacecraft. The few kilometer per second relative velocity between the spacecraft and the dust grains is sufficient to fully vaporize the impacting grains and in part ionize the produced gas. The expanding plasma cloud causes the detected noise, and leaves an ionization signal. This signal has the interest of being local, but they have a limited space coverage since it can only be made along a trajectory of available space probes.

Additional data can be obtained by images taken through filters at various phase angles. They can be a source of data for the spatial and size distribution of the dust particles, but they can only reveal properties integrated along the line of sight. 

Recently, we proposed a new technique to derive the dust grain characteristics with the help of a wire dipole antenna. Charged dust grains passing by the antenna induce an electric potential change for the time of the flyby. These "waveforms'' were studied as a function of the characteristics of the dust grain (its charge and velocity vector) and the plasma parameters. The thermal noise level due to flyby, emission, and impacts of the ambient plasma electrons is calculated and compared with the magnitude of the dust signal. This recently proposed dust-detection technique has been called the Radio Dust Analyzer (RDA).

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