Comparison Of Measured Flux With Models

The 27 dust impacts measured in a period of 72 days leads to a dust flux of 0.4±0.1 impacts per day. To compare this dust flux with models, the sensitive area of the large and the small target for different angles from the symmetry axis was computed. We assume 70% transmission for the entrance grid, independent of the impact direction. In Figure 2 the measured flux is compared with different models. Divine's interplanetary dust flux model [5] is in good agreement with the measured flux. However the model by Staubach [1] underestimates the flux. Comparing the two models at 1 AU with the isotropic model by Grün et al. [6], which gives a flux of 0.8/day, we find that the Divine model is quite close to the isotropic flux (0.3/day) whereas the Staubach model is more than an order of magnitude (0.03/day) less than the isotropic model. It is important to note that the Divine model was constrained by absolute count rates of the Galileo and Ulysses dust detector only, whereas Staubach took directional information into account. As Cassini is not a spinning spacecraft, the Staubach model is therefore the most appropriate model. We must conclude that the dust flux measured by CDA cannot be explained with the interplanetary dust flux alone.

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