Comet P/Halley's dust production rate at Giotto encounter derived from Halley Multicolour Camera observations

Optical constants for the dust from Comet P/Halley have been determined from Halley Multicolour Camera observations by applying the dust size distribution and the total mass impacting the Giotto spacecraft. The quantity of dust is found to be 0.080 rho exp 2/3 where rho is the dust particle bulk density in g/cu cm at an effective wavelength of 653 nm. The density must be low, suggesting the existence of rough, fluffy particles. A reevaluation of the dust production rate and the dust-to-gas ratio Chi about one, although values up to 40 cannot be ruled out.