Halley Multicolor Camera (HMC)

Description

The Halley Multicolor Camera (HMC) is designed to provide high-resolution images of the nucleus and the coma of Halley's comet in nine colors and two polarizations. The camera operates in a spin-scan mode and uses a 1-m focal length Ritchey-Chretien telescope with an effective f number of 7.68. The instanteous field of view is 1.5 deg with no vignetting and the whole sphere can be viewed using rotation of the camera, tilting of the 45-deg deflecting mirror, and the spacecraft spin. The entrance collimator is at 90 deg with respect to the telescope axis of symmetry, which is the axis of rotation for the whole system. The light is deflected by 90 deg by a mirror that can be adjusted by about 1 deg about an axis perpendicular to the plane of symmetry of the telescope. The sensors are two area charge-coupled devices (CCD) and one Reticon. The CCDs have two segments each that provide 390 x 292 pixels while the Reticon has 2 x 936 pixels. The pixel size in micrometers is 22.3 x 22.3 for the CCDs and 30 x 375 for the Reticon. The spectral response of the whole system is about 350 to 1100 nm and a filter wheel is used to obtain 4 bands simultaneously for color and polarization or 11 broad and narrow bands alternately. The resolution in observing the comet is 11 m/pixel at a slant range of 500 km.