Mars Imaging Camera (MIC)
The Mars Imaging
Camera (MIC) is a visual wavelength CCD camera designed to obtain color images of Mars and
its satellites. The scientific objectives include studies of surface scattering
properties, the polar caps, atmospheric phenomena, the satellites Phobos and Deimos, and
possible martian dust rings.
Instrument Description
The overall size of the MIC is 9.2 cm x 15.0 cm x 23.5 cm. It has a radiation hardened lens with a 2.14 cm aperture, a 3.0 cm focal length, and an F number of 1.4. The image is focused on to three linear CCD arrays which operate successively in pushbroom fashion using three color filters: red (650 nm), green (550 nm), and blue (450 nm). The CCD has an integration time of 0.512 ms. Each array is 1 x 4104 pixels, of which 2560 are used for imaging. Each pixel is 12 micrometers wide with a resolution of about 74 arc seconds. The field of view along the array is 54.2 degrees and perpendicular to the array (in the spacecraft spin direction) is limited only by the 1 Mbyte of on-board memory. The 8-bit images will be compressed on-board using a standard JPEG algorithm. The camera has four gain settings, one for dark surfaces, two for bright surfaces and Phobos and Deimos, and one for the polar caps.
Instrument Operations
The MIC will take one image per orbit. The Nozomi orbital period will be different from the rotational period of Mars which is about 24 hours and 40 minutes, so the imaged longitude will shift with each orbit. The orbit is not sun-synchronous, so atmospheric and surface properties can be observed at different local times, allowing a study of diurnal properties. Seasonal changes will also be studied. The camera will obtain images with resolution better than 100 m per pixel near the lowest periapsis passes. The camera can be operated in two modes; command mode, the normal mode in which the imaging start time is sent directly to the spacecraft and the image is gathered until a pre-set size is reached, or auto mode, in which the imager is turned on continuously and when a pixel value exceeding a certain threshold is recorded the camera begins collecting an image of a pre-set size. The latter mode is used primarily for observations of Phobos and Deimos.