MICS

The Multi-spectral Imaging Camera System (MICS) instrument will be the main imaging payload onmics_system_overview_small the Flying Laptop. It is designed for two purposes. The main purpose is Earth observation of specific targets from multiple angles, which may be used to determine the bidirectional reflectance distribution function (BRDF). In a second application MICS will be used for Earth observation in the nadir pointing mode, as well as in the target pointing mode. Among other things this can be used for the in-orbit verification of the AIS receiver system on board the satellite. Since  the first application is more ambitious MICS is designed for multi-angle Earth observation, fulfilling the second application in the best possible manner.


MICS is designed as matrix scanner with the spectral channels red, green and near-infrared. The major requirement for the multi-angular Earth observation is a good signal-to-noise ratio (SNR), while a particularly high ground sample distance (GSD) is not mandatory. As a result the system has a GSD of 21.5 m for an orbit altitude of 600 km. The corresponding swath width is 22 km. The system consists of three separate cameras aligned on an optical bench in a triangular position (see figure above). Each camera has an identical design including the optic. The only difference are the filters used and - resulting from the chromatic aberration - the exact position of the focal plane. MICS has been designed around the CCD interline sensor Kodak KAI-1003M.

Each camera consists of nine main components (see figure below). First the electronics housing, the read-out electronics, the CCD sensor including the sensor board, the electronics flange, the optics, the optics brackets, the filter, the baffle and at last the on-board calibration system. The optics frame is made of titanium to allow for minimal thermal expansion. Materials not sensitive to the radiation environment in orbit are selected for lenses and filters. Camera control, data processing and data storage is handled by the Payload On-Board Computer (PLOC).

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MICS is mounted on an optical bench to minimize missalignment between the cameras due to thermal expansion. The optical bench is made of an aluminum sandwich structure with carbon fiber reinforced plastic as cover plates. The star trackers are mounted on the same bench for highly accurate pointing information.

The filters are designed for scientific earth observation purposes. Thus, the definition of the channels is strongly driven by the atmospheric absorption, as illustrated below, which shows the defined spectral channels and the absorption of the atmosphere. In addition to a preferably high transmission within the channels, the filters must block the radiation within the sensor sensible spectrum between 200 nm - 1000 nm.

 

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To characterize and calibrate the cameras in the laboratory, an optical test facility was established in a shaded area of the integration room. Details can be found here. Each camera is equipped with a newly developed LED calibration system to detect possible degradation of the sensor or the optics in orbit.

 

The following image shows on of the cameras within the setup used for the mechanical qualification test.

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