VIA Technologies EPIA SN-Series Specifications download pdf (Page 18)

Background

that best fits the implementation of a system for the acquisition of satellite images is a

CCD (although CMOS based devices are currently the best choice in order to reduce

power consumption). This stems mainly from the high sensitivity of silicon at

wavelengths of less than 1.1 μm, ideal if one is interested in capturing images in the

visible spectrum (0.4-0.7 μm) or nIR (near infrared).

Among all manufacturers taken into consideration, the selected device is a DALSA

FTF 2020M which is a squared full frame CCD with 2048x2048 pixels (12 µm side) with

100% optical fill factor and a considerably high dynamic range (which represents an

equivalent measure for the contrast the device is able to achieve). As stated by the final M

in the product code the sensor is monochrome with no reported Bayern filter in front of

the sensible area.

Figure 1: Dalsa FTF2020M sensor

Figure 2: Dalsa demoboard with FTF2020M sensor

support

Typically, in digital still cameras, multispectral capabilities are achieved by using

mechanical wheels that rotate optical filters in front of the sensor. To avoid moving parts

inside the instrument, which could compromise the success of the entire mission, a LCD

continuous tuneable filter will be placed in-between the sensor and the optics, to provide

better multispectral capabilities than the mechanical wheel. Multispectral images will be

generated overlapping single band images and creating arrays with a maximum of 10

spectral bands. The time the filter takes to switch between one wavelength to another is

typically 50 to 150 ms depending on the value of λ. AMSC will be one of the first

spaceborne instrument based on the use of a tunable filter.

CRI (Cambridge Research Inc, manufacturer of the filter) has already tested the

correct operation of the filter in vacuum conditions; it was found that the filter did not

experience mechanical damages or deformations during the test and that the optical

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VIA Technologies EPIA SN-Series Specifications Page 18