Building Earth Observation Cameras

229Submeter Imaging

A smaller pixel size also requires the optics to operate at a higher spatial

frequency. For example, a device with 13-μm pixel size as in LISS-1 has a

Nyquist frequency of 38.5 cycles/mm, while for a 5-μm device it is 100 cycles

per millimeter. Realizing telescope optics at higher frequency has its own

fabrication complexities. The major advantage of using a device having a

smaller pixel size is that the telescope focal length can be smaller and hence

to achieve same f-number a smaller aperture can be used thereby reducing

the telescope realization time and cost. The system designer has to weigh all

the pros and cons and of ...