Efficient approach to designing a Schmidt-Cassegrain objective for a remote sensing satellite

Abstract

This paper presents an efficient approach to designing a Schmidt-Cassegrain objective for a remote sensing satellite. The objective is required to have multispectral operational bands, with three spectral channels distributed along the range (0.5 to 0.9 mum), as well as a panchromatic channel; 4 degrees field of view; distortion smaller than 0.3%; and a modulation transfer function, at 50 lines/mm spatial frequency, better than 0.5 and 0.35 at the center and edge of the field of view. The proposed design approach is based on Slyusarev's theory of aberrations and optical design. An image quality index is formulated as a function of optical system component powers and axial distances. For each combination of parameters, there exists a possible solution that can be realized into a thin lens system by solving Seidel sum equations. The final design is then reached by a simple and quick optimization step. The best three designs are compared in terms of initial values of optical system parameters and final design specifications. The best system image quality is thoroughly analyzed. All three presented designs meet and exceed the required design specifications.

Modulating substrate specificity of histone acetyltransferase with unnatural amino acids

“…The ability to direct the activity and more importantly the selectivity of enzymes is critical in protein design. 1,2 Several key tools including directed evolution, 3 structure-based design 4 and computational approaches 5 have been developed to enable scientists to re-fashion existing proteins with altered function.…”