## Abstract

A lensless scanning telescope composed of two circular apertures and having good response with minimum aliasing is described. By analogy with an arrangement of two slits, the modulation transfer function (MTF) of this telescope is derived. The MTF of a lensless telescope scanning the earth’s surface from 500-km orbit is developed for both the scan and cross-scan directions. Response of 48% or better at 100-km wavelength in both directions is shown with aliasing errors due to sampling of 1% or less.

© 1980 Optical Society of America

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### Equations (4)

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(1)
$${\text{TF}}_{(\text{rect})}=\frac{\text{sin}\pi a/\mathrm{\lambda}}{\pi a/\mathrm{\lambda}},$$
(2)
$${\text{TF}}_{(\text{diamond})}={\left(\frac{\text{sin}\pi a/\mathrm{\lambda}}{\pi a/\mathrm{\lambda}}\right)}^{2},$$
(3)
$$\begin{array}{l}{\text{TF}}_{(\text{circle})}=\frac{2{J}_{1}(\pi af)}{\pi af},\\ {\text{TF}}_{(\text{telescope})}={\left(\frac{2{J}_{1}(\pi af)}{\pi af}\right)}^{2},\end{array}$$
(4)
$${\text{TF}}_{(\text{telescope})}=\frac{2{J}_{1}(\pi {a}_{1}f)}{\pi {a}_{1}f}\times \frac{2{J}_{1}(\pi {a}_{2}f)}{\pi {a}_{2}f},$$