Restoration of chopped and nodded images in infrared astronomy

In thermal infrared astronomy a differential technique is used for extracti ng the weak astronomical image from the large background due to the environ ment. The resulting images, the so-called chopped and nodded images, presen t large negative values and provide reliable representations uniquely in th e case of isolated sources. In this paper we discuss the mathematical prope rties of the problem of restoring the original image from its chopped and n odded version and we investigate an iterative regularization method, the so -called projected Landweber method, for approximating non-negative solution s of the problem. This method provides satisfactory results in some cases b ut, in general, the restored images are still affected by several artifacts . We suggest an observation strategy which, combined with our proposed rest oration method, can significantly reduce the effect of these artifacts.