Innovative focal plane design for large space telescope using freeform mirrors

Increasing the size of low-orbiting space telescopes is necessary to attain high-resolution imaging for Earth or planetary science, which implies bigger and more complex imaging systems in the focal plane. The use of homothetic imaging systems such as the Spot and Pleiades push-broom satellites would lead to prohibitive linear focal plane dimensions, especially for IR missions requiring large-volume cryostat. We present two optical TMA telescopes using an image-segmentation module based on astronomical image slicer technology developed for integral field spectroscopy, made of a set of freeform mirrors defined by Zernike polynomials. Each telescope has a linear 1.1° field of view; the first one considers a matrix detector and the second one considers several linear TDI detectors currently used in space missions. We demonstrate that such systems provide efficient optical quality over the full field and offer a substantial gain in terms of volume of the focal plane arrays.