Feasibility of NEO detection with a primary objective grating telescope

Abstract

We explore a novel design for “Trip Wire Optics" (TWO), which is a near-Earth object (NEO) detection observatory, arising from the emerging technology of primary objective grating telescopy (the Dittoscope). The design consists of two Schmidt telescopes viewing a large transmission primary objective diffraction grating (POG) at large exodus angle, deployed in a ground based north-south orientation. This document serves to establish a baseline understanding of such an instrument, evaluating the system geometry, light collection efficiency, effects of atmospheric turbulence, and potential for NEO observation. While the atmospheric turbulence precludes diffraction-limited images, the Dittoscope design is no more effected than a conventional telescope and imager. We define a new figure of merit, modified etendue, to compare the light gathering power of a Dittoscope to that of a conventional telescope. We have not succeeded in creating a ground-based imaging survey that collects more light, as measured by modified etendue, with a POG than it did using the same two Schmidt telescopes with conventional imagers. However, the properties of the Dittoscope design differ from conventional surveys, and could potentially be scaled to enormous size. Our evaluation of the POG design suggests it would be more advantageous for applications that require large collection areas for small wavelength ranges (spectroscopy) or to achieve high resolution observations in space.