Primary objective grating telescopy: optical properties and feasibility of applications

Abstract

We develop the theoretical foundation for primary objective grating (POG) telescopy.In recent years, a wide range of telescope designs that collect the light over a large grating and focus it with a secondary receiving optic that is placed at grazing exodus have been proposed by Thomas D. Ditto and are sometimes referred to as Dittoscopes. Applications include discovery and characterization of exoplanets, discovery of near-Earth asteroids, and spectroscopic surveys of the sky. These telescopes would have small aerial mass, and therefore, provide a path forward to launch large telescopes into space. Because this series of telescope designs departs from traditional telescope designs, it has been difficult to evaluate which applications are most advantageous for this design. We define a figure of merit, the "spectral étendue," that characterizes the photon collection capability of a POG. It is demonstrated that the diffraction limit for observations is determined by the length of the grating. We evaluate the effects of atmospheric seeing for ground-based applications and the disambiguation of position versus wavelength in the focal plane using a second dispersing element. Finally, some strategies for fully reaping the benefits of POG optical characteristics are discussed.

BLOCT: the bifurcated light optical coronagraphic telescope

“…DICER and BLOCT are related to BLOC which derives from the primary objective grating (POG) Dittoscope 13 first disclosed in 2002 14 now called THE MOST and reported under NIAC Phase I and Phase II studies. 15 .…”