Basic and advanced Fourier telescope performance for imaging the sky in hard x rays

摘要

Abstract: Presently, a Fourier telescope design is flying on the Japanese Solar-A satellite providing hard x-ray images of the Sun. Fourier designs are presently being considered for the next generation of high energy observing instruments (e.g., HESP). Hard x-rays (10 - 500 keV) are produced by solar flares and cosmic sources such as the Crab nebula. Imaging these x-rays will allow insight to be gained as to processes at work in these energetic sources. Hard x-rays, while not imageable by conventional means, may be imaged by Fourier telescopes. In this paper, an advanced rotating modulation collimator (RMC) design using several spatial frequencies is numerically modeled and examined using an end-to- end photo counting simulation. It is then compared to two basic Fourier telescopes measuring only two spatial frequencies, a spatial modulation collimator and a RMC. While the more advanced telescope provided better images, diminishing improvement with more spatial frequencies for simple sources is clearly indicated. In addition, a tradeoff was identified for low flux sources in that for simple sources the basic telescope required fewer photons to achieved a stable image than did the more advanced version.!7