<title>Enhancing a moderate resolution x-ray telescope with a rotating modulation collimator</title>

Abstract

We investigated the theoretical performance of a rotating modulation collimator (RMC) situated in front of a moderate angular resolution focusing X-ray telescope. By ray tracing we investigated the RMC's ability to improve the positioning capability and reduce the incidence of source confusion. The moderate angular resolution (two arcmin) telescope can have high collecting area; the factor of four reduction due to the RMC would leave the system with about as much throughput as a high angular resolution telescope of comparable dimensions. This system is likely to be lighter and less costly to construct than a high resolution telescope and could operate over the entire field of a very wide field of view telescope. The wire thickness and spacing are only slightly finer than those of previous RMC's. The effects of possible errors in wire spacing and misalignments of the two wire planes, of the RMC are included in the simulations. Diffraction is also included. Results are encouraging. With 100 detected source counts plus background, we obtain positions with a statistical error below 5 arcseconds. We can resolve and position two, 400-count point sources 25 arcseconds apart. However, this system does not improve upon the telescope resolution in the case of extended sources such as clusters of galaxies.