Optimizing Field Geometry for Modular Micropore-Optics Soft X-ray Time-Domain Surveys

Abstract

Wide-field micropore (lobster eye) optics enable focusing soft X-ray instruments with fields of view of hundreds of square degrees, but square-format modules require careful geometric arrangement to support both wide-area surveys and sensitive pointed observations. We examine this design problem using the X-ray TRansient Array / Micropore Optics X-ray Imager trade study, developed for a NASA Small Explorer mission concept, as a worked example. Single-module performance scaling is combined with geometric survey simulations to compare modular field layouts, overlap regions, and repeated survey tilings. For realistic micropore-optic parameters, increasing module size primarily expands the field of view once the boresight-centered effective area saturates, making modular architecture and field geometry central design variables. A three-module tri-petal configuration, formed by differentially rolling and offsetting three 10 x 10 sq deg square fields, produces a compound field of approximately 240 sq deg with one-module discovery regions, two-module bridge regions, and a compact three-module core. When repeated in a dense hexagonal lattice, the footprint closes gaps, builds a more uniform exposure floor, and provides enhanced-depth survey regions. This geometry offers an efficient compromise among survey coverage, pointed sensitivity, system complexity, and resilience, and can be scaled to larger persistent soft-X-ray monitoring architectures.