Early Architecture Concepts for the Habitable Worlds Observatory -- System Design, Modeling, and Analysis

The Habitable Worlds Observatory (HWO), NASA's next flagship science mission, follows in the tradition of the Nancy Grace Roman Space Telescope and other preceding great observatories. HWO will directly image and characterize Earth-like exoplanet and their atmospheres, with the capability to detect biosignatures and potentially answer the question of whether we are we alone. HWO will also serve as a powerful general astrophysics observatory, enabling breakthroughs in galaxy evolution, stellar astrophysics, and dark matter studies. Currently in pre-formulation, the project has established Exploratory Analytic Cases (EACs), a series of architectural concept designs used to assess the mission's demanding science objectives while exploring challenging engineering parameters. This paper describes the first three EACs, starting with observing strategies and error budget formulation and then progressing to design formulations, trade studies and lessons learned; this paper also discusses the integrated modeling pipeline, a key multidisciplinary system-level analysis capability, and analysis findings as applied to the first EAC. These activities set the stage for the follow on EACs 4 and 5, which will further explore the trade space and prepare for the baseline design that will support the Mission Concept Review (MCR).