Mitchell Kirshner, Steward Observatory, University of Arizona; Eric Pearce, Steward Observatory at the University of Arizona
Keywords: constellations, space telescopes, systems architecture
Abstract:
Modern space surveillance technologies leverage the engineering of constellations, system-of-systems comprised of multiple individual nodes. These constellations, which benefit from coordination through ground stations or directly through space-based communication, can accomplish multiple complex missions that an organization might have. Enterprises benefit from the optimization of their systems to accomplish as many of their goals as possible with minimized hardware costs. Trade studies assessing key performance parameters for optical systems provide evidence for decision-makers that specific design configurations best accomplish mission goals. Model-Based Systems Engineering (MBSE) provides an alternative to traditional document-based methods that is best suited for handling complexity in systems architecture design.
MBSE can be accomplished using several methodologies, tools, and programming languages; historically, large-scale ground-based telescopes like the European Extremely Large Telescope (E-ELT) and the Thirty Meter Telescope (TMT) has had success levering the systems modeling language SysML and its associated Object Oriented Systems Engineering Methodology (OOSEM). NASA has also used SysML for extraterrestrial satellite projects such as the Europa Clipper orbiter, and has developed an extension to OOSEM at the Jet Propulsion Laboratory for TMT research called the Executable Systems Engineering Methodology (ESEM). ESEM provides a formal methodology by which to automate the systems engineering requirements verification process to ensure that specific system configurations meet all requirements, down through the subsystem and component hierarchical levels.
The Steward Observatory team at the University of Arizona led by Dr. Eric Pearce has developed SysML models in 3DS Cameo Systems to automate mission and systems-level technical and stakeholder requirements for constellations of balloon-borne and satellite-based telescopes. As opposed to taking a functions-rooted approach in modeling an SDA constellation for multiple missions such as a synoptic cislunar space surveillance, low lunar orbit surveillance, and lunar surface reconnaissance, we have chosen to take a requirements-based approach. Altering conditions in the individual balloon or satellite nodes of our constellation through parameterizing our context models built in Cameo SysML, as well as testing effects of developing heterogeneous constellations comprised of differently sized or designed system constituents, forms the basis of a trade space by which to determine optimal mission configuration as determined by requirements. This allows for full verification of system compliance to specified tolerances as listed by requirements. While several methodologies exist for managing requirements, SysML and OOSEM provide a means by which to digitally connect those requirements to representations of the constellation structure and mission elements.
The novelty in our approach permits modeling and simulation at a higher fidelity than traditionally possible through OOSEM and ESEM. We use digital thread software bridges to connect the SysML representation of the system and architecture to external digital engineering tools. SysML authoring software Cameo Systems Modeler has a simulation plug-in with a computer programming interpreter, allowing for native execution of algorithms and programs housed external to the SysML model. Additional software like Systems Toolkit (STK) and optical design data from Zemax OpticStudio can connect directly to parameters in our SysML model through programming scripts or digital thread handling software like ModelCenter. Through integrating these software, our group can include detailed physics-based data in instances of our constellation’s logical architecture and maintain a compendium of different acceptable designs within Cameo Systems Modeler, complete with automated verification through ESEM. In this way, our requirements-based approach will inform decision makers whether or not a design alternative is acceptable without having to manually perform verification for every requirement.
This paper reports on the preliminary results of our modeling endeavor, including system roll-up calculations of the following considerations for space-borne optical systems: time-delayed integration (TDI), bandwidth, solar exclusion angle, clear aperture size, camera performance requirements, and more. Each system in our constellation must meet the system-level requirements; the satisfying of constellation and mission-level requirements are also included in our model for holistic and detailed trade study results. With SysML’s ability to both model and simulate the requirements, structure, behavior, and constraints hierarchically in a system-of-systems, program managers can rapidly evaluate design alternatives using visual programming techniques that raise the layer of abstract from line-by-line programming in one digital environment that enables renewable artifact generation for traditional documentation methods for stakeholders unfamiliar with MBSE.
An added benefit to our MBSE approach is the reusability of our data products, allowing us to generalize and extend the logical architecture used for our trade study towards other applications. While for now our constellation architecture for cislunar SDA utilizes an off-axis three mirror design and considers free-form optics for generating design alternatives managed by SysML, the modeling of the mission context surrounding our space-borne payload can be reused to test other systems of interest in similar environments. This paper will depict relevant SysML diagrams for various viewpoints of our system-of-interest and demonstrate the use of digital thread software linkages for requirements-based MBSE such that readers are able to repeat the methodology for their own field and use cases.
Date of Conference: September 17-20, 2024
Track: Space Domain Awareness