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Distributed space systems, and specifically spacecraft formations, have been identified as a new paradigm for addressing important science questions. However, when it comes to verifying and validating these systems before launch, there is the added challenge of figuring out how to test the formation’s holistic operations on the ground since a full end-to-end mission simulation is likely infeasible due to the need for costly testing infrastructure/facilities. Building on established methods for single-spacecraft testing, this paper presents a two-phase testing methodology that can be applied to precision formation flying missions with budget, timeframe, and resource constraints. First, a testing plan with unique considerations to address the coordinated and coupled nature of precision formation flight is devised to obtain high system confidence on the ground, and second, the formation’s holistic behavior is refined on orbit during the mission’s in-space commissioning. This approach structures the pre-launch testing to make efficient use of the limited test infrastructure on hand and leverages a sequential configuration process combined with built-in operational flexibility on orbit to safely finish characterizing the formation’s performance so that it can meet mission requirements 

The VIrtual Super Optics Reconfigurable Swarm (VISORS) mission is a distributed telescope consisting of two 6U CubeSats separated by forty meters that will obtain high-resolution images of active solar regions in the extreme ultraviolet spectrum. This mission is challenging because the CubeSats must autonomously control their relative motion with unprecedented accuracy while operating in close proximity. This paper presents three contributions that enable the VISORS mission to meet its challenging requirements. First, passively safe absolute and relative orbit designs for distributed telescopes that provide regular periods of alignment with inertial targets are developed using relative eccentricity/inclination vector separation. Second, a guidance, navigation, and control system design is proposed to meet the demanding relative motion control requirements. Third, a concept of operations is proposed that minimizes mission operations load when the formation is not actively performing observations. This concept of operations includes a safety plan to address on-orbit anomalies. The performance of the guidance, navigation, and control system is validated through Monte Carlo simulations including all significant error sources and operational constraints. These simulations show that the mission requirements are met with margin, providing a preliminary demonstration of the feasibility of accurate autonomous formation control with CubeSats. 

This paper presents the preliminary system design of the Virtual Super-resolution Optics with Reconfigurable Swarms (VISORS) mission, a multi-CubeSat distributed telescope which will image the solar corona to investigate the existence of underlying energy release mechanisms. VISORS was conceived in the National Science Foundation (NSF) CubeSat Innovations Ideas Lab Workshop held in 2019 to address NSF science goals with innovative technologies. This mission will gather imagery that directly pertains to theories of coronal heating. In the paper, novel technologies are described that enable the VISORS mission to meet its challenging requirements and achieve the mission and science goals. The VISORS formation is composed of two 6U CubeSats that fly 40 meters apart during science imaging as a distributed space telescope, with the lead spacecraft containing the optics and the trailing spacecraft containing the detector. An orbit maneuver planner utilizes GNSS carrier-phase measurements to provide a high-precision navigation solution, and a series of ceramic antenna arrays employ a novel 5.8 GHz inter-satellite crosslink. A 3 degrees-of-freedom (3DOF) propulsion system provides the capability for formation adjustments and active collision avoidance. The remaining spacecraft functions are handled by a spacecraft bus supplied by a commercial vendor, and the system integration is conducted by the VISORS mission team. Careful analysis of the system design and concept of operations led to the development of a safety plan which significantly reduces the risk of collision in a large subset of off-nominal scenarios. With a completed preliminary design review in Q4 2020 and a projected launch date in late 2023, this collaboration among 10 different universities, NASA, and a commercial partner is an upcoming mission that will demonstrate a new assembly of highly equipped CubeSats and their ability to conduct a state-of-the-art science mission in a cost and time effective manner. 

The Virtual Super-Resolution Optics with Reconfigurable Swarms (VISORS) mission is a multi-CubeSat distributed telescope which will image the solar corona to investigate the existence of underlying energy release mechanisms. Such a task requires angular resolutions of less than 0.2 arc-seconds in extreme ultraviolet, which cannot be economically done with a conventional space telescope. Performing such a mission requires unprecedented relative navigation tolerances, a need for active collision avoidance, a development of inter-satellite communication, and a propulsion system that enables the relative navigation maneuvers. The mission was initially conceived as a three 3U satellite formation in the NSF CubeSat Innovations Ideas Lab to address NSF science goals with innovative technologies. Once beginning conceptual subsystem design, it was evident that significant constraints linked to the three 3U satellite formation configuration limit the likelihood of mission success and increase mission risk. A trade study was conducted to determine potential resolutions to the problems associated with the initial three 3U satellite formation configuration. The completion of the trade study resulted in a major design change to a two 6U satellite configuration that resolved the issues associated with the initial configuration, improved mission success while reducing risk, and intends to incorporate novel CubeSat technologies, all of which enable the mission to move forward. This paper discusses the path that led the team to conduct the trade study, the design alternatives considered, and the innovative subsystem technologies that were conceived as a result of updating the satellite formation configuration.