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1. Maximizing Mission Utility within Operational Constraints for the SWARM-EX CubeSat Mission

   https://doi.org/https://doi.org/10.2514/6.2022-0236  

   David J. Fitzpatrick, Evan Bauch (September 2022, AIAA SCITECH 2022 Forum)

   With space more accessible than ever, academic institutions like the University of Colorado (CU) Boulder have exhibited that CubeSats (compact, homogeneous, rectangular satellites with masses below 14 [kg]) can be leveraged for remarkable space missions capable of making significant advances to both scientific and technological fields. One such CubeSat project is the NSF-funded Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX), which will launch three 3U CubeSats into a “swarm” that will demonstrate autonomous formation flying capabilities while simultaneously studying the spatial and temporal variability of ion-neutral interactions in the equatorial Ionosphere-Thermosphere region. Although the small stature of CubeSats and their standardized deployer options help to lower unit development cost and facilitate launch opportunities, the physical size limits of CubeSats prove to be a double-edged sword vis-à-vis sustaining a stable power state while hosting instruments with high power demands and often strict pointing requirements. For SWARM-EX, this issue is magnified by the mission’s ambitious goals; to comply with mission requirements, a SWARM-EX spacecraft is required to concurrently (1) point the science instruments no more than 30° off ram when they are operational, (2) point the GNSS patch antenna no more than 30° off zenith when the spacecraft are separated by ≤ 10 [km], (3) point the X-Band patch antenna no more than 18° off boresight from the ground station during downlink, (4) maximize the differential ballistic coefficient during differential drag maneuvers, and (5) maximize solar array power generation at all times. Consequently, advanced CubeSat Missions like SWARM-EX require innovative systems engineering solutions to remain power-positive during on-orbit operations. Through a combination of intricate pointing profiles, orbital simulations, a comprehensive and coordinated ConOps, battery state of charge simulation tools, and expertise from previous CubeSat missions, the SWARM-EX team has conceived a plan to successfully meet all these mission requirements; it is the aim of the authors to illuminate these strategies as a case study. 

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2. Preliminary Design of a Distributed Telescope CubeSat Formation for Coronal Observations

   https://doi.org/10.2514/6.2021-0422  

   Gundamraj, Athreya; Thatavarthi, Rohan; Carter, Christopher; Lightsey, E Glenn; Koenig, Adam; D'Amico, Simone (January 2021, AIAA Scitech 2021 Forum)

   null (Ed.)

   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. 

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3. CubeSat Radiation Hardness Assurance Beyond Total Dose: Evaluating Single Event Effects

   Braden Oh, Celvi Lisy (August 2022, Small Satellite Conference)

   Radiation poses known and serious risks to smallsat survivability and mission duration, with effects falling into two categories: long-term total ionizing dose (TID) and instantaneous single event effects (SEE). Although literature exists on the topic of addressing TID in smallsats, few resources exist for addressing SEEs. Many varieties of SEEs exist, such as bit upsets and latch ups, which can occur in any electronic component containing active semiconductors (such as transistors). SEE consequences range from benign to destructive, so mission reliability can be enhanced by implementing fault protection strategies based on predicted SEE rates. Unfortunately, SEE rates are most reliably estimated through experimental testing that is often too costly for smallsat-scale missions. Prior test data published by larger programs exist, but may be sparse or incompatible with the environment of a particular mission. Despite these limitations, a process may be followed to gain insights and make informed design decisions for smallsats in the absence of hardware testing capabilities or similar test data. This process is: (1) Define the radiation environment; (2) identify the most critical and/or susceptible components on a spacecraft; (3) perform a search for compatible prior test data and/or component class data; (4) evaluate mission-specific SEE rates from available data; (5) study the rates alongside the mission requirements to identify high-risk areas of potential mitigation. The methodology developed in this work is based on the multi-institutional, National Science Foundation (NSF) Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX) mission. The steps taken during SWARM-EX’s radiation analysis alongside the detailed methodology serve as a case study for how these techniques can be applied to increasing the reliability of a university-scale smallsat mission. 

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4. Systems Architecture and Conceptual Design of a CubeSat Formation Serving as a Distributed Telescope

   https://doi.org/10.2514/6.2020-4174  

   Thatavarthi, Rohan; Gundamraj, Athreya; Carter, Christopher A.; Lightsey, Edgar G. (November 2020, ASCEND 2020)

   null (Ed.)

   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. 

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5. Daedalus MASE (mission assessment through simulation exercise): A toolset for analysis of in situ missions and for processing global circulation model outputs in the lower thermosphere-ionosphere

   https://doi.org/10.3389/fspas.2022.1048318  

   Sarris, Theodore E.; Tourgaidis, Stelios; Pirnaris, Panagiotis; Baloukidis, Dimitris; Papadakis, Konstantinos; Psychalas, Christos; Buchert, Stephan Christoph; Doornbos, Eelco; Clilverd, Mark A.; Verronen, Pekka T.; et al (January 2023, Frontiers in Astronomy and Space Sciences)

   Daedalus MASE (Mission Assessment through Simulation Exercise) is an open-source package of scientific analysis tools aimed at research in the Lower Thermosphere-Ionosphere (LTI). It was created with the purpose to assess the performance and demonstrate closure of the mission objectives of Daedalus, a mission concept targeting to performin-situmeasurements in the LTI. However, through its successful usage as a mission-simulator toolset, Daedalus MASE has evolved to encompass numerous capabilities related to LTI science and modeling. Inputs are geophysical observables in the LTI, which can be obtained either throughin-situmeasurements from spacecraft and rockets, or through Global Circulation Models (GCM). These include ion, neutral and electron densities, ion and neutral composition, ion, electron and neutral temperatures, ion drifts, neutral winds, electric field, and magnetic field. In the examples presented, these geophysical observables are obtained through NCAR’s Thermosphere-Ionosphere-Electrodynamics General Circulation Model. Capabilities of Daedalus MASE include: 1) Calculations of products that are derived from the above geophysical observables, such as Joule heating, energy transfer rates between species, electrical currents, electrical conductivity, ion-neutral collision frequencies between all combinations of species, as well as height-integrations of derived products. 2) Calculation and cross-comparison of collision frequencies and estimates of the effect of using different models of collision frequencies into derived products. 3) Calculation of the uncertainties of derived products based on the uncertainties of the geophysical observables, due to instrument errors or to uncertainties in measurement techniques. 4) Routines for the along-orbit interpolation within gridded datasets of GCMs. 5) Routines for the calculation of the global coverage of anin situmission in regions of interest and for various conditions of solar and geomagnetic activity. 6) Calculations of the statistical significance of obtaining the primary and derived products throughout anin situmission’s lifetime. 7) Routines for the visualization of 3D datasets of GCMs and of measurements along orbit. Daedalus MASE code is accompanied by a set of Jupyter Notebooks, incorporating all required theory, references, codes and plotting in a user-friendly environment. Daedalus MASE is developed and maintained at the Department for Electrical and Computer Engineering of the Democritus University of Thrace, with key contributions from several partner institutions. 

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