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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. ABET & Engineering Accreditation - History, Theory, Practice: Initial Findings from a National Study on the Governance of Engineering Education

   Akera, A. ( January 2019 , ASEE Annual Conference proceedings)

   Who and by what means do we ensure that engineering education evolves to meet the ever changing needs of our society? This and other papers presented by our research team at this conference offer our initial set of findings from an NSF sponsored collaborative study on engineering education reform. Organized around the notion of higher education governance and the practice of educational reform, our open-ended study is based on conducting semi-structured interviews at over three dozen universities and engineering professional societies and organizations, along with a handful of scholars engaged in engineering education research. Organized as a multi-site, multi-scale study, our goal is to document differences in perspectives and interest the exist across organizational levels and institutions, and to describe the coordination that occurs (or fails to occur) in engineering education given the distributed structure of the engineering profession. This paper offers for all engineering educators and administrators a qualitative and retrospective analysis of ABET EC 2000 and its implementation. The paper opens with a historical background on the Engineers Council for Professional Development (ECPD) and engineering accreditation; the rise of quantitative standards during the 1950s as a result of the push to implement an engineering science curriculum appropriate to the Cold War era; EC 2000 and its call for greater emphasis on professional skill sets amidst concerns about US manufacturing productivity and national competitiveness; the development of outcomes assessment and its implementation; and the successive negotiations about assessment practice and the training of both of program evaluators and assessment coordinators for the degree programs undergoing evaluation. It was these negotiations and the evolving practice of assessment that resulted in the latest set of changes in ABET engineering accreditation criteria (“1-7” versus “a-k”). To provide an insight into the origins of EC 2000, the “Gang of Six,” consisting of a group of individuals loyal to ABET who used the pressure exerted by external organizations, along with a shared rhetoric of national competitiveness to forge a common vision organized around the expanded emphasis on professional skill sets. It was also significant that the Gang of Six was aware of the fact that the regional accreditation agencies were already contemplating a shift towards outcomes assessment; several also had a background in industrial engineering. However, this resulted in an assessment protocol for EC 2000 that remained ambiguous about whether the stated learning outcomes (Criterion 3) was something faculty had to demonstrate for all of their students, or whether EC 2000’s main emphasis was continuous improvement. When it proved difficult to demonstrate learning outcomes on the part of all students, ABET itself began to place greater emphasis on total quality management and continuous process improvement (TQM/CPI). This gave institutions an opening to begin using increasingly limited and proximate measures for the “a-k” student outcomes as evidence of effort and improvement. In what social scientific terms would be described as “tactical” resistance to perceived oppressive structures, this enabled ABET coordinators and the faculty in charge of degree programs, many of whom had their own internal improvement processes, to begin referring to the a-k criteria as “difficult to achieve” and “ambiguous,” which they sometimes were. Inconsistencies in evaluation outcomes enabled those most discontented with the a-k student outcomes to use ABET’s own organizational processes to drive the latest revisions to EAC accreditation criteria, although the organization’s own process for member and stakeholder input ultimately restored much of the professional skill sets found in the original EC 2000 criteria. Other refinements were also made to the standard, including a new emphasis on diversity. This said, many within our interview population believe that EC 2000 had already achieved much of the changes it set out to achieve, especially with regards to broader professional skills such as communication, teamwork, and design. Regular faculty review of curricula is now also a more routine part of the engineering education landscape. While programs vary in their engagement with ABET, there are many who are skeptical about whether the new criteria will produce further improvements to their programs, with many arguing that their own internal processes are now the primary drivers for change. 

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3. The ELFIN Mission

   https://doi.org/10.1007/s11214-020-00721-7  

   Angelopoulos, V. ; Tsai, E. ; Bingley, L. ; Shaffer, C. ; Turner, D. L. ; Runov, A. ; Li, W. ; Liu, J. ; Artemyev, A. V. ; Zhang, X.-J. ; et al ( August 2020 , Space Science Reviews)

   null (Ed.)

   Abstract The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or heretoforth simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar (∼93 ∘ inclination), nearly circular, low-Earth (∼450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (T orbit ∼ 90 min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50 keV to 5 MeV electrons with $\Delta $ Δ E/E < 40% and a fluxgate magnetometer (FGM) on a ∼72 cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC to 5 Hz Nyquist (nominally) with <0.3 nT/sqrt(Hz) noise at 1 Hz. The spinning satellites (T spin $\,\sim $ ∼ 3 s) are equipped with magnetorquers (air coils) that permit spin-up or -down and reorientation maneuvers. Using those, the spin axis is placed normal to the orbit plane (nominally), allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250 keV – 5 MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018 and launched by the ELaNa XVIII program on a Delta II rocket (with IceSatII as the primary). Mission operations are currently funded by NASA. Working under experienced UCLA mentors, with advice from The Aerospace Corporation and NASA personnel, more than 250 undergraduates have matured the ELFIN implementation strategy; developed the instruments, satellite, and ground systems and operate the two satellites. ELFIN’s already high potential for cutting-edge science return is compounded by concurrent equatorial Heliophysics missions (THEMIS, Arase, Van Allen Probes, MMS) and ground stations. ELFIN’s integrated data analysis approach, rapid dissemination strategies via the SPace Environment Data Analysis System (SPEDAS), and data coordination with the Heliophysics/Geospace System Observatory (H/GSO) optimize science yield, enabling the widest community benefits. Several storm-time events have already been captured and are presented herein to demonstrate ELFIN’s data analysis methods and potential. These form the basis of on-going studies to resolve the primary mission science objective. Broad energy precipitation events, precipitation bands, and microbursts, clearly seen both at dawn and dusk, extend from tens of keV to >1 MeV. This broad energy range of precipitation indicates that multiple waves are providing scattering concurrently. Many observed events show significant backscattered fluxes, which in the past were hard to resolve by equatorial spacecraft or non-pitch-angle-resolving ionospheric missions. These observations suggest that the ionosphere plays a significant role in modifying magnetospheric electron fluxes and wave-particle interactions. Routine data captures starting in February 2020 and lasting for at least another year, approximately the remainder of the mission lifetime, are expected to provide a very rich dataset to address questions even beyond the primary mission science objective. 

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4. 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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5. 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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