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On the Challenges Posed by Non-Machian Solutions to Relationalism in General Relativity
No full textThe relationship between Mach’s Principle and solutions to Einstein’s field equations is examined, with special attention to Friedmann-Lematre-Robertson-Walker (FLRW) cosmology. Mach’s Principle is outlined, and the extent to which general relativity fulfills Machs vision is assessed. It is argued that several important solutions to Einsteins equations, particularly the FLRW cosmological models, embody key Machian features. In order to elucidate the FLRW cosmological model, the associated energy-momentum tensor for a perfect fluid under the assumptions of large-scale homogeneity and isotropy is derived and used to obtain the Friedmann equations that govern cosmic expansion. It is shown that FLRW cosmology can be understood as Machian in three important respects: ontologically (inertial structure arises from the global massenergy content of the universe), geometrically (the evolution of the scale factor and the emergence of a preferred foliation tie inertial motion to spacetime geometry), and topologically (in cases where the universe’s spatial curvature is positive, a complete description of inertial frames requires multiple overlapping local charts, emphasizing the relational nature of spacetime). The appendices provide detailed derivations and example calculations related to the mathematical framework supporting these claims
Ethical Concerns and Implications of Expanded Carrier Screening
No full textThe rapid evolution in the field of genetics is often met with uncertainty and skepticism. With the advancements in genetic technologies, expanded carrier screening (ECS) has emerged as a powerful tool in reproductive medicine. Traditionally, carrier screening was provided less broadly, often relying on ethnic-based approaches. However, further advancements have deemed this practice no longer equitable or widely accepted. While ECS provides prospective parents with insight into their genetic risk and may prevent severe genetic conditions, it also raises serious ethical questions for many. These concerns span medical, political, and societal facets including medicalization, defining severity, abortion, legislation, insurability, the disability rights critique, and cultural/religious perspectives. This paper serves as a literature review introducing the history of ECS as well as interpreting and analyzing information from a collection of sutdies regarding the implications noted above, and proposals for implementing equitable universal screening. Additionally, this paper will review a pending case study concerning a patient who had several pregnancies with abnormal ultrasound findings before undergoing screening and learning of her positive carrier status. This case demonstrates the inaccuracies of ethic-based screening as well as the importance of offering universal ECS. While ECS has the potential to inform reproductive decision-making, it is crucial that these challenges be addressed before ECS can be implemented universally
Mitigation Strategies for Pattern Mismatching in Star Trackers
No full textStar tracker mismatching, although infrequent, can be detrimental to satellite operation and becomes more likely with worsened conditions including high slew rates, radiation, and stray light. Rocket Lab’s ST-16 Star Trackers use several methods to test for match validity; however, in general, there are trade-offs between matching robustness and hardware performance, and it is impractical to entirely remove the possibility of false positive returns.
To understand the types of scenarios where false positives occur, a review of existing datasets from the ST-16 was completed, and false positives were identified. The likelihood of false positive matching grows exceedingly rare as the number of matched stars increases, and the existing onboard matching algorithm accurately rejects marginal three-star matches. Therefore, most observed false returns were comprised of four-star matches. To study the occurrences of different failure methods, a test dataset with a significant number of false-positive returns was generated on-ground using a hardware-in-the-loop simulator. Some of the observed failure methods included matching non-cataloged objects, mismatching similar star patterns, and flat polygons—those with points nearly in line.
With this understanding, several mitigation techniques are proposed, including catalog changes that target patterns prone to mismatching, additional filtering, and methods combining both. One such catalog change implements a method using hash tables to evaluate and remove similarities within a star catalog. After implementing these mitigation techniques, the false positive rate was decreased more than 4 times from the control dataset with an increase in true positive availability. These methods were implemented without adding significant processing complexity or increased hardware requirements, enabling future integration with current star trackers in orbit
CubeSat-Compatible Q/V Band Phased Array Antenna Design for High-Bandwidth mmWave Inter-Satellite Communications for Scalable LEO Satellite Constellations
Get PDFAs instruments and payloads aboard satellites increasingly demand higher data rates to fulfill scientific objectives, the shift by industry and governments toward small satellite platforms necessitates high-performance communication systems tailored to these compact designs. With the growing use cases for multi-agent satellite constellations, particularly in Low Earth Orbit (LEO), frequency band congestion remains a critical challenge. To address this spectrum scarcity and enable adaptive, inter-satellite communication for multi-agent satellite constellations, this paper explores the design of a Q/V band patch antenna array to enable adaptive beamforming, high data rate inter-satellite communication for scalable satellite constellations. The use of millimeter wave (mmWave) technology for high data rate communication in CubeSats remains an underexplored area, with few studies addressing the design of antenna systems capable of supporting such communication. To the best of the author’s knowledge, this paper presents the first phased array antenna system for high data rate communication in CubeSat constellations. The antenna system is the primary scientific payload for the CubeSat Optimized mmWave-Enabled Telecommunications (COMET) mission. The COMET mission is planned to launch in LEO, and will utilize this antenna for 56 MHz bandwidth, low-latency inter-satellite communication, along with beamforming and link stability enhancements. This paper introduces the COMET mission with a focus on the inter-satellite communication system. The design of the patch antenna array is presented along with simulations done in Ansys HFSS. The design process is explained in detail, with single-element antenna simulations followed by the development of a multi-element phased array for beam steering and improved performance. This paper also provides a detailed link budget for the mmWave inter satellite crosslink, as well as for the Earth-to-satellite VHF/UHF link. This work lays the foundation for demonstrating scalable mmWave inter-satellite communication, offering a viable solution to address spectrum congestion and support future satellite constellations with high-bandwidth, low-latency communication
Conceptual Design of an Integrated Small Satellite Environmental Testing Platform: Addressing Subsystem Integration Challenges
No full textEnvironmental testing for small satellites often relies on separate systems to simulate space conditions, resulting in inefficiencies, increased operating costs, and challenges in accurately modeling the complex environment. This paper presents the conceptual design of an integrated testing platform that combines thermal, vacuum, solar, magnetic, navigation, and attitude control simulations into a single piece of hardware to provide reliable mission assurance. The design emphasizes the modifications required to overcome unique interactions between subsystems, enabling simultaneous, realistic environmental qualification of small satellites while reducing cost and complexity.
The fully integrated environmental testing system incorporates a thermal vacuum chamber (TVAC) with an integrated rotational platform, supporting dynamic attitude testing for attitude determination and control systems (e.g., magnetorquers, magnetometers, reaction wheels, star trackers, horizon sensors, and sun sensors). A solar simulation system replicates the UV, visible, and IR radiation for testing solar panel performance and thermal interactions. A magnetic field generation system using Helmholtz coils simulates Earth’s magnetic environment, while a GNSS simulator provides dynamic orbital navigation signals. Additional features include a star field projector for attitude determination tests, a horizon modeling system to replicate Earth’s thermal emissions and curvature, and an Earth albedo simulation module using collimated light sources and reflective Earth models.
This paper focuses on the design modifications needed to integrate these traditionally independent systems into a single platform. Unique challenges are addressed, such as managing heat buildup in the Helmholtz coils operating under vacuum conditions, providing three degrees of rotational freedom in a vacuum environment, and ensuring a uniform solar simulation within the constraints of thermal and vacuum conditions. Additional considerations include the interaction of simulated Earth albedo with horizon sensor testing, the effects of rotational platform vibrations on sensor calibration, and the alignment of star field projections with other dynamic subsystems.
Preliminary trade studies and modeling explore the feasibility of these design modifications, quantifying their impact on system performance and system cost. Results demonstrate that the integrated platform can operate these subsystems concurrently without significant performance degradation. Example use cases, such as CubeSats designed for Earth observation or interplanetary navigation, illustrate how the platform can validate mission-critical satellite subsystems in realistic scenarios.
By addressing the inherent challenges of subsystem integration, this conceptual design represents a significant advancement in small satellite environmental and functional testing. The proposed platform offers a unified, adaptable, and efficient solution for comprehensive small satellite qualification, addressing the increasing need for streamlined testing and reliable mission assurance
Qualification Challenges of an SADM Using the Slipring Technology
No full textThe SADM-200 (Solar Array Drive Mechanism for 200W) is a new mechanism developed at Comat in order to provide a solution for solar array rotation and power transfer for small satellite applications. This mechanism is designed to be as compact as possible while providing a reliable angular positioning and electrical power transfer from the solar array to the satellite. Robust mechanical guidance and high quality components selection allows an accurate positioning with low angular play while withstanding the tough mechanical and thermal environment faced during launch and in-orbit operations. The development focused on keeping the cost as low as possible through the use of COTS (Component Off the Shelf) while maintaining a high quality requirement. This paper describes the challenges faced by the development team during the qualification campaign that recently succeeded
Foresail-1 Prime 3U Science CubeSat
No full textThe Foresail-1 Prime is a satellite mission developed by Aalto University in association with the Finnish Centre of Excellence in Research of Sustainable Space (FORESAIL). The mission carries scientific payloads such as the Particle Telescope (PATE), Plasma Brake Experiment (PB), magnetometer MATTI and features fully in-house developed subsystems. This is the fourth satellite, developed by Aalto University, building on heritage of Aalto-1, Aalto-2 and Foresail-1 satellites
Simulation-Based Evaluation of Dual-Mode Propulsion Strategies for Small Satellite Collision Avoidance
No full textAs Low Earth Orbit (LEO) becomes increasingly congested, small satellite missions face growing challenges in executing effective collision avoidance maneuvers under limited time and propellant constraints. Dual-mode propulsion systems, combining high-thrust chemical and high-specific impulse electric modes, offer a promising approach to balance rapid response with propellant conservation. This paper evaluates how such systems can be applied to reduce the Probability of Collision (PC) within constrained maneuver windows using sequential chemical-electric burns.
A FreeFlyer-based simulation framework models dual-mode collision avoidance maneuvers across synthetic LEO scenarios. For each case, user-defined mission parameters, such as lead time, PC threshold, and orbital altitude, are used to generate candidate maneuvers by sweeping combinations of thrust direction (parameterized by alpha and beta angles in the Radial-Intrack-Crosstrack frame) and the fraction of the burn duration allocated to chemical and electric propulsion. All burns use fixed thrust and specific impulse per mode. PC is evaluated at the time of closest approach under ideal state knowledge and execution. This method identifies near-optimal maneuver configurations that meet risk constraints while minimizing propellant use, allowing for clear comparisons across candidate maneuver profiles.
Results show that dual-mode strategies can outperform single-mode approaches by enabling faster risk reduction than electric-only systems and lower fuel use than chemical-only systems. The framework supports flexible mission planning across a range of scenarios, demonstrating how dual-mode propulsion expands the decision space for small satellite conjunction response. Findings reinforce the value of adaptable, multi-mode propulsion in maintaining orbital safety in crowded environments
Testing, Verification, and Qualification of a Self-Developed PCDU for the Student-Built CubeSat SOURCE
No full textPoster presented during the 2025 SmallSat Conference
The Occultation Wave Limb Sounder
No full textThe Occultation Wave Limb Sounder (OWLS) is a mission designed to investigate how Earth’s thermosphere responds to atmospheric gravity waves. The dissipation of gravity waves in the thermosphere has the potential to both heat and cool the atmosphere, with published simulation results reaching conflicting conclusions on whether gravity wave heating or cooling dominates. Comprised of two instruments, the Extreme Ultraviolet Occultation Photometers (EUV-OP) and Compact Spectrograph for Occultations on the Limb (CSOL), OWLS will seek to resolve this controversy. Properties of the atmosphere will be retrieved by both instruments through solar occultations. EUV-OP will retrieve thermospheric temperatures using this technique, while CSOL will measure gravity wave activity in the Mesosphere – Lower Thermosphere