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Space Systems Design Laboratory (SSDL)

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https://hdl.handle.net/1853/70747

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Daniel Guggenheim School of Aerospace Engineering

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https://finding-aids.library.gatech.edu/agents/corporate_entities/1138

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Publication Search Results

Now showing 1 - 10 of 399

Design of the Hosted Software Application for the VISORS Mission

(Georgia Institute of Technology, 2023-08) Arunkumar, Ebenezer ; Paletta, Antoine ; Lightsey, E. Glenn

The VIrtual Super Optics Reconfigurable Swarm (VISORS) mission is a distributed space telescope consisting of two 6U CubeSats that utilize precision formation flying to detect and study the fundamental energy release regions of the solar corona. The inherent complexities and risks associated with two spacecraft operating in close proximity, as well as the unique restrictions of the spacecrafts’ design, make careful autonomous execution crucial to the success of the mission. To address these challenges, this paper outlines the development of the Hosted Software Application (HSA) flight software which manages the Guidance, Navigation, and Control (GNC) algorithms, the payload finite state machine, and the spacecraft and formation level fault management system. An overview of the HSA provides context for the motivation and requirements driving the design of the flight software system. The architecture of the HSA is presented and shown to be derived from the Mission Events Timeline (MET) for each of the relevant phases of the mission. Finally, this paper briefly discusses the software's implementation and test campaign.
Development of an Autonomous Distributed Fault Management Architecture for Spacecraft Formations Involving Proximity Operations

(Georgia Institute of Technology, 2023-08) Paletta, Antoine ; Arunkumar, Ebenezer ; Lightsey, E. Glenn

CubeSat formations have been identified as a new paradigm for addressing important science questions but are often early adopters of new technologies which carry additional risks. When these missions involve proximity operations, novel fault management architectures are needed to handle these risks. Building on established methods, this paper presents one such architecture that involves a passively safe relative orbit design, interchangeable chief-deputy roles, a formation level fault diagnosis scheme, and an autonomous multi-agent fault handling strategy. The primary focus is to enable the reliable detection of faults occurring on any formation member in real time and the autonomous decision making needed to resolve them while keeping the formation safe from an inter-satellite collision. The NSF-sponsored Virtual Super-resolution Optics with Reconfigurable Swarms (VISORS) mission, which consists of two 6U CubeSats flying in formation 40 meters apart as a distributed solar telescope, is used as a case study for the application of this architecture. The underlying fault analysis, formulation of key elements of the fault detection and response strategies, and the flight software implementation for VISORS are discussed in the paper.
The Orbital Calibration 2 (OrCa2) CubeSat Mission

(Georgia Institute of Technology, 2023-08) Gunter, Brian C. ; Gregoire, Alaric ; Badura, Gregory ; Valenta, Christopher

The Georgia Institute of Technology (Georgia Tech), in collaboration with the Georgia Tech Research Institute (GTRI), has developed the Orbital Calibration 2 (OrCa2) mission in an effort to improve space domain awareness. OrCa2’s external panels have precise and well-characterized reflective properties that will permit various calibration activities from ground-based optical sensors, with the goal of improving the tracking and detection of resident space objects (RSOs). OrCa2 is a 12U CubeSat designed, fabricated, assembled, and tested almost entirely in-house using GT/GTRI facilities. It will be regularly observed using Georgia Tech’s Space Object Research Telescope (GT-SORT). A number of experiments can be conducted with these measurements, such as pose estimation, validation of RSO trajectory propagations with complementary ground-based laser ranging data, multi-spectral analysis, low-light detection algorithms, and validation of atmospheric scattering models. An onboard imager will serve as both a low-accuracy star camera, as well as an on-orbit optical tracking system capable of RSO streak detection, with a mission goal of gathering simultaneous ground-based and space-borne tracking data of one or more RSOs. Additionally, the OrCa2 spacecraft will host an experimental radiation dosimeter, an experimental software defined radio (SDR) receiver, and an experimental power system. OrCa2 is currently manifested to launch in Q1 2024. An overview of the design, concept of operations, and expected outcomes of the mission will be presented.
Design to Delivery of Additively Manufactured Propulsion Systems for the SWARM-EX Mission

(Georgia Institute of Technology, 2023-08) Tong, Kevin ; Hart, Samuel T. ; Glaser, Mackenzie ; Wood, Samuel ; Hartigan, Mark C. ; Lightsey, E. Glenn

Recent progress in miniaturized spacecraft propulsion technology has allowed for the development of complex, multi-vehicle missions which enable the cost-effective realization of science goals that would previously have been prohibitively expensive. The upcoming NSF-funded Space Weather Atmospheric Reconfigurable Multiscale EXperiment (SWARM-EX) mission leverages these swarm techniques to demonstrate novel autonomous formation flying capabilities while characterizing the spatial and temporal variability of ion-neutral interactions in the Equatorial Ionization Anomaly and Equatorial Thermospheric Anomaly. SWARM-EX will fly a trio of 3U CubeSats in a variety of relative orbits with along-track separations ranging from 3 km to 1300 km. To achieve the required orbital variability, the mission uses a novel hybrid approach of differential drag and an onboard cold gas propulsion system. Mission requirements necessitate a propulsion system that provides each spacecraft with 15 m/s of ΔV and a maximum thrust greater than 5 mN in a volume of roughly 0.7U (7 cm x 10 cm x 10 cm). Unlike many other CubeSat-scale cold gas propulsion systems which are used to provide attitude control and perform reaction wheel desaturation burns, the primary objective of the SWARM-EX propulsion system (SEPS) is to provide ΔV during maneuvers. The Georgia Institute of Technology Space Systems Design Laboratory (SSDL) is conducting the design, assembly, and testing of three identical SEPS. By leveraging additive manufacturing technology, the propellant tanks, nozzle, and tubing are combined into a single structure that efficiently utilizes the allocated volume. The propulsion system uses two-phase R-236fa refrigerant as a propellant, which allows for the storage of the majority of propellant mass as a liquid to maximize volumetric efficiency. The final design allows for 17 m/s of total ΔV per spacecraft and a measured maximum thrust of approximately 35 mN for short pulse lengths at room temperature. Each individual propulsion system has a volume under 0.5U (489 cm3), making them among the smallest formation-flying CubeSat-scale propulsion systems developed thus far. Owing to their two-phase propellant storage and single nozzle, the SEPS have a high impulse density (total impulse provided per unit of system volume) of 176 N-s/L. Additionally, process improvements to mitigate known failure modes such as propellant leaks and foreign object debris are implemented. This paper describes the entire design-to-delivery life cycle of the SWARM-EX propulsion units, including pertinent mission requirements, propulsion system design methodologies, assembly, and testing. Major lessons learned for future small satellite propulsive endeavors are also detailed.
Lunar Crater Identification using Triangle Reprojection

(Georgia Institute of Technology, 2023-08) Thrasher, Ava C. ; Christian, John A. ; Molina, Giovanni ; Hansen, Michael ; Pelgrift, John Y. ; Nelson, Derek S.

Image-based terrain relative navigation is a critical capability for future lunar exploration missions. Images of the lunar surface containing craters can be compared to on-board maps to identify craters and estimate the spacecraft position. While there are many ways to accomplish the crater identification task, this work explores a method using triangulation and crater triangle pattern projections. Specifically, potential matching crater patterns from the catalog and image are used to triangulate the spacecraft position, allowing for construction of line-of-sight directions to the potential matching catalog craters. The projection of these directions in the image can be compared to the observed craters to accept or reject the match hypothesis. In this paper, we demonstrate the algorithm's capability in handling various types of input errors and what tolerances can be tuned to achieve a desired performance. Additionally, an initial look at flight software implementation is included.
Model Predictive Path Integral Control for Spacecraft Rendezvous Proximity Operations on Elliptic Orbits

(Georgia Institute of Technology, 2023-08) Sasaki, Tomohiro ; Ho, Koki ; Lightsey, E. Glenn

This paper presents a nonlinear control framework for spacecraft rendezvous and proximity operations on elliptic orbits using Model Predictive Path Integral (MPPI) control. Path integral control is a sampling-based nonlinear stochastic optimal control algorithm that can avoid linear and quadratic approximations in both dynamics and cost functions. While this control method has gained popularity in the robotics community due to its algorithmic effectiveness, it remains unexplored in astrodynamics. This paper demonstrates a comprehensive closed-loop simulation of spacecraft rendezvous employing MPPI and evaluates its control performance through these simulations.
Validation of a Simulation Environment for Future Space Traffic Management

(Georgia Institute of Technology, 2023-08) Gregoire, Alaric C. ; Gunter, Brian C. ; Borowitz, Mariel ; Newman, Laurt K. ; Schweiger, Gerald A.

This study presents initial results of a newly developed simulation environment intended to explore and assess future Space Traffic Management (STM) scenarios. The number of new Resident Space Objects (RSOs) in near-Earth orbit is expected to increase significantly with the expected future deployment of a number of large constellations. These future scenarios involve the addition of many tens of thousands of new RSOs, making the analysis into their impact on collision risk extend beyond what traditional data-mining of present-day conjunction data can reliably predict. To address this, a robust simulation environment was developed that implements a full force-model for orbit propagation, and computes continuous all-on-all conjunction statistics for arbitrarily large catalog sizes and simulation timeframes. Collision avoidance and station-keeping maneuvers can be optionally implemented based on configurable user inputs including physical characteristics and spacecraft meta-data (e.g., commercial/government, owner country, etc.). Constellation build-out and de-orbit scenarios were also implemented and modeled based on real-data analysis. Validation of the simulation results was a critical component of the simulation development, and was done using the current catalog with comparisons against both public and internal NASA data-sets. The comparisons demonstrate that, with the appropriate settings, representative levels of conjunction rates and probabilities can be obtained, providing confidence that the simulation tool can generate meaningful outcomes for test scenarios. As an initial demonstration of the tool's capabilities, year-long simulations with station-keeping were conducted to examine conjunction histories using both the current object catalog (5800 active satellites) and a hypothetical 60,000 object scenario involving five potential large constellations. Output metrics include the number of conjunction events, estimates of collision consequence (fragmentation), delta-V maneuver costs, and the probability of at least one collision occurring. The results highlight the potential that the simulation tool has for incorporating and running performance comparisons between, e.g., various sets of maneuver guidelines, industry norms, and definitions of risk, with the overall objective of providing actionable data to STM policy makers. The presentation will provide an overview of the simulation development and validation efforts, as well as a discussion of observations gathered from the initial simulations performed.
Translunar Logistics with Low-Energy Transfers

(Georgia Institute of Technology, 2023-08) Gollins, Nick ; Shimane, Yuri ; Ho, Koki

Low-energy lunar transfers (LETs) utilize three-body mechanics with fourth-body (solar) perturbations to provide an alternative to direct lunar transfers. The offer of reduced lunar orbit insertion cost in exchange for longer time-of-flight and potentially higher transfer insertion cost presents an interesting trade-off when planning the logistics of multi-mission lunar exploration campaigns. This is particularly true for logistics featuring spacecraft with a variety of launch vehicles and propellant types, as the logistics of each spacecraft are impacted by the costs and benefits of LETs differently. This paper presents a translunar logistics model featuring LETs, discusses the trade-offs versus direct transfers through some case studies, and highlights the scenarios in which LETs prove most useful.
Lunar Reflectance Modeling for Terrain Relative Navigation

(Georgia Institute of Technology, 2023-08) DeVries, Carl ; Christian, John A.

Feature matching techniques often encode a brightness pattern from an image without knowledge of the underlying scene. This makes feature matching difficult when illumination conditions change significantly between images or are not consistent with onboard maps. The brightness patterns in images of the lunar surface can be partially described by a surface reflectance model which can often be parameterized by quantities known onboard from a sun sensor and calibrated camera. Unfortunately, these models can be intractable due to their complexity. This work develops a reduced-order lunar reflectance model for future illumination-informed feature descriptor development.
Initial Orbit Determination Using Relative Position Measurements

(Georgia Institute of Technology, 2023-08) Henry, Sébastien ; Christian, John A.

This work explores the problem of initial orbit determination (IOD) using relative position measurements between a pair of spacecraft in Keplerian orbits. We first show that the solution to this problem is not unique, even under certain classes of perturbations. We propose an algorithm to retrieve the inertial state of both orbiting spacecraft using the relative acceleration and Lambert's problem. Various options are compared to estimate the relative acceleration from a set of relative position measurements. Simulation results suggest that the proposed IOD algorithm is suitable for onboard navigation filter (re)initialization, and can thus improve constellation and formation-flying mission autonomy.