CubeSat Autonomous Rendezvous and Docking Software

No abstract availabl

Going Up. A GPS Receiver Adapts to Space

Current plans for the space station call for the GPS receiver to be installed on the U.S. lab module of the station in early 2001 (ISS Assembly Flight SA), followed by the attachment of the antenna array in late 2001 (Flight 8A). At that point the U.S. ISS guidance and control system will be operational. The flight of SIGI on the space station represents a "coming of age" for GPS technology on spacecraft. For at least a decade, the promise of using GPS receivers to automate spacecraft operations, simplify satellite design, and reduce mission costs has enticed satellite designers. Integration of this technology onto spacecraft has been slower than some originally anticipated. However, given the complexity of the GPS sensor, and the importance of the functions it performs, its incorporation into mainstream satellite design has probably occurred at a very reasonable pace. Going from providing experimental payloads on small, unmanned satellites to performing critical operational functions on manned vehicles has been a major evolution. If all goes as planned in the next few months, GPS receivers will soon provide those critical functions on one of the most complex spacecraft in history, the International Space Station

Relative Attitude Determination of Earth Orbiting Formations Using GPS Receivers

Satellite formation missions require the precise determination of both the position and attitude of multiple vehicles to achieve the desired objectives. In order to support the mission requirements for these applications, it is necessary to develop techniques for representing and controlling the attitude of formations of vehicles. A generalized method for representing the attitude of a formation of vehicles has been developed. The representation may be applied to both absolute and relative formation attitude control problems. The technique is able to accommodate formations of arbitrarily large number of vehicles. To demonstrate the formation attitude problem, the method is applied to the attitude determination of a simple leader-follower along-track orbit formation. A multiplicative extended Kalman filter is employed to estimate vehicle attitude. In a simulation study using GPS receivers as the attitude sensors, the relative attitude between vehicles in the formation is determined 3 times more accurately than the absolute attitude

Development and Testing of a Miniaturized, Dual­Frequency, Software­Defined GPS Receiver for Space Applications

Aerospace Engineering and Engineering Mechanic

Design to Delivery of Additively Manufactured Propulsion Systems for the SWARM-EX Mission

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 ∆V 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 ∆V 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 ∆V 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

Development of a COTS-Based Propulsion System Controller for NASA’s Lunar Flashlight CubeSat Mission

The Lunar Flashlight mission is designed to send a 6U CubeSat into lunar orbit with the aim of finding water-ice deposits on the lunar south pole. The Glenn Lightsey Research Group (GLRG) within Georgia Tech’s Space Systems Design Laboratory (SSDL) is developing a low-cost propulsion system controller for this satellite using commercial-off-the-shelf (COTS) parts, with an emphasis on overcoming the harsh environment of lunar orbit through careful architecture and testing. This paper provides in-depth coverage of the Lunar Flashlight Propulsion System (LFPS) controller development and testing processes, showing how an embedded system based on COTS parts can be designed for the intense environment of space. From the high-level requirements architecture to the selection of specific hardware components and software design choices, followed by rigorous environmental testing of the design, radiation and other environmental hardening can be achieved with high confidence

Lessons Learned from the GT-1 1U CubeSat Mission

With more universities conducting low-cost small satellite development programs, resources for students starting off in satellite design are essential to avoid common pitfalls. Hardware integration and testing of the GT-1 CubeSat revealed both design flaws and strengths that led to a comprehensive list of lessons learned applicable to future CubeSat missions at the Georgia Institute of Technology Space Systems Design Laboratory (SSDL) and within the broader academic community. GT-1 was originally slated to be designed, built, and delivered in nine months with an orbital lifespan of around seven months. However, various schedule delays resulted in the mission spanning over two years. This paper provides a resource to those beginning a small satellite development program at the university level by presenting a case study of lessons learned from the GT-1 mission. Detail will be provided for topics including best practices for enabling modular design, creating effective documentation, structural design for proper fit-up and manufacturability, testing, and planning a realistic mission scope

Operations Systems Engineering for the Lunar Flashlight Mission

Lunar Flashlight, a 6U CubeSat developed by NASA\u27s Jet Propulsion Laboratory (JPL) and operated by students at the Georgia Institute of Technology (GT), was launched in December 2022 with a mission to demonstrate novel small satellite technologies, including a first-of-its-kind green monopropellant system, and to map surface water ice in permanently shadowed regions of the lunar south pole using near-infrared laser reflectometry. As operations systems engineers, the GT team has maintained, developed, and refined models of spacecraft subsystems as well as coordinated the project\u27s approach to anomaly response and fault protection. This paper reports how analysis of flight data and post-launch experiences have allowed the team to make more efficient use of the spacecraft\u27s capabilities by taking advantage of margins, synthesizing data, and adapting flight rules and constraints. In-flight anomalies have required substantial rework of the mission\u27s concept of operations, and anomaly management and resolution has leaned heavily on modeling and predictions from the operations systems engineers. The GT operations team has made full use of available data, including telemetry and observed system behavior, to swiftly recognize and address anomalies, support strenuous recovery efforts, and make possible a realignment of the concept of operations despite significant challenges

Systems Integration and Test of the Lunar Flashlight Spacecraft

Lunar Flashlight is a 6U CubeSat launching in late 2022 or early 2023 that will search for surface water ice content in permanently shadowed regions at the south pole of the Moon using infrared relative reflectance spectroscopy. The mission will act as a technology demonstration of an Advanced Spacecraft Energetic NonToxic (ASCENT) green propulsion system and active laser spectroscopy within the CubeSat form-factor. This paper provides an overview of the entire Systems Integration and Test campaign which took place at the Jet Propulsion Laboratory and the Georgia Institute of Technology. From initial testing of the isolated avionics and payload subsystems to the final tests with a fully integrated spacecraft, the project’s integration and test campaign is reviewed, with a focus on lessons learned

The CuSPED Mission: CubeSat for GNSS Sounding of the Ionosphere-Plasmasphere Electron Density

The CubeSat for GNSS Sounding of Ionosphere-Plasmasphere Electron Density (CuSPED) is a 3U CubeSat mission concept that has been developed in response to the NASA Heliophysics program's decadal science goal of the determining of the dynamics and coupling of the Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs. The mission was formulated through a collaboration between West Virginia University, Georgia Tech, NASA GSFC and NASA JPL, and features a 3U CubeSat that hosts both a miniaturized space capable Global Navigation Satellite System (GNSS) receiver for topside atmospheric sounding, along with a Thermal Electron Capped Hemispherical Spectrometer (TECHS) for the purpose of in situ electron precipitation measurements. These two complimentary measurement techniques will provide data for the purpose of constraining ionosphere-magnetosphere coupling models and will also enable studies of the local plasma environment and spacecraft charging; a phenomenon which is known to lead to significant errors in the measurement of low-energy, charged species from instruments aboard spacecraft traversing the ionosphere. This paper will provide an overview of the concept including its science motivation and implementation