Session
Poster Session 1
Location
Salt Palace Convention Center, Salt Lake City, UT
Abstract
The undergraduate-led Polarization-modUlated Laser Satellite Experiment (PULSE-A) at the University of Chicago seeks to demonstrate the feasibility of circular polarization shift keyed satellite-to-ground laser communication. Free-space optical communications offer significantly improved data rates and lower power requirements than radio frequency communications for a similar form factor, which makes optical communications of particular interest for future satellite missions as on-orbit data collection rates increase. PULSE-A’s low-cost open-source bus serves as the backbone of the mission and has been designed in tandem with the Payload, with design driven by strict requirements for pointing accuracy, component alignment, power demand, and thermal stability. This work presents the design and testing of the PULSE-A bus.
The spacecraft bus was designed to fill two major needs, (1) to meet the requirements of the PULSE-A mission, and (2) to be easily configurable for future missions that desire enhanced capabilities over other low-cost open-source designs (including follow-on missions to PULSE-A). At its core, the bus features dual Beagle-Bone Black Industrial compute units—selected for their flight heritage—integrated via a PC/104 header standard. The open-source power system builds on existing designs from Hawai’i Space Flight Laboratory’s Artemis CubeSat kit and Stanford’s PyCubed kit, adapted to meet PULSE-A’s demanding requirements. While these kits are designed for low-power, modular payloads, PULSE-A’s power system is capable of continuous higher-power operation while preserving the modularity fundamental to these open-source designs. PULSE-A implements Goddard Space Flight Center’s core Flight System (cFS), which takes a modular software architecture approach and is built in C, unlike Artemis, which relies on Arduino C++, and Py-Cubed, which was developed in Python. The use of C as the primary language aligns with the expertise of the University of Chicago’s Computer Science department, allowing for ease of development by PULSE-A’s undergraduate flight software team. The stack is designed to interface with commercial off-the-shelf Attitude Determination and Control Systems that implement their own control algorithms to ease development of the optical tracking system.
The CubeSat structure utilizes Gran Systems’ 3U frame, modified to accommodate openings for various ports and deployable components including sensors, antennas and solar panels. Inside, the avionics stack uses the PC/104 standard quad rails which terminate in PULSE-A’s custom-designed Payload Box that houses all of the Payload components and optical fiber runs. The Payload-to-bus interface enables precise thermal control of sensitive components through careful selection of interface screw sizes and pad materials. Lastly, the optical mounts and Payload box are designed to be easily manufacturable in most university machine shops, further contributing to their ease-of-implementation. This work also covers the techniques and iterative engineering processes used to develop the thermal control and dissipation mechanisms for the specific requirements, under volume, mass and temperature-range constraints.
Document Type
Event
Development of an Open-Source Spacecraft Bus for the PULSE-A CubeSat
Salt Palace Convention Center, Salt Lake City, UT
The undergraduate-led Polarization-modUlated Laser Satellite Experiment (PULSE-A) at the University of Chicago seeks to demonstrate the feasibility of circular polarization shift keyed satellite-to-ground laser communication. Free-space optical communications offer significantly improved data rates and lower power requirements than radio frequency communications for a similar form factor, which makes optical communications of particular interest for future satellite missions as on-orbit data collection rates increase. PULSE-A’s low-cost open-source bus serves as the backbone of the mission and has been designed in tandem with the Payload, with design driven by strict requirements for pointing accuracy, component alignment, power demand, and thermal stability. This work presents the design and testing of the PULSE-A bus.
The spacecraft bus was designed to fill two major needs, (1) to meet the requirements of the PULSE-A mission, and (2) to be easily configurable for future missions that desire enhanced capabilities over other low-cost open-source designs (including follow-on missions to PULSE-A). At its core, the bus features dual Beagle-Bone Black Industrial compute units—selected for their flight heritage—integrated via a PC/104 header standard. The open-source power system builds on existing designs from Hawai’i Space Flight Laboratory’s Artemis CubeSat kit and Stanford’s PyCubed kit, adapted to meet PULSE-A’s demanding requirements. While these kits are designed for low-power, modular payloads, PULSE-A’s power system is capable of continuous higher-power operation while preserving the modularity fundamental to these open-source designs. PULSE-A implements Goddard Space Flight Center’s core Flight System (cFS), which takes a modular software architecture approach and is built in C, unlike Artemis, which relies on Arduino C++, and Py-Cubed, which was developed in Python. The use of C as the primary language aligns with the expertise of the University of Chicago’s Computer Science department, allowing for ease of development by PULSE-A’s undergraduate flight software team. The stack is designed to interface with commercial off-the-shelf Attitude Determination and Control Systems that implement their own control algorithms to ease development of the optical tracking system.
The CubeSat structure utilizes Gran Systems’ 3U frame, modified to accommodate openings for various ports and deployable components including sensors, antennas and solar panels. Inside, the avionics stack uses the PC/104 standard quad rails which terminate in PULSE-A’s custom-designed Payload Box that houses all of the Payload components and optical fiber runs. The Payload-to-bus interface enables precise thermal control of sensitive components through careful selection of interface screw sizes and pad materials. Lastly, the optical mounts and Payload box are designed to be easily manufacturable in most university machine shops, further contributing to their ease-of-implementation. This work also covers the techniques and iterative engineering processes used to develop the thermal control and dissipation mechanisms for the specific requirements, under volume, mass and temperature-range constraints.
