Open Source CubeSat Design Specifications

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URL = https://journals.sagepub.com/doi/abs/10.1177/02704676211041900


“This article examines a community producing complex space technology. We attempt to highlight which aspects of the community’s activities can help democratize high-tech development while providing a context for similar cases involved in developing and manufacturing nonhigh-technological artefacts. We discuss how this has been made possible by using a technology-determined organizational approach based on the CubeSat open platform infrastructure, blending formal and hands-on education, open communication, specific recruitment and working practices, and a genuine passion for technology. We identify as critical enablers for community-based collaborative development of space technology the open-source architecture standard called CubeSat Design Specifications, the modularization of work in subsystems and between different organizations, and the open and participatory approach work tasks distribution and decision making. Moreover, we argue that the digital/informational aspect of this technology allows the community to implement organizational practices that resemble how open-source movements over the internet produce complex digital artefacts like Wikipedia or Linux. ESTCube can shed light on community-driven complex technology development, providing lessons on what a democratized version of high technology would resemble and how open and digitalized technology can help develop the capacities of a community.”


Excerpt

CubeSat

By Lucas Lemos and Chris Giotitsas:

“A CubeSat is a one unit (1U) 10-centimetre side cube-shaped satellite. By combining the volume of two or more 1U CubeSats, the size of the CubeSat can be arithmetically increased (2U, 3U, nU). CubeSats are based on an open source architecture standard known as the CubeSat Design Specification (CDS; Mehrparvar et al., 2014; Swartwout, 2013; Toorian et al., 2008). CubeSats carry payloads—tech nological artefacts intended to be tested/demonstrated with the mission, like a camera or a propulsion system.

A CubeSat is like “a box” with two distinctive features. First, it ticks all the formal requirements to be loaded in a rocket launcher and safely deployed into orbit. Second, it is designed to operate in the extreme conditions of outer space, protecting its content. Besides the protective shield of the “space box” container, and its contained artefacts (payloads), a CubeSat needs to perform other functions to be operative. These operative functions (e.g., navigation, communication) are organized in different subsystems (e.g., attitude determination and control system, communications system) based on specific hardware (e.g., gyroscopic sensors, microstrip antenna; Ehrpais et al., 2016; Slavinskis et al., 2016).

As a means to safely launch the payloads that constitute the CubeSat mission objective (test/demonstrate technology artefacts), CDS provides a frugal platform for prototyping space technology. Its construction, development, and launching costs are relatively low, with shorter technology development periods (Selva & Krejci, 2012; Woellert et al., 2011). CDS is open to everyone, and it has been very beneficial to startups, universities, developing states, and communities (Woellert et al., 2011). In the next section, we are going to examine what makes technology complex, and how technology complexity can be conceptualized.”

(https://journals.sagepub.com/doi/abs/10.1177/02704676211041900)


ESTCube Program

By Lucas Lemos and Chris Giotitsas:

“The Estonian Student Satellite Program (ESTCube Program) is a locally adapted version of the CubeSat Program. Through this program, a workforce of volunteers is recruited to work on ESTCube CubeSats (Noorma et al., 2013; Slavinskis, Reinkubjas, et al., 2015). Tartu Observatory (TO) and the University of Tartu (UT) have been the main hosts of the program. Since 2018, the former is an institute within the latter. They provide working space, labs, and testing facilities (Iakubivskyi et al., 2020). Several ESTCube members have become department leaders, researchers, and engineers in these host institutions.

Typically, college-level students join the ESTCube Program, but the recruitment process starts earlier. To inform about space science and their work, ESTCube members organize and take part in several activities: workshops, presentations, and science outreach events. During summers, there are special activities to train high-school students. The Summer Academy brings together high school and university students to TO (Janson, 2018). There, students can participate in ESTCube activities through the Science Camp (Teaduslaager) and the Science Task Force (Teadusmalev). The ESTCube Program provides hands-on education for students, complementing their formal education. Students work on goal-oriented tasks related to some aspect of the CubeSat. Responsibilities, the difficulty level of the work tasks, and other features are decided on aptitudes, capacities, experience, and disponibility of the students. Team leaders supervise and coordinate students, but students are expected to work independently on their work tasks. Recruitees often write their theses (BSc, MSc, or PhD) on some aspect of the CubeSat. The first satellite produced by ESTCube, called ESTCube-1, has resulted in over 30 BSc, 20 MSc, and 2 PhD defended theses (Slavinskis, Reinkubjas, et al., 2015). ESTCube members are also involved in other peripheral activities, often as amateurs. Passion for science and technology is their core intrinsic motivation, along with meeting like-minded people. Their areas of interest include radio communication, robotics, science Olympiads, hackathons, programming, game development, or desktop fabrication. For example, an ESTCube member has created an online database on nanosatellites (nanosats.eu). This database was originally supported by an EU grant, but since 2014 it is regularly updated every 2 or 3 months.

During the development of their ESTCube-1 (2008- 2013), the ESTCube community did not formalize the initiative into any legal form. ESTCube members were tied by shared values, having a common goal: to produce and launch a CubeSat, making Estonia a space nation (Noorma et al., 2013). They envision space exploration as an activity that should benefit humanity as a whole. Membership is open for everyone who shares their vision and their values and is will ing to contribute to the project with inclusive community development prioritized over efficiency.

Community building on shared values is crucial for ESTCube community persistence through the long CubeSat development periods. The principal stress factor came from working with an accelerated schedule after accepting an earlier-than-expected launch opportunity from Arianespace (Slavinskis, Pajusalu, et al., 2015). The iterative prototyping of satellites is only possible through successive prototypes and models of the flight-ready satellite. Once a CubeSat is in orbit, there is no possibility to bring it down to Earth for hardware improvements or reparations. Simulations (digital models) and physical tests in testing facilities (e.g., testing functions, systems integration tests, and environmental tests) are performed to test the technology. ESTCube members report strong life-long bonds with other team members, developed through years of close collaboration—especially during the latest stages of development of ESTCube-1.

In the case of ESTCube, researchers, engineers, and space enthusiasts were the instigators. ESTCube is “a combination of various initiatives—education, science, technology, as well as student and volunteer organizations” (Kalnina et al., 2018, p. 2). The ESTCube community does not own fixed assets or property: the host organizations provide working space and lab access.

To this day, ESTCube does not have one principal source of funding. Several outlets are used to finance the costs of manufacturing technology for the CubeSats, the launching costs, and to financially support its members. The European Commission, The European Space Agency (ESA), and Estonian grants and scholarships (Lätt et al., 2014), a crowd funding campaign (Kalnina et al., 2018), donors, or sponsor ships, are some of the funding sources that ESTCube has been tapping through the years. The complexity of ESTCube’s organizational model gradually expanded. Having an international network of partners, over 200 students divided into a larger number of working tasks, involvement in international regulatory bod ies, partnering with ESA, among other areas of activity, become an administrative burden. The organization could not operate much longer without a formal legal structure. At the beginning of 2017, 32 new and old members of ESTCube founded the Estonian Student Satellite Foundation. The initial objective of ESTCube was to build one CubeSat and launch it into orbit. The mission was accomplished in 2013, when ESTCube-1 was launched into Earth's orbit. The initiative was refounded after launching ESTCube-1. The transition period from ESTCube senior leaders to the new generation leading ESTCube-2 satellite took approximately 2 years. Currently, the second CubeSat (ESTCube-2) is in an advanced development phase under the guidance of the Estonian Student Satellite Foundation. ESTCube-1 provided Estonia with the space technology proficiency needed to attain permanent membership status in the ESA. The status of Estonia as a member in ESA brought new opportunities for ESTCube and its host organizations to expand their involvement in new activities, both locally and internationally. The same year that Estonia joined ESA, ESTCube-1 micro-camera was selected to be a payload of the European Student Earth Orbiter satellite (the third mission within ESA's Education Satellite Program; Noorma, 2016). Also, in 2019 Estonia was invited to participate in ESA's “Comet Interceptor” mission. ESTCube also influences some decisions of its hosting institutions. Acquisition of lab testing machinery, rearrangement of departments and academic curricula, selection of grants and project proposals take into consideration the ESTCube needs and outcomes. Producing knowledge and technology in-house is one of the priorities of ESTCube and its hosting organizations. However, procuring the machinery to manufacture space technology was never an option. Instead, a network of exter nal partners is used to produce components designed and developed by ESTCube members."

(https://journals.sagepub.com/doi/abs/10.1177/02704676211041900)


Discussion

Technology-Determined Organizational Structure

By Lucas Lemos and Chris Giotitsas:

CubeSat technology greatly determines the organization of work. ESTCube-1 consisted of seven subsystems and two ground support systems (Table 1). The communication and interrelations between subsystems must be well-defined and effectively executed. Each subsystem has a team leader who coordinates the work tasks inside the subsystem team. Also, team leaders coordinate tasks among themselves. All subsys tem teams engage in discussing the main choices from the early stages of design. All issues are open for discussion, and all members are involved in making crucial decisions, like choosing a launch provider (Slavinskis, Pajusalu, et al., 2015). Team leaders use transversal groups created on the spot to deal with newfound coordination needs. In areas of limited impact or requiring specific expertise, the discussion and decision making are entrusted to task-force groups. Students are usually involved in developing more than one subsystem to gain practical multidisciplinary collaborative working skills.

ESTCube outreach efforts resulted in more than 15 aca demic journal articles (and several conference papers and posters) documenting the technology, the design, the results, and the know-how of the project. Payloads and subsystems and thoroughly described from functions to hardware, and from technical specifications to the justification of design choices. These academic publications appeared mostly dur ing condensed periods—especially right after the development of ESTCube-1, and we could split them into two areas. First, publications connected with the CubeSat technology (design and flight results), including areas like the main pay loads (Iakubivskyi et al., 2020; Lätt et al., 2014); the electri cal power system (Pajusalu et al., 2014); or the command and data handling subsystem (CDHS) and its firmware (Laizans et al., 2014; Sünter et al., 2016). Second, publica tions dealing with the project and the community (know how), including a compilation of lessons learnt (Slavinskis, Pajusalu, et al., 2015); the working processes and the funding (Kalnina et al., 2018); and the management of the com munity (Noorma et al., 2013; Slavinskis, Reinkubjas, et al., 2015). We can say that, in the case of ESTCube, technology determines their organizational model, and their academic outcomes reflect the impact of technology determinations over how they organize themselves. These academic publications follow the same modular structures (payloads, subsystems) of the CubeSat.

ESTCube uses a network of partners to develop and man ufacture CubeSat’s technology. Often, companies agree to provide services or discounts to support ESTCube. During the development of ESTCube-1, the preference was to use customized components off-the-shelf (Slavinskis, Pajusalu, et al., 2015). However, not all components are available in Estonia, and in some cases, they were shipped from the United Kingdom, Germany, or the United States. Hardware components are provided with different—primarily closed— licenses. Students usually utilize proprietary software pro vided by the universities to students and academic staff. This tendency is shifting as the advantages of working with open source software become more evident to ESTCube members.

The ESTCube-1 CubeSat incorporated open-source soft ware. The mission control system of ESTCube-1 used open source software “Hummingbird” codeveloped with an Estonian company (ESTCube, 2020). The open-source “FreeRTOS” operating system was used on the satellite’s main onboard computer (CDHS) and the camera, while the also open-source TinyOS operating system was used on the communication module. As part of the results and lessons learnt from ESTCube-1 experience, the use of an operating system that “provides most of the needed functionality, for example, a form of embedded Linux” (Slavinskis, Pajusalu, et al., 2015, p. 18) is recommended.

It is, however, during the development of ESTCube-2 that open-source software becomes widely used. The open source “tech stack” (a set of technologies used to build a single application) of ESTCube-2 developers consists of nearly 20 digital technologies including languages (Python, Go, Apache Groovy), databases (PostgreSQL, SQLite) and satellite specific software like Skyfield (see Table 2). Besides, the development setup (Microsoft Visual Studio Code), and the repositories (Git) used are open source. To provide quality assurance, open-source coding standards (Python 3, Docker, React JS) are used, data exchange standards are fol lowed when possible (XTCETM, C2MS), and compliance with international standards is followed (European Space Components Coordination, European Cooperation for Space Standardization, Consultative Committee for Space Data Systems, and others).

During the final stages of ESTCube-1, a difficult period marked the core design decisions for ESTCube-2. The launcher provider offered an earlier launching date. The ESTCube team decided to speed up the development time to make it into the new launching date —the CDS version of ESTCube-1 was selected to fit into Arianespace’s Vega rocket. In the end, everything went well except for one thing: the tether of the main payload failed to deploy on orbit, and the principal experiment did not take place.

As a consequence of the shortcomings detected in the ESTCube-1 subsystems organization and the critical failure on the principal payload, ESTCube-2 follows a unified organizational structure. It aims to maximize the use of common components, allowing reusability and “facilitat[ing] mobility of team members between subsystems” (Slavinskis, Pajusalu, et al., 2015). This integrated-system approach reduces the number of subsystems and improves the resilience and stout ness of the hardware. Building all subsystems as independent components connected only by cables resulted in an overall weak system structure in ESTCube-1. The ESTCube-2 orga nization of work is the same as ESTCube-1: the satellite plat form is developed in Tartu, while the payloads (one in ESTCube-1) are developed in specific places. The main difference is that ESTCube-2 is a 3U (three-unit) CubeSat and can carry more payloads. ESTCube-2 teams are based on dif ferent academic institutions (TO, UT Institute of Physics, Aalto University, Dresden University of Technology, Ventspils University of Applied Sciences and the Finnish Meteorological Institute). Each team focuses on a single pay load. Each payload is related to the expertise of the academic institution in which each team is based.

This technology-determined organization of work resulted in one more important defining trait of ESTCube: open and efficient personal communication skills. Different subsys tems demand expertise from different scientific and technical fields. Most ESTCube members tended to use jargon and technical terminology when communicating their work and findings, which complicated both the coordination between subsystem teams and the communication with external par ties. To solve this issue, ESTCube members take communication skills training and are generally encouraged to publicly talk and write about their work (Olesk, 2019). For internal communication, like task coordination or decision making, ESTCube first adopted an Estonian communication platform called Fleep (Liibert, 2017) and later moved into the open source oriented Discord platform. Using channel lists to organize working tasks and topics, every member can find the relevant information and documentation and take part in the conversations at any time in the same domain. "

(https://journals.sagepub.com/doi/abs/10.1177/02704676211041900)

Conclusion

By Lucas Lemos and Chris Giotitsas:

“A community aiming to produce highly complex technology needs to find access to expensive materials and costly machinery. The ESTCube strategy to produce space technology is twofold. First, in-sourcing the key production capacities like knowledge, know-how, and design. Second, outsourcing manufacturing capacities through a network of partners. Building key capacities in house is necessary to secure the community’s long-term sustainability.

ESTCube’s approach to producing complex technology resembles the approach employed by open-source move ments producing complex digital artefacts, like Wikipedia or Linux. In the latter, wide-spread access to the Internet and the use of privately owned tools for producing digital information (computers) allow distributed networks of collaborators to coordinate their efforts. Hence, such initiatives are producing highly complex digital systems and technology without appropriating the material infrastructure that makes their endeavors possible.

Following Benkler (2006), the production of information depends on three main inputs: already existing information; the mechanical means to sense, process, and communicate information; and human communicative capacity. Regarding digital information, Benkler posits that human communicative capacity “becomes the primary scarce resource in the networked information economy” (Benkler, 2006, p. 52), thus the most valuable asset in information production. In the case of ESTCube, the 6-year-long period of development of the ESTCube-1 CubeSat is mainly a digital information process. The manufacturing of ESTCube-1 technology was the material output of a collaborative intellectual process. It entailed over 100 people coordinating their work tasks through the Internet, using software programs installed on their personal computers to produce a 10-centimetre cube shaped artefact.


Using an analogy between the production of digital information and the production of technology, we can adapt Benkler’s categories to suit the ESTCube case:

• The CubeSat open platform (CDS) and current space scientific knowledge would correspond to Benkler’s first input (existing information). • The manufacturing capacities, like specialized machinery, and the CubeSat’s components would belong to the second category (mechanical means). • The ESTCube members' communicative capacities and the ESTCube Program (know-how) would correspond to the third category (human communicative capacity).


Moreover, there are certain similarities on how open-source movements through the Internet are democratizing knowledge, and how a grassroots initiative like ESTCube is approaching the production of highly digitized complex technology. In the former, a collective consciousness was developed to pursue the democratization of information digitally. In the latter, a similar awareness process may be taking place through groups of space enthusiasts having access to outer space through the CDS open technology platform. The core concept allowing such initiatives to democratize and reappropriate information technology is the digital/modular. Two aspects align it to what open-sour ce movements have been doing to democratize information. A digital-oriented organization of work, and the decreasing costs of technology manufacturing in its mature phase. First, a CubeSat is “mostly digital.” The largest part of its production is related to manipulating digital information. Open-source movements produce specific practices and organizational models well suited for peer-to-peer networks. Likewise, a community of space enthusiasts can use similar organizational patterns producing a CubeSat. Second, the closer the CubeSat industry gets to its maturity phase, the simplest and more cost-efficient the manufacturing of its components should become. In the case of open-source movements, the ubiquity of personal computers and afford able wide-spread access to the Internet was necessary to reach a critical mass of participants. Outsourcing manufacturing capacities also frees ESTCube from the limitations and financial burdens of risky fixed capital investment in the non-standardized- yet CubeSat industry.

It appears that, in the case of ESTCube, the appropriation of complex technology seems to be a highly digitized pro cess that entails certain organization forms adapted from the open-source movements to the technological demands of CubeSats. The organizational structure of the community is flexible and adapted around the needs of the technological development processes. These processes are complex and interdependent, thus they are compartmentalized in nonrigid structures that follow the evolving needs around the project. Furthermore, the community uses what we identify as a three-fold strategy to produce complex technology that helps overcome the disadvantages of using closed tools and closed manufacturing capacities. First, by using an open-source platform (CDS) as the base to produce the artefact, along with a community organizational model (CubeSat Program). Second, by using open-source software to develop the technology. This is highly relevant as most of the software is pro \duced and transmitted to the CubeSat after it is in orbit. Third, by producing open knowledge academic publications documenting (a) the design of the CubeSat, payloads, and subsystems; (b) the results of the space mission, including the technology’s performance; (c) the know-how (lessons learnt, the ESTCube Program, the experience). Open communication, both internally and externally, is one of the configuring aspects of ESTCube’s open-source approach. It allows them to partially overcome some of the limitations imposed by restrictive hardware and software licenses they use. The closed-licensed hardware manufactured by their partners can be, up to a point, “opened” by document ing the technology design, results, and know-how. Expanding the communication skills of the members to “open” the initiative was fundamental to connect the project with the general public, making space science more accessi \ble. The role of technology-related hobbies and enthusiastic amateur involvement of ESTCube members in other activi ties provided a shared sense of belonging for the community and opportunities for recruitment, funding, promotion, and establishing partnerships. The long term viability of the ini tiative depends on transmitting and nurturing the shared values of the community, generating tight bonds between its members, building the resilience needed for the initiative to not disband after long years of hard work and unpaid contributions. Wide and early recruitment events are utilized to attract interest. Indeed, as opposed to more accessible types of technology development, special effort is required when it comes to sophisticated technologies for younger people and those with specialized skill sets to be involved. In turn, wider participation provides unique opportunities for volunteers to develop knowledge and know-how and seek employment in a sector that would otherwise be largely inaccessible. It becomes evident that such a model of increased participation in the development of high technology is possible. Yet for it to be sustained and adopted more widely, significant institutional support would be required as well as wide structural change. This illustrates how the current discussion on how to reap the benefits of publicly funded research is not enough to provide radical options which may build on the insight provided by cases like ESTCube. It can point the way toward genuine democratic participation in the development and appropriation of such technology in society.”

(https://journals.sagepub.com/doi/abs/10.1177/02704676211041900)

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