In the last two decades, CubeSats have changed the perception of satellite missions aided by standardization and usage of commercial-off-the-shelf components. CubeSats have also proven the feasibility of low cost and short development time space missions. The PocketQube with a form factor of 5x5x5 cm has been proposed as the next class of spacecraft to benefit from miniaturization. This paper presents a comparison between the two standards and analyzes the impact of miniaturization on spacecraft design and performance. At satellite level, the reduction of volume has a tremendous impact on the available power and makes energy management and efficiency critical. Thermal issues become important due to the reduced thermal capacitance, leading to higher thermal swings and larger temperature variations than CubeSats. The other important impact on the satellite bus is the reduced communication capacity due to several reasons: the reduced volume limits the available antenna size and also the available power available. At mission level, other factors have a substantial impact: de-orbit time becomes a major criterion in the launch selection process to comply with orbital debris policy. The volume reduction also affects the radar cross-section making the satellite more difficult to detected for space surveillance radars. Despite these challenges, PocketQubes are an attractive standard currently for academic and research groups as a way to reduce the cost and development time considerably. Payload capabilities also can force a paradigm shift from single to multiple satellites more than it was already happening with CubeSats: PocketQubes could better fit certain niches where high spatial or temporal resolutions are required instead of full resolution. Distributed space weather monitoring could be an interesting application where specific phenomena could benefit from multi-point sensing. All these strong points can also be coupled with a bigger satellite to complement and enhance its capabilities. Delfi-PQ is a PocketQube currently being developed at TU Delft using an agile approach, contrary to the typical V-model design. Shorter life cycle development benefits students, allowing them to get more involved in every iteration. The reduction in cost and development cycle increases the launch frequency. Incremental engineering becomes fundamental, also providing benefits on the reliability side because flight experience becomes more frequent than when following traditional development strategies. End-to-end development motivates students and provides them with a better insight into real-world engineering opportunities and training experiences. With this strategy, technical and educational objectives are more aligned, and the integration of such a project in the curriculum is facilitated. @en

This thesis provides an innovative architecture for CubeSats and PocketQubes to improve their performance and reliability. CubeSats and PocketQubes are standard satellite form factors composed of one or more cubic units of 10 cm and 5 cm respectively. It is found that the current modular subsystem approach and the electrical interfaces are not optimal in terms of performance and use of technical resources. Reliability is also a concern for CubeSats. Only 35% are able to achieve full mission success. Available literature provides no comprehensive studies on these matters and there is thus a gap in knowledge to be filled. The objective of this study is to identify and quantify the performance and reliability issues related to the physical arrangement of subsystems and the electrical interfaces and to develop an innovative bus architecture which is reliable, flexible and allows for increased performance. The overarching research question is: ”Which satellite bus architecture provides a reliable solution to the needs and constraints of a CubeSat and a PocketQube mission?” @en

Driven by wide interest among TU Delft (Delft University of Technology) students to acquire focussed knowledge on space engineering, missions and planetary exploration, a new spaceflight minor was developed for the minor program of the university. With its minor program, TU Delft affords its students an opportunity to dedicate the first semester of their 3rd BSc year to a set of courses chosen among the numerous options offered specifically by the TU Delft or another university. Students are not only allowed but encouraged to explore topics and study fields outside their main BSc track. The spaceflight minor is designed as a multidisciplinary, thematic program, in which the students gain insight in the demand for space applications, mission analysis, system requirements and sizing. This multidisciplinary setup is facilitated by the recently established TU Delft Space Institute (DSI), of which all the faculties involved in the minor are members. The minor and the DSI provide a unique opportunity to strengthen space education and research across TU Delft. The minor covers two quarters of the academic year, spanning twenty weeks, and includes six courses. Offered in the first quarter are: Introduction to Spaceflight (for students without Aerospace Engineering background) or Electronic Circuits (for the other students); Space Exploration, with basics and examples of planetary and astronomical exploration and an introduction to space law; Earth Observation, covering basics of remote sensing of the Earth. The second quarter includes: Spacecraft Technology, providing an overview of the technology of spacecraft subsystems with emphasis on small satellites; Satellite Tracking & Communication, on telecommunications, ground station operations and telemetry analysis from a theoretical and practical point of view; Spaceflight Assignment, the final project in which students produce real, small-scale space deliverables, and reflect on the process and results of development and analysis in the complex space engineering and scientific environment. In total, 15 lecturers from three TU Delft faculties and one from Leiden University contributed to the minor. Many of the courses employ innovative education techniques, such as flipped classrooms and videos produced by the lecturers. Some courses are simultaneously offered to campus students and external participants in a full online format. The first edition of the minor, delivered from September 2015 to January 2016 to 44 students from various TU Delft faculties, can be considered a success with excellent feedback from participants. The paper elaborates on the minor design and learning objectives, showing how multidisciplinary, innovative education can be effectively implemented for students with different academic backgrounds. @en

The objective of this paper is to investigate which approach would lead to more reliable CubeSats: full subsystem redundancy or improved testing. Based on data from surveys, the reliability of satellites and subsystems is estimated using a Kaplan–Meier estimator. Subsequently, a variety of reliability models is defined and their maximum likelihood estimates are compared. A product of a Lognormal distribution addressing immaturity failure and a Gompertz distribution addressing wear-out is found to best represent CubeSat reliability. Bayesian inference is used to find realistic wear-out parameters by using failure data of small satellites. Subsystem reliability estimates are subsequently found using a similar approach. A reliability model for CubeSats with redundant subsystems is established, verified and applied in a Monte Carlo simulation. The results are compared with a model for reduced immaturity failure. Allocating resources to reduction of immaturity failures through improved testing is considered to be superior to allocating these resources to the implementation of subsystem redundancy.@en

PocketQubes are a form factor of highly miniaturized satellites with a body of one or more cubic units of 5 cm. In this paper, the characteristics of PocketQubes in terms of their constraints and their (potential) utility are treated. To avoid space debris and limit collision risk, the orbits of PocketQubes need to be constraint. An analysis of orbital decay characteristics has been carried out which, considering existing space regulations and a pro-active attitude, PocketQubes should preferably be launched in low Earth orbits below 400 km altitude. Due to technical constraints, such as form factor, power and attitude control, the domain of applications for single PocketQube missions is limited. Still, they can act as low-cost training and technology demonstration platforms. To make PocketQubes an attractive platform for other types of missions, not only the launch cost, but also the development, production and operations cost should be significantly lower than CubeSats. When the PocketQube platform matures and produced in high numbers, networks of PocketQubes can enable new applications. Applications considered feasible are in the field of (but not limited to) continuous surveillance using optical instruments, gravity field monitoring using precise orbit determination, in-situ measurements of the space environment, low data rate or bandwidth communication services and inexpensive probes around other celestial bodies.@en

Since the first successful CubeSat missions in the early 2000s, payloads for this form factor have emerged and have increased in technical performance level. This trend is likely to continue in the near future. However, despite the subsequent increase in data load and the increasing modularity of components, there are no clear trends for a new electro-mechanical interface standard. The only widely adopted data bus in CubeSats, I2C, is limited in terms of data rate and reliability. Custom solutions overcoming these limitations are generally not well documented, and especially implementation results in CubeSats are lacking. Therefore, there exists a need to increase the performance and reliability of the CubeSat bus platform. This paper proposes an innovative CubeSat data bus architecture, including performance and reliability tests. The first need is to increase the feasible data rates to be compatible with future large-data payloads. Secondly, the system’s reliability must be increased compared to the current I2C standard, as many launched CubeSats using this data bus experience severe problems such as bus lockups and even a few catastrophic failures. The concept proposed in this paper is to separate the main bus used for telemetry and command from the data bus used for payload data, which provides room for optimising the performance of both buses. The selected bus technology standards used to drive the hardware were found through a survey and subsequent trade-off of available serial bus standards. For the main bus, this trade-off results in either a CAN bus or RS485 bus to both increase the robustness of the internal network and potential data throughput. For the payload bus, a USB-based bus is selected to provide a high data rate with increased reliability compared to often-used standards. The combination of both options optimises performance while keeping electrical power consumption at a minimum. Making use of the common modular designs of CubeSats and recent developments in the respective data bus technologies, a flexible, robust and high performance data bus architecture is devised. A practical setup simulating a CubeSat with multiple realistic subsystems generating pseudo data is used to validate the operations of such a data bus. To find the maximum capacity of the network, multiple subsystems are connected with varying high and low data rates, thereby simulating current typical CubeSat subsystems and potential future payloads requiring high capacity data networks. Furthermore, methodologies are developed for implementation and qualification of the proposed bus in future CubeSat missions.@en

This paper presents the design of a multi-frequency deployable antenna system for femto-satellites as part of the Delfi-PQ project, a PocketQube with a size of 50x50x178 mm which is being developed by the Delft University of Technology. This new form factor brings its own challenges on every subsystem and it is seen as a stepping stone towards even more miniaturised satellites. In this paper we present the design trade-offs, the analysis and the and measurements on the antenna system. The system is designed to operate in 4 different bands to guarantee communications and payload operations. Due to the very limited available space on the external faces of the spacecraft, it was decided to deploy all the antennas and multiplex the different bands on the available antenna elements. VHF and UHF are used for satellite telemetry and commanding while a dual-frequency GPS receiver is intended as payload. The satellite design is presented, together with design drivers for such a system to justify the design choices. Three RF configurations are analysed and compared for omni-directional coverage and peak gain. RF measurements on one of the configurations is also presented to validate the simulations. The deployment system is also presented, giving details on the design and expected tests to complete the qualifications.@en