The paper presents the initial outcomes of a project, currently ongoing under the supervision of the European Space Agency, having the main objective to specify and design a Fault Detection Isolation and Recovery (FDIR) system by making use of relevant RAMS (Reliability, Availability, Maintainability, Safety) analyses for missions in non-deterministic environment with limited resources. The initial project tasks have been to select a study case represented by a CubeSat complex mission, analyse in detail both its mission and system requirements and, based on them, define a set of relevant RAMS analyses to be carried out in the second phase of the project, as inputs for the development of a FDIR concept aimed at a careful balance of the limited spacecraft resources in case of critical failures. Two possible study cases have been identified: LUMIO, a 12U CubeSat mission for the observation of micro-meteoroid impacts on the Lunar farside, and M-ARGO, a 12U deep-space CubeSat which will rendezvous with a near-Earth asteroid and characterize its physical properties for the presence of in-situ resources. Although both missions are characterized by a high level of autonomy and complexity in a harsh environment, LUMIO has been eventually selected as study case for the project. In the paper, the challenges and features of this mission are shortly presented. The specificities of the RAMS analysis and FDIR concept for this specific class of small satellite missions (including the selected study case) are highlighted in the paper, looking in particular at aspects such as the improvement of reliability while maintaining the CubeSat philosophy, the tuning of mission and system requirements in view of facilitating the design and implementation of the FDIR concept, and the current gaps within the RAMS/FDIR body of knowledge. The conclusions drawn during this first project phase provide a real view of how systems engineering must work in tandem with RAMS analyses and FDIR to achieve a more robust and functional mission architecture, thus improving the mission reliability.

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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.

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PocketQubes represent a new type of cube-shaped platforms with dimensions of 50x50 mm and mass of 250 g. Just like the CubeSats, these platforms are also split in units which are referred to as 1P. The Delft University of Technology has been working on Delfi-PQ, a 3P PocketQube with the dimensions of 50x50x178 mm. This miniaturized size brings its own challenges on every subsystem. In this paper, structural design, integration and kill switch mechanisms will be explained.@en

In the study of Near Earth Objects (NEO), it is crucial to advance our current modelling capabilities of Potentially Hazardous Asteroids and imminent impactors, especially smaller size ones. This would allow for more accurate and more timely prediction of their effects and, ultimately, for a more effective protection of our planet. This objective can be achieved by enabling key technologies that can be utilised in support to missions to NEOs, in particular for in-situ validation of theoretical models of their properties. The design requirements for these technologies are derived from the modelling needs of the target body (asteroid dynamics, surface characteristics, topography, temperature in various locations) in terms of modelling capabilities, parameters to be measured for model validation, required measurement accuracy and resolution.
One of the in-situ characterization technologies currently under investigation at Delft University of Technology is the so-called “Smart-Net”, which makes use of the PocketQube satellite platform developed by the Space Systems Engineering group. PocketQubes are cube-shaped platform based on 50 mm3 units with a mass of less than 250 g each. Delft University of Technology has embarked in the design and development of this class of picosatellites in order to further advance its research on satellite miniaturization: a PocketQube, by definition, has 8 times less volume when compared to a CubeSat. Potentially, deep space and interplanetary missions can gain even more advantage from the use of large networks of these very small satellites, by reducing costs, improving redundancy and assure high scientific return through their use in big numbers.
In the innovative Smart-Net, a number of PocketQube devices, equipped with a full suite of sensors and radio beacons, are used to sense the surface of an asteroid, measure its temperatures in various locations and its dynamics and rotational speed, while directly transmitting the gathered scientific information to the Earth. These PocketQube units represent the nodes of a net that can fully wrap and cover the entire surface of a small asteroid up to a few meters in size, with the net wires representing at the same time an antenna for direct communication from the PocketQubes to the Earth or a mother spacecraft. The PocketQube units are also equipped with hooks, to increase the chances for anchoring a body with very low gravity field. This paper presents the preliminary design of the Smart-Net and the expected challenges for its development and in-situ validation in an actual space mission.
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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

Miniaturized spacecraft, such as the well-known CubeSats, have become more and more popular in the last decade, allowing for dramatic reductions of the mission costs. However, it is not fully clear at the present moment which access to space option is the most convenient and affordable one for this class of satellites, with micro-launchers still penalized by their intrinsically bad structural efficiency and propulsion performance. It seems to be preferable to use onboard propulsion for the orbital transfer of these small spacecraft after being inserted in Low Earth Orbit as a piggyback payload of a larger launcher. However, in turn, this increased autonomy due to the presence of a propulsion system raises significant issues in terms of safety to the other surrounding spacecraft in orbit. Strict measures are expected to be applied in the future regulations, in scenarios such as a thrust-direction failure in a small spacecraft, with consequent damage to other spacecraft creating debris. This problem becomes even more critical in Low Earth Orbit due to the presence of the International Space Station. This paper presents a general overview of the current access to space options for small satellites, and the existing propulsion technology for their orbital transfer. A preliminary analysis is performed on the design requirements related to potential scenarios and recovery actions related to propulsion system failures for small satellites operating in Low Earth Orbit. @en

This papers gives an insight on different sub topics related to a micro-propulsion subsystem for a PocketQube. First, PocketQubes will be introduced and then Delfi-PQ will be presented, providing an overview of the mission for which this micro-propulsion system will be used. Step by step, the paper will explain the subsystem, its challenges, mechanical aspects, electronics aspects and future work. In the long term, these miniaturized micro-propulsion systems might play an important role for micro satellites for attitude control, low-altitude orbital maintenance, formation flying, orbital transfer and several other potential applications.@en

As a further step in the research towards miniaturization of satellite components and sub-systems, the Department of Space Systems Engineering at the Delft University of Technology has recently embarked in the end-to-end engineering of the Delfi-PQ picosatellite platform, designed according to the PocketQube size standard. This new satellite platform, inspired by the success of previous Delfi satellite projects, is seen as a great opportunity for innovativeness and offers great research challenges. Since a consolidated standard for PocketQubes has not been established yet, a significant amount of design freedom can be harnessed despite the small volume available. The miniaturization process required to integrate the core bus forces the team to think differently about space technology: it is not sufficient to simply down-scaling existing concepts used in larger satellites, and it is often necessary to develop and qualify completely new components and integration methods. The paper is about systems engineering process, technology developments, and verification and validation for the design and development of the micro-propulsion payload for PocketQubes and its integration with the core bus platform.@en

PocketQubes are a new form factor of highly miniaturized satellites with a body of one or more cubic units of 5 cm. The characteristics of PocketQubes in terms or legal and regulatory aspects, the technological readiness levels and financial considerations are assessed. In particular, an analysis of orbital decay characteristics has been carried out which together with existing space law suggest that PocketQubes should preferably be launched in very low Earth orbits below 500 km altitude. To make PocketQubes attractive platforms, not only the launch cost, but also the development, production and operations cost should be significantly lower than CubeSats . Due to technical constraints, such as form factor, power and attitude control, the domain of applications is, especially for single PocketQube mission constrained. Still, they can act as low cost training or technology demonstration platforms. When launched in high numbers, networks of PocketQubes can enable new applications for Earth observation and niche communication services. 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 and low data rate or bandwidth communication services.@en

Delft University of Technology has embarked on PocketQubes to showcase as the next class of miniaturized satellites. In the past decade, CubeSats have grown towards a successful business with mature capabilities. PocketQubes, however, are still in their infancy. The small size of the PocketQubes will trigger innovations in miniaturization and will force one to think differently about space technology. It is not sufficient to simply down-scale existing concepts used in CubeSats, there is a necessity to develop and qualify completely new components through which new applications can be enabled in the future. The new satellite platform, called Delfi-PQ, inspired by the success of previous Delfi satellite projects is seen as an opportunity for innovation and offers research challenges in the miniaturization field of systems and components. The focus of this paper is to highlight those innovations and challenges, and to communicate the progress that has been made with respect to building a core platform and standardized bus. The mission of Delfi-PQ is to demonstrate a reliable core bus and outer structure for a three unit PocketQube that shall be tested in flight as a first iteration of a series of PocketQubes to be developed by Delft University of Technology. The core bus shall fit in one unit - 1P (50x50x50mm), having as aim that after further miniaturization and optimization, the second unit shall contain an advanced subsystem (e.g. advanced Attitude Determination and Control System - ADCS) and the third unit shall consist of a scientific payload (e.g micro-propulsion, lensless camera). For Delfi-PQ, the focus was on the miniaturization process and on the structure of the PocketQube. The core platform of the first Delfi-PQ consists of the Electrical Power System (including two 3.7V batteries and solar panels with two cells/each X-Y face), On-board Computer, Communications System, ADCS (including two magnetorquers and three magnetometers), as well as: temperature sensors and two different sensors for assessing the rotational speed of the PocketQube.@en