Delft University of Technology Cubesats to pocketqubes Opportunities and challenges Speretta, Stefano; Pérez Soriano, Tatiana; Bouwmeester, Jasper; Carvajal Godínez, Johan; Menicucci, Alessandra; Watts, Trevor; Sundaramoorthy, Prem; Guo, Jian; Gill, Eberhard Publication date 2016 Document Version Submitted manuscript Published in Proceedings of the 67th International Astronautical Congress (IAC) Citation (APA) Speretta, S., Pérez Soriano, T., Bouwmeester, J., Carvajal Godínez, J., Menicucci, A., Watts, T., Sundaramoorthy, P., Guo, J., & Gill, E. (2016). Cubesats to pocketqubes: Opportunities and challenges. In Proceedings of the 67th International Astronautical Congress (IAC): Guadalajara, Mexico [IAC-16-B4.7.5_A] IAF. Important note To cite this publication, please use the final published version (if applicable). Please check the document version above. 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CUBESATS TO POCKETQUBES: OPPORTUNITIES AND CHALLENGES Dr. Stefano Speretta* Delft University of Technology (TU Delft), The Netherlands, [email protected] Mrs. Tatiana Perez Soriano Delft University of Technology (TU Delft), The Netherlands, [email protected] Mr. Jasper Bouwmeester Delft University of Technology (TU Delft), The Netherlands, [email protected] Mr. Johan Carvajal-Godinez Delft University of Technology (TU Delft), The Netherlands, [email protected] Dr. Alessandra Menicucci Delft University of Technology (TU Delft), The Netherlands, [email protected] Mr. Trevor Watts Delft University of Technology (TU Delft), The Netherlands, [email protected] Mr. Prem Sundaramoorthy Delft University of Technology (TU Delft), The Netherlands, [email protected] Dr. Jian Guo Delft University of Technology (TU Delft), The Netherlands, [email protected] Prof. Eberhard Gill Delft University of Technology, The Netherlands, [email protected] * Corresponding Author Abstract 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. Keywords: PocketQube CubeSat agile development Delfi-PQ Page 1 of 10 1. Introduction constant and it was shown in both cases). The inertia CubeSats have been getting a steady growth in has been calculated as the inertia of a cube supposing a popularity in the past years after they were first constant density D. The magnetic moment has been proposed in 1999. The concept of a modular standard considered for his implications with attitude control and coupled with a simple and (relatively) inexpensive is expected to be generated by a coil (magnetorquer). deployment system allowed an institution with limited budgets a direct access to space [1]. CubeSats are based on standard modules of 10x10x10 cm (also called units Table 1: Length scaling of key parameters or just U) that can be coupled together in different fashions. CubeSat PocketQube In the push to further democratize this, PocketQubes 1 were proposed to evolve regarding reducing costs and Side � � system size: now the core building block has been 2 1 shrunk to 5x5x5 cm (small enough to fit in someone Area �& �& pocket, as the name was originally conceived) [2]. 4 1 Both standards became the most popular for two Volume �( �( different class of satellites: CubeSats typically span 8 � from 1kg till 10kg in mass (but bigger and heavier Mass ��( �( examples have also been proposed) while PocketQubes 8 � target the range between 0.1 and 1kg. Solar power ��& �& This paper presents a comparison between the 4 different satellite classes rather than on the specific ��, ��, Inertia standards or configurations to highlight challenges and 6 64 opportunities for PocketQubes. In section 2 the Magnetic 6� 2 � dependence of the key features of size are discussed, moment ��( 3 ��( and the ability of current systems to track these tiny spacecraft is addressed. Delfi-PQ is the PocketQube currently being developed at the Delft University of Technology. The 2.1 Satellite Tracking preliminary design of Delfi-PQ is presented in section 3 This section focuses on the tracking of PocketQubes and the development strategy for the PocketQube line of and CubeSats, analyzing a real case: the launch of the spacecraft is provided in section 4. Dnepr-19 on Nov 21st, 2013. This launch was the first (and only one at the time of writing) with PocketQubes 2. Size comparison and CubeSats. 31 satellites were launched, 23 of them Several parameters can be used to characterize the directly from the deck and 8 of them from a micro- different satellite classes but, since both “standards” are satellite (UNISAT-5) 49 minutes after deployment from focused towards a small building block that can be the rocket [3][4]. The comparison is performed based on repeated multiple times, we will look at the basic the data provided by NORAD by analyzing the TLE of building block. In CubeSats, as it was already pointed each satellite [5]. Position accuracy cannot be estimated out, this is a 10x10x10 cm cube while in the at this stage due to the lack of a second reference, like a PocketQubes this is a 5x5x5 cm cube. GPS receiver onboard some of the satellites, but To make an effective comparison, a set of common tracking update rate and TLE acquisition time can be and constant factors have been considered. For example, compared. satellite side (L) that was established to 10cm (as in The first parameter considered was the acquisition CubeSats); satellite density (D) is assumed to be time, defined as the time in between satellite constant due to the common concept the satellite are deployment from the rocket (07:11 UTC on Nov 21st, built on; solar power conversion efficiency (η) 2013) and the time the first TLE was available for each considering that the same type of solar cells is used. A satellite. Figure 1 shows the acquisition time for all the brief comparison is presented in Table 1 based on these satellites deployed as a function of the approximate constants. Side, area and volume are straightforward, satellite cross-section (estimated from public while other quantities require a bit more investigation. information about the satellite size). PocketQubes and Solar power depends on the available area for solar cells CubeSats are highlighted in the figure showing no major (making the hypothesis of a constant fill factor) and on difference in object acquisition performances. It can the conversion efficiency (which is supposed to be also be seen that statistically bigger objects are acquired Page 2 of 10 first, and smaller objects took on average more time significant. It is interesting to notice that the TLE update (with exceptions, as is evident from the figure). rate for nano- and pico- satellites increased after August Most likely due to the limited ∆v provided during 2015 (an improvement in update rate can be noticed this deployment, the satellites remained too close to be from Figure 3 for small satellites probably due to a detected. After approximately nine days most of the system upgrade).