Announcement of Opportunity University of Bristol CubeSat Payloads
Authors: Ignacio Hernandez-Arroyo Dr Mark Schenk Dr Lucy Berthoud Website: www.uobsat.uk
Version: Date issued:
1.0 21st July 2015
Table of Contents 1
Introduction .......................................................................................................................... 2 1.1
CubeSat platform .......................................................................................................... 2
1.2
CubeSat payloads .......................................................................................................... 3
1.3
University of Bristol CubeSat Programme ..................................................................... 3
2
Call for UoB CubeSat Payloads .............................................................................................. 4
3
CubeSat Payload Constraints ................................................................................................ 4 3.1
Volume Budget .............................................................................................................. 5
3.2
Mass Budget .................................................................................................................. 6
3.3
Power Budget ................................................................................................................ 6
3.4
Data Budget ................................................................................................................... 7
3.5
Orbits ............................................................................................................................. 7
3.6
Launch Loads/Vibrations ............................................................................................... 7
3.7
Commercial interests .................................................................................................... 7
4
Proposals Evaluation/Selection Criteria ................................................................................ 8
5
Proposal Structure / Key Points ............................................................................................ 9
6
5.1
Project Title ................................................................................................................... 9
5.2
Executive Summary ....................................................................................................... 9
5.3
Project Description ........................................................................................................ 9
5.4
Technical Details of the Payload ................................................................................... 9
5.5
Integration into Educational Curriculum ....................................................................... 9
Points of Contact ................................................................................................................. 10
References/Bibliography: ............................................................................................................ 11
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1 Introduction Over the next few years the University of Bristol satellite programme plans to design, build, test and launch a series of nano-satellites, called CubeSats. The aim of this programme is to involve UoB students and academic staff in developing and operating nano-satellites. In addition to the potential research outcomes, one of the main objectives of this programme is its integration into the teaching curriculum of the University of Bristol. The CubeSat programme hopes to provide our students with valuable hands-on experience in a real spacecraft project. The ‘payload’ is the reason for a satellite mission and this can range from imaging systems, scientific experiments, and technology demonstrations, to artistic or educational projects. The aim is to collect exciting payload ideas from across the university, to feature on-board the University of Bristol CubeSat. The payloads influences the satellite design, and with an initial selection of potential payloads the satellite development can be kicked off. This document is the Announcement of Opportunity for Payloads for the University of Bristol CubeSat Programme. It provides guidance and background information to payload proposers, and is used in conjunction with the Payload Proposal Template. If you have any questions, please do not hesitate to ask any of the contacts listed in Section 6.
1.1 CubeSat platform The University of Bristol satellite programme will make use of the ‘CubeSat’ platform. A CubeSat is a standardised form factor for nano-satellites, and consists of 10 x 10 x 10 cm modules with a mass of approximately 1 kg; this is defined as 1U (one unit). The cross-section remains fixed at 100 x 100 mm, but the length can be varied with multiples of 1U; see Figure 1.
Figure 1: Depiction of the most typical CubeSat sizes, 1U, 2U, 3U (image courtesy of Clyde Space).
The standardisation means that a range of off-the-shelf components is available, facilitating rapid development of the satellites. Crucially, the standardisation allows CubeSats to be fitted as secondary payloads on launches, providing relatively low-cost launch opportunities [1]. The CubeSats are launched and deployed using a dedicated deployment system, such as the ISIPOD [2] or the P-POD [3]; see Figure 2.
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Figure 2: ISIPOD CubeSat deployer (image courtesy of ISIS).
A CubeSat consists of essentially the same subsystems as larger satellites. These may be simplified and/or reduced in size, and include power, communications, attitude determination and control, data handling, structure and propulsion [4]. These subsystems provide the platform for the mission payload.
1.2 CubeSat payloads Despite their diminutive size, CubeSats have been successfully used for a wide variety of missions, including Earth Observation (EO), biological experiments, space science, technology demonstration, arts and outreach. A selection of CubeSat missions is collected in this document: https://drive.google.com/file/d/0ByJZZ2f0jdmXTGNYc2hVYnIzWFk/view which may offer inspiration for payload ideas. The dimensions of the UoB CubeSat have not yet been decided, and will depend on the proposed payloads. Therefore any payload proposals compatible with CubeSat sizes up to 3U are welcomed.
1.3 University of Bristol CubeSat Programme The programme to develop a University of Bristol CubeSat, named UoBSat, was initiated at the first IAS Workshop on Space Research in January 2015 as a way of bringing together researchers across the university with an interest in space research. One of the main objectives is to incorporate the development of the satellite into the teaching curriculum, across different schools and faculties. The first step is to set up a UoB ground station, allowing students to communicate with satellites in orbit. Preliminary funding and equipment has already been obtained, and it is expected that the ground station will become operational in the 2015/2016 academic year. The current university-wide call for payloads is aimed at obtaining payloads ideas around which to develop the satellite platform. The first exploratory student projects on the subsystem design are expected to start in September 2015, with group design projects to follow. The option to set up a dedicated student society, similar to the approach taken by Formula Student, is being explored. The CubeSat will be developed over the course of three or more years, and it is expected that early iterations might be launched on a sounding rocket through the European Space Agency’s REXUS programme [5], to gain experience needed for a full launch. More information on the CubeSat project will be hosted on www.uobsat.uk in due course. 3
2 Call for UoB CubeSat Payloads An important step in the UoB CubeSat programme is this Call for Payloads, as the payloads will drive the design of the mission and satellite. Key dates are: 23rd June 2015 21st July 2015 16th September 2015 28th September 2015 July 2016
Pre-announcement for call for payloads Announcement of Opportunity and opening of the payload proposal submission. Deadline for payload proposal submission. Submission by emailing the completed Payload Proposal Template to
[email protected] Release of short-list of payload ideas to be further developed in the 2015/2016 academic year. Selection of payloads for UoBSat1
We welcome payload ideas from across all faculties and departments, and by any member of the university (student proposals will need an academic member of staff as supervisor). Section 5 provides some guidelines for the proposal structure. The proposals can be submitted by sending the completed Payload Proposal Template to:
[email protected] In September 2015 the proposed payloads will be evaluated according to the criteria in Section 4 of this document, and a short-list will be released. Those shortlisted payloads will be further developed over the 2015/2016 academic year (similar to a Phase A study) and, based on the results of those feasibility studies, a final selection will be made in July 2016.
3 CubeSat Payload Constraints The CubeSat platform imposes certain constraints on the potential payloads. This section is intended to provide guidance on what is achievable with a CubeSat. However, do not feel discouraged if at first glance your payload idea does not appear compatible. For example, power can be increased by adding deployable solar panels, etc. The aim of this section is to make people aware of some of the constraints, without wishing to limit the imagination. The CubeSat platform is defined by an official specification document, provided by California Polytechnic State University (CalPoly): http://wdww.cubesat.org/images/developers/cds_rev13_final2.pdf It includes general information, certification guidance, a short description of the P-POD, as well as a range of mechanical, electrical, operational and testing requirements. Note that many of the CubeSat requirements and specifications are aimed at ensuring it does not damage or affect the primary satellite payloads on the launch. In addition to the requirements from the CubeSat specification, there are further limitations in terms of volume, mass, power, etc. available to the payloads. The information in the following sections is compiled from CubeSat part suppliers and/or representative missions, and can only be considered as indicative.
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3.1 Volume Budget The cross-section of a CubeSat is fixed at 100 x 100 mm, and only the length can be varied. A 1U, 2U and 3U CubeSat respectively have a bus height of 100 mm, 213 mm, and 327 mm. Not all that space will be available for the payload, as a significant portion is taken up by the electronic systems necessary for the satellite to function (power, communications, etc.). 1U CubeSat: As it can be seen in the assembly diagram of the SwampSat [6] in Figure 3, the communications, electronics, and other subsystems occupy approximately 40% of the volume of the 100 x 100 x 100 mm module. Remarkably, a miniature Control Moment Gyro (CMG) assembly was squeezed into the remaining space as the satellite payload.
Figure 3: Exploded view of the 1U SwampSat assembly (image credit: UFL)
2U CubeSat: As an illustrative example of a 2U CubeSat, the QB50 platform solution by Clyde Space [7] has a platform electronics stack that includes the Electrical Power System (EPS), onboard computer (OBC), and communications system. This occupies a height of approximately 72 mm, leaving 100 x 100 x 132 x mm available for the payload; see Figure 4.
Figure 4: QB50 Clyde Space 2U CubeSat platform volume distributions (image courtesy of Clyde Space).
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3U CubeSat: For the 3U case, the SCOTSAT conceptual architecture of Clyde Space and the University of Strathclyde [1] can be seen in Figure 5, with approximately 1U occupied by the satellite subsystems, and 2U available for the payload.
Figure 5: Outline of the SCOTSAT conceptual architecture. (Image courtesy: Clyde Space)
It is important to note that these configurations consider only essential subsystems, and if more complexity were required (e.g. full 3-axis attitude control were needed by the payload) the volume of the platform subsystems would increase. Miniaturisation of the payloads is always recommended, to allow multiple payloads to be accommodated on the CubeSat.
3.2 Mass Budget For a 1U CubeSat, estimates of the allocated mass for payload are around 200 g [8][9][10], in order to stay within the 1 kg standard. For a 2U CubeSat the mass budget for a payload rises to approximately 900 g [8][10], assuming the same subsystems are still being used, and accounting for the bigger structure and solar panels. Finally a 3U CubeSat would have a payload mass budget of approximately 1600 g [8][10]. It is important to note that these mass budgets have been estimated assuming a 1 kg limit per module, as stated in the CubeSat specifications (maximum of 3 kg advised) [2][3]. However, the ISIPOD deployer can accommodate up to 6 kg for a 3U, allowing for a greater payload mass. Nonetheless, it is worth remembering that launch cost is coupled to the mass of the satellite, so payload mass should be minimised!
3.3 Power Budget Satellites are powered using solar cells, and the amount of power available depends on the total surface area, which in the case of CubeSat is limited. Indicative values for a 1U, 2U and 3U CubeSat are respectively 1 – 2.5 W, 2 – 5 W and 7 – 20 W [11][12]. These power budgets must be taken as estimates, especially the upper limits, as they will depend greatly on the final design of the spacecraft and the mission. Please note that payloads that require greater amounts of power are not necessarily precluded, as the satellite can provide more power over shorter intervals.
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3.4 Data Budget Communication with CubeSats is generally done over amateur radio frequencies, in VHF and UHF bands, with frequencies around 425-437 MHz or 2-13 GHz [13]. This limits the amount of data that can be downloaded from the satellite (and thus from the payload). Recent missions (2009-2011) have suggested that the data communication rates of CubeSats commonly range from 1.2 to 9.6 Kbps, with some exceptional cases of custom communications protocols and/or UHF communications reaching 1-1.5 Mbps [13][14], and it is possible that the data rates could eventually reach up to 2-4 Mbps [15]. Consequently, payloads should be designed to be economical with the amount of data required to achieve mission success.
3.5 Orbits As the CubeSats are launched as secondary payload, the precise orbit will depend on the launches available [16]. This means that a payload cannot be designed around specific orbit requirements. The orbit altitude for CubeSat is, in practice, limited to approximately 650 km, to ensure timely deorbiting.
3.6 Launch Loads/Vibrations During launch the satellites are subjected to very high vibration loads. The numerous previous missions and extensive testing showed that the CubeSat standards are sufficient to withstand them [17][18]. This means that any experiments and/or instruments included in the CubeSat would need to adhere to these standards and prove to be able to withstand the loads and vibrations to demonstrate their feasibility.
3.7 Commercial Interests Commercial interests cannot use amateur radio frequencies, which is what UoB ground station will be relying on for its communications. So no company can have a financial interest in the satellite communications, otherwise the station will no longer be amateur. In addition, every data transmission from an amateur radio station must be ‘in the clear’. In the clear means that: (1) technical descriptions of all emissions, codes, and formats are made publicly and widely available; (2) technical descriptions must be sufficient to enable any technically competent licensed amateur radio operator to use the system. As a consequence, of course, all transmissions will be open to reception by anyone. Encryption for critical spacecraft tele-command functions is accepted. More details are available at: http://www.amsat.org/amsat/intro/using-ham-freqs.html
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4 Proposals Evaluation/Selection Criteria After submission, the payload proposals will be evaluated by a cross-disciplinary panel. The following broad criteria will be considered when assessing the proposal for the UoB CubeSat.
Impact: How exciting is the payload? Will it enthuse students to work on the project? Can it be used in public outreach, raise the public profile of the university? What is the scientific impact of the payload, can it lead to publications?
Feasibility: The degree to which the payload idea could be used as a payload in the CubeSat platform will be evaluated, comparing against the constraints detailed in Section 3. This should not should not deter any payload ideas from being submitted even if the proposer cannot currently describe how the payload might be implemented in a CubeSat! Promising payload ideas can still be short-listed for the more detailed feasibility study.
Development time: After the feasibility study, the payload development is expected to start fully in the 2016/2017 academic year. It is therefore important that the experiments, technologies, and ideas selected as prospective payloads are at a sufficiently high TRL (Technology Readiness Level) to be considered for the UoB CubeSat.
Educational benefits: Given that this is a university project, any positive impact the development of the payload could have on the education of the University of Bristol students would be judged favourably. This would include the integration of the payload development into the teaching curriculum, the possible use of data from the mission for educational purposes, or any other activity that could enhance the experience of the students and academics.
Please note that multiple payloads can be hosted on the same CubeSat, so it is hoped that several payloads will be short-listed in September 2015.
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5 Proposal Structure / Key Points The Payload Proposal Template is intended to help with preparing the proposal, and includes brief descriptions in each section as guidance. It is recommended to use the proposal template, even if the payload is currently just an inkling of an idea and few technical details are available. The key points of the proposal are here briefly highlighted.
5.1 Project Title This should be a short, concise and engaging name for the payload and the mission itself (after all, the payload determines the goals and objectives of the mission). The objective is to have a memorable and appealing name to present to the public and to anyone involved in the project.
5.2 Executive Summary The executive summary should convey the mission in a brief yet complete way. It is intended to be the shortest presentation of the mission possible, while showing the key points and main objectives of the project.
5.3 Project Description The description of the project should be an extension of the executive summary, not only presenting but also explaining and detailing the key points of the mission: objectives, intended outcomes, benefits and advantages of the payload. Any extra information included such as diagrams, images, background information and references to articles and work on the subject previously published that will show the feasibility and reliability of the payload idea will also be welcome..
5.4 Technical Details of the Payload This purpose of this section is to consider the various technical aspects of the payload, and assess the compatibility with the constraints and system budgets imposed by the CubeSat platform, as described in the Section 3. At this early stage of the payload design, it is not expected that all the sections in the template can be addressed. All payload ideas are welcome, no matter how far developed they are!
5.5
Integration into Educational Curriculum
Given the importance of the educational side of the project, this section should detail how the payload could be planned to be integrated into the teaching curriculum of the university or offered as an extra-curricular activity. Any contacts established and/or planning already done should be included.
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6 Points of Contact For questions, about the UoB CubeSat programme in general or specifically about payload ideas, please contact any of the following: Engineering:
Dr Mark Schenk (
[email protected]) Dr Lucy Berthoud (
[email protected])
Sciences:
Professor Mark Birkinshaw (
[email protected]) Dr Matt Watson (
[email protected])
Arts and Humanities:
Professor Kate Robson-Brown (
[email protected])
Other faculties obviously also welcomed!
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References/Bibliography: [1]
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[2]
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[3]
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[4]
NASA, “Small Spacecraft Technology State of the Art,” no. February, pp. 1–197, 2014.
[5]
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[6]
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[7]
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[8]
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[9]
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[10]
“CubeSat Kit System Chart.” [Online]. Available: http://www.cubesatkit.com/docs/cubesatkitsystemchart.pdf. [Accessed: 14-Jul-2015].
[11]
S. S. Arnold, R. Nuzzaci, and A. Gordon-Ross, “Energy budgeting for CubeSats with an integrated FPGA,” IEEE Aerosp. Conf. Proc., 2012.
[12]
H. Heidt, “CubeSat: A new Generation of Picosatellite for Education and Industry LowCost Space Experimentation.” [Online]. Available: http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=2069&context=smallsat. [Accessed: 14-Jul-2015].
[13]
P. Muri and J. McNair, “A survey of communication sub-systems for intersatellite linked systems and cubesat missions,” J. Commun., vol. 7, no. 4, pp. 290–308, 2012.
[14]
L. Frenzel, “What’s The Difference Between Bit Rate And Baud Rate?,” Electronicdesign.com, 2012. [Online]. Available:
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http://electronicdesign.com/communications/what-s-difference-between-bit-rate-andbaud-rate. [Accessed: 16-Jul-2015]. [15]
S. Greenland and C. Clark, “CUBESAT PLATFORMS AS AN ON-ORBIT TECHNOLOGY VALIDATION AND VERIFICATION VEHICLE,” Pestana Conference Centre, 2010. [Online]. Available: http://www.clyde-space.com/documents/1805. [Accessed: 16-Jul-2015].
[16]
LLNL, “Launching Traffic Cameras into Space (Lawrence Livermore National Laboratory).” [Online]. Available: https://missions.llnl.gov/defense/space-traffic. [Accessed: 12-Jul-2015].
[17]
C. Esionwu, “Comprehensive List of CubeSat Missions,” 2003. [Online]. Available: https://www.academia.edu/7787703/List_of_CubeSat_Missions.pdf.
[18]
H. R. Chiranjeeve, K. Kalaichelvan, and A. Rajadurai, “DESIGN and VIBRATION ANALYSIS of a 2U-CUBESAT STRUCTURE USING AA-6061 for AUNSAT – II,” IOSR J. Mech. Civ. Eng., pp. 61–68, 2014.
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