naosat: a scalable nanosatellite · pdf filesubsystems in order to be interchangeable between...

63rd International Astronautical Congress, Naples, Italy. Copyright ©2012 by the International Astronautical Federation. All rights reserved.

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IAC-12. B4.7A.6

NAOSAT: A Scalable Nanosatellite Architecture

Francisco García-de-Quirós Emxys S.L., Spain, [email protected]

José Antonio Carrasco Hernández

Emxys S.L., Spain;

The reusability of components in small (micro and nano) satellites is a key issue concerning the mission

development cycle and, thus, the overall costs. The Cubesat standard has been extensively used to implement low cost and short cycle missions with many purposes (Science, technology demonstration, educational outreach, etc) mainly due to the standardization of aspects like the main structure (allowing the implementation of subsystems from different providers) or the simplifying of the interface to launch vehicle through standard PODs. Nevertheless, the Cubesat standard is still very limited in size and volume to enable complex Science experiments, which would require high power demand, bulky instruments, etc. For this reason, Emxys developed the NAOSAT architecture, as a scalable nanosatellite platform control section that can be implemented either in standard 3U Cubesat structures or in an extended version, and named XCube. XCube is a 20 x 20 x 40 cm 15Kg platform, intended to extend the capabilities of Cubesats with a minimum design effort. This contribution describes the technical approach for the design of XCube and the difficulties and lessons learned during the development of the different platform subsystems in order to be interchangeable between both platforms.

I. INTRODUCTION Small-satellite platforms are playing a key role in

the development of modern Space research programs. Since its appearance in the early 2003, more than 40 Cubesat missions have been sent to orbit, mostly related with academic and research purposes. From the first Cubesat projects, mainly involving academic institutions such as universities and technology colleges, the Space community has been witness of the growing relevance and impact of this kind of missions, in special those based in the Cubesat platforms, in more demanding fields like in scientific research, technology demonstration or even Defence.

Many motivating factors boost the development of

Small satellite platforms, some of them are: • Very low mass and volume budget, which

impacts dramatically in the total mission costs. • Fast mission cycle, which impacts on total

engineering effort and enables to get more flight experience by a fraction of the time costs (i.e. more missions means more flight heritage through experience and lessons-learned).

• The lower complexity levels open the door to operationally responsive Space systems.

• Missions based in Small satellite make affordable to put in operation systems with shorter operational life, this means that can be

replaced in short time by more sophisticated and powerful versions, adapted to new technologies.

• As a consequence of the point above, the adoption of the newest technologies by the Space industry is being strongly stimulated, since the requirements of reliability over time are much more relaxed than in regular missions with life spans in the order of 10 years.

Among the last mentioned factors, one specific

aspect of Cubesat platform standard has motivated its rapid spread along all the Space domains: the simplicity of integration through standardized POD dispensers. These dispensers are based in a spring-actuated Push-Out deployment concept that, since it requires a minimum interface with the launch vehicle, simplifies dramatically the mechanical and electrical integration and of these devices in the LV as well as the associated acceptance processes, thus allowing the accommodation of several of those deployers in a single vehicle, reducing in an important factor the launch costs per Cubesat.

However, the accession of Cubesat and other minor

representatives of small satellite platforms to the front line of Space technology did not happened by chance. Late advancements in miniaturization in technologies like microelectronics, photonics and MEMS technology, as well as the availability of higher density Li-Ion batteries and high efficiency triple-junction solar cells


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have pave the way to the implementation of complex digital and analogue electronics in small form-factors, with data processing capabilities once only conceivable in large computers.

Nevertheless, the Cubesat platform has also some

drawbacks. From our experience, dealing with partners both at scientific and technology research domains such as Astronomy and Astrophysics, High-Energy and Nuclear physics, Life Sciences, Materials Sciences, Quantum Optics, Photonics etc., the main hurdle to use the Cubesat platform in more demanding scientific experiments reduces to a single one: Volume. Many of our partners agree in that with 3,5Kg of electronics, detectors and batteries, a lot of highly interesting science can be done but the limited 3 dm3 are really little when, for example, optics or upper atmosphere physics is involved.

This fact motivated our team to face the

development of an upgraded version of our platform NAOSAT, originally intended for 3U (30 x 10 x 10cm) Cubesats, to a larger format of (in principle) 20 x 20 x 30 cm which could evolve to a size of 20 x 20 x 60 cm. The name of this new platform format is XCUBE.

The main ideas behind this development are:

• Reusability of Components: The platform section developed for 3U Cubesats must be reusable with no or minor changes.

• Portability of Payloads: Payloads developed for the Cubesat NAOSAT platform have to be portable to the extended platform with no changes.

• Push-Out deployment concept or equivalent: The platform is designed to be dispensed with the simplest LV integration scenario.

In this sense, different developments were performed from the mechanical point of view, to allow the implementation of the currently developed components in this larger platform

II. THE NAOSAT PLATFORM The NAOSAT architecture is composed by a set of

interrelated components implementing a scalable and versatile 3U Cubesat platform, specifically conceived to perform scientific and technology research missions with multiple experiments in a ride-share philosophy.

Fig. 1: Rendition of the POLITECH.1 Satellite, the first NAOSAT based mission, from the Universidad Politécnica de Valencia (Spain) The first mission implemented on the NAOSAT

architecture will be the POLITECH.1 Nanosatellite form the Polytechnic University of Valencia (Spain). It will carry on-board three experiments from such university:

• HiDAC: A C-Band deployable Patch

Antenna for High-Data rate communications in Cubesats.

• SatFOSS: Fiber-Optics based sensors for Small satellite platforms.

• GEODEYE: Deployable Telescope camera for Geodesy.

Together with an additional experiment involving Upper Atmosphere research from NASA Goddard Spaceflight Centre.

The main features of the NAOSAT architecture are:

• On-Board computer based in ARM CORTEX 32 bits Microcontroller + Watchdog FPGA device.

• Power Bus: Unregulated 4.2 V with a nominal discharge current of 1,4 A, maximum discharge of 5A and Discharge pulses up to 30 A. Regulated 3,3V 200 mA.

• Solar Panels: Triple-junction solar cells with MPPT management system.

• ADCS sensors including tri-axial magnetometer and gyroscope, coarse Sun sensors and one fine Sun- sensor. 0,2º accuracy.

• ADCS actuators consisting in three miniature Reaction Wheels and three magnetorquers.

• TTC antenna: Double dipole, reception in VHF band and transmission in UHF band.


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As it can be appreciated in the figure below, the system is designed to allow the distribution of experiments along the satellite platform in a seamless way.

Fig. 2: NAOSAT internal distribution. The main structure is designed on a stacked concept,

in which the different elements (platform components and payload sub-systems) are stacked over Aluminium rings that plays the role of both mechanical support of the PCBs and fixation elements of the lateral parts which give mechanical stability to the whole and allow the connection of the solar panels. The mechanical parts of the main structure are manufactured in Aluminium 7075.

In the figure below, a functional architecture of the

NAOSAT platform is shown. The payload bus is configured to provide a seamless interface with the different experiments, which could consist on a single PCB assembled in the stack or more complex devices. Together with the Power bus mentioned above, a set synchronous communication buses are included such as I2C and CAN 2.0 which enables the communication between the OBDH and the different experiments, as well as a number of general purpose digital I/O that makes possible to drive directly simple experiments.

A large number of internal parameters are measured

and controlled by the OBDH like temperatures, current and voltages at critical points, etc.

Fig. 3: NAOSAT Functional architecture.

III. THE XCUBE PLATFORM During the design of the XCUBE platform, the most

important milestone was to design the mechanical elements to keep the upward compatibility with the currently developed NAOSAT components, originally intended for the 3U Cubesat platform.

The effort was made maintaining the same concept

as in the NAOSAT mechanical structure, but designing the ring interface elements in a way that would be compatible with the former components and making possible the use of the volume inside the XCUBE platform in different ways: either keeping the Cubesat like distribution of components, thus the XCUBE can be seen as 4 3U Cubesats connected, or combining this idea with the distribution of components in a free mode as the ring elements allow to accommodate subsystems centred with respect to the symmetry axis of the platform.

Concerning the Power System, XCUBE is upgraded

with a bigger power budget (12W) due to increased solar panels area. This is translated in the availability of two unregulated voltage busses: the 4.2V bus to maintain compatibility with NAOSAT sub-systems and a new 8.4V unregulated bus to supply loads with bigger current demand.

In the figure below, different internal configurations

of XCUBE platforms are depicted. The ring-oriented design allows different distributions of the internal volume, either for traditional Cubesat standard systems


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or for more a flexible distribution in case the experimental payload demands it.

Fig. 4: Different configurations and internal distribution of elements for the XCUBE platform. This aspect is clearly advantageous in terms of

systems-level engineering: the harness of the different sections can be kept from its original Cubesat style whilst the distribution of elements on the central axis and around is still possible in a different ring. This way, attitude control systems and heavy elements, such as battery packs, can be distributed to ensure that the

centre of mass of the whole system is in the symmetry axis, simplifying the implementation of the attitude control algorithms.

IV. CONCLUSIONS The latest XCUBE satellite platform from Emxys

has been presented in the context of the current Small Satellites industry scenario. The XCUBE platform is a second generation satellite platform that has been developed with a clear goal in reusability and modularity, with the aim of reducing costs and effort in the transition from Cubesat developments to a bigger platform able to accommodate larger instruments, as often required in disciplines like Optical Communications, Astronomy or Earth Observation. Different aspects and difficulties found during the project were reported and discussed.

naosat: a scalable nanosatellite · pdf filesubsystems in order to be interchangeable between...

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