14/07/2023
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Imagine building yourself a small satellite out of standardised 10-cm boxes. Such humble nanosatellites are called CubeSats, first devised as an educational tool but increasingly performing valuable work in space. ESA’s CubeSat Systems Unit has been utilising CubeSats for a decade now to test out innovative new technologies – resulting in seven missions to date with many more on the way.
“Back then there was a perception in some quarters that CubeSats were gimmicky and most likely to fail,” explains Roger Walker, overseeing the Unit.
“We have become the longest running non-educational part of the Agency to work with CubeSats, and feel like we’ve won the argument on their effectiveness; our more than 80% success rate for these high risk missions speaks for itself.
“So now CubeSats have penetrated into many other areas of ESA, for instance through our Small Satellite Platform Unit, the InCubed, Scout and Phi-Sat programmes of ESA’s Directorate of Earth Observation, the ARTES programme of the Directorate of Connectivity & Secure Communications, and coming initiatives for the Directorates of Navigation and Human and Robotic Exploration. The European Union is also making use of CubeSats for their In-Orbit Demonstration and Validation initiative – managed by ESA on their behalf.”
In-orbit demonstration of new technology
The Technology CubeSats managed by the CubeSats Systems Unit are tasked with the early demonstration of innovative technologies in orbit, supported through the ‘Fly’ Element of ESA’s long-running General Support Technology Programme, to boost the competitiveness of Europe’s space industry.
“We follow a twin track approach” adds Roger. “We utilise CubeSats to cost-effectively and rapidly demonstrate new technologies for use in future operational missions, but the other part is to combine complementary technologies in such a way as to drive an overall step change in CubeSat system capability: for instance to match an antenna development with a transponder, or electric propulsion system with a high-power solar array and dedicated solar array drive mechanism.”
As well as implanting current missions, the Unit also works to generate ideas for future CubeSats through a series of ‘SysNova’ challenges – supported through ESA’s Discovery and Preparation programme via the Open Space Innovation Platform – inviting the space community to propose ideas for advanced future CubeSat missions and awarding winners study contracts, including sessions at ESA’s Concurrent Design Facility to refine them to a stage where they might make the grade as a future GSTP IOD mission.
Roger notes: “Capitalising on the results of the studies, we also coordinate closely with GSTP and other ESA technology programmes to identify promising CubeSat technologies and raise their level of technological readiness, so they can be a part of future missions.”
How to make a CubeSat
Traditional ESA programmes follow a set bible of mission development, called the European Coordination on Space Standardization, ECSS, and are limited to the use of reliable but costly ‘space-grade’ components and parts.
One of the advantages of CubeSats is that they can forego some of the strict ECSS processes and space-grade parts in favour of a lean approach and use of the latest ‘commercial off-the-shelf’ parts, often boasting superior performance. The challenge has been to maximise such advantages without compromising on overall mission reliability.
“Our projects are run to a standard management and engineering approach, aiming to maximise mission success and managing risk, while sticking to a tight schedule and cost,” says Roger. “That’s our added value, really, for the Member States that choose us to manage a mission: our accumulated knowledge and experience, ability to source technical advice from all across ESA’s Directorate of Technology, Engineering and Quality, and utilisation of ESTEC’s test facilities.”
The Unit has also been working to tailor ECSS standards and prepare a set of complementary engineering guidelines and advice for CubeSat developers. “These are supplied to the companies developing our CubeSat missions under contract, but they are also useful to the various new players entering the European CubeSat market, so we will be releasing the current version of these guidelines during our CubeSat Industry Days this September.
“Year by year, these CubeSat Industry Days have really let us see the development of the sector with our own eyes, as the number of companies attending has grown from dozens to hundreds.”
Roger attributes the high reliability of ESA’s Technology CubeSat missions to two main factors: “Firstly construction of each CubeSat flight models is preceded by a functional and electrical engineering model called a ‘FlatSat’, to check the combination of hardware and software works as it should, ahead of the flight model itself being rigorously tested. This by itself derisks a lot of problems with interfaces between units. Secondly we are rigorous on the acceptance of off the shelf hardware. The CubeSat supply chain is still maturing, so we can’t assume on trust alone that what it says on a product sheet is what we get. The last thing we want is a defective item turning up during testing, on the runup to launch.”
CubeSats beyond Earth orbit
Looking ahead, the Unit’s next big challenge is in ensuring sufficient reliability for CubeSat missions venturing beyond Earth orbit, starting with the Juventas and Milani CubeSats flying on ESA’s Hera asteroid spacecraft, as well the ’12-unit’ M-Argo CubeSat designed to fly to an asteroid on its own power and the HENON CubeSat that will venture more than 10 million km from Earth to serve as a prototype space weather forecaster.
Deep space represents a new and difficult operating environment, riddled with radiation, requiring the hardening of electronics to ensure continued reliability and long-term survival, and a whole new testing regime for candidate components.
In addition, many more flight opportunities are coming for European CubeSats, thanks in part to the new generation of micro-launchers supported through ESA’s Boost! programme, which should also offer access to more exotic orbits in turn, enabling novel mission possibilities – including the usage of swarms of CubeSats, the subject of a current Open Space Innovation Platform call for ideas.
The CubeSat Systems Unit’s next Technology CubeSat is scheduled to launch at the end of this summer, aboard ESA’s next Vega launcher: the PRETTY CubeSat being led for ESA by Beyond Gravity Austria will test a new way of utilising satnav signals to measure sea surface height through reflectometry techniques.
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