01Association for Advanced and Resilient Satellite Communications
Quantum keysfrom orbit
CLAU is a 6U CubeSat taking quantum key distribution to space: an optical channel that generates keys nobody can intercept without leaving a trace.
02About us
A student
association that
builds satellites
ACSAR is a student association based at Campus del Baix Llobregat in Castelldefels [university affiliation pending permission]. We design, build and operate advanced, resilient space communication systems.
We are around fifty people and an international community: part of the team comes from outside Spain. We work with concurrent engineering, traceable requirements and real technical reviews — the same framework used to run a professional mission.
ACSAR also operates as a junior enterprise: we can offer engineering services to companies in the sector and reinvest the income in our missions, hardware and team training.
Base · Room D7-010 · Building D7 · Campus del Baix Llobregat · Castelldefels
03CLAU mission
Laser CubeSat
for Ultra-secure
Applications
Every encrypted conversation depends on a shared secret key. If someone intercepts it on the way, the conversation is no longer secret — and nobody finds out.
Quantum key distribution (QKD) solves this with physics rather than mathematics: the key travels encoded in individual particles of light. Measuring a quantum particle disturbs it, so any attempt to eavesdrop introduces detectable errors. Both parties check those errors and, if there are too many, discard the key and generate a new one.
That is why we call them ultra-secure: security does not rest on how hard a mathematical problem is, but on the laws of physics. A future quantum computer does not break it.
What the
satellite does
CLAU is a 6-unit CubeSat in low Earth orbit carrying two complementary links. The quantum optical channel sends the light states that generate the key down to a ground station. The classical radio-frequency link handles telemetry, spacecraft control and the public part of the protocol, where both ends compare notes to distil the final key without revealing it.
The protocol is BB84, the reference standard for quantum key distribution. A pass over the satellite lasts only a few minutes: every design decision — pointing, stability, power and data handling — is driven by making the most of that window.
Note. The payload design is confidential. On this site the quantum channel is described at high level only.
Platform 01
6U CubeSat
Six 10-cm units: the smallest viable class that fits the optical terminal and the pointing accuracy it needs.
Protocol 02
BB84
The reference standard for quantum key distribution, formulated in 1984 and proven on real links.
Links 03
Optical + RF
Quantum optical channel for the key and a classical radio link for telemetry and distillation.
Orbit 04
LEO
Low Earth orbit, with the ground station at Campus del Baix Llobregat. [orbital parameters to be confirmed]
03.1Why it matters
No CubeSat has yet demonstrated secure key generation in orbit.
It is an open goal for the sector, and it is what CLAU is after.
Built by students, with the same engineering rigour as an institutional mission.
Below that size there is no room for the optical terminal and the pointing control a quantum link demands.
Europe's quantum communication infrastructure foresees a space segment; CLAU works towards it at CubeSat scale.
04Roadmap
From the optical
bench to orbit
CLAU has been shortlisted for Design Booster 3 of the European Space Agency's Fly Your Satellite! programme. This is the schedule up to the end of the programme.
- Shortlisted
Training week at ESTEC
The team attends the Design Booster 3 training week at ESA's technical centre in Noordwijk, the Netherlands, alongside the other shortlisted missions.
- Milestone
Final selection decision
ESA announces which missions continue in the programme after the training week.
- Laboratory
Laboratory experiments
Validating the operating principle on a controlled optical bench, with repeatable measurements and component characterisation.
- Engineering
Detailed satellite design
Full subsystem definition, mass, power and link budgets, integration plan and verification plan.
- Field
Free-space experiments
The link leaves the lab: open-air propagation between two sites, with real turbulence and background light.
- Programme
End of the Design Booster
The programme closes with the mission design consolidated and documented.
05How we work
Concurrent
engineering
More than twenty students from several European universities work on CLAU, organised by subsystem around a shared mission model.
Every subsystem has owners, its own documentation and requirements traceable to the mission objectives. Nothing is considered settled until it can be verified.
Solar generation, storage and power distribution across the orbit.
Attitude determination and control: pointing the satellite with the accuracy the optical link demands.
Flight software, mode management, data handling and spacecraft health monitoring.
Classical telecommand and telemetry link, and support for the public part of the protocol.
Mechanical configuration of the 6U, interfaces, stiffness and thermal control.
Receiving station, operations, satellite tracking and processing of the downlinked data.
The quantum optical channel. Design details are confidential.
COMET methodology
We use ESA's concurrent engineering approach: all subsystems iterate at once on a single mission model. A decision on mass, power or pointing propagates to everyone immediately and its impact is visible right away, instead of surfacing three months later.
Agile sprints
Work is organised in short sprints with verifiable goals and reviews open to the whole team. That lets people with very different course loads contribute without blocking anyone else, and keeps the real state of the project visible at all times.
06Join us · Collaborate
There is room
for you
A space mission needs far more than aerospace engineering. If you want to take part, write to us and let's talk.
Students
We are looking for people in engineering, physics, computer science and related fields, and also for anyone who wants to help with communication, management or institutional relations. No prior space experience needed: what matters is commitment and wanting to learn by doing.
I want to join →Companies
As a junior enterprise we offer engineering services in communications and space systems, and we collaborate on R&D projects. We also take on specific technical challenges as team projects.
Let's talk projects →Sponsors
Financial and in-kind support makes the hardware, the laboratory testing and the mission's technical travel possible. Sponsor benefits are [to be defined].
Support CLAU →07Contact
Write to us
acsarteam@gmail.comBaseRoom D7-010 · Building D7Campus del Baix Llobregat
08860 Castelldefels · Barcelona · Spain
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