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QKDSat (Quantum Key Distribution Satellite)

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May 2021: Keeping information secure in today's interconnected world is becoming ever more important, so ESA is supporting efforts to ensure that future communications are kept confidential. 1)

A new generation of supercomputing power, delivered by quantum computers, is currently being developed that will be almost unimaginably powerful at cracking the most complex problems upon which encryption is based.

ESA has formed a Partnership Project with Arqit – a leader in the quantum encryption field, based in the UK – to keep information safe in a world where quantum computers are becoming commonplace.

ArQit Quantum Inc. recently announced that it was merging with a subsidiary of Centricus, a global investment firm, in a transaction expected to provide Arqit with up to €330 million in gross proceeds.


Figure 1: Artist's rendition of the QKDSat (image credit: QinetiQ)

QKDSat is a highly innovative Partnership Project of ESA to demonstrate how a space-based infrastructure employing the laws of quantum mechanics can be used to keep secure the exchange of sensitive information between several parties. 2)

The QKDSat Partnership Project will provide secure cryptographic key delivery services to customers on the ground for a range of applications, serving private and government sectors where the security and confidentiality of shared information is crucial.

This Partnership Project will significantly boost Europe's capabilities in cybersecurity and secure communications. It is helping to reinforce European scientific leadership and excellence in quantum secure communication, and to increase Europe's autonomy in this strategic field.

ESA is developing QKDSat with private partner ArQit, a British quantum key distribution services operator. ArQit is leading an industrial consortium that includes: QinetiQ of Belgium; British Telecom and Teledyne e2v of the United Kingdom; and several key players in Germany, Austria, Canada, the Czech Republic and Switzerland.


Development status

• May 30, 2022: A spacecraft computer is not much use if it cannot keep on running in space conditions – so this qualification model of QinetiQ Space's new onboard computer design has just spent two weeks in a thermal vacuum chamber in ESA's Mechanical Systems Laboratory at ESTEC in the Netherlands, exposed to the equivalent hard vacuum and temperature extremes of Earth orbit and deep space. 3)


Figure 2: This same onboard computer design is already planned for use by various ESA missions currently in development, including the Hera mission for planetary defence, QKDSat to test quantum key distribution from orbit, and Altius to map ozone and other trace gas profiles in Earth's atmosphere, as well as aboard the carrier platform for an in-orbit technology demonstration mission from the European Commission's Horizon 2020 Programme (image credit: ESA)

- "This onboard computer unit has been developed for the company's general purpose Proba-Next platform, serving small satellite missions", explains ESA small satellite engineer Stefano Santandrea, overseeing testing.

- "It is one of four avionics units, altogether forming the Proba-Next platform's core avionics set, called the ADPMS3 (Advanced Data and Power Management System 3rd Generation). These units are designed with a modular approach, for use by satellites either to complement each other or separately, based on particular mission needs. Their versatility also allows for either redundant or ‘single-lane' use."

- The combined ADPMS3 system, designed and manufactured in accordance with all applicable ECSS (European Coordination on Space Standardization) standards, comprises an onboard computer (OBC), a power control and distribution unit (PCDU) which handles the supply of power to all satellite subsystems, units and payloads, a remote terminal unit (RTU) which serves as a kind of extension of the OBC for the management of specific subsystems such as propulsion, and a mass memory unit (MMU) for payload data storage.

- The first generation of the ADPMS was developed for use aboard the small family of Proba satellites, and was used for the first time for the ESA's Sun-watching Proba-2 mission, in orbit since 2009, with ADPMS2 – an evolved version integrating the mass memory function – serving on the Earth-observing Proba-V and the double-satellite Proba-3 formation flying mission, due to be launched late next year.

- Stefano adds: "We're currently performing a complete qualification of the new ADPMS3 set of avionics units, which has four times the processing power of its predecessor, can manage and distribute a sensibly higher amount of electrical power, while being fully compliant to ESA's latest design evolutions, including end-of-life passivation and space debris mitigation regulations, requiring, between other factors, the complete passivation of the satellite at the end of its mission.

- "Testing is being shared between the ESTEC technical laboratories and ESTEC Test Centre managed by European Test Services, including vibration, shock and electromagnetic compatibility as well as thermal vacuum cycling. The complete avionics set qualification campaign began a month ago and is planned to last run until the summer break; so far the results are looking extremely promising."

• June 23, 2021: UK-based startup Arqit is on track to start delivering unbreakable quantum encryption keys all over the world using satellites in just two years. 4)

- Arqit, which recently announced collaborations with U.S. defense giant Northrop Grumman and the U.K. telecommunications behemoth BT, aims to launch two quantum key distribution satellites in 2023 from Spaceport Cornwall in the U.K. aboard Virgin Orbit's LauncherOne.

- Quantum Key Distribution (QKD) is a secure communication technique that uses quantum properties of photons, the elementary particles of light, to encrypt secret keys that can be shared by two parties to protect their communications. The technique, deemed unhackable since any attempt to eavesdrop on the communication changes the state of the photons and destroys the keys, already works in fiber optic cables but only for relatively short distances of about 60 miles (100 km) as the signal gradually wanes.

- "The problems with fibre optic is that at above about 300 km (186 miles), it's possible to get some quantum information transmitted but at less than about one bit per second," David Williams, Arqit chairman and founder, told "In a world that talks about megabits per second or gigabits per second, that's not a practical product. In order to do QKD on a global scale, the only solution is to use satellites."

- However, in the vacuum of space, the information-carrying photons can easily travel across distances of hundreds of miles. A satellite orbiting at the altitude of 430 miles (700 km), such as the Arqit QKD satellites, can provide "a good quality transmission down to Earth," Williams said.

- Previously, Chinese researchers successfully sent quantum-encrypted keys between three sites in Asia and Europe using the experimental spacecraft Micius.

- But Williams (who is also a founder and former CEO of communication satellite operator Avanti) told that Arqit is "far ahead of the world in launching a commercial [quantum key distribution] service."

- The two satellites the startup plans on launching in 2023 are only part of Arqit's solution, Williams explained. Arqit is already providing a regional commercial quantum key distribution service through fiber-optic cables using special software that, according to Williams, solves an old conundrum of quantum key distribution.

- "There is a big problem in the known satellite QKD protocols that you can either send keys globally or trustlessly, but you can't do both," Williams said.

- Trustless sharing means that no piece of infrastructure between the sender and the recipient can be trusted. That means the quantum encrypted key can never be converted into the ordinary ones and zeros of digital encryption because those could be hacked. That is, however, what happens in larger fiber optic QKD networks, which need to revitalize the quantum signal about every 60 miles (100 kilometers) as it gradually weakens inside the fiber. It also happens in satellites when they store the key on board after receiving it in the quantum form.

- "The problem is that with the existing BB84 [quantum key distribution] protocol, if you want to send a key between London and New York, both sides benefit from the quantum security of space to Earth transmission," Williams said. "But the satellite, as it flies over the Atlantic, is storing the key in an ordinary memory device on board, and that could be hacked."

- The satellite could send the quantum-encrypted key to the recipient immediately without storing it on board. But that would only work for certain distances as the satellite would have to "see" the sender and the recipient at the same time. With a low Earth orbit satellite like that of Arqit, that distance would be only about 430 miles (700 km), Williams added.

- Arqit, which has some cryptography heavy-weights on its board including Taher Elgamal who is dubbed "the father of SSL", a widely used protocol that encrypts internet traffic, invented a completely new quantum key distribution protocol which, according to Williams, overcomes the problems of trustless versus global distribution.

- "With our ARC19 [quantum key distribution ] protocol, the satellites can distribute keys on a global basis and the satellite never remembers the key," Williams said. He, however, couldn't reveal how the patented protocol works.

- Arqit's satellites, which will be 660 lbs. (300 kg) each, are, according to Williams, designed based on "standard components" and didn't require the design of "any new significant systems."

- "Most of the intelligence is done in the software protocol and that means that the satellite can be relatively straightforward," Williams added.

- The satellites will circle Earth in sun-synchronous orbit, an orbit above Earth's poles which will take the satellites over every spot on Earth at the same local time each day. Each satellite, Williams explained, will revisit every place in the world about three times a day, sending quantum-encrypted information to ground terminals at Arqit data centers, which will distribute them to users using a secure software protocol.

- QKD is high on the agenda of security researchers worldwide. The increasing data-crunching power of current computers makes traditional digitally encrypted keys ever more vulnerable. The advent of super-powerful quantum computers capable of carrying out massive amounts of parallel calculations looms large, causing concerns that traditional digital encryption will not suffice in the future.

- In May of this year, a team of researchers from Canada and the U.K. announced they were developing an experimental QKD payload that will be tested aboard the Quantum Encryption and Science Satellite (QEYSSat) after 2022. The researchers aim to send quantum encrypted keys between ground stations on both sides of the Atlantic.

• May 27, 2021: Keeping information secure in today's interconnected world is becoming ever more important, so ESA is supporting efforts to ensure that future communications are kept confidential. 5)

- A new generation of supercomputing power, delivered by quantum computers, is currently being developed that will be almost unimaginably powerful at cracking the most complex problems upon which encryption is based.

- ESA has formed a Partnership Project with ArQit – a leader in the quantum encryption field, based in the UK – to keep information safe in a world where quantum computers are becoming commonplace.

- ArQit recently announced that it was merging with a subsidiary of Centricus, a global investment firm, in a transaction expected to provide ArQit with up to €330 million in gross proceeds.

- The deal fully finances ArQit's endeavors to develop state-of-the-art satellites for quantum key distribution – dubbed QKDSat – through its key provision platform.

- Most of the world's communications systems rely on public key infrastructure to establish keys that are used to encrypt communications between two distant points. These encryption keys are intended to ensure the confidentiality, integrity and authenticity of the information – but the infrastructure will become vulnerable to hackers using quantum computers.

- QKDSat distributes symmetric keys through a cloud-based system to end-use devices, with a tiny computational load of less than 200 lines of code, leveraging the laws of quantum physics to prevent any eavesdropper from gaining access to the encryption key.

- A series of QKDSat satellites will enable the exchange and distribution of secure encryption keys to countless locations and billions of devices anywhere in the world, thanks to their optical quantum space-to-ground link. This improves resilience to future hacking threats because the quantum keys are generated from high-quality random sources and distributed across the cloud network.

- QKDSat is being developed as an ESA Partnership Project, which brings together the skills, expertise and resources of the agency to support the development of commercial applications of space technology in a public-private partnership.

- In 2019 ESA has placed a contract with ArQit co-funding the development of the first QKDSat satellite. The development is progressing well and the satellite is due for launch in 2023.

- Under UK-based ArQit's leadership, QKDSat is being developed by a pan-European team from a number of other ESA member states including Austria, Belgium, Canada and the Czech Republic.

- David Williams, chief executive of ArQit, said: "Our technology solves the most challenging security threats of modern times and, with the deployment of QKDSats, we will be able to hyperscale our distribution capabilities and geographical reach."

- Elodie Viau, ESA's Director of Telecommunications and Integrated Applications, said: "I am proud to see our industrial partner ArQit making a decisive step to move the QKDSat project forward and to raise the required funding on the market. This is proof of the competitiveness of our industry and the willingness of private players to partner with us and invest in the future. It confirms that the public support is well invested.

- "Quantum key distribution is crucial for many security-critical services such as finance, and key to ensuring our commercial digital sovereignty. We are witnessing the power NewSpace can bring to the commercialization of space, with telecommunications as the leading service market of the space economy."

• April 09.2019: Today's interconnected world is ever more vulnerable to cyberattacks, emphasising the importance of secure encryption to protect Europe's critical infrastructure and communications. An agreement forged today between the European Commission and the European Space Agency marks the first steps towards creating a highly secure, pan-European quantum communication infrastructure. 6)

- The development of terrestrial components of the quantum communication infrastructure will be under the responsibility of the EC's Directorate-General for Communications Networks, Content and Technology (DG Connect).

- It would comprise a series of quantum communication networks, linking institutional users and their critical infrastructures, and sensitive communication and data sites in Europe.


Figure 3: The space-based component, known as SAGA (Security And cryptoGrAphic mission), would be developed under ESA's responsibility and consists of satellite quantum communication systems with pan-European reach (image credit: ESA)


1) "Quantum communication in space moves ahead," ESA Applications, 27 May 2021, URL:

2) "Secure communication via quantum cryptography," ESA Applications, 2021, URL:

3) "Vacuum soak for satellite brain," ESA Enabling & Support, 30 May 2022, URL:

4) Tereza Pultarova, "UK company to start sending secret quantum keys with satellites in 2023,", 23 June 2021, URL:

5) "Quantum communication in space moves ahead," ESA Applications, 27 May 2021, URL:

6) "European quantum communications network takes shape," ESA Applications, 09 April 2019, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (


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