Towards better protection of communication satellites against space radiation

Scientists are working on the design of protection for terrestrial communication satellites sent into space.

In a collaboration between the European Space Agency (ESA) and the Institute of Materials Science of Madrid (ICMM), dependent on the Higher Council for Scientific Research (CSIC) in Spain, the laboratory of ICMM researcher Isabel Montero studies the development of treatments that preserve the integrity of the satellites against electron emissions, reduce the corrosion of the aluminum that makes up most satellites and protect their radio frequency devices from possible electron discharges that could prevent communication with the Earth.

Much of this work at ICMM is done by simulating conditions in space.

“What we do in this laboratory is simulate the conditions to which satellites are subjected in space,” describes Montero. The scientist remembers that, in space, any object is subjected to very high power radiation where the presence of free electrons is also inevitable. The conjunction of solar rays together with other energetic electrons produces potential differences of more than 10,000 volts, “which can damage or destroy the solar panels of satellites,” explains the physicist.

On the outside of the satellite, only the Sun's rays already produce such an emission of electrons (photoemission) that the satellite becomes positively charged: “It is the extreme ultraviolet, it does not reach the Earth because the atmosphere protects us, but the satellites are exposed to him,” he points out. Satellites are also exposed to other energetic radiation that comes from sources such as cosmic rays: “They are electrons so energetic that they become implanted within the materials.”

To protect communications, the ICMM leads a contract with ESA with the aim of increasing the communication capabilities of the satellites and their useful life. “We measure the electron emission performance to determine the discharge thresholds,” says Montero. In this way, they have developed surface treatments with which they manage to reduce the emission of electrons “inhibiting the discharge to increase the working power.”

This is not the only collaboration between both institutions: “In relation to the electrical charge that accumulates on the surface of satellites, we are responsible for measuring the quantum performance of electron photoemission of materials for satellites and we characterize these materials to see how “They are and what they can withstand,” describes the research professor. “Simulations are also developed to check what maximum power devices on board satellites can reach after these radiations,” she adds.

The ICMM is the only center in Europe that carries out these measurements for the ESA within this tender, which has just started. In fact, this means that the relationship between both institutions has been maintained for more than two decades. Montero also reveals that in his laboratory they are also developing innovative treatments to reduce the emission of secondary electrons in space devices, “to avoid their multiplication in an avalanche,” he details.

Isabel Montero carrying out measurements within the framework of her work for ESA. (Photo: Ángela R. Bonachera / ICMM / CSIC)

New protection formulas

These low electron emission surface treatments are performed on silver using liquid phase methods. “They are the most interesting for use in the space industry, in contrast to other treatments that require a vacuum,” explains Montero. “We have an international patent with ESA and Airbus Germany (world leader in the aerospace sector), which is extended to the United States and Canada,” lists the researcher, who is currently also collaborating with Thales Alenia Space (the largest European satellite manufacturer) and ESA in exploring improvements to these coatings for the Galileo system (the Global Navigation Satellite System). The objective is to increase the power of the radio frequency devices that are carried inside the satellites: they need to protect these devices from possible electron discharges that would prevent communication with the Earth and, therefore, could make space missions fail.

“In this project we also have to find innovative anti-corrosion treatments for aluminum alloys,” he adds. Satellites need to be manufactured with various lightweight materials, hence the choice of aluminum alloys, which will require protection against corrosion. “Since treatment with chromium VI has been definitively prohibited as it is considered carcinogenic, we have to look for another anti-corrosion treatment, and this has a lot of economic relevance worldwide,” defends Montero, who recalls that the Ministry of Science, Innovation and Universities “is being fundamental in these investigations.”

In space, there are many dangers that threaten anyone who dares to go outside, and one of the most dangerous charged particles is atomic oxygen, since it is corrosive. The work to verify its damage and protect itself from it does not stop, and this is also where this laboratory comes in, which has received a request from the ESA to be the one to carry out the secondary emission measurements of the materials before and after receiving the impact of these particles. “They do the treatment and send it to us so we can measure the results, it is a sign of the trust they place in the ICMM,” concludes the scientist. (Source: ICMM / CSIC)