Institute of Experimental and Applied Physics

Detector developed at ÚTEF will search for water on the Moon

Detectors based on Timepix sensors developed at the Institute of Technical and Experimental Physics of the Czech Technical University (ÚTEF) have been successfully conquering space for many years. They are used on the International Space Station (ISS) and on a number of satellites and orbiters, the European Space Agency (ESA) is counting on them for the Gateway mission, and in the near future they should also help search for water on the Moon.

 

 

Timepix-based detectors have been operating on international space stations, satellites and orbiters since 2012, when ÚTEF researchers, together with the University of Houston and the American space agency NASA, placed six detectors in USB format on the International Space Station (ISS). There, they served as personal dosimeters, and astronauts could use them in online mode, which was an advantage over previously used devices. The Timepix pixel detector technology was developed as part of an international collaboration founded by CERN and of which ÚTEF has been a participant from the beginning. The detectors were originally intended for accelerators, and are still located, for example, around the Atlas detector, where, like a cloud chamber, they monitor the number of particles. From the beginning, the collaboration motivated its members to continue using Timepix technology for any other applications. The ÚTEF Detector Technology Laboratory was the first to decide to apply Timepix also in devices intended for space research. The basic idea was that if the chips can survive in the world's largest accelerator, they should also survive in space, which has been proven true. In developing dosimeters based on Timepix sensors, ÚTEF researchers were meeting the needs of NASA, which wanted to have a real-time overview of the doses of radioactivity to which astronauts are exposed. The devices developed by ÚTEF are still successfully used on the ISS today, and the use of Timepix technology in space has become an entire field that CERN can now boast of.

 

On satellites

The cooperation with the ISS became an imaginary "gateway to space" for the Laboratory of Detector Technologies of the Institute of Electromagnetic Fields, but the real test of its equipment was still to come. The conditions on the space station are not much different from those on Earth - there is a stable temperature, atmosphere and only slightly excessive radiation, because the station is shielded against the radioactive particle flow. The detectors are much more burdensome to use in open space. So their placement on satellites and satellites became a real stress test for them. At the same time, their function also changed: from now on, they were to monitor the radiation environment in which the satellite is located. Unlike conventional dosimeters, which can only measure the deposited amount of radiation and determine the radiation damage that electronics or astronauts receive, more sophisticated radiation detectors such as HardPix can also characterize the radiation environment. That is, to precisely determine the spectrum of energies – the number of protons, electrons and heavy ions and to determine their energy and quantity in a given radiation field for a given period of time. And at the same time, they can examine whether the particles come from the sun or from the galactic background – from behind the solar system. Thanks to this, it is possible to predict, for example, solar storms or spots, which can not only damage the infrastructure on space devices, but also affect the transmission of high voltage or satellite telecommunications on Earth. The first device for space flight, Satram (Space Application of Timepix Radiation Monitor), was developed by scientists from the Institute of Electromagnetic Radiation and Radiation Engineering together with the Kroměříž company BD SENSORS. It went into space in 2013, on the European Space Agency (ESA) satellite Proba-V, which was supposed to study environmental changes on Earth. During such flights, the device finds itself in open space at an altitude of up to 820 km. It is located in a vacuum, is exposed to a much higher radiation flux of particles, must withstand significant temperature extremes, and the development of the readout electronics that communicates with the Timepix sensor must also adapt to this. The Satram detectors have withstood these demanding conditions: they are still operating on the Proba-V satellite today, although the mission has exceeded its planned lifetime several times. 

 

 

Since Satram was the first device with the Timepix chip to survive in open space, other workplaces conducting space research began to turn to the detector laboratory of the Institute of Space Research. Gradually improved versions of the detector (RISEPix, ????) completed several other missions, including with the Czech CubeSat VZLUSAT-1 (2017) or with the Japanese satellite RISESAT (2019). And also a sixteen-minute ballistic flight on a NASA test rocket (2018), which lasted 16 minutes and was supposed to confirm the correct orientation of the unique Czech telescope developed by the Czech company Rigaku. Although the same sensor was used for all the aforementioned missions, the device had to be developed and designed from scratch for each mission to suit the shape of the satellite. And in order to avoid this lengthy and costly process, researchers from the Institute of Radiation and Nuclear Physics (ITEF) developed a universally usable prototype of the Miram detector (Miniaturized radiation monitor) in 2018, based on previous successful experiences, which later gave rise to its definitive and widely used HardPix form. The European Space Agency provided funding for the development of both devices as part of its projects, seeing potential in them for itself. From the beginning, the agency expected that a device like HardPix could eventually be placed on all of its satellites. So the specifications included a requirement for the detector to have a small size and volume. Compared to the SREM (Standard Radiation Environment Monitor) or NGRM (New Generation Radiation Monitor) devices used so far, it was to be reduced by one order of magnitude while maintaining maximum functionality. The original analog detectors weigh more than 1 kg and have a volume of approximately 1 l, so they are practically impossible to integrate into the increasingly used CubeSats. They operate on the principle of absorption layers, with the energy of a particle being determined by how many absorbers the particle can pass through before stopping. Whereas detectors developed on the basis of the Timepix chip are also capable of measuring the energy of particles that pass through it. In order to find out which particle has passed through the detector and what its energy is, one layer is enough, and this allows us to create a device that is orders of magnitude smaller in terms of design. Researchers from the Institute of Electromagnetics and Radiation Protection (ITEF) aim for HardPix detectors for monitoring the radiation environment to become an indispensable part of CubeSat satellites in the future, which can be cheaply constructed from components commonly available on the market. Commercial companies could therefore also be interested in HardPix detectors in the future. And they could also help satellite developers optimize the shape of individual satellite components. If a satellite is to fly in a certain orbit for a certain specified period of time, the design must adapt to radiation degradation of the components – solar panels and all electronics. Until now, companies have relied on simulations or extrapolations of measurements taken in other orbits when developing satellites. Whereas a network of HardPix radiation monitors offers the possibility of precisely determining the dose to which a satellite is exposed at a given location and time, and accordingly optimizing the material for manufacturing components so that it is not too resistant, but not too resistant either, because radiation-resistant components are much more expensive and not very powerful. However, interest from commercial companies is not yet very high. And so ÚTEF cooperates primarily with space agencies. They can also save money when developing satellites thanks to the described capabilities of the HardPix detectors, but what is especially interesting for them is the scientific aspect: obtaining data for monitoring "space weather" and its ideal forecast. And ÚTEF, which often provides its partners with detectors free of charge, can in turn participate in evaluating the data. Joint publications and completed doctorates are then a measure of scientific performance and prestige, which helps the institute obtain funding from its parent CTU and other partner institutions.

 

Data transmission

The first prototype detectors developed at the Institute of Meteorology and Geophysics transmitted large volumes of raw data from space, which had to be processed on Earth. This meant a time delay. In the case of the ISS or the Satram satellite, which use the ESA ground station network and can constantly download large volumes of data via gigabit links, this is not a big problem. The problem arises with small CubeSats, which depend, for example, on a station of a smaller company or school, which can only transmit data in limited quantities and often only when the satellite flies over it. Overall, this is a very lengthy process: after downloading, the data is transmitted to the meteorological office in the UK, where it is processed using algorithms provided by the Institute of Meteorology. However, the planned modifications to the detector would allow for the acquisition of already processed information online.

 

 

 

 

 

And this is a new challenge for the researchers at the Institute of Photonics and Astrophysics. Recently, they have been working on developing special software based on AI or neural networks, which allows the evaluation of the acquired data directly in the HardPix detector, i.e. directly in space. If the hardware of the detectors has already reached its limits, the ability to process data “on board” can significantly increase their value. In addition to its small size, weight and consumption, its advantage could also be the limited volume of necessary data transfer. Given the high costs of developing such a device, cooperation with an agency like ESA, which finances similar projects almost 100%, is especially important for the Institute today. It is essential that, thanks to previous successes, it already has a good reputation with this agency, and therefore has a great chance of succeeding in tenders. One example of successful cooperation is the planned Gateway space station. ESA is preparing to send the first module into space, which will provide propulsion and energy for the station with the help of solar panels. And it has decided to place all the internal and external radiation monitors that have proven themselves in the past on it. And so it also approached the Institute of Electromagnetics and Radioactivity, saying that it wants to place two HardPix detectors outside the ERSA module, and a similar MiniPIX TPX3 device developed on the basis of the Institute of Electromagnetics patents by ADVACAM on the inside. Also promising is the cooperation with the Robinson Institute from New Zealand, which develops superconducting magnets and wants to find out what effect a superconducting magnet has on the radiation environment in space. Two HardPixes will be placed on their device, which will be sent into space and mounted on the ISS shell. And finally, the Institute of Electromagnetics has been planning to use the Tmepix-based device as a neutron spectrometer for a long time. Neutrons have so far been overlooked in the study of the radiation environment in space, even though they can also be very harmful. The goal of the Institute of Electromagnetics researchers will be their detection. And with the help of neutron spectrometers, they are also going to search for water on the Moon. If a body like the Moon or Mars does not have a magnetic field and atmosphere, its surface is constantly bombarded by radiation, mainly from the Sun. This then interacts with the planet's surface and emits neutrons from the nuclei of the surface material. And if there were water or hydrogen there, we would notice a slowdown of the neutrons when measuring the energy spectrum. Ideally, of course, it would be to place the device on a robotic rover that could examine the surface locally. The Curiosity mission has already attempted something similar on Mars, but it could be a world premiere on the Moon. ESA is planning a similar mission in the future. But smaller commercial companies are also trying to conquer the Moon today, which could also be interested in the detectors developed at the Institute of Electromagnetics and Physics, thanks to their low weight and size.

 

Robert Filgas

November 10, 2024