## 1 Introduction  
Modularity, complexity, and miniaturization have been the watchwords of industrial design in recent decades. Nowadays, we can see the direct technological impact of these trends on the space industry, especially in connection with the technological approach of nanosatellites and CubeSats implementations. According to [1,2], a total of 1960 CubeSats have been launched as of 1 January 2023, of which 338 were in 2022, while 1135 are still operational. The CubeSat standard, introduced in 1999, opened the path to nanosatellite standardization, leading to the fast commercialization of this spacecraft segment. As a consequence, the CubeSats, initially developed as a university project for educational purposes, quickly transformed into a technology testing platform and finally became an economically advantageous scientific apparatus. Today, the CubeSats are widely used in various scientific and research missions, such as Earth observation science [3, 4, 5, 6, 7, 8, 9, 10], quantum communication from Earth to LEO [11], asteroid impact prevention [12, 13], optical observations [14], stellar astrophysics observations of stars and planets [15, 16, 17], and solar [18, 19] or lunar [20, 21] science. Concerning the technological solutions of the CubeSats, most of the scientific papers focus on topics related to Attitude Determination and Control Systems (ADCS), which typically contain magnetometers [22] and electromagnetic actuators [23, 24, 25, 26] used for position controlling and stabilization. The sensitive magnetometers and electromagnetic actuators working on the principle of magnetic field interactions are the main study area of our team. We have participated in the Slovak CubeSat program since the first Slovak satellite--skCUBE [27]. Although the mission's primary scientific goal was not reached due to the communication failure between an onboard computer and a radio transmitter, the mission was successful from a technological point of view, especially concerning the integrated electromagnetic actuators. Consequently, the skCUBE was taken as a basis for the following pure scientific GRBAlpha mission [28], designed to test a CubeSat-size gamma-ray detector [29]. In the case of both missions, the skCUBE and the GRBAlpha, a special calibration method [30] was used to calibrate their onboard magnetometers in an ordinary laboratory environment without the use of a shielding chamber. During the skCUBE mission, innovative electromagnetic actuators have been developed. The structure of these actuators consisted of a solenoidal winding with a ferromagnetic core made of soft amorphous ribbons, the volume and shape of which were designed to optimize overall actuator performance. The conceptual design phase was performed by using only an analytical method. Ultimately, the produced actuators were tested by an external fluxgate magnetometer to measure their current/magnetic field transfer curve. Although we were able to measure the B-H characteristics of the core's material sample, it was unable to measure the state of magnetization of the whole core due to the limits of the apparatus used and the measurement method. Concerning changes in the core shape, usually associated with the machining process, they can significantly affect its magnetic properties since a magnetic anisotropy alters as a result of such structural intervention. The significant one is a shape anisotropy, manifesting through a demagnetizing field, which occurs during the open-ended sample's magnetization and leads to modifications of its hysteresis curve. Consequently, the final product's magnetic parameters differ from the raw material parameters stated by manufacturers. Since these steps are difficult to simulate using numerical methods, the possibility of measuring the magnetic hysteresis curve of the core, or generally any magnetic component, is beneficial for the designer to validate the design before producing the complex device; in our case, the CubeSat actuator.