## 3 Antenna Fabrication and Test
The utilized measurement system for vibration (sine, random, and shock) tests is given in Figure 9.  
The radiation performance measurements are repeated after the vibration test (AV) to verify that the manufactured antenna maintains its structural integrity when exposed to vibration and to observe whether vibration affects the radiation performance of the antenna. Both measurement results that are obtained before and after the vibration tests for the gain, cross-polarization, and axial-ratio are compared with the simulation results, as illustrated in Figure 10, Figure 11, and Figure 12, respectively. Figure 8: Radiation pattern measurement of the fabricated antenna. Figure 10: Comparison of the gain results. Figure 9: The used setups for the vibration resistance test of the fabricated antenna. Considering the operating conditions of the proposed GNSS antenna in the space environment, the antenna structure needs to be resistant to vibrations caused by launch vehicles and temperature changes due to orbital motion. The produced antenna structure successfully passed visual and X-ray inspections to observe possible structural deformations under high-intensity vibration conditions. On the other hand, the proposed DCF structure for spacecraft antennas was also implemented on IMECE, the first earth observation satellite of Turkiye with sub-meter resolution, and its thermal resistance is also verified operationally [24]. In spite of all the challenging test conditions, the proposed GNSS antenna provides approximately 7.2 dBic gain with a maximum \(\pm\)0.3 dB fluctuation observed in all GNSS frequency bands with an axial ratio better than 3 dB. Also, the cross-polarization level, i.e., relative magnitude level of the left-hand circular polarization (LHCP), is less than \(-\)13 dBic, even in the worst case, for the whole GNSS bands from 1.164 to 1.610 GHz. In addition, the center frequencies of E1 and E5a bands of Galileo, L1, L2 and L5a bands of GPS, and G1 band of GLONASS are selected to observe the co- and cross-polarization radiation patterns of the fabricated antenna. The measurement results for two principal cut-planes are also shown in Figures 13 and 14. Evaluation of the pattern measurement results indicates that the antenna has a very satisfactory radiation pattern with a wide angular range. As a result of this feature, the proposed antenna is not only able to receive signals from a larger number of GNSS providers but also significantly increases the signal reception time window with each of them. Thus, the positioning accuracy and reliability of the spacecraft are significantly increased by using only a single compact and lightweight antenna. Figure 5:0 Comparison of the cross-polarization results. Figure 5:1 Comparison of the axial ratio results. The proposed antenna is also a strong candidate when compared with existing GNSS antennas for space launch vehicles. A comparable spacecraft compatible GNSS antenna study is the patch excited cup (PEC) antenna for precise orbit determination of low Earth orbit (LEO) satellites [25; 26]. This PEC antenna also has very similar dimensions with the antenna proposed in this study. However, it does not support all-band GNSS operations and only has two operational frequency bands, L1 at 1.575 GHz and the combined L2 plus L5/E5a at 1.227 and 1.176 GHz. Although these operating frequency bands cover the entire GPS bands and allow use in multi-frequency applications, they are not suitable for applications with multiple different PNT providers. On the other hand, the results of the antenna proposed in this study show that it is not only compatible with multi-frequency applications but also is suitable to operate this application with different GNSS operators, such as Galileo, Compass, GLONASS, and GPS.