## 3 Antenna Fabrication and Test  
The designed antenna is implemented on a metallic reflective ground plane fabricated with a monolithically hollow cylindrical mast to increase the vibration resistance of the structure. The radiator part is fixed to the DCF with PEEK screws, and the inner conductor of coaxial feed is connected to the center of the radiator, as shown in Figure 6a. The monolithic nature of the ground plane with the mast is critical in terms of structural deterioration problems that may occur due to the potential for sudden flexing between the side walls where the radiator substrate is mounted and the central feeding connection point, which is the weakest point of the structure against vibration. On the other hand, the monolithic cylindrical mast provides circumferential support by soldering its outer perimeter to the bottom surface of the radiator and increases the vibration strength of the central feeding connection in its perforated interior, as shown in Figure 6b. In addition, choosing the substrate that is compatible with deformation-free flexing as much as possible reduces the transmission of vibration within the structure and reduces the possibility of structural fracture. The assembly process is completed by a radome made of the same PEEK material with a thickness of \(T_{rndome}\). The total weight of the built-to-launch structure \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameter** & **Value** & **Description** \\ \hline Rsub & 64.6 mm & substrate radius \\ L & 42.5 mm & length of triangular patch \\ \(\alpha\) & 80\({}^{\circ}\) & triangular patch angle \\ Ri & 7.4 mm & inner radius of phase delay line \\ Wi & 1.6 mm & phase delay line width \\ H & 43 mm & radiator height from the ground \\ Rmast & 4.25 mm & cylindrical mast outer radius \\ Rcoax\_diel & 1.54 mm & outer radius of coaxial cable dielectric \\ Rcoax\_in & 0.46 mm & radius of coaxial cable inner conductor \\ T DCF & 8 mm & wall thickness of DCF \\ Hradome & 6.15 mm & air gap from radiator to radome \\ Tradome & 1.1 mm & radome thickness \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Antenna design parameters. Figure 5: Exploded view of simulated space vehicle compatible antenna structure. is 493 gr, the diameter is 138.8 mm, and the height is 60.8 mm. The achieved overall volume reduction is 35%, and the weight reduction is 30% compared to the second prototype presented in [21; 22], and the achieved structural reductions increase when compared to the first prototype presented in [20], as 57% and 48%, respectively. The reflection coefficients of the fabricated antenna versus the frequency are measured and compared with the simulation results, as shown in Figure 7. The fabricated antenna provides a return loss of better than 10 dB in all GNSS bands and less than 15 dB in most of these bands. The results demonstrate that the antenna presents a very satisfactory return loss performance from 1164 MHz to 1610 MHz and provides a very efficient operating performance covering all GNSS bands. This means that in all bands, at least 90% of the antenna's input power, which is very limited in space applications since the power is obtained through solar panels and batteries, is transmitted as radiation despite all practical material losses. SATIMO StarLab is used in the antenna radiation performance, including axial ratio and co- and cross-polarization radiation pattern measurements. The utilized measurement system for the radiation pattern performance is shown in Figure 8.  
The proposed antenna is exposed to variable vibration levels standardized by the European Cooperation for Space Standardization (ECSS), and its operational performance  
Figure 6: Fabricated antenna: (**a**) The radiator without radome; (**b**) Connection between the radiator and cylindrical metallic hollow mast. Figure 7: Simulated and measured S\({}_{11}\) results comparison of the fabricated antenna. is examined in terms of vibration resistance [23].