## 6 Discussion  
All the mission objectives required to deduce the TVWC as a time delay measurement are demonstrated in this study using low-cost commercial off-the-shelf components. Since this study is a continuation of Kyutech SPATIUM satellites, as mentioned in the objectives of SPATIUM-I and SPATIUM-II [19; 29; 35], the need for the ISL network to enhance 3D mapping of the atmosphere and ionosphere was demonstrated using this system. SPATIUM-I and SPATIUM-II satellites primarily focused on technology demonstrations for the mea \begin{table}
\begin{tabular}{l l c c} \hline \hline
**Frequency** & **MHz** & **400.15** & **460.00** \\ \hline \hline
**Modulation** & & **SS-BPSK** & **SS-BPSK** \\ \hline \hline
**Data rate** & **kbps** & **0.25** & **0.25** \\ \hline \hline Satellite \(A\) (Transmission) & & & \\ \hline \hline \multirow{3}{*}{Transmitter Output Power} & SDR Output & W & 0.1 & 0.1 \\ \cline{2-4}  & Amplifier Output & W & 30.0 & 30.0 \\ \cline{2-4}  & Total & dBw & 14.8 & 14.8 \\ \hline Gain of Transmitting Antenna & dBi & 2.1 & 2.1 \\ \hline Transmission Line Loss + Hardware Degradation & dB & 3.0 & 3.0 \\ \hline Equivalent Isotropic Radiated Power (EIRP) & dBw & 13.9 & 13.9 \\ \hline Transmission Path & & & \\ \hline Distance between satellites & km & 4600 & 4600 \\ \hline Antenna Pointing Loss & dB & 3.0 & 3.0 \\ \hline Polarization Loss & dB & 3.0 & 3.0 \\ \hline Atmospheric and Ionospheric Losses & dB & 1.4 & 1.4 \\ \hline Free Space Loss & dB & \(157.7\) & \(159.0\) \\ \hline Isotropic Signal Level at Spacecraft & dBw & \(-151.3\) & \(-152.5\) \\ \hline Satellite \(B\) (RX Power Sensitivity) & & & \\ \hline Antenna Pointing Loss & dB & 3.0 & 3.0 \\ \hline Gain of Receiving Antenna & dBi & 2.1 & 2.1 \\ \hline Transmission Line Loss + Hardware Degradation & dB & 3.0 & 3.0 \\ \hline \multirow{3}{*}{Received Power at LNA input} & dBw & \(-155.2\) & \(-156.4\) \\ \cline{2-4}  & dBm & \(-125.2\) & \(-126.4\) \\ \hline Required Signal power at the Spacecraft & dBm & \(-116.0\) & \(-116.0\) \\ \hline System Link Margin & dB & \(-9.2\) & \(-10.4\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Link budget for ISL network. surement of _TEC_ using a ground-to-satellite communication network. This study deals with both total electron content and atmospheric water vapor measurements using the ISL communication network. Furthermore, the procedure for deducing atmospheric water vapor is presented as a time delay measurement. Kyutech expects to launch a constellation of satellites, which could be more than a thousand satellites, and this makes the desired spatiotemporal resolutions achievable [19]. The ground test results demonstrated that the shortest possible time to reconfigure frequencies and processing has been found to be within 1 s at sampling rates of 1 MSPS and below. The computed system link margin has a deficiency of at most \(-10.4\) dB when the transmission frequency and separation distance between satellites are 460.00 MHz and 4600 km, respectively. It could be improved by implementing state-of-the-art UHF antennas with high gain. [PERSON] et al. [62] proposed the use of deployable helical antenna with a gain of approximately 13 dBi, and it could stow into a volume of approximately 0.5U. By adopting a similar antenna, the system link margin becomes positive and ISL communication network could be established between the satellites. Cross polarized linear arrays such as a Yagi-Uda [63; 64; 65] also exhibited superior gains of up to 11.5 dBi at UHF frequencies compared to dipole antennas. Using the Yagi-Uda type of antenna could also be considered a solution for this mission. The use of a directive antennas requires attitude control to point the antenna towards the target [66]. In addition, [PERSON] et al. [63] suggested the use of circular polarization in antenna designs for small satellites to eliminate polarization mismatch losses due to antenna misalignment and this guarantees higher link reliability in ISL networks.