## 2 Simulation Setup and Estimation
### Estimated Parameters  
An overview of the estimated parameters, with respect to each measurement technique, is given in Table 5. The estimated Solar Radiation Pressure (SRP) parameters are discussed in more detail in Section 2.5. Furthermore, we estimated station-specific tropospheric wet zenith delays for the L-band (two-hour sampling), but we did not estimate troposphere parameters with respect to the OTWL measurements. We did not estimate ground station \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**Optical Link Measurement Errors**} & \multicolumn{2}{c}{**Description/Remark**} \\ \hline \multirow{4}{*}{Measurement noise} & Flicker-phase noise & Induced by various effects (e.g., trapping of charge carriers in semiconductors) and occurs in all electronic devices. Selected noise level up to 0.5 mm. \\ \cline{2-3}  & & A ranging distance-dependent error. Noise when varying between minimum and maximum ranging distance: \\  & Locked Loop (PLL) & - OTWL: 1.2–1.4 mm (MEO) and 1.7–1.9 mm (GSO). \\  & - OISL: 0.1–1.5 mm. \\ \hline \multirow{4}{*}{Troposphere offset (for OTWL only)} & \multicolumn{2}{c}{Simulated error: half the difference between the models of [30; 31].} \\  & - & Air pressure and temperature information from GPT [32]. \\ \cline{1-1}  & - & Relative humidity was set individually per ground station: min. 75\%, \\ \cline{1-1}  & - & max. 90\%. Varies randomly per station and epoch, each up to around \(\pm\)6\%. \\ \cline{1-1}  & - & Max. error at 30\({}^{\circ}\) elevation 5 mm; min. error at 90\({}^{\circ}\) elevation 0.4 mm. \\ \hline Bias due to the repeatability & \multirow{2}{*}{Uniformly distributed for each transmitter–receiver pair within \(\pm\)0.5 mm.} \\ \cline{1-1}  & of the link & \\ \hline Bias related to the equipment & \multirow{2}{*}{Bias per transmitter and receiver, randomly distributed between \(-\)0.5 and 0.5 mm;} \\ \cline{1-1}  & calibration quality & represents an inter-system bias, which affects the clock and the range. \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Simulated OTWL and OISL measurement errors. A detailed description of the different errors is given in [15]. \begin{table}
\begin{tabular}{c c c} \hline \hline \multicolumn{2}{c}{**L-Band Measurement Errors**} & \multicolumn{2}{c}{**Description/Remark**} \\ \hline \multicolumn{2}{c}{Measurement noise} & White noise of 15 cm for code and 1.5 mm for phase measurements for each frequency. \\ \hline \multirow{2}{*}{Troposphere modeling errors} & Simulation & Gridded VMF1 [28] model as an accurate model. \\ \cline{2-3}  & Solution & GMF model [29] as a less accurate model. \\ \hline \multirow{3}{*}{Phase Center Variations (PCV)} & A different pattern for each of the 16 ground stations and satellites, for transmitter and receiver. Multiplication by factor 50 for receiver and transmitter code measurements represents the worst-case scenario. The signatures are with resemblance to the multipath. \\ \hline \multirow{3}{*}{Constant phase bias} & A different phase bias per satellite, randomly distributed up to 5 mm. This represents hardware delays in the phase. \\ \hline Variation with once & A different variation in the phase bias per satellite, randomly distributed up to 5 mm; \\ \cline{1-1} per revolution & represents a temperature-dependent inter-technique bias per satellite. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Simulated L-band measurement errors. coordinates. Satellite and ground station clock parameters were estimated epoch-wise. For the optical measurements, we estimated a daily range and clock synchronization bias for each transmitter and receiver. As we also simulated variable biases for the optical links, the estimation of daily biases did not fully represent the model. The simulated inter-technique bias also had a phase bias contribution, but for the L-band we did not estimate range and clock synchronization biases. We estimated phase ambiguities (float) for the L-band. The phase biases are absorbed by the ambiguity estimation to a great extent.