## 4 Measurement Setup  
In this section, the setup for the simulations, hardware-in-the-loop (flatsat), and satellite measurements is explained, including the configuration of the measurement software.  
One measurement is defined as one C++ programme execution, and a _measurement set_ contains a group of measurements. Each measurement has a _duration_ and generates a file with date and time as filename. The measurements within a set have a periodicity (time between the start time of two consecutive measurements).  
The configuration of the measurements is presented in Table 1. The center frequency was chosen based on the lowest frequency in the UHF amateur radio band measured in Reference [11; 13]. In addition, the frequency \(435\) MHz is in the middle of the ground radar band \(420\)-\(450\) MHz. To reduce software computational power, the sampling frequency was \(600\) kSps, rounding up the minimum value (\(521\) kSps). To satisfy the Nyquist criterion and avoid aliasing, the RF bandwidth shall be, at least, half of the sampling frequency [26]. The bandwidth setting was chosen to be \(200\) kHz so that there is a margin with regard to Nyquist; the sampling frequency is then three times the bandwidth.  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Parameters** & **Values** \\ \hline RF centre frequency (MHz) & 435.00 \\ \hline RF bandwidth (kHz) & 200.00 \\ \hline Sampling frequency (kSps) & 600 \\ \hline Duration (s) & 5 \\ \hline Period between measurements (s) & 60 \\ \hline Frequency bins & 128 \\ \hline Time windows (ms) & 0.21, 0.43, 0.85, 1.71, 3.41, 6.83, 13.6, and 27.3 \\ \hline Number of outputs & 10 \\ \hline Number of bits & 32 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Configuration parameters for simulations, as well as flatsat and in-orbit measurements.  
The measurement duration should be long enough to find stationarity, but short enough not to measure the spatial variability due to the satellite's movement. The duration was five seconds as a trade-off. This interval corresponds to a movement of a 0.3\({}^{\circ}\) angle from nadir (center of Earth). The time between measurements is one minute, which defines the spatial resolution. To resolve the 3\({}^{\circ}\) beamwidth (rounding up) used by type A space-tracking radars, a corresponding spatial sampling is performed. Thus, measurements were one minute apart.  
There is no maximum bandwidth for the 435 MHz according to the International Amateur Radio Union (IARU) band plan [27], but the Norwegian band plan recommends between 12-20 kHz [28]. Therefore, the frequency resolution should be higher than these values and traded-off against the data size to downlink since the number of frequency bins is proportional to the data size. The number used was 128 to obtain a frequency resolution better than 5 kHz. The resolution for time variability is determined by the first time window, chosen to be 0.21 ms, since it is lower than the shortest pulse width of the radars mentioned in Section 1. The smallest step between windows, which is 2, was chosen for this first round of measurement campaigns. The maximum number of outputs and number of bits was configured to obtain better temporal variation resolution and reduce bit quantisation errors.  
To verify the implementation of the proposed estimator, it was first tested on a set of simulated signals describing different possible interference scenarios using the same configuration. The same scenarios were then tested on the TOTEM SDR in the flatsat setup, generating the signals with another SDR to verify the hardware.