## 5 Results
### In-Orbit Results
#### 5.2.1 Measurements over Non-Populated Areas  
To analyse in-orbit interference measurements, it is important to measure over non-populated areas to estimate the noise floor. Since absolute power levels cannot be obtained  
Figure 5: Comparison of bin difference in theory, simulations and measurements with the flatsat. The pulse and the chirp signal have a pulse length of 5 s and a period of 16.67 ms. (**a**) AWGN bin difference. (**b**) CW bin difference. (**c**) Complex pulse bin difference. (**d**) Complex chirp bin difference.  
from the satellite, these measurements can be used as a lower bound for the power. The estimation of the in-orbit noise floor can be compared to the AWGN measurements with the flatsat setup to verify that the spectrum shape is as expected.  
The measurements over non-populated areas were taken over the South Pacific and South Atlantic, as shown in Figure 6a. In total, 60 measurements were performed in this area, but five of them contained CW interference (red circles in the map). Thus, they were grouped with the measurements over populated areas since they were obtained close to the South American coast.  
The average power spectrum (\(m_{2k}\)) was estimated over five seconds for each of the measurements. In Figure 6b, the 90% percentile, median, and 10% percentile of the average power for each bin of all average power spectra are shown. The shape of the spectrum is very similar to the result obtained in the lab (Figure 3a). In the bandwidth of interest (434.8-435.2 MHz), the median value of all measurements and all frequency bins is \(-41\) dB. The 10% percentile is \(-44\) dB, and the 90% percentile is \(-39\) dB, including all frequency bins. In Figure 6c, the coefficient of variation \(c_{k}\) was calculated using Equation (7) and compared to the theoretical value of AWGN in Equation (10), which is approximately 0.52. The CV for noise in-orbit measurement is similar to that of the AWGN but slightly higher for the median and the 90% percentile.  
Figure 6: Time-frequency behaviour of measurements over non-populated areas. (**a**) Sub-satellite points for measurements over non-populated areas (blue circles) and close to populated areas (red circles). (**b**) Spectrum of average power (\(m_{2k}\)). (**c**) Coefficient of variation (CV). A high coefficient indicates high spread in the measured envelope.  
The variability of the LME as a function of averaging window length was also measured (Figure 7). All measurements have similar temporal behaviour, so a representative example of the normalised LME second moment for all the frequencies is presented in Figure 7a. The normalised LME second moment follows the AWGN time behaviour converging to approximately \(\pi/4\). This trend can also be seen in Figure 7b, where the normalised LME second moment was plotted for all frequency bins of all noise floor measurements (blue circles). The blue dashed line represents the theoretical trend for the AWGN, the red crosses show the highest bin measured in the flatsat setup, and the dotted line \(\pi/4\). The in-orbit results show a slightly higher deviation from the flatsat results for AWGN for longer windows.