# Low-Cost _Ka_-Band Satellite Receiver Data Preprocessing for Tropospheric Propagation Studies
## 3 Results  
In this section, we go on to describe, through specific examples, the main characteristics of the templates extracted on non-rainy days, as well as the impact of some local meteorological parameters. Note that our ensuing analyses were based on locally measured meteorological information at the receiver location. However, it is worth mentioning that it is the whole path's parameters that condition the measured received levels. In Figure 5, we analyze a clear-sky day (19 August 2018) recording together with associated concurrent local meteorological information. We show the extracted template, the ambient temperature, and the dew point along the day. Note again that the absolute signal levels shown here were not calibrated to dBm and were the result of the processing of the in-phase and quadrature digitized input signal. Since the overall raw data are also affected by some level of unavoidable mispointing, our correlation analyses should be regarded with care given that we only studied here the impact of the ambient temperature and other meteorological variables. Even though we are aware of the fact that the correlation levels observed for meteorological parameters can be disturbed by the correlation between the raw data and the pointing errors, these  
Figure 4: Example of excess and rain attenuation for a rainy day: 28 August 2018. Figure 3: Example of raw beacon level and extracted template for a rainy day: 28 August 2018.  
results continue to be relevant for deriving that particular day's template. The fact that both the thermal cycles and the satellite positioning errors show the same period does not completely imply that the correlation coefficients due to one phenomenon and the other have the same strength. We saw a clear negative correlation with the ambient temperature. Furthermore, this temperature was always far from the dew point. This kind of behavior has been observed in most of our non-rainy recordings, with high levels of anti-correlation always below \(-0.9\). Additionally, we also include in Figure 6 a plot showing the template and the relative humidity, where high correlation values are also apparent, indicating another possible relevant influencing factor in the evolution of the template. Clear sky is a very common condition during the year. The negative correlation between template and temperature is significant. For the month of August 2018, full-day (no morning fog) clear-sky conditions were met during Days 2-5, 10-11, 15, 18-20, 23, 26, and 31. Their corresponding correlation values with the ambient temperature are listed in Figure 7. They never went above \(-0.91\). Figure 5: Template, ambient temperature, and dew point for a clear-sky day: 19 August 2018. Figure 6: Template and relative humidity for a clear-sky day: 19 August 2018. However, we did not find a deterministic behavior in the observed signal levels, as illustrated in Figure 8, which shows that the templates extracted in clear-sky days were not necessarily identical from day to day. As complementary information, we also provide the corresponding day-to-day ambient temperature plots in Figure 9.  
Coming back to the templates in Figure 8, the changes in their daily average levels, not in their peak-to-peak dynamic ranges, could be fundamentally attributed to a longer term upward or downward drift in the orbit cycle, which is only reset when stationkeeping maneuvers are carried out on a periodic basis. These effects completely mask out the water vapor and cloud effects, which are of lower magnitude. Under these constraints, the use of an all-time, single template is not feasible, and thus, it is necessary to employ the current day's template (or, at most, one involving the previous and following days.) Figure 8: Templates for the days in August 2018 with all full-day clear sky. Days: 2–5, 10–11, 15, 18–20, 23, 26, and 31. Figure 7: Correlations between template and ambient temperature for the days in August 2018 with all full-day clear sky. Days: 2–5, 10–11, 15, 18–20, 23, 26, and 31.